The CANADIAN FIELD-NATURALIST
A JOURNAL OF FIELD BIOLOGY AND ECOLOGY
Promoting the study and conservation of northern biodiversity since 1880
i Ps
ath) \.
Volume 133, Number 1 ¢ January—March 2019
Ottawa Field-Naturalists’ Club Club des naturalistes d’Ottawa
The Ottawa Field-Naturalists’ Club
FOUNDED 1863 (CURRENT INCORPORATION 1879)
Patron Her Excellency the Right Honourable Julie Payette, C.C., C.M.M., C.O.M., C.Q., C.D. Governor General of Canada The objectives of this Club shall be to promote the appreciation, preservation, and conservation of Canada’s natural heritage; to encour- age Investigation and publish the results of research in all fields of natural history and to diffuse information on these fields as widely
as possible; to support and cooperate with organizations engaged in preserving, maintaining, or restoring environments of high quality for living things.
Honorary Members
Ronald E. Bedford Michael D. Cadman J. Bruce Falls Robert E. Lee Allan H. Reddoch
Charles D. Bird Paul M. Catling Peter W. Hall John Mcneill Joyce M. Reddoch
Fenja Brodo Francis R. Cook Christine Hanrahan Theodore Mosquin Dan Strickland
Irwin M. Brodo Bruce Di Labio C. Stuart Houston Robert W. Nero John B. Theberge
Daniel F. Brunton Anthony J. Erskine Ross A. Layberry E. Franklin Pope Sheila Thomson 2019 Board of Directors
President: Diane Lepage Annie Bélair Edward Farnworth Dwayne Lepitzki Henry Steger
1st Vice-President: Jakob Mueller Fenja Brodo Catherine Hessian = Bev McBride Ken Young
Recording Secretary: Elizabeth Moore Robert Cermak Anouk Hoedeman Gordon Robertson Eleanor Zurbrigg
Treasurer: Ann Mackenzie Owen Clarkin Diane Kitching Jeff Saarela
To communicate with the Club, address postal correspondence to: The Ottawa Field-Naturalists’ Club, P.O. Box 35069, Westgate P.O., Ottawa, ON, K1Z 1A2, or e-mail: ofnc@ofnc.ca. For information on club activities, go to www.ofnc.ca.
The Canadian Field-Naturalist
The Canadian Field-Naturalist is published quarterly by The Ottawa Field-Naturalists’ Club. Opinions and ideas expressed in this jour- nal do not necessarily reflect those of The Ottawa Field-Naturalists’ Club or any other agency.
Website: www.canadianfieldnaturalist.ca/index.php/cfn
Editor-in-Chief: Dr. Dwayne Lepitzki Assistant Editor: Dr. Amanda Martin
Copy Editors: Sandra Garland and Dr. John Wilmshurst Layout: Robert Forsyth
Book Review Editor: Dr. Barry Cottam Online Journal Manager: Dr. Bill Halliday
Subscription Manager: Eleanor Zurbrigg Author Charges Manager: Ken Young
Associate Editors: Dr. Ron Brooks Dr. Jennifer R. Foote Dr. Donald F. McAlpine _ Dr. Jeffery M. Saarela Dr. Carolyn Callaghan Dr. Graham Forbes Dr. Garth Mowat David C. Seburn Dr. Paul M. Catling Thomas S. Jung Dr. Marty Obbard Dr. Jeffrey H. Skevington
Dr. Francois Chapleau
Chair, Publications Committee: Dr. Jeffery M. Saarela
All manuscripts intended for publication—except Book Reviews—should be submitted through the online submission system at the CFN website: http://www.canadianfieldnaturalist.ca/index.php/cfn/user. Click the “New Submission” link on the right side of the webpage and follow the prompts. Authors must register for a cfn account at http://www.canadianfieldnaturalist.ca/index.php/cfn/user/ register in order to submit a manuscript. Please contact the Online Journal Manager (info@canadianfieldnaturalist.ca) if you have any questions or issues with the online submission process. In only rare, exceptional circumstances will submissions other than online be considered and, in these cases, authors must contact the Editor-in-Chief (editor@canadianfieldnaturalist.ca) prior to submission. In- structions for Authors are found at http://www.canadianfieldnaturalist.ca/public/journals/1/CFNAuthorinstructions. pdf.
Book-review correspondence, including arranging for delivery of review copies of books, should be sent to the Book Review Editor by e-mail: b.cottam@rogers.com.
Subscriptions and Membership: Subscription rates for individuals are $40 (online only), $50 (print only), or $60 (print + online). libraries and other institutions may subscribe for $120 (online only or print only) or $180 (print + online). All foreign print subscrib- ers and members (including USA) must add $10 to cover postage. The Ottawa Field-Naturalists’ Club annual membership fee of $40 (individual), $45 (family), or $20 (student) includes an online subscription to The Canadian Field-Naturalist. Members can receive printed issues of CFN for an additional $30 per volume (four issues). For further details, see http://ofnc.ca/membership-and-donations. The club’s regional journal, Trail & Landscape, covers the Ottawa District and regional Club events and field trips. It is mailed to all club members. It is available to libraries at $40 per year. Subscriptions, applications for membership, notices of changes of address, and undeliverable copies should be sent to subscriptions@canadianfieldnaturalist.ca or mailed to: The Ottawa Field-Naturalists’ Club, P.O. Box 35069, Westgate P.O., Ottawa, ON, K1Z 1A2 Canada. Canada Post Publications Mail Agreement number 40012317. Return postage guaranteed.
The Thomas H. Manning fund, a special fund of the OFNC, established in 2000 from the bequest of northern biologist Thomas H. Manning (1911-1998), provides financial assistance for the publication of papers in the CFN by independent (non-institutional) authors, with particular priority given to those addressing Arctic and boreal issues. Qualifying authors should make their application for assistance from the fund at the time of their initial submission.
Cover: Rock Ptarmigan (Lagopus muta townsendi) on Amchitka Island, Alaska, in late May to very early June. Male Rock Ptarmigan on mainland Alaska and northern Canada during this same period are mostly white, a difference that has been used to describe subspecies of Rock Ptarmigan. See the article in this issue by Clait Braun et al., pages 49-55. Photo: Steve Ebbert, 10 June 2015.
The Canadian Field-Naturalist
Characteristics of Wolverine (Gulo gulo) dens in the lowland boreal forest of north-central Alberta
MICHAEL E. JOKINEN'*, SHEVENELL M. WEBB’, DOUGLAS L. MANZER?’, and ROBERT B. ANDERSON?
‘Alberta Conservation Association, 817-4th Avenue South, Lethbridge, Alberta T1J OP6 Canada
*Maine Department of Inland Fisheries and Wildlife, 650 State Street, Bangor, Maine 04401 USA
-Alberta Conservation Association, P.O. Box 1139 Provincial Building, Blairmore, Alberta TOK OEO Canada “Corresponding author: mike.jokinen@ab-conservation.com
Jokinen, M.E., S.M. Webb, D.L. Manzer, and R.B. Anderson. 2019. Characteristics of Wolverine (Gulo gulo) dens in the lowland boreal forest of north-central Alberta. Canadian Field-Naturalist 133(1): 1-15. https://doi.org/10.22621/cfn. v13311.2083
Abstract
We investigated Wolverine (Gu/o gulo) denning ecology in the boreal forest of northern Alberta. During winters 2015/2016 and 2016/2017, we used live traps to capture four female Wolverines and fitted them with global positioning system (GPS) collars programmed to take a location every two hours. We determined reproductive status at capture and GPS location data were used to identify den sites. One female denned in one of the two years, one female denned in two consecutive years, and two females did not den during the study. Seven of the eight Wolverine den sites were in mature or old Black Spruce (Picea mariana) stands, where dens consisted of a hollow, moss-covered mound originating from a partially uplifted root mass caused by a leaning or fallen tree. One den was located under decayed logging debris with an overstorey dominated by dense deciduous regeneration. Maximum snow depth recorded (December—March) at weather stations in the study area was 32-51 cm. Spring snow coverage was scarce in our study area (<1%) and always associated with ice cover on lakes and large ponds; mean distance from dens to nearest spring snow coverage was 15.19 km (SD = 2.73, n= 8). Female Wolverines appear to be using locally-available denning structures in the lowland boreal forest, despite a lack of deep snow, persistent
spring snow cover, or large boulders documented in other studies.
Key words: Alberta; boreal forest; den; lowlands; snow; Wolverine
Introduction
Wolverines (Gulo gulo) are well adapted to cold, snowy environments with their compact body, large paws, dense, frost-resistant fur, and capacity to store significant body fat (Banci 1994). Because Wolverines give birth in winter, females must find suitable den sites that are protected from predators, disturbance, cold temperatures, and melting spring snow (Magoun and Copeland 1998). Most verified Wolverine dens were under 1-5 m of snow (Pulliainen 1968; Magoun and Copeland 1998), suggesting that a deep snowpack of- fers important benefits throughout the denning sea- son (Magoun and Copeland 1998). The majority of Wolverine den locations documented around the world (n = 562 dens) overlapped areas with persis- tent spring snow; a small subset of dens that were outside this mapped area of persistent spring snow cover (hereafter, the spring snow coverage) were vis- ited and later confirmed to be snow dens (Copeland et al. 2010).
Deep snow and/or persistent spring snow cover has been associated with Wolverine dens throughout
©The Ottawa Field-Naturalists’ Club
their distribution (Magoun and Copeland 1998; Cope- land et al. 2010; May et al. 2012), but few dens have been described in low elevation, forested habitats. The majority of published information on Wolverine dens is from regions where deep snow was associ- ated with steep, rugged terrain, and large boulders in Norway (May ef al. 2012), woody debris and boul- ders in British Columbia (Krebs and Lewis 2000), long complex tunnels (Magoun and Copeland 1998) and drainage features in Alaska (Magoun ef al. 2017), and fallen trees or boulders in Idaho (Copeland 1996; Magoun and Copeland 1998). A Wolverine denned under large boulders and downed trees in the low-ele- vation boreal forest of Ontario (n = 1 den; Dawson et al. 2010) and females used boulder complexes in mature, mixed-coniferous boreal forests in Sweden (n = 49 dens; Makkonen 2015). Given a lack of steep terrain and large boulders, a shallow snowpack, and relatively early spring snowmelt in the lowland boreal forest of northern Alberta (Webb ef a/. 2016), it was unclear what resident Wolverines were using for den- ning structures.
2 THE CANADIAN FIELD-NATURALIST
Similar to Wolverines, American Black Bear (Ur- sus americanus) gives birth in winter and need to select den sites that will keep cubs dry, warm, and safe. In the northern boreal forests, most black bear dens are excavated, typically beneath ground level, under the roots of standing or partially blown-down trees, into hillsides, or into riverbanks (Fuller and Keith 1980; Klenner and Kroeker 1990). American Black Bear dens are typically in more upland forest stands, and peatland is avoided (Tietje and Ruff 1980). We hypothesized that in northern boreal landscapes, Wolverine dens located in upland habitat with mature forest cover and deeper snowpack would provide the best protection and insulation available, while more lowland, wet areas would not be used.
Although long-term fur harvests and images cap- tured at camera traps suggest a reproducing popu- lation of Wolverines in northern Alberta (Webb ef al. 2016), very little is known about denning ecol- ogy. Documenting den structures, snow conditions near dens, and duration of use, particularly in areas outside of the expected distribution of spring snow cover, could help clarify the relationship between Wolverines and snow and be useful information for timber harvest planning. Currently, Alberta’s tim- ber harvest guidelines list Wolverine dens under the “other species/sensitive site” section of the docu- ment, suggesting a forested buffer distance of 100 m (Alberta Agriculture and Forestry 2016); yet, there is no description of how to identify a potential Wolverine den. Our objectives were to: (1) document the general forest characteristics and specific struc- tures associated with Wolverine den sites; (2) char- acterize snow, land cover, and industrial disturbance surrounding Wolverine den sites; and (3) summar- ize female Wolverine movements during the denning period (February—May).
Methods
The study area, roughly 4600 km? in size, is lo- cated ~500 km north of Edmonton and 100 km north- east of Red Earth Creek in north-central Alberta (S7°N, 114°W; Figure 1). The landscape is typical of Alberta’s boreal region (Natural Regions Committee 2006), with a mosaic of aspen (Populus spp.)-domin- ated and aspen/White Spruce (Picea glauca (Moench) Voss) mixedwood forests in the uplands and exten- sive areas of Black Spruce (Picea mariana (Miller) Britton, Sterns & Poggenburgh) treed fens and bogs in the surrounding wetlands. Approximately 42% of the study area is comprised of wetlands (fens, bogs, swamp, open water, and marsh), which were pre- dominantly peatland forms (fens or bogs; 30% of the study area; AEP 2015). Mean elevation of overlap- ping townships within the study area is 616.98 m (SD
Vol. 133
= 89.56, n = 75 townships) and ranged from 500 to 800 m. Summers are short and cool, and winters are cold with snow typically covering the ground from November to mid-April. Mean August temperature in the study area was 13.68 + 1.86 (SD) °C (mean max- imum August temperature = 18.2°C, n = 5 weather stations, 2003-2009; ACIS 2015).
The study area supported low numbers of Moose (Alces americanus) and White-tailed Deer (Odo- coileus virginianus), and had a limited number of American Beaver (Castor canadensis), Gray Wolf (Canis lupus) occurred in small numbers when com- pared to other regions of the province. Caribou (Ran- gifer tarandus) are rare, but known to occur in the northern portion of the study area. American Black Bear, Canada Lynx (Lynx canadensis), American Marten (Martes americana), Fisher (Pekania pen- nanti), Ermine (Mustela erminea), Snowshoe Hare (Lepus americanus), Red Squirrel (Tamiasciurus hud- sonicus), Spruce Grouse (Falcipennis canadensis), and Ruffed Grouse (Bonasa umbellus) were common.
The study area is remote and uninhabited, with little human activity due to limited access and exten- sive wetlands. The industrial footprint is small and comprised primarily of oil and gas development (e.g., all-season gravel roads, seismic lines from past exploration, and well-sites), with active forest har- vesting occurring only in the extreme southern por- tion of the study area. Many of the seismic lines had experienced considerable regrowth of alder (Alnus spp.) and other shrubs. Active wells are visited on a regular basis by oil field staff, while unmaintained wells in the area (some of which were reclaimed and having shrub regrowth) receive little to no winter visitation based on our observations while working there. Gravel road and well-site density (including active and unmaintained wells) was 0.04 km/km7? and 0.13 wells/km7?, respectively. Large wildfires were the primary disturbance in the area and approximately one-third of the study area had burned in the past 50 years (1961-2016).
We used baited run pole camera traps during win- ters 2014/2015 (n = 8 run poles), 2015/2016 (n = 7 run poles), and 2016/2017 (n = 14 run poles) to docu- ment the presence of individual Wolverines based on unique markings (Magoun ef a/. 2011). During win- ters 2015/2016 and 2016/2017 (November—March), we live-trapped Wolverines using 10 and 17 log box traps, respectively (Copeland et al. 1995). The run poles and live traps were spaced ~S—10 km apart and were baited with beaver carcasses. Traps were outfit- ted with TT3 trap transmitters (Vectronic Aerospace, Berlin, Germany), which instantly sent an email mes- sage via satellite communication when a trap was triggered. On the advice of a wildlife veterinarian,
oO
Edmonton e
CJ y -P
| Fl Mar-Aug 2016 |
‘ Poke a
=
||| Perennial lake ee Wildfires: 1961 - 2016
115° W
JOKINEN ET AL.: WOLVERINE DENS IN BOREAL FOREST 3
}| F2 Nov—Jan 2017
ee: OL
4, F3 Mar—Apr 2017
114° W
FicurE 1. Wolverine (Gulo gulo) den locations (stars) and 100% minimum convex polygon home ranges for three female Wolverines from 2015-2017 in north-central Alberta, Canada (inset).
Wolverines were immobilized using a jab stick (Dan-Inject, Borkop, Denmark) loaded with keta- mine hydrochloride, 100 mg/ml (Ketalean; Bimeda- MTC Animal Health Inc., Cambridge, Ontario) and medetomidine hydrochloride, 1 mg/ml (Cepetor; Mod- ern Veterinary Therapeutics, Miami, Florida, USA) at a dosage of 10.6-11.9 mg/kg and 0.1-0.12 mg/kg, respectively. Wolverines were equipped with Tellus ultralight global positioning system (GPS) collars (Followit, Lindesberg, Sweden) that were programmed to take a location every two hours. Atipamezole hydrochloride 5 mg/ml (Revertor; Modern Veterinary Therapeutics) was hand injected to reverse the effects of the sedative. The animals were returned to the trap on a bed of spruce boughs until fully recovered and then released.
Collars uploaded data to a secure website via sat- ellite communication, but there was typically a 2-3 day time lag until locations became available. We vis- ually inspected GPS collar data to identify potential reproductive den sites. Potential dens had a repeated pattern of collar locations within 100 m of each other and movements to/from a localized area, in addition to associations with long periods of GPS time-outs when we assumed females were underground in the den and
satellites were not able to get a fix (February—April). The primary den was the first den we documented and secondary dens were subsequent dens used by female Wolverines (Makkonen 2015). We used the terms primary and secondary dens, similar to Makkonen (2015), because collaring sometimes occurred after kits were born; therefore, we could not be certain that the primary den was actually the natal den.
We used a geographic information system (ArcMap 10.4, Esri, California, USA) for all spa- tial calculations. We created a 5 km buffer around each den (estimated average female home range dur- ing the denning season; Makkonen 2015) and calcu- lated density of gravel roads and well-sites (active and unmaintained). We measured distance of each den site to nearest gravel road and well-site rounded to the nearest whole number. We used multiple sources of data to characterize the study area climate. During winter 2016/2017, we established winter weather sta- tions (n = 12) that were 10—20 km apart to measure local climate variables throughout the study area. Air temperature was recorded every hour using a Kimo KT50 compact temperature logger (Chevry-Cossigny, Seine-et-Marne, France). The temperature logger was not able to record temperatures below —40°C; how-
4 THE CANADIAN FIELD-NATURALIST
ever, these were infrequent events. Snow depth was recorded by field staff on a weekly to biweekly basis using a stationary metal metre stick. Study weather stations were established in areas avoiding direct sun- light and unnatural tamping, drifting, or interception of snow. In addition to the winter weather stations we established, we summarized long-term (2005-2017) mean monthly temperature (°C) at the nearest (<20 km) five government-maintained weather stations surrounding the study area (1.e., Trout Mountain/ Peerless Lake, Chipewyan Lake, Loon River, Panny River, and Picadelly; ACIS 2015).
We used the spring snow coverage data from Copeland et al. (2010), which was estimated across the Wolverine’s circumboreal range using MODIS, to classify 500 x 500 m pixels over seven years (2000— 2006). For each year, pixels received a one when the raster image was classified continuously as snow without any bare ground during the approximate end of the Wolverine denning period (24 April—15 May), the total number of years with continuous snow cover until mid-May was summed to get a value between one and seven for each pixel (Copeland ef al. 2010). We created a 5 km buffer around each den site and calculated percent of area with spring snow coverage. We also used snow depth data from the Canadian Meteorological Centre (CMC) which was derived using interpolation models that incorporated actual daily snow measurements from weather stations, meteorological aviation reports, and special aviation reports from the World Meteorological Organization information system (Brasnett 1999; Brown and Brasnett 2010). We summarized long-term (1998— 2014) mean monthly snow depths for CMC locations within our study area. We also inferred snow condi- tions using remote cameras and ground and aerial observations during a field visit in April 2017.
We created a 500 m buffer around each den site to characterize upland land cover (circa 2010; Castilla et al. 2014) and wetlands (circa 2015; AEP 2015). Land cover near dens included coniferous forest, broadleaf/deciduous forest, mixed forest, grassland, and shrubland. Wetland classes near dens included swamp, fen, and bog. We also overlapped den sites with the Derived Ecosite Phase, which is a represen- tation of the vegetation, soil, and moisture condi- tions (wetland and upland; Figure 2) based on Alberta Vegetation Inventory and LiDAR (circa 2017; Alberta Agriculture and Forestry 2017).
We collected additional details related to forest structure and ecological classification at den sites during November and December 2017. Forest struc- ture data were collected at five, 5.64 m radius plots. One plot was established at the den and the additional four plots were 30 m from the den in the four cardinal
Vol. 133
directions. Plot trees were identified to species and diameter at breast height was measured using a steel diameter tape for all trees >5 m in height. Tree heights were measured with a clinometer and tree ages were determined using an increment borer, typically from the two trees having the largest diameter within each plot. We defined stand age class as young (20—49 years), mature (50-119 years), and old (=120 years), similar to Stelfox (1995). Each plot was classed to an ecosite phase, which is an Alberta-based field guide that subdivides forest types using site characteris- tics (moisture and nutrient regime), plant community type, soil type, and forest productivity information (Beckingham and Archibald 1996). Internal den dimensions were strictly based on a visual estimate as we did not want to enlarge the entrance and alter den structures.
Means + SD are reported for all parameters, un- less otherwise indicated.
Results
The nature of the terrain (bogs and extensive wetlands), limited our ability to operate in the field beyond March. The transition from frozen to thawed ground occurred quickly (early April) and access to our remote field camp and the bulk of the study area was impractical. Therefore, we were unable to collect weather station data or monitor dens and litters dur- ing the denning months of April and May.
Female Wolverines
We captured four females (Fl, F2, F3, and F4) over two winters (2015/2016 and 2016/2017). A year prior to our live captures, we identified F1 from cam- era images at run poles. Fl’s home range during the denning season (March—May) was similar (859 km7?, 100% minimum convex polygon [MCP], 1 = 746 locations) to her overall home range from 21 March to 2 August 2016 (869 km’, 100% MCP, = 1046 loca- tions; Figure 1). We had no evidence that she was lac- tating or denning.
We captured F2 during two winters. F2’s home range 19 December 2015 to 15 May 2016 was 2254 km? (100% MCP, n = 1642 locations; Figure 1), which was similar to her home range during the denning sea- son that year (February—May; 2219 km’, 100% MCP, n = 1163 locations). She showed no sign of lactation or denning during this first winter and we suspect that she may have been a young female that ultim- ately took over the neighbouring FI’s territory. We recaptured F2 on 30 November 2016 and again on 21 February 2017, and discovered she was lactating. Based on her subsequent movements and GPS time- outs, we believe she gave birth to her first litter of kits on or shortly after 22 February 2017, ~9 km from where she was captured. Her collar largely timed-out
JOKINEN ET AL.: WOLVERINE DENS IN BOREAL FOREST Bi)
Wetlands
* Wolverine dens
FiGurE 2. Upland and wetland matrix surrounding F3 (a) and F2 (b) den locations during 2016 and 2017 in north-central Alberta—only one den (F3 den 2, 2016) was within the upland category.
over a week-long period starting on 23 February and continued to time-out on a regular basis over the next several weeks. We monitored her movements until 9 April 2017 (premature collar failure) and documented her primary and secondary den (Figure 2b). F2 dem- onstrated strong fidelity to the primary den during the first four weeks (Table 1). The greatest movement she made was ~12.5 km from her secondary den on 23 March 2017 to a location she had visited earlier in the winter, to feed on remnants of an American Black Bear hide. F2 used her primary den 22 February—13 March and secondary den until at least 26 March; the distance between the two dens was ~700 m. We suspect that F2 had another den (26 March—9 April), but we were not able to locate a third den when we searched a cluster of locations in late April. At a loca- tion where F2 had spent time (1-9 April), we did find three mounds of dead spruce limbs that had recently been broken off the lower section (~0.8 m) of spruce trees. The breaking and piling of limbs appeared deliberate and bed-like, similar to the observation reported by a Finnish Wolverine hunter/trapper in
Pulliainen (1968). F2’s home range from November to January was 484 km’(100% MCP, n= 555 locations), and 90 km? (100% MCP, n = 309 locations) while she was denning (February—April; Figure 1). F2’s mean daily movements from February to April were <5 km, providing further evidence of raising young in 2017, especially when compared to the previous year when she did not raise young and her daily movements were 8-15 km during the same time period (Table 1).
We captured F3 during two winters. During the first winter, our staff set up trail cameras close to her secondary den and she moved immediately after- wards to a third den (Figure 2a); camera images documented F3 and her three kits leaving the den on the evening of 19 April 2016. Based on this experi- ence, we chose not to visit female den sites during the denning period as we would not be able to deter- mine whether the use of multiple dens was natural or influenced by researchers. We did receive collar loca- tion data for F3 after 4 May 2016, which was the last day she occupied den 4. Over the next 27 days, F3 Spent six days at one GPS cluster location and three
TABLE 1. Summary of daily movements (number of days, mean + SD km) made by female Wolverines (Gulo gulo) in each month of the denning season during 2016 and 2017 in north-central Alberta.
Female_Year February
Fl 2016 — — 11 F2 2016 29 8.22+7.12 31 F2 2017 7 2.674 4.22 31 F3_ 2016 — — 9 F3 2017 — — 10
March April May 8.58 + 6.10 30 11.18 + 8.80 31 =: 11.19+5.13 10.92 + 7.26 30 15.19+ 8.16 15 13.03+4.95 3.62 + 5.03 8 458+43.31 — — 6.89 + 6.65 30 10.23 + 8.50 31 8.48+8.12 911+45.64 23 13.83 + 10.69 — —
6 THE CANADIAN FIELD-NATURALIST
days at two additional locations but these remaining GPS clusters were not visited. F3’s home range dur- ing the denning season (March—May) was 315 km? (100% MCP, n = 500 locations), which was similar to her overall home range 22 March—16 August 2016 (338 km’, 100% MCP, n = 878 locations; Figure 1). We recaptured F3 on 21 March 2017 and she was lac- tating; indicating that F3 had litters in two consecu- tive years. F3 used her primary den until 9 April and then occupied a secondary den 400 m away until at least 23 April (premature collar drop; Figure 2a). Her home range 21 March—27 April 2017 was 406 km? (100% MCP, n = 193 locations; Figure 1). Distance between F3’s 2016 and 2017 primary dens was ~8 km. Although home range size was similar between years, F3 moved further distances in 2017 compared to 2016, and daily movements were much greater than the denning F2 (Table 1).
We captured F4 twice during March 2017, but she showed no signs of lactation in camera images or while we handled her 2 March and 26 March 2017. Her collar malfunctioned and we were not able to determine home range.
Den descriptions
Because we did not not disturb females while dens were in use and due to the challenges of work- ing in the study area during April and May, most den sites were confirmed the following winter season. We found that using repeated patterns of GPS collar locations in combination with long periods of GPS
sid . .
Vol. 133
time-outs to be an effective method of estimating den site locations. In 2016, F3’s primary den was 20 m off our estimated GPS location and was confirmed with fresh Wolverine tracks leading in and out of the den. F3’s secondary den in the regenerating cutblock was 10 m off our estimated location and was confirmed by very high frequency (VHF) signal and trail camera images. In 2017, F2’s primary den was 10 m off our estimated location and was confirmed with packed snow/paths leading into the den. The remaining den locations that were visited the following season were an average of 21 m off the point derived from GPS clusters and time-outs. Alternative den structures in the immediate area of the estimated den locations were limited.
Seven of the eight Wolverine dens (n = 3 primary, n=5 secondary) were in the hollow created by a par- tially uplifted root mass (i.e., root ball, root wad; here- after uplifted root mass) of a leaning or fallen spruce tree. Seven of eight dens were located in mature (S0— 119 years) or old (+120 years) Black Spruce stands. Two of the seven dens were in mossy formations ori- ginating from an uplifted root mass where the trees had decayed, while the other dens were braced by the roots of intact leaning or fallen spruce trees. Root mass dens require little to no excavation by a Wolverine because a natural cavity is created when a thick moss blanket separates from the soil below as the shallow roots of a leaning or fallen tree upheave. Essentially, the lateral roots form the skeleton of the den, which supports a dense mat of soil and moss
FiGurE 3. Wolverine (Gulo gulo) F3 2016 primary den was ina partially uplifted root mass of a leaning spruce tree. The den
entrance 1s located along the upper side of the tree trunk in the centre of the den cavity. Photo: Michael Jokinen.
JOKINEN ET AL.: WOLVERINE DENS IN BOREAL FOREST 7
ie uF ee ir ris
Ficure 4. An example of a Wolverine (Gu/o gulo) den underneath a partially uplifted root mass (F3 den 4, 2016) in the low-
ils =
land boreal forest of north-central Alberta. The den entrance is located at the exposed root; the tree is lying on the ground (upper right) while the lateral roots opposite the entrance have curved, creating a natural cavity. Photo: Michael Jokinen.
creating the den walls (Figures 3 and 4). It is import- ant to note that these root dens are not wind throw trees characterized by roots that have been pulled out of the ground and are left standing on end. Such trees also existed within the study area, but exposed stand- ing roots do not create the mound and associated cav- ity that the Wolverines used in our study.
Estimated internal den dimensions were slightly variable in size, but den size was ultimately deter- mined by the extent of the root heave (~1 m x 1 m). A soccer ball-sized opening (~30 cm) often created the den entryway and most dens had alternate openings or potential escape routes in the walls. No material was brought into the dens by Wolverine, but spruce cone bracts often lined the floors. Cone seeds have been reported in Wolverine scat (Copeland 1996). However, we observed Red Squirrel caching of intact cones and cone feeding sites, where stripped cones lay beside piles of cone bracts in and around the den location. We did not observe animal remains or Wolverine scat inside or outside the dens. Snowshoe Hare sign was widespread around denning areas when we visited sites in November and December 2017.
One of the eight dens was located under decayed logging debris, which appeared to have been within or adjacent to a landing area used during previous forest harvesting activities. At the time of the ob- served den use, the overstorey was dominated by dense deciduous regeneration; the landing area and within-block roads were no longer apparent on the ground. We estimated that the cutblock was 27 years old based on tree aging and historical imagery from Google Earth (Google, Mountainview, California, USA), which suggested that the block was harvested in 1987. We could not determine the interior charac- teristics of this den without destroying the integrity of the structure.
Ecosite classification at den sites
Three primary and three secondary dens were re- visited in November and December of 2017 to col- lect forest structure data. Two of F3’s secondary dens from 2016 were not included in this den site forest assessment; however, they were similar in struc- ture (uplifted root mass) and were dominated by old spruce forest based on observations made dur- ing a September 2016 visit. The study area is located
8 THE CANADIAN FIELD-NATURALIST
within the transition zone of the Boreal Mixedwood and Boreal Highlands ecological areas (Beckingham and Archibald 1996). The Boreal Mixedwood and Highlands are ecologically similar, but the Highlands are slightly cooler (1.7°C cooler in summer) and have higher precipitation in both summer and winter (28 mm higher in summer; winter comparison not avail- able; Beckingham and Archibald 1996).
Based on the ecosite field guide of Beckingham and Archibald (1996), three of five dens (not includ- ing the den in the regenerating aspen stand) were an ecosite of Common Labrador Tea (Rhododendron groenlandicum (Oeder) Kron & Judd)/horsetail (Equisetum spp.) in the Boreal Mixedwood ecological area and two were an ecosite of horsetail and White Spruce in the Boreal Highlands. Of the three Boreal Mixedwood den locations, all sample plots but one (treed poor fen) were identified to a Labrador Tea/ horsetail phase. The most common indicator spe- cies that we found at these ecosites included Black and White Spruce, alder, Labrador Tea, and horse- tail. All but one sample plot (Labrador Tea-hygric Black Spruce-Jack Pine (Pinus banksiana Lambert)) at the two dens located in the Boreal Highland eco- logical area were identified to a horsetail and White Spruce ecosite phase. Indicator species at the two dens in this ecosite were similar to those found at Boreal Mixedwood ecosites. The conifer forest bor- dering the regenerating deciduous cutblock, in which F3’s secondary den was located, appeared to consist primarily of a Labrador Tea/horsetail ecosite class of the Boreal Mixedwood. Table 2 lists the tree spe- cies, count and average tree diameter, height, and age measured at sample plots.
Disturbance, land cover, and climate
The elevation of dens ranged from 535 to 687 m above sea level (601.5 + 52.6 m, n = 8; Table 3). F2’s dens were at similar elevations to the mean eleva- tion of the surrounding township (681 m). F3 denned in the same township over two consecutive winters (township elevation = 557 m). Dens were typically far
Vol. 133
from roads and wells (Table 3); however, that could simply reflect available habitat within the study area. Gravel road density within a 5 km buffer of each den was 0—0.18 km/km/? (0.07 + 0.08 km/km?, n= 8 dens). Well density (active and unmaintained) within the 5 km buffer of each den was 0.04—0.08 wells/km/? (0.06 + 0.02 wells/km?, n = 8 dens).
Conifer forest was the dominant land cover within the 5 km buffer for six of the eight dens (range: 50—100%). One den was 54% deciduous for- est, 21% mixed forest, 21% conifer forest, and 3% shrub within this buffer area. The area surrounding the logging debris den had been classified as 65% shrub (primarily regenerating Populus spp. within a cutblock), 30% conifer forest, 3% grassland, and 2% deciduous forest; however, the regenerating cut- block had reached heights >10 m by 2016. There was a wide range in the amount of wetland within 500 m of each den (range: 10-74%; 33.7 + 21.28%, n = 8 dens). The wettest den (74% wetland) was classi- fied as 53% swamp, 18% fen, and 3% bog within 500 m (F2’s primary den). Six of the eight dens, however, had 10-35% wetland (mostly peatlands) within 500 m. Moreover, based on the Derived Ecosite Phase data, six of eight dens fell within the wetland cat- egory. This category is described as hydric/poor dominated by shrubby, treed bog vegetation (Alberta Agriculture and Forestry 2017).
Wolverine dens were 4—7 km to the nearest study weather station. Mean snow depths for each month were 32.4 + 12.6 cm in December, 37.6 + 11.1 cm in January, 41.4 + 14.7 cm in February, and 34.0 + 17.8 cm in March (n = 12 stations; Table 4). Maximum snow depth recorded (December—March) at individ- ual weather stations was 32-51 cm. Hourly temper- atures in the study area increased by the latter half of March (16-29 March, daily —3.6°C), as compared to the first half of the month (1-15 March, —16.8°C). Mean monthly temperatures increased slightly with each month, while monthly ranges were highly vari- able: December —14.4 + 6.8°C (range —36.0 to 2.9°C),
TABLE 2. Forest stand structure (count, mean + SD) associated with Wolverine (Gu/o gulo) dens (n = 6) during 2017 in the
lowland boreal forest of north-central Alberta.
Den Tree DBH* (cm) Tree height (m) Tree age (yrs) Stem count?
F3_1_ 2016 32. + 491+4204 10 76247 10 116.9+44.9 23 Sb, 8 Sw, 1 Lt F3_ 2 2016 83." (33 2105 10 1A S35 1 26622" .0:7 19 Pb, 18 Aw, 15 Sw F2_1 2017 113° 23.4+12.2 10 13.4431 10" 705: 4227 87 Sb, 19 Sw, 7 Lt F2 2 2017 84 3064159 10 16.0+4.1 10 85.8+4287 51 Sb, 22 Sw, 10 Lt F3_1_ 2017 70 = =42.84257 10 190+6.1 LO 121 9 375 70 Sb
H3: 2.2017 40 576+25.5 10 24.2442 10 114.6+ 18.3 40 Sb
*Diameter at breast height (DBH). ‘Trees in plot >5 m tall. Species: Trembling Aspen (Aw; Populus tremuloides Michaux), Balsam Poplar (Pb; Populus bal- samifera L.), Black Spruce (Sb; Picea mariana (Miller) Britton, Sterns & Poggenburgh), Tamarack (Lt; Larix laricina (Du
Roi) K. Koch), and White Spruce (Sw; Picea glauca (Moench) Voss).
2019
JOKINEN ET AL.: WOLVERINE DENS IN BOREAL FOREST 9
TABLE 3. General summary of Wolverine (Gu/o gulo) dens found in the lowland boreal forest during 2016 and 2017 in north-
central Alberta.
Entrance aspect
Den Date occupied Elevation (m)
F3_1_ 2016 mid Feb—9 Apr* 561 S F3_2 2016 10 Apr—19 Apr 590 S F3_3_ 2016 20 Apr—23 Apr 607 E F3 4 2016 24 Apr—4 May 615 NW F291 2017 22 Feb—13 Mar 673 N
F2. 2.2017 14 Mar—26 Mar 687 SE F2 3 2017. 27 Mar—9 Apr? _ = F3 1 2017 mid-Feb—9 Apr* 544 W F3_2 2017 10 Apr—23 Apri 535 S
Nearest road (km) Nearest active wellsite (km)
2.0 2.0 0.4 0.4 1.0 0:9 1.0 0.9 1250) 10.4 12.0 10.3 10.0 10.9 10.0 11.0
*F3 denning start date is approximate, as she was collared after kits were born in both instances.
*Collar failure or premature collar drop. {Unconfirmed den location.
January —14.0+ 10.2°C (range —40.0 to 10.5°C), February —12.7+ 10.1°C (range —40.0 to 19.2°C), and March —10.6+ 10.8°C (range —38.8 to 14.4°C; Table 4). Mean monthly temperatures were similar between long-term data from nearby government stations (2005-2017) and monthly study station temperatures measured during winter 2016/2017 (Table 4).
CMC model grid points were 7-13 km from Wolverine den sites and indicated that snow depths are typically shallow in our study area (December-— March, 21.66 + 1.77 cm, range 19.74—25.03 cm, n = 10 stations; Brown and Brasnett 2010). Snow depths interpolated for points within the study area were slightly higher than mean monthly snow depth trends in the boreal forest of Alberta (February: 25.57 cm, March: 24.24 cm, n = 686 stations; Webb ef al. 2016).
Spring snow coverage (Copeland et a/. 2010) was limited (0.38%) and patchy (mean size 1.6 + 2.68 km’, n = 11 patches) in our study area. There were no instances of spring snow coverage predicted near Wolverine dens. Mean distance from dens to nearest spring snow coverage was 15.19 + 2.73 km (n = 8). All patches of the spring snow coverage in the study area corresponded to lakes or large ponds that would
be expected to retain at least some ice cover beyond when snow in the forest had melted.
We used trail cameras to document spring snow conditions for F3’s primary and secondary dens in 2016. Her primary den was completely snow-cov- ered on 30 March 2016 and 20 days later the snow had all melted. There was no snow cover surround- ing the area of F3’s secondary den on 19 April 2016. We visited the study area 25—27 April 2017 to retrieve dropped radio collars and observed patchy snow cov- er across the entire region, from the air (Figure 5) and on the ground. We used an Argo (New Hamburg, Ontario, Canada) to access the area of F2’s primary den (2017) as she had not used this den for several weeks and patchy snow cover was encountered at the time. We did not locate F2’s secondary den until November 2017 as we were not confident that she was finished using the den during our April visit. We flew over (Figure 5) and hiked within 1 km of F3’s 2017 dens while retrieving her dropped radio collar and encountered sparse snow cover throughout the area.
Discussion Wolverine pregnancy is largely dependent on body
TABLE 4. Mean temperature and snow depths (+ SD) recorded at study weather stations (2017), government weather sta- tions (2015-2017), and Canadian Meteorological Centre (CMC) locations (1998-2014) during December—May in north-
central Alberta.
Weather station December January Study stations Temperature (°C) -144+6.8 -14.0+ 10.2 n=12 Snow depth (cm) 32.4+ 12.6 37.6+ 11.1 n=12 Government stations and CMC estimates Temperature (°C) =15 3) 2057 -18.1+0.8 n=5 Snow depth (cm) 147+1.2 213 165
n= 10
February March April May A272 10,1 S10,622510.8 — _ 4144147 34.0+ 17.8 — — —13.9+0.8 7 oO QS £02 8.7+40.2 26.5+2.1 24.2426 5.6+1.2 0.2+0.1
10 THE CANADIAN FIELD-NATURALIST
Vol. 133
FiGureE 5. Snow cover near Wolverine (Gu/o gulo) F3 primary den on 27 April 2017 in north-central Alberta. Photo: Michael Jokinen.
condition and winter food availability (Persson 2005), because of delayed implantation (Banci 1994). It has been hypothesized that dens that provide females and their offspring with secure shelter from disturbance (e.g., predation, weather, people), thermal insulation (Magoun and Copeland 1998), and access to adequate food resources (Inman et a/. 2012) may be more likely to produce successful litters. Nearly all documented Wolverine dens in the world have been associated with deep snow (Magoun and Copeland 1998) and/or persistent spring snow cover (Copeland et al. 2010), however, Wolverines have not been studied equally across their range (Banci 1994), particularly in North America. We recognize that our sample size of den- ning females was small and that reproductive suc- cess was not measured for those females; however, our study detected a Wolverine denning strategy that is largely undescribed. We documented Wolverine dens in low elevation forests lacking boulders and deep or persistent spring snow, where a core, resi- dent population has supported Wolverine harvests for over 30 years (Webb et a/. 2016). Our results pro- vide further evidence that Wolverines are adapted to exploiting cold, low productivity environments, but
females appear to be selecting denning habitat that differs from what we hypothesized and what has been reported elsewhere.
In addition to shallow snow cover, our study area had other unique differences from other Wolverine studies. Ungulates can be important in the diet of female Wolverines (Banci 1994; Inman ef al. 2012), yet ungulates were in low abundance in our study area and in much of the boreal forest, where smaller prey including American Beaver, Snowshoe Hare, and grouse are more common. Female Wolverine in north- ern British Columbia were positively associated with rugged terrain in alpine environments, where Hoary Marmot (Marmota caligata) and Columbian Ground Squirrels (Urocitellus columbianus) were common (Krebs et al. 2007). Although the Omineca region of British Columbia is at similar latitude, our study area does not support this prey or terrain selection. Not unlike the difference between northern mountain and boreal ecotypes of Woodland Caribou (Wood and Terry 1999; ASRD & ACA 2010), Wolverines in our study area must meet their needs in a very differ- ent environment. Although we lacked data on win- ter food availability, we documented one female that
2019
denned in two consecutive years, with three kits con- firmed to be alive at ~4—6 weeks of age in the first year. Snowshoe Hare and Canada Lynx sign was common during our study. Based on Canada Lynx harvests, Snowshoe Hare cycle peaks in Alberta have occurred around 1980, 1990, 2000, and 2010 (Webb et al. 2013). Snowshoe Hare numbers were increasing during our study (N. Kimmy pers. comm. 30 January 2019). The habitat within our study area was highly mosaic, likely a result of frequent fires and abun- dant wetlands. Female Wolverines may rely on hunt- ing small prey, such as Snowshoe Hare (Banci 1994; Scrafford and Boyce 2015), and this varied land- scape may provide hares the forage, concealment, and thermal cover to persist in relatively good num- bers throughout the various habitat types (Hodges 2000; Gigliotti et a/. 2018). Krebs et al. (2018) state that the Snowshoe Hare is one of the few prey species available to predators during the winter in the bor- eal forest. All avian and mammalian predators in the boreal forest eat Snowshoe Hare (Krebs ef al. 2018). Wolverine and Canada Lynx harvest data have shown that a pattern may exist between Wolverine harvest and the Snowshoe Hare cycle (Webb ef al. 2013; Boonstra et al. 2018). By denning within mature con- ifer, female Wolverines in the boreal forest may have access to a prey source in close proximity.
Inman et al. (2012) suggest there may be a con- nection between food storage, persistent spring snow cover, and Wolverine denning requirements. If deep snow may provide an opportunity for food cach- ing in other settings, it begs the question: How are Wolverines meeting this need in a landscape where snow is far less abundant? We do not have the data required to answer this question, but local knowledge may have provided a hypothesis worth testing with future studies. On three independent occasions, trap- pers in our study area observed a Wolverine having depredated a harvested Canada Lynx from a trap, bringing it into an adjacent peatland area, and cach- ing it. In each case, the trapper reported seeing that the Wolverine had dug through the snow and down into the organic peat layer, then buried the carcass up to 45 cm below the surface with a mixture of snow, moss, and other vegetation. In one case, the trapper reported that the Wolverine had urinated on top of the location before leaving; another reported finding it very challenging to dig into the cache as the infill had frozen solid. Scrafford and Boyce (2015) also documented Wolverines caching in bogs in northern Alberta. We observed instances where it appeared that a wolverine had returned to a peatland cache and excavated and fed on food remnants (M.E.J. unpubl. data). Burying foods into bogs may help preserve excess food for later use (Verhoeven and Liefveld
JOKINEN ET AL.: WOLVERINE DENS IN BOREAL FOREST 11
1997, Moldowan and Kitching 2016) or hinder com- petitors from locating it. Future research into boreal Wolverine ecology should seek to test this hypothesis.
Wolverine dens have been documented under wind-drifted snow, large boulders, and trees in areas with deep snow (Magoun and Copeland 1998; Krebs and Lewis 2000; Copeland et al. 2010; May et al. 2012; Makkonen 2015; Magoun ef a/. 2017), but these features are lacking in the boreal forests of north- ern Alberta. Instead, most dens in our study (n = 7) were under partially uplifted root masses of leaning or fallen trees in older spruce forests, while one den was under decayed logging debris in an ~30 year old regenerating deciduous forest. We realize that our sample size of two denning females and their choice of denning structure could be a result of individual preference. However, Scrafford and Boyce (2015) also found Wolverines denning in an uplifted root mass and timber slash pile near Rainbow Lake in north- western Alberta. Approximately 42% of our study area is comprised of various wetland forms, includ- ing a majority made up by peatlands, with a mean ele- vation of 600 m. Makkonen (2015) notes that no dens were found in peat bogs, despite their abundance on the boreal landscape in Sweden, but Wolverines had access to and used large boulders at higher elevations for denning. Pulliainen (1968) found that half of the Wolverine dens in the boreal forest of Finland were associated with standing or fallen spruce trees; how- ever, the dens and tunnels were established under the length of a fallen tree and were always under deep snow cover (>I m). In contrast, maximum snow depth in our study rarely exceeded half a metre and was meaningfully absent for the final third of the denning season.
American Black Bears use a variety of den struc- tures across their range, but adequate thermal cover is critical for successful reproduction in northern cli- mates. The most common black bear den was under the roots or stumps of standing or partially blown down trees in the boreal forest of Ontario (Kolenosky and Strathearn 1987), Manitoba (Klenner 1982), and Alberta (Tietje and Ruff 1980), and the den cham- ber was similar in size to what we measured inside Wolverine dens (~1 m3). Contrary to black bear dens, however, the Wolverine dens we investigated were not deliberately lined with other materials (e.g., grass, moss, leaves, twigs; Klenner 1982). Instead, most of the Wolverine dens had cone bracts inside that had been discarded by feeding Red Squirrels. Squirrel middens have also been associated with marten den sites (Ruggiero et al. 1998) and Western Toad (Anaxyrus boreas) hibernation sites (Browne and Paszkowski 2010), where it has been suggested that they may provide some thermal benefit. Marten
12 THE CANADIAN FIELD-NATURALIST
will utilize root masses of fallen trees for winter rest sites (Gilbert et al. 1997) and den sites can occur underground (Bull and Heater 2000). Browne and Paszkowski (2010) note that Western Toad hiberna- tion sites in north-central Alberta were also located within peat hummocks and decayed root channels.
Mosses are the prevalent ground cover in the wetland environments of the boreal forest. Instead of deep snow (>1 m) providing thermal protection (Magoun and Copeland 1998), it is possible that the thick moss layer insulates Wolverine dens from cold temperatures and excess moisture. Snow accumula- tion in our study area averages only 30-40 cm, but when combined with the thick, mossy root layer, these den structures may provide adequate thermal insula- tion. Moss was traditionally used by Laplanders and other circumpolar people for bedding and insulation in both dwellings and clothing (Kimmerer 2003). Various species of moss have been shown to have thermal properties that insulate and limit the fluctua- tion of soil temperature and moisture (Soudzilovskaia et al. 2013). Marchand (2014) suggests that under 40-50 cm of snow, air temperature fluctuations have little influence on subnivean conditions. We sus- pect that typical late winter snow depth in our study area, 1n combination with the layer of moss, may also approximate those conditions.
The ecosites in which our dens were located are naturally wet and are rated as having high excess moisture (Beckingham and Archibald 1996). Even though these ecosites have elevated water tables near the ground surface, the den cavities are shallow and not far below the mossy forest floor. Because snow cover is relatively light and the den floor close to ground level, the probability of the den flooding dur- ing spring melt would be low.
Wind-throw hazard (i.e., potential for trees to become partially or completely uprooted) is rated as medium-high/high for the ecosites where dens were found in our study area (Beckingham and Archibald 1996). The potential for ready-to-move-in den struc- tures in this forest type is therefore greater. The lat- eral roots and soil lining create a barrier, although the walls are relatively thin (~15—30 cm) and appear fra- gile even when snow-covered. The root mass walls provide limited protective shielding from potential danger, so females may be more susceptible to dis- turbance. However, this did not seem to result in them moving denning sites more frequently, as other stud- ies documented similar number of dens per female as we did (Magoun and Copeland 1998). The prox- imity of a den structure to potential human disturb- ance is likely important (Banci 1994). Our study area was remote and most dens were located far from roads and trails, where encounters with people would
Vol. 133
be rare. In addition to potential direct disturbance at the den, Scrafford et a/. (2018) suggested that roads may negatively influence Wolverines by altering both habitat use and movement rates through habitat near roads. However, the density of roads near den sites in our study was an order of magnitude less than that of Wolverine home ranges in their study, suggesting that these females may be less impacted by roads. In addi- tion, ungulates were not abundant in our study area, so wolf numbers were not high. This may lessen the need to have a secure den structure as would be pro- vided by a snow cave or large boulders.
Forest companies seeking to provide long term Wolverine denning habitat within low elevation bor- eal forests have been operating with a paucity of information, trying to determine how to apply what is known about dens from a mountain environment to one largely devoid of boulders and a deep, per- sistent snow pack. Although our observations are limited, these females, and those of the Scrafford and Boyce (2015) study, provide a glimpse into the unique denning ecology of boreal Wolverines. Until more detailed information can be obtained, forest companies should retain mature representative sam- ples of high-wind-throw-risk ecosites within their planning area. In some cases, forest harvesting may have the potential to create future suitable denning habitat when structure is left behind (e.g., brush piles, log landings). Although the availability of par- tially wind thrown trees may not be limiting on the boreal landscape, their suitability for den sites may be influenced by the degree of disturbance in the sur- rounding area.
In the absence of deep snowpack, Wolverines in our study area have found a way to persist in the lowland boreal forest. Our small sample size lim- its our ability to draw robust conclusions. As such, our observations and speculation about potential eco- logical processes should be viewed as the basis for hypotheses that can be tested with further study. In a landscape lacking deep snowpack and large boul- ders, we speculate that Wolverines are able to meet their needs through locally available features such as the cavity created by a partially uplifted root mass, the thermal properties of thick moss, and the caching opportunities provided by deep peat accumulations. Wolverines are resourceful and may be more flexible in their denning requirements than documented by studies in other landscapes.
Author Contributions
Writing — Original Draft: M.J., S'W., and R.A.; Writing — Review & Editing: M.J., S.W., and R.A.; Conceptualization: M.J., SW., D.M., and R.A.; In- vestigation: M.J., S.W., and R.A.; Methodology: M.J.,
2019
S.W., and R.A.; Formal Analysis: M.J., S.W., and R.A.; Funding Acquisition: R.A., D.M., and S.W.
Acknowledgements
A special thank you goes to Neil Kimmy and Bill Abercrombie (Alberta Trappers’ Association mem- bers) for assisting with project establishment. A huge thank you goes to the Kimmy family for providing field accommodation and field support, while Duncan Abercrombie and Dan Mclean of Animal Damage Control contributed with their time and expertise in the field. John Hallett, Registered Professional Forester, Alberta Conservation Association (ACA), made a special contribution by providing forestry and ecosite classification expertise and Corey Rasmussen, ACA, was an essential member of the immobiliz- ation crew. A special thank you to all ACA staff (there were many) who participated in the field. Matt Scrafford, University of Alberta, and staff at Animal Damage Control, contributed by establishing the first Wolverine live traps within the study area. Mark Boyce, University of Alberta, who has been a collab- orator on much of our Wolverine work in the province, loaned us equipment. We thank Dr. Michelle Oakley, Doctor of Veterinary Medicine (DVM), and Dr. Mark Johnson, DVM, for their immobilization training and guidance and Dr. Glenn Meyers, DVM, for providing immobilization agents. We also appreciate the spring snow coverage GIS data from Jeffrey Copeland. This study was supported by Alberta Conservation Association, Alberta Environment and Parks, Al- berta Trappers’ Association, Alberta-Pacific Forest Industries Inc., Crowsnest Conservation Society, Daishowa-Marubeni International Ltd., McGill Uni- versity, Roadrunner Leasing and Sales Ltd., Shell FuellingChange, TD Friends of the Environment, and the University of Alberta. Capture and handling protocols and run pole camera traps were approved by the following Government of Alberta Research Permit and Collection Licences (#56202, 56203, 56900, 56901, 57157, 57158, 58403, 58404).
Literature Cited
ACIS (Alberta Agriculture and Forestry, AgroClimatic Information Service). 2015. Weather stations data view- er. Accessed 20 January 2019. http://agriculture.alberta. ca/acis/.
AEP (Alberta Environment and Parks). 2015. Alberta Wetland Classification System. Accessed 1 February 2018. https://geodiscover.alberta.ca/geoportal/catalog/ search/resource/details.page? uuid={A73F5A E1-4677- 4731-B3F6-700743A 96C97}.
Alberta Agriculture and Forestry. 2016. Alberta timber harvest planning and operating ground rules framework for renewal. Alberta Forest Management Branch. Ac- cessed 29 January 2018. https://wwwl.agric.gov.ab.ca/ $department/deptdocs.nsf/all/formain15749/$FILE/
JOKINEN ET AL.: WOLVERINE DENS IN BOREAL FOREST 13
TimberHarvestPlanning-OperatingGroundRules Framework-Dec2016.pdf.
Alberta Agriculture and Forestry. 2017. Derived Ecosite Phase Version 1. Accessed 1 March 2019. https://open. alberta.ca/opendata/derived-ecosite-phase#summary.
ASRD & ACA (Alberta Sustainable Resource Develop- ment and Alberta Conservation Association). 2010. Status of the Woodland Caribou (Rangifer tarandus caribou) in Alberta: Update 2010. Alberta Sustainable Resource Development. Wildlife Status Report No. 30 (Update 2010). Edmonton, Alberta, Canada. Accessed 1 March 2019. https://open.alberta.ca/dataset/OScdc28e- 5fbf-4906-9adf-eefbb26a2d1e/resource/9dd98304- Oddc-40cb-b94c-44158ca4bad8/download/4782681- 2010-status-woodland-caribou-alberta-update-2010. pdf.
Banci, V. 1994. Chapter 5: Wolverine. Pages 99-127 in The Scientific Basis for Conserving Forest Carnivores: American Marten, Fisher, Lynx, and Wolverine in the Western United States. Edited by L.F. Ruggiero, K.B. Aubry, S.W. Buskirk, J.-L. Lyon, and W.J. Zielinski. U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. Fort Collins, Colorado, USA.
Beckingham, J.D., and J.H. Archibald. 1996. Field Guide to Ecosites of Northern Alberta. Natural Resources Cana- da, Canadian Forest Service, Northwest Region Forestry Centre, Edmonton, Alberta, Canada.
Boonstra, R., S. Boutin, T.S. Jung, C.J. Krebs, and S. Taylor. 2018. Impact of rewilding, species introductions and climate change on the structure and function of the Yukon boreal forest ecosystem. Integrative Zoology 13: 123-138. https://doi.org/10.1111/1749-4877.12288
Brasnett, B. 1999. A global analysis of snow depth for numerical weather prediction. Journal of Applied Me- teorology 38: 726-740. https://doi.org/10.1175/1520-04 50(1999)038<0726:agaosd>2.0.co;2
Brown, R.D., and B. Brasnett. 2010. Canadian Meteo- rological Centre (CMC) daily snow depth analysis data. Environment Canada, National Snow and Ice Data Cen- tre, Boulder, Colorado, USA. Accessed 1 February 2018. https://nsidc.org/data/NSIDC-0447.
Browne, C.L., and C.A. Paszkowski. 2010. Hibernation sites of Western Toads (Anaxyrus boreas): characteriza- tion and management implications. Herpetological Con- servation and Biology 5: 49-63.
Bull, E.L., and T.W. Heater. 2000. Resting and denning sites of American martens in Northeastern Oregon. Northwest Science 74: 179-185.
Castilla, G., J. Hird, R.J. Hall, J. Schieck, and G.J. McDermid. 2014. Completion and updating of a land- sat-based land cover polygon layer for Alberta, Canada. Canadian Journal of Remote Sensing 40: 92-109. https://doi.org/10.1080/07038992.2014.933073
Copeland, J.P. 1996. Biology of the wolverine in cen- tral Idaho. M.Sc. thesis, University of Idaho, Moscow, Idaho, USA.
Copeland, J.P., E. Cesar, J.M. Peek, C.E. Harris, C.D. Long, and D.L. Hunter. 1995. A live trap for wolverine and other forest carnivores. Wildlife Society Bulletin 23: 535-538.
14 THE CANADIAN FIELD-NATURALIST
Copeland, J.P., K.S. McKelvey, K.B. Aubry, A. Landa, J. Persson, R.M. Inman, J. Krebs, E. Lofroth, H. Golden, J.R. Squires, A. Magoun, M.K. Schwartz, J. Wilmot, C.L. Copeland, R.E. Yates, I. Kojola, and R. May. 2010. The bioclimatic envelope of the wolverine Gulo gulo: do climatic constraints limit its geographic distribution? Canadian Journal of Zoology 88: 233-246. https://doi.org/10.1139/Z09-136
Dawson, N.F., A.J. Magoun, J. Bowman, and J.C. Ray. 2010. Wolverine, Gulo gulo, home range size and den- ning habitat in lowland boreal forest in Ontario. Cana- dian Field-Naturalist 124: 139-144. https://doi.org/10. 22621 /cfn.v124i2.1052
Fuller, T.K., and L.B. Keith. 1980. Summer ranges, cover type use and denning of black bears Ursus americanus near Fort McMurray, Alberta, Canada. Canadian Field- Naturalist 94: 80-83. Accessed 1 February 2018. https:// biodiversitylibrary.org/page/28088961.
Gigliotti, L.C., B.C. Jones, M.J. Lovallo, and D.R. Die- fenbach. 2018. Snowshoe hare multi-level habitat use in a fire-adapted ecosystem. Journal of Wildlife Manage- ment 82: 435—444. https://doi.org/10.1002/jwmg. 21375
Gilbert, J.H., J.L. Wright, D.J. Lauten, and J.R. Probst. 1997. Den and rest-site characteristics of American Marten and Fisher in northern Wisconsin. Pages 135— 145 in Martes: Taxonomy, Ecology, Techniques, and Management. Edited by G. Proulx, H.N. Bryant, and P.M. Woodard. The University of Alberta Press. Edmonton, Alberta, Canada.
Hodges, K.E. 2000. The ecology of Snowshoe Hares in northern boreal forests. Pages 117-161 in Ecology and Conservation of Lynx in the United States. Edited by L.F. Ruggiero, K.B. Aubry, S:W. Buskirk, G.M. Koehler, C.J. Krebs, K.S. McKelvey, and J.R. Squires. Depart- ment of Agriculture, Forest Service, Rocky Mountain Research Station. Fort Collins, Colorado, USA.
Inman, R.M., A.J. Magoun, J. Persson, and J. Mattis- son. 2012. The wolverine’s niche: linking reproductive chronology, caching, competition, and climate. Journal of Mammalogy 93: 634-644. https://do1.org/10.1644/ 11-mamm-a-319.1
Kimmerer, R.W. 2003. Gathering Moss. Oregon State Uni- versity Press, Corvallis, Oregon, USA.
Klenner, W. 1982. Seasonal movements, home range util- ization, and denning habits of black bears (Ursus ameri- canus) in western Manitoba. M.Sc. thesis, University of Manitoba, Winnipeg, Manitoba, Canada.
Klenner, W., and D.W. Kroeker. 1990. Denning be- havior of black bears Ursus americanus, in western Manitoba. Canadian Field-Naturalist 104: 540-544. Accessed 1 February 2018. https://biodiversitylibrary. org/page/34347100.
Kolenosky, G.B., and S.M. Strathearn. 1987. Winter den- ning of Black Bears in east-central Ontario. Bears: their biology and management. Pages 305-316 in Papers from the Seventh International Conference on Bear Research and Management, Plitvice Lakes, Yugoslavia.
Krebs, C.J., R. Boonstra, and S. Boutin. 2018. Using ex- perimentation to understand the 10-year snowshoe hare cycle in the boreal forest of North America. Journal of Animal Ecology 87: 87-100. https://doi.org/10.1111/13
Vol. 133
65-2656.12720
Krebs, J.A., and D. Lewis. 2000. Wolverine ecology and habitat use in the North Columbia Mountains: progress report. Pages 695-703 in Proceedings of Biology and Management of Species and Habitats at Risk. Edited by L.M. Darling. University College of the Cariboo, Kamloops, British Columbia, Canada.
Krebs, J.A., E.C. Lofroth, and I. Parfitt. 2007. Multiscale habitat use by wolverines in British Columbia, Canada. Journal of Wildlife Management 71: 2180-2192. https:// doi.org/10.2193/2007-099
May, R., L. Gorini, J. van Dijk, H. Broseth, J.D.C. Linnell, and A. Landa. 2012. Habitat characteristics associated with wolverine den sites in Norwegian mul- tiple-use landscapes. Journal of Zoology 287: 195-204. https://doi.org/10.1111/j.1469-7998 .2012.00907.x
Magoun, A.J., and J.P. Copeland. 1998. Characteristics of wolverine reproductive den sites. Journal of Wildlife Management 62: 1313-1320. https://doi.org/10.2307/380 1996
Magoun, A.J., C.D. Long, M.K. Schwartz, K.L. Pilgrim, R.E. Lowell, and P. Valkenburg. 2011. Integrating motion-detection cameras and hair snags for wolverine identification. Journal of Wildlife Management 75: 731— 739. https://doi.org/10.1002/jwmg.107
Magoun, A.J., M.D. Robards, M.L. Packila, and T.W. Glass. 2017. Detecting snow at the den-site scale in wol- verine denning habitat. Wildlife Society Bulletin 41: 381-387. https://doi.org/10.1002/wsb.765
Makkonen, T. 2015. Den site characteristics of female wol- verine (Gulo gulo) in Scandinavian forested landscape. M.Sc. thesis, University of Oulu, Oulo, Sweden.
Marchand, P.J. 2014. Life in the Cold: an Introduction to Winter Ecology. Fourth Edition. University Press of New England, Hanover, New Hampshire, USA.
Moldowan, P.D., and H. Kitching. 2016. Observation of an Eastern Wolf (Canis sp. cf. Lycaon) caching food ina Sphagnum bog in Algonquin Provincial Park, Ontario. Canadian Field-Naturalist 130: 351-354. https://do1.org/ 10.22621/cfn.v13014.1930
Natural Regions Committee. 2006. Natural regions and subregions of Alberta. Compiled by D.J. Downing and WW. Pettapiece. Government of Alberta. Pub. No. T/852. Accessed | January 2018. https://open.alberta.ca/ publications/0778545725.
Persson, J. 2005. Female wolverine (Gulo gulo) repro- duction: reproductive costs and winter food availabil- ity. Canadian Journal of Zoology 83: 1453-1459. http:// dx.do1.org/10.1139/z05-143
Pulliainen, E. 1968. Breeding biology of the wolverine (Gulo gulo) in Finland. Annales Zoologici Fennici 5: 338-344.
Ruggiero, L.F., E. Pearson, and S.E. Henry. 1998. Characteristics of American marten densites in Wy- oming. Journal of Wildlife Management 62: 663-673. https://doi.org/10.2307/3802342
Scrafford, M.A., T. Avgar, R. Heeres, and M.S. Boyce. 2018. Roads elicit negative movement and _habitat- selection responses by wolverines (Gulo gulo luscus). Behavioral Ecology 29: 534-542. https://doi.org/10.1093 /beheco/arx182
2019 JOKINEN ET AL.: WOLVERINE DENS IN BOREAL FOREST 15
Scrafford, M.A., and M.S. Boyce. 2015. Effects of in- dustrial development on wolverine (Gulo gulo) ecol-
Sphagnum. Acta Botanica Neerlandica 46: 117-130. Webb, S.M., R.B. Anderson, D.L. Manzer, B. Aber-
ogy in the boreal forest of northern Alberta. Wolverine Project Progress Report — Winter 2014/2015. Accessed 1 February 2018. http://wolverinefoundation.org/wp- content/uploads/2011/02/Scrafford-and-Boyce_2015_ Wolverine-Project-Progress-Report.pdf.
Soudzilovskaia, N., P. Bodegom, and J. Cornelissen.
2013. Dominant bryophyte control over high-latitude soil temperature fluctuations predicted by heat transfer traits, field moisture regime and laws of thermal insula- tion. Functional Ecology 27: 1442-1454. https://do1.org/ 10.1111/1365-2435.12127
Stelfox, J.B. 1995. Relationships between stand age, stand
structure, and biodiversity in aspen mixedwood forests in Alberta. Jointly published by Alberta Environmental Centre (AEC V95-R1), Vegreville, Alberta, and Canadi- an Forest Service (Project No. 0001A), Edmonton, Al- berta, Canada. Accessed 1 February 2018. http://cfs. nrcan.gc.ca/pubwarehouse/pdfs/19534. pdf.
Tietje, W.D., and R.L. Ruff. 1980. Denning behavior of
black bears in boreal forest of Alberta. Journal of Wild- life Management 44: 858-870. https://doi.org/10.2307/ 3808314
Verhoeven, J.T.A., and W.M. Liefveld. 1997. The eco-
logical significance of organochemical compounds in
crombie, B. Bildson, M.A. Scrafford, and M.S. Boyce. 2016. Distribution of female wolverines relative to snow cover, Alberta, Canada. Journal of Wildlife Manage- ment 80: 1461-1470. https://doi.org/10.1002/jwmg. 21137
Webb, S., D. Manzer, R. Anderson, and M. Jokinen.
2013. Wolverine harvest summary from registered trap- lines in Alberta, 1985—2011. Technical Report, T-2013- 001, produced by the Alberta Conservation Association, Sherwood Park, Alberta, Canada. Accessed 11 Janu- ary 2019. https://www.ab-conservation.com/downloads/ report_series/wolverine_harvest_in_alberta_1985-2011. pdf.
Wood, M.D., and E.L. Terry. 1999. Seasonal movements
and habitat selection by Woodland Caribou in the Omi- neca Mountains, north-central British Columbia Phase 1: The Chase and Wolverine Herds (1991-1994). Peace/ Williston Fish and Wildlife Compensation Program, Report No. 201. Prince George, British Columbia, Canada. Accessed 1 March 2019. http://www.env.gov. bc.ca/wildlife/wsi/reports/4737_WSI_4737_RPT_ OMINECA_1991_ 1994. PDF.
Received 31 July 2018 Accepted 28 February 2019
The Canadian Field-Naturalist
Note Wolf (Canis sp.) attacks life-like deer decoy: insight into how
wolves hunt deer?
THOMAS D. GABLE!" and DANIEL P. GABLE?
‘University of Minnesota, 2003 Upper Bufford Circle, St. Paul, Minnesota 55108 USA
23176 E Siebert Road, Midland, Michigan 48642 USA “Corresponding author: thomasd.gable@gmail.com
Gable, T.D., and D.P. Gable. 2019. Wolf (Canis sp.) attacks life-like deer decoy: insight into how wolves hunt deer? Canadian Field-Naturalist 133(1): 16-19. https://doi.org/10.22621/cfn.v133i1.2044
Abstract
We know of no documented observations of wolves (Canis sp.) detecting and then attacking a White-tailed Deer (Odocoi- leus virginianus) during spring, summer, or fall. We describe an observation of a wolf attacking a life-like, two-dimensional deer decoy in November 2017 near Killarney Provincial Park, Ontario, Canada. The wolf appeared to locate the decoy by sight rather than sound or scent, suggesting that the profile of a deer is sufficient to trigger an attack by a wolf.
Key words: Wolf; Canis; carnivore; hunting behaviour; predation; predator-prey; White-tailed Deer; Odocoileus virgini-
anus; Killarney Provincial Park
White-tailed Deer (Odocoileus virginianus) are the primary prey of wolves (Canis sp.) throughout much of the southern boreal ecosystem in North America (Potvin et al. 1988; Benson et al. 2017; Gable et al. 2018). How and where wolves hunt and kill deer during winter is well understood because of the ease of observing wolf-hunting behaviour and lo- cating kill sites from the air (Mech and Frenzel 1971; Fuller 1989; Mech et al. 2015). However, equiva- lent information for the snow-free months is rare, as wolves and deer primarily co-occur in densely for- ested areas (Demma et al. 2007). For example, there are no estimates of wolf kill rates of White-tailed Deer (adults or fawns) during spring to fall, and lit- tle information exists about where and how wolves successfully hunt and kill deer during this period (Demma et al. 2007; Mech ef al. 2015). In a compre- hensive review of wolf—deer interactions, Mech et al. (2015) provided descriptions of eight such inter- actions during the snow-free season. However, all of these observations occurred after the wolf or wolves had already detected and attempted to chase deer. To our knowledge, there are no observations that dem- onstrate how wolves find deer during spring to fall. Herein, we document a wolf (Canis sp. according to Rutledge et al. 2016) attacking a life-like deer decoy that provides rare insight into how wolves locate and
detect deer during this period.
During the first week of November, D.P.G. was hunting White-tailed Deer on McGregor Island (46° 04'49""N, 81°35'18"W), about 2 km west of Killarney Provincial Park, Ontario, Canada. Before hunting, D.P.G. set-up a life-like, two-dimensional decoy of a squatting doe (“Estrous Betty”, Montana Decoys, Hummelstown, Pennsylvania, USA). The decoy con- sisted of a life-size photograph of a deer with an inter- nal wire frame, ~1.3 cm thick, for support (Figure 1). The decoy was oriented in an east—west direction so that profile views of the decoy could be seen from the north or south (Figure 2). D.P.G. also left doe urine (details on manufacturer not available) on a branch 1.5 m off the ground 1 m north of the decoy.
At about 1515, after setting up the decoy and dis- pensing the doe urine, D.P.G. situated himself ina tree stand on a rocky point 23 m west of the decoy. The stand faced east and overlooked a 100-m wide valley dominated by mature Sugar Maple (Acer saccharum Marshall) forest between two steep rock ridges (north and south of the stand; Figure 2). On both sides of the valley at the base of the ridges were prominent deer trails running east to west. Immediately to the west of the tree stand was a dense Balsam Fir (Abies balsamea (L.) Miller) lowland. About 50 m north of the northern ridge was a 0.5—1.0 km wide channel of
A contribution towards the cost of this publication has been provided by the Thomas Manning Memorial Fund of the Ottawa
Field-Naturalists’ Club.
©The Ottawa Field-Naturalists’ Club
GABLE AND GABLE: WOLF ATTACKS DEER DECOY 17
of Killarney Provincial Park, Ontario, Canada, during the first week of November 2017. Photo: Daniel Gable.
water; this channel surrounds McGregor Island. The maple forest that the stand overlooked had minimal understorey for about 150 m before transitioning to marshy lowland, which abutted a small shallow cove that was connected to the main water channel. D.P.G. accessed the stand by parking his boat at the north- western opening of this cove (~300 m east by north- east of the stand). There was no snow cover during this period.
The sky was overcast with moderate (8—16 km/h) winds blowing from the west/southwest. At 1600, D.P.G. noticed a wolf about 150 m east by south- east of the stand trotting along the deer trail on the southern edge of the valley (Figure 2). Given the pos- ition of the decoy and the structure and arrangement of the trees, the wolf would have been unable to see the decoy when D.P.G. first spotted the wolf. We later verified this by walking to the wolf’s location. The wolf continued at the same pace, moving east to west, until it was about 70 m southeast of the decoy (Figure 2). Without stopping, the wolf turned abruptly and started travelling directly toward the decoy. As the wolf approached, it appeared to be intently focussed on the decoy; however, it maintained a trotting pace
for another 30 m. When about 40 m from the decoy, the wolf suddenly sprinted toward the decoy and, when only a few metres away, lunged at it, latching onto its neck, leaving punctures in the fabric of the decoy. The force of the contact ripped the decoy from the ground and caused the wolf and decoy to tum- ble for about 10 m (total time 2-3 s). After the wolf had stopped its fall, it promptly stood up and jumped back about 10 m. It stood looking at the decoy for a few seconds with both ears and tail lowered. Within a few more seconds, the wolf ran quickly over the steep ridge to the south and disappeared from view.
We know of no other observation of a wolf trav- elling, detecting, and then attacking a deer or deer facsimile during the snow-free season. Although the decoy was not an actual deer, it looked exactly like a deer (Figure 1) and behaved (stood still staring at the wolf) as deer do when approached by predators (DeYoung and Miller 2011; Mech ef al. 2015). Given this and the observed changes in the wolf’s behaviour after it appeared to detect the deer, we believe that the wolf was convinced the decoy was a deer. As a result, we assert that the wolf’s behaviour on detecting and approaching the decoy provides insight into how this
18 THE CANADIAN FIELD-NATURALIST
CC ee SPP ee LLL TL Lie
Deer trails
. Sanmne,
.
“a. Cr "es henge ntti tae,
“Semennny *
Vol. 133
ane a® a?
Parry geneuue — gee™ eueeeee™ ” ote "egnat®
Open maple Y | forest Wind direction
Where wolf was first observed
FiGurE 2. Route taken by a wolf (Canis sp.) that detected and then attacked a life-like decoy of a White-tailed Deer (Odo- coileus virginianus) near Killarney Provincial Park, Ontario, Canada, in early November 2017.
wolf, and likely other wolves, may locate deer.
The wind direction and consistent wind flow would have made the doe urine difficult, and likely impos- sible (Conover 2007), for the wolf to detect during its approach, which strongly suggests that the wolf lo- cated the decoy visually. Wolves are thought to be adept at visually detecting slight movements, which likely helps in locating prey (Harrington and Asa 2003), but our observation suggests that wolves are capable of detecting motionless prey from consider- able distances. We estimate that the wolf detected the decoy about 70 m away, although detection was likely aided by the minimal understorey and daylight conditions.
Although wolves likely rely on scent to locate deer when hunting (Mech ef a/. 2015), it appears they can also use visual detection, even if not associated with odour, sound, or any other cues. Dense vegetation throughout most of wolf—deer range likely limits vis- ual detection of deer during the summer. However, events that reduce forest or understorey cover (e.g., forest fires, clear-cuts) could enhance the ability of wolves to detect deer and increase encounter rates between wolves and deer (Whittington et a/. 2011)
and possibly wolf kill rates (Sand et a/. 2005; Vander Vennen et al. 2016).
Mech ef al. (2015: 26) noted that “when wolves detect deer, they usually proceed slowly and deliber- ately, ever on the alert”. However, this wolfapproached relatively rapidly after detecting the decoy, closing a ~70 m distance in a matter of seconds. Once 30 m away from the decoy, the wolf apparently decided that the deer (1.e., the decoy) was indeed vulnerable, possibly because it did not move, and sprinted toward it. Wolves generally assess the vulnerability of deer by approaching, chasing, and testing them. Most deer are not vulnerable to predation because they are in sufficiently good physical condition to easily out-run and evade wolves; therefore, most hunting attempts are short lived as wolves realize their efforts are futile (Mech et al. 2015).
Our observation provides the only information we are aware of about how at least one wolf approached and attacked what it thought was an adult White- tailed Deer during the snow-free season. Thus, whether the observation is the exception or represents normal behaviour is unknown. Still, it does provide new insight into the predatory behaviour of wolves.
2019
The lack of information on wolf predation of deer— both fawns and adults—during the snow-free season is Surprising given the amount of research on wolves, deer, and their interactions. Because of this, we rec- ommend intensive research on wolf—deer interactions during summer as has been done recently with cari- bou (Rangifer tarandus, e.g., Whittington et al. 2011; Latham et al. 2013; Mumma eft al. 2017). Indeed, as the range of White-tailed Deer continues to expand northward (Dawe and Boutin 2016), thereby increas- ing the area that wolves and deer co-occur, such information will only become more valuable and rel- evant for the conservation and management of both species (Latham et al. 2011).
Acknowledgements
We thank L. David Mech for reviewing an earlier version of this manuscript and providing constructive comments to improve it.
Literature Cited
Benson, J.F., K.M. Loveless, L.Y. Rutledge, and B.R. Patterson. 2017. Ungulate predation and ecological roles of wolves and coyotes in eastern North America. Eco- logical Applications 27: 718-733. https://doi.org/10.10 O2/eap.1499
Conover, R. 2007. Predator—prey Dynamics: the Role of Olfaction. CRC Press, New York, New York, USA.
Dawe, K.L., and S. Boutin. 2016. Climate change is the primary driver of white-tailed deer (Odocoileus vir- ginianus) range expansion at the northern extent of its range; land use is secondary. Ecology and Evolution 6: 6435-6451. https://doi.org/10.1002/ece3.2316
Demma, D.J.,S.M. Barber-Meyer, and L.D. Mech. 2007. Testing global positioning system telemetry to study wolf predation on deer fawns. Journal of Wildlife Man- agement 71: 2767-2775. https://do1.org/10.2193/2006-382
DeYoung, R.W., and K.V. Miller. 2011. White-tailed deer behavior. Pages 147—180 in Biology and Management of White-tailed Deer. Edited by D.G. Hewitt. CRC Press, Boca Raton, Florida, USA. Fuller, T.K. 1989. Population dynamics of wolves in north- central Minnesota. Wildlife Monographs 105: 3—41. Gable, T.D., S.K. Windels, J.G. Bruggink, and S.M. Barber-Meyer. 2018. Weekly summer diet of gray wolves (Canis /upus) in northeastern Minnesota. Amer- ican Midland Naturalist 179: 15-27. https://doi.org/10. 1674/0003-0031-179.1.15
Harrington, F.H., and C.S. Asa. 2003. Wolf communica- tion. Pages 66-103 in Wolves: Behavior, Ecology, and Conservation. Edited by L.D. Mech and L. Boitani. University of Chicago Press, Chicago, Illinois, USA.
GABLE AND GABLE: WOLF ATTACKS DEER DECOY 19
Latham, A.D.M., M.C. Latham, K.H. Knopff, M. Heb- blewhite, and S. Boutin. 2013. Wolves, white-tailed deer, and beaver: implications of seasonal prey switch- ing for woodland caribou declines. Ecography 36: 1276— 1290. https://doi.org/10.1111/j.1600-0587.2013.00035.x
Latham, A.D.M., M.C. Latham, N.A. Mccutchen, and S. Boutin. 2011. Invading white-tailed deer change wolf—caribou dynamics in northeastern Alberta. Jour- nal of Wildlife Management 75: 204-212. https://doi. org/10.1002/jwmg.28
Mech, L.D., and L.D. Frenzel, Jr. 1971. Ecological studies of the timber wolf in northeastern Minnesota. Research paper NC-52. United States Department of Agriculture Forest Service, North Central Forest Experimental Station, St. Paul, Minnesota, USA. Accessed 18 July 2019. https://www.nrs.fs.fed.us/pubs/rp/rp_nc052.pdf.
Mech, L.D., D.W. Smith, and D.R. MacNulty. 2015. Wolves on the Hunt: the Behavior of Wolves Hunting Wild Prey. University of Chicago Press, Chicago, Illinois, USA.
Mumma, M.A., M.P. Gillingham, C.J. Johnson, and K.L. Parker. 2017. Understanding predation risk and individual variation in risk avoidance for threatened boreal caribou. Ecology and Evolution 7: 10266-10277. https://doi.org/10.1002/ece3.3563
Potvin, F., H. Jolicoeur, and J. Huot. 1988. Wolf diet and prey selectivity during two periods for deer in Quebec: decline versus expansion. Canadian Journal of Zoology 66: 1274-1279. https://doi.org/10.1139/z88-186
Rutledge, L.Y., J.M. Fryxell, K. Middel, B.N. White, and B.R. Patterson. 2016. Patchy distribution and low effective population size raise concern for an at-risk top predator. Diversity and Distributions 23: 79-89. https:// doi.org/10.1111/ddi.12496
Sand, H., B. Zimmermann, P. Wabakken, H. Andrén, and H.C. Pedersen. 2005. Using GPS technology and GIS cluster analyses to estimate kill rates in wolf—un- gulate ecosystems. Wildlife Society Bulletin 33: 914— 925. https://doi.org/10.2193/0091-7648(2005)33[914:ugt agc]2.0.co;2
Vander Vennen, L.M., B.R. Patterson, A.R. Rodgers, S. Moffatt, M.L. Anderson, and J.M. Fryxell. 2016. Diel movement patterns influence daily variation in wolf kill rates on moose. Functional Ecology 30: 1568-1573. https://doi.org/10.1111/1365-2435.12642
Whittington, J., M. Hebblewhite, N.J. Decesare, L. Neu- feld, M. Bradley, J. Wilmshurst, and M. Musiani. 2011. Caribou encounters with wolves increase near roads and trails: a time-to-event approach. Journal of Applied Ecology 48: 1535-1542. https://doi.org/10.1111/ j.1365-2664.2011.02043.x
Received 3 February 2018 Accepted 16 January 2019
The Canadian Field-Naturalist
Birds of Mansel Island, northern Hudson Bay ANTHONY J. GASTON
Science and Technology Branch, Environment and Climate Change Canada, Carleton University, Ottawa, Ontario KIA 0OH3 Canada; email: tonygastonconsult@gmail.com
Gaston, A.J. 2019. Birds of Mansel Island, northern Hudson Bay. Canadian Field-Naturalist 133(1): 20—24. https://doi.org/ 10.22621/cfn.v13311.2153
Abstract
A recent review of bird distributions in Nunavut demonstrated that Mansel Island, in northeastern Hudson Bay, is one of the least known areas in the territory. Here, current information on the birds of Mansel Island is summarized. A list published in 1932 included 24 species. Subsequent visits by ornithologists since 1980 have added a further 17 species to the island’s avifauna. The list includes 17 species for which breeding has been confirmed and 10 for which breeding is considered prob- able. The island seems to support particularly large populations of King Eiders (Somateria spectabilis) and Tundra Swans (Cygnus columbianus) and the most southerly breeding population of Sabine’s Gull (Xema sabini) and Red Knot (Calidiris
canuta, probably). Key words: Mansel Island; Hudson Bay; birds; breeding
Introduction
At 3180 km?, Mansel Island, Qikiqtaaluk Region, Nunavut, is the 28th largest island in Canada. It is one of three large islands in northern Hudson Bay, the others being Southampton and Coats Islands. Although the birds of Coats and Southampton Is- lands have been documented (Sutton 1932a; Gaston and Ouellet 1997), those of Mansel Island are com- paratively poorly known. Only one publication pro- vides information on the avifauna of the island: a list prepared by G.M. Sutton (1932b) based on speci- mens provided to him by A.T. Swaffield, the Hudson Bay manager who established the trading post at Swaffield Harbour, near the northern tip of the is- land, in 1929.
At its nearest point, Mansel Island is 56 km from the mainland of Quebec (Figure 1). The topography is mostly low elevation (maximum 138 m), without any prominent hills or gullies except for a shallow central valley running east—west across the island. Underlying bedrock throughout is Silurian limestone, which is covered, over large parts of the island, by raised beach deposits of Holocene age. There are ex- tensive wetlands throughout, especially in the south- west portion of the island. Sutton (1932b: 41) com- mented: “an exceedingly flat, dull-gray piece of land”. Dry areas support low-growing shrubs, including willow (Salix spp.), cranberry (Vaccinium spp.), and Four-angled Mountain Heather (Cassiope tetragona (L.) D. Don), as well as the tussock forbs, Entire-
leaved Mountain Avens (Dryas integrifolia Vahl) and Purple Mountain Saxifrage (Saxifraga oppositifolia L.). Marshes support extensive sedge (Carex spp.) meadows.
The Hudson Bay post on the island closed in 1945, and there has been no permanent habitation on the island since then, although people from the nearby Inuit community of Ivujivik, Nunavik, sometimes visit in summer to hunt Caribou (Rangifer tarandus) and Polar Bear (Ursus maritimus; Gaston et al. 1985).
Sutton’s list comprised 24 species, but only 17 of them were collected in summer and, hence, potential breeders, and no evidence of breeding was included (Sutton 1932b). Species were collected at various dates between September 1929 and June 1930. Sutton com- mented on their likely breeding status, but there was no definite evidence available to support his sugges- tions. Subsequent ground surveys, all of only one or two days’ duration, have added another 17 species to the island’s list, and breeding has been confirmed for some. Although this information is based on very brief visits, it is assembled here to give an up-to-date summary of what little is known about the avifauna of Mansel Island.
Methods
Subsequent to Swaffield’s collection, three ground surveys have been carried out by ornithologists. In July 1984, R. Decker visited the island for one day by helicopter, landing at several sites. Information
A contribution towards the cost of this publication has been provided by the Thomas Manning Memorial Fund of the Ottawa
Field-Naturalists’ Club.
©The Ottawa Field-Naturalists’ Club
2019
rk * : ‘Mansel Island
HUDSON BAY
QUEBEC
ONTARIO
GASTON: BIRDS OF MANSEL ISLAND DA
FicurE 1. a. Location of Mansel Island in Hudson Bay. b. Localities visited in 1992 and 2016. Source: Mansel Island, Nuna- vut, 61°59'23.31"N, 79°56'12.54"W. Google Earth Pro 7.3.2.5776. Imagery date: 13 December 2015. Data provider: Landsat/
Copernicus 2018. Accessed: 30 July 2018.
from his survey was incorporated into the Land Use Information Series map of Mansel Island (Environ- ment Canada 1970), which includes a list of “avian species which occur or are thought likely to occur within this map-area’, but I have only included spe- cies definitely sighted on the island during the survey. On 8 and 9 August 1992, A.J.G., V. Johnston, and I. Storm landed from the MV. Teregluk near the east- ernmost point of the island and spent 10 h ashore sur- veying an area of lakes, ponds, and marshes adjacent to a shallow bay (Figure 1).
On 20 and 21 June 2016, Y. Aubry, M. Robert, F. Shaffer, and C. Marcotte carried out systematic surveys of breeding birds in two areas (Figure 1), using the protocol of the Program for International and Regional Shorebird Monitoring (PRISM; Bart and Johnston 2012). In addition to total bird counts, Species presence or absence was recorded by l-ha squares. They also touched down at several other sites to make additional observations.
In addition, on 12 July 1984, an aerial survey (Cessna 337) was carried out by R. Decker along the
entire coastline and over selected parts of the interior. I did not have access to the original data, but some information from this survey was incorporated into a general survey of larger birds in Foxe Basin and northern Hudson Bay (Gaston et al. 1986).
Results and Discussion
Combining the species listed by Sutton (1932b) with subsequent surveys yields 41 species reported from Mansel Island to date, of which definite evi- dence of breeding, in the form of nests or flightless young, has been obtained for 17 species. A further 10 Species were considered by at least one survey to be “probably breeding” (Table 1). Major concentrations of Arctic Terns (Sterna paradisaea) and Common Eiders (Somateria mollissima) were noted on the aer- ial surveys of 1984, with an estimated 1000 pairs of Common Eiders on Awrey Island and several col- onies of 50-75 pairs of Arctic Terns on the east and southwest coasts (Gaston et al. 1986).
Because of the timing of surveys, breeding could be confirmed for fewer than half of the species recorded during the breeding season. The 1992 survey
Vol. 133 © i
Ud §q
ud
THE CANADIAN FIELD-NATURALIST
jaaee
u
=
aeaaoeN es
ud
Jsnjeys poulquio’)
22
ud ud
Od
SON GLUT AK StS Ss SS or oS OS OO Se ANS ee OSS SoS en CR ee oS o Ou
d ud
N
popiossr = SMBS
SADAINS
WON
N
ie
Ol SC
€ €
uaes ‘ON Juasoid sarenbs ‘ON
910c WSTad
NM ON
ee
Ol
(6 Cc
eas 18
ud Od
Od
ud
ud
snjqei1s 766] SSUNIYSIS
Ol
Oc
OC LV
udeS ‘ON
ame
ud
(snye}js) p86l FOIE = AcEeeT UOHNS
Tea
Te
Tea JOIN Jouruns Jouruns
Jouruns
Jourwuns Jouruns
Jouruns Tea
Jouruns Jouruns
Jouruns
Jouruns Jouruns Jouruns
Jouruns Jouruns
Jouruns Tea
(uoseas)
(D1AUO] D1A/]) BINA, P2T[IG-JOL (SNPNDIIBUO] SNIADAOIAAJG) 1IBIeL PI[Ie}-suo'T (SNd1JISDADA SNIADAOIAAIS) IIBICL ITYISVICY (vapsippivd DusajS) UII], DIV (SNUDIUOSYJIWS SNADT) |[NH SULLIIY (snasogiadAy snavT) [IND snoonepH
(vau.inga vjlydosn) {ND AIOAT
(WIgDs DUAX) |[ND S,ouIges
(sniapaynf sndoapjoy) sdoreyeyg poy (snjoqo] sndoavjpy) sdoseyeyd Ppoyxoou-poy (sauduajul DiaDUualy) SUO\sUINT, Appny (buldjp siapije)) urjund
(s1yjoa1asn{f s1apyv) Jodidpues padumn-syy (DUIJ1ADU SLAPIJDD) Jadidpues siding (oyjisnd siipyoD) Jadidpues poyewyediwuas (DINU S1IpIVD) UY POY
(sndoapyd sniuawnn) [2a1quity A (snJpujodimas snispoADYD)) IAO]g poyewyediwias (vaIUIWOP SIJPIAN]Z) JdA0|d-UdSpyOH uesI3aWYy (vjoavjonbs sipian]q) 1A0|g Potf[oq-yoelq (42WU1 DIADD) UOO'T UOWTWIOD
(volfiond D1IADD) U00'T syle
(DJD]J21S DIADD) UOO'T poyeoly}-poy
(sndosp] sndosvT) uesiwieid MOTI (S1jp19b]8 snapwujn.7) LeWU[N] UIIYIION (sijpuady pjnsuvnjD) Yond psytej-suo TJ (syiqpjaads p1dajouos) Jopiq SUTy] (DUISSI]JOW D1AAJDUOG) Jopiy UOWIUIOD (4OJDALIS SNBAIP ) JOSUCBIDI POISCIIq-Poy (adojauad spuy) [reg UIOYION (snupiqunjos snusd)) UeMS eIpuNny, (ojoludag DjudAg) yueIg
(sisuapouDdd DJUDAG) ISOOD epeuedy (1uOSUIYIINY DJUDAG) ISOODH BUI;YIVD (SUdISAaJNAADI AASUP) 9SOOD MOUS
sorsadg
‘PURIST OY} WOLF SIQISTA Ud9Q DALY ISI SPIIG dy} SIOYM POPNIOUI de SPIOIOI BIS-IV ‘S]9S BLP INOJ UO pase puUrIS] JasuULY Ie ..SNILIS SUIP9EIG pUB SUOTJAIOSQO PIIg *[ ATAV$
2019 GASTON: BIRDS OF MANSEL ISLAND 23
was conducted after most shorebirds would have com- pleted breeding, and breeding could not be confirmed in that season for any shorebird species. Those species
Combined statust PR PO B (17), PR (10)
ri for which breeding could be confirmed were those that
have longer breeding periods. Conversely, surveys in
= 2016 found the island partly covered in snow, which
oS poo a ae presumably delayed breeding for many species, mak-
3 5 ing the surveys earlier than ideal. Breeding could be
a confirmed for only five species, although it was con-
2 i sidered probable for another 15 species. Among spe-
s 2 Ro a cies for which breeding was confirmed, Canada and
7 Cackling Geese (Branta canadensis, Branta hutchin-
g soni), Northern Pintail (Anas penelope), and Dunlin
o| 3 00 a] 9 (Calidris alpinus) are not shown as breeding on Man- = S N sel Island by Richards and Gaston (2018).
2 z Only seven species were reported by all four sur-
Py 5 veys: Cackling Goose, Tundra Swan (Cygnus colum-
E 5 bianus), King Eider (Somateria spectabilis), Long-
5 + + =| tailed Duck (Clangula hyemalis), Red-throated Loon
sf (Gavia stellata), Sabine’s Gull (Xema sabini), and
e Herring Gull (Larus argentatus). Black-bellied Plover
Z (Pluvialis squatarola), American Golden-plover (Plu-
vialis dominica), and Arctic Tern were recorded on
pee ae les all three post-1930 surveys. According to the 2016
a 5 = a {4 survey, the most widespread species (Seen in nine
ay or more survey squares) were Canada Goose, King
B= 5 Eider, and Herring Gull. In 1992, 38 pre-flying King
ch| & nN a S Eider ducklings were seen in four separate creches,
7 S i i along with nine adults and the species was the second
5 most widespread on the 2016 survey. These observa-
ng | 2 tions suggest that Mansel Island may be an import-
E 2 = 5 ant breeding area for this species. Likewise, Tundra
B =| < Swan, as well as being seen on all surveys, was the
S most widespread species reported on the aerial sur-
vey in 1984. Mansel Island appears to support a sig- nificant population of this species.
Overall, the avifauna of Mansel Island is very similar to that of the better-known Coats Island, im- mediately to the west (Gaston and Ouellet 1997). Like Coats, it supports Caribou but apparently not lemmings (Dicrostonyx and Lemmus spp.; Gaston et al. 2012). The absence of the latter probably deter- mines the lack of specialist lemming predators, such as Snowy Owl (Nyctea scandiaca) and Long-tailed Jaeger (Stercorarius longicaudus). The very flat top- ography, lacking cliffs, may determine the absence of Peregrine Falcon (Falco peregrinus) and Common Raven (Corvus corax) and the relative paucity of
(season)
Fall
Sutton 1932b Decker 1984 Summer Summer
24 probable breeding, PO
+Combined breeding evidence from all surveys to give likeliest status.
definite evidence of breeding, PR $A geolocator-tracked Ruddy Turnstone spent the summers of 2014 and 2015 on Mansel Island and showed evidence of incubation in 2015 (R. Porter pers. comm. August 2018).
tA satellite-tracked Red Knot was recorded in summer on Mansel Island by Lathrop et al. (2018).
Black Guillemot (Cepphus grylle) Horned Lark (Eremophila alpestris) Lapland Longspur (Calcarius lapponicus) Snow Bunting (Plectrophenax nivalis)
S 3
~ NX
Ss &
oD ~~ i S Snow Bunting (Plectrophenax nivalis), all common X : : : < 3 z mn on adjacent parts of mainland Quebec (Gaston ef al. R ee 2 1985). However, the breeding of Sabine’s Gull and the S) 2c 3 probable breeding of Red Knot (Calidris canutus) on =I ee ie = Mansel Island represent the most southeasterly ex- ; 8 z E Si! tension of these species’ known ranges in Canada ell w Ao el & (Richards and Gaston 2018).
24 THE CANADIAN FIELD-NATURALIST
Acknowledgements
Iam very grateful to Yves Aubry for providing me with information on the 2016 surveys, to R. Porter of the Delaware Bay Shorebird Project for information on satellite-tracked birds, and to my companions in the 1992 visit, Vicky Johnston, Ilya Storm, and the crew of the MV. Teregluk.
Literature Cited
Bart, J.R., and V.H. Johnston. 2012. Arctic Shorebirds in North America: a Decade of Monitoring. Studies in Avian Biology 44. University of California Press, Ber- keley, California, USA.
Environment Canada, Lands Directorate, Conservation and Protection. 1970. Mansel Island, District of Kee- watin, Northwest Territories (map). Land use infor- mation series. Surveys and Mapping Branch, Energy, Mines and Resources Canada, Ottawa, Ontario, Can- ada. Accessed 22 May 2019. http://sis.agr.gc.ca/cansis/ publications/maps/nluis/250k/lu/nluis_250k_lu_35el_ 45hijpg.
Gaston, A.J., D.K. Cairns, R.D. Elliot, and D.G. Noble. 1985. A natural history of Digges Sound. Report 46. Canadian Wildlife Service, Ottawa, Ontario, Canada.
Gaston, A.J., R. Decker, F.G. Cooch, and A. Reed. 1986. The distribution of larger species of birds breeding on
Vol. 133
the coasts of Foxe Basin and northern Hudson Bay. Arctic 39: 285-296. https://doi.org/10.14430/arctic2089
Gaston, A.J., M. Gavrilo, and C. Eberl. 2012. Ice bridg- ing as a dispersal mechanism for Arctic terrestrial ver- tebrates and the possible consequences of reduced sea ice cover. Biodiversity 13: 182-190. https://doi.org/10. 1080/14888386.2012.719177
Gaston, A.J., and H. Ouellet. 1997. Birds and mammals of Coats Island, NWT. Arctic 50: 101-118. https://doi. org/10.14430/arcticl1094
Lathrop, R.G., L. Niles, P.A. Smith, M. Peck, A. Dey, R. Sacatelli, and J. Bognar. 2018. Mapping and mod- eling the breeding habitat of the Western Atlantic Red Knot (Calidris canutus rufa) at local and regional scales. Condor 120: 650-665. https://doi.org/10.1650/ condor-17-247.1
Richards, J., and A.J. Gaston. 2018. The Birds of Nuna- vut. University of British Columbia Press, Vancouver, British Columbia, Canada.
Sutton, G.M. 1932a. Birds of Southampton Island. Carne- gie Institute, Washington, DC, USA.
Sutton, G.M. 1932b. Notes on a collection of birds from Mansel Island, Hudson Bay. Condor 34: 41—43. https:// dot.org/10.2307/1363790
Received 5 November 2018 Accepted 12 February 2019
The Canadian Field-Naturalist
Note
Behaviour of a porcupine (Erethizon dorsatum) swimming across a small boreal stream
THOMAS S. JUNG
Department of Environment, Government of Yukon, Whitehorse, Yukon Y1A 2C6 Canada and Department of Renewable Resources, University of Alberta, Edmonton, Alberta T6G 2H1 Canada; email: thomas jung@ gov yk.ca; tyung@ualberta.ca
Jung, T.S. 2019. Behaviour of a porcupine (Erethizon dorsatum) swimming across a small boreal stream. Canadian Field- Naturalist 133(1): 25-27. https://doi.org/10.22621/cfn.v133i1.2107
Abstract
The swimming behaviour of North American Porcupine (Erethizon dorsatum) is largely unrecorded, even though much of its habitat is bisected by innumerable rivers and streams. Moreover, the literature is inconsistent regarding how readily por- cupines take to the water and how well adapted they are for swimming. I observed a porcupine swimming across a relatively placid and shallow braid in the Klondike River (Yukon, Canada), after it had aborted three apparent attempts to swim at a relatively fast-flowing, deep channel upstream. This observation provides evidence of porcupine swimming across moving
water and suggests that they may be reluctant to do so and selective of where they cross rivers and streams.
Key words: Behaviour; Erethizon dorsatum; North American Porcupine; swimming
Observations of North American Porcupine (Ere- thizon dorsatum) swimming are rare in the literature, suggesting that it may be uncommon behaviour. Yet, much of their range is within the boreal forest (Woods 1973; Roze and Ilse 2003), which is interspersed and divided by numerous water bodies. The few obser- vations reported involve swimming in ponds and lakes (Dean 1950; Woods 1973; Roze 2009), with no observations of them crossing rivers or streams. An unusual observation of a Bull Trout (Sa/velinus con- fluentus) embedded with porcupine quills provided circumstantial evidence of a porcupine swimming in moving water (Cott and Mochnacz 2007).
The willingness of porcupines to swim is unclear, particularly across rivers and streams. Some author- ities suggest that porcupines are not averse to swim- ming (Roze and Ilse 2003; Roze 2009), and that swimming is an important means for them to ac- cess seasonal food resources. For instance, there are observations of porcupines feeding on water lilies (Nymphaeaceae) in shallow ponds and swimming to retrieve food items that they then bring to shore to consume (Dean 1950; Roze and Isle 2003). Moreover, their quills may also be adapted, in part, to help them swim; specifically, Roze and Ilse (2003: 376) surmised that “their watertight, sponge-filled inte- riors aid in floatation, enhancing the porcupine’s
©The Ottawa Field-Naturalists’ Club
swimming capabilities”. Alternatively, Woods (1973: 4) opined that “they do not like to swim”, although he conceded that they have been observed crossing small water bodies. In an early “experiment”, Murie (1926: 112) noted:
One day I tried to make a porcupine swim across a narrow stream. I shoved it toward the water with a stick and intercepted it whichever way it turned. Nothing could induce it to swim, al- though I almost shoved it bodily into the water. It came straight toward me, rather than cross the stream, and I finally gave up the attempt.
Here, I provide an observation of a porcupine swimming across a small boreal stream and note its apparent indecision in doing so.
While angling ona braid of the Klondike River, ~15 km east of Dawson City, Yukon, Canada (64.059°N, 139.433°W), I observed a porcupine approaching and, eventually, swimming across the river. At ap- proximately 1705 Pacific Daylight Time, on 6 July 2018, an apparently full-grown porcupine emerged from tall shrubs on the far side of the stream. I did not know its age or sex. The porcupine came to the shore (point A in Figure 1) and, after about 15 s of apparently sniffing toward the far shore, it stepped about 30 cm into the stream, immersing its front
26 THE CANADIAN FIELD-NATURALIST
Vol. 133
, names Pe eee Se —.
ee) asc ee era ae
get a a
we ~ > = . — - = : _ > : - a al _ = a SS Sa = —
a ‘ — = a = =
Figure 1. Photograph of the site where a North American Porcupine (Erethizon dorsatum) swam across a braid in the Klondike River, Yukon, Canada. At sites A, B, and C, the porcupine stepped into the stream but did not cross it; the dashed line (D) indicates where it swam across the stream. Photo: T.S. Jung.
legs. However, rather than swim across the stream, it backed out of the water and sniffed across the stream again. It immediately moved about 6 m downstream and repeated the same actions at point B (Figure 1). The porcupine moved another 15 m downstream along the shore to point C (Figure 1) and again en- tered the stream, this time without apparently sniff- ing the far shore, and it waded deeper until its belly and both legs were under water; however, it again re- turned to the shore within approximately 30 s. The porcupine then moved into the shrubs and was not seen for about 5 minutes. I then observed it ~35 m downstream of point C, at point D (Figure 1), where it entered the water and swam across the stream, after standing in the stream with both legs and its belly under the water for about 1 minute. The porcu- pine reached the far shore after swimming for about 2 minutes, and then entered the forest on the other bank and was no longer observed.
I do not know why the porcupine crossed the stream. It was on a small island in the Klondike River that was largely covered with willow (Salix spp.) and alder (A/nus spp.), whereas, the other side of the stream was covered by mature boreal forest, domin- ated by Balsam Poplar (Populus balsamifera L.) and White Spruce (Picea glauca [Moench] Voss) trees. It may have been attracted to something not available on the island at that time.
Points A—C, where the porcupine entered the stream but did not cross it, were in the section of the stream with the swiftest water and a relatively deep channel (~1.2 m deep). In contrast, point D (Figure 1),
where the porcupine entered and crossed the stream, was immediately downstream of the riffle, and the water there was more placid and only about 0.5 m deep. However, the stream here was about 30 m wide, compared to about 8 m wide at the riffle (points A—C). It appeared that the porcupine was hesitant to enter the stream and cross the riffle and selected a location to cross where the stream was comparatively slow flowing. This observation suggests that porcupines may not be strong swimmers and seek areas with slow-moving water to cross rivers and streams.
This observation is of scientific value from two perspectives. First, to the best of my knowledge, this is the first record of a porcupine crossing a stream or river, despite the fact that this must be relatively com- mon behaviour for porcupines given the innumerable streams and rivers in the boreal forest, even if it is not regularly observed by humans. Second, given the apparent indecision of the animal about whether to cross the stream, this observation suggests that some porcupines may be averse to swimming, supporting the assertion of Woods (1973). In addition, this obser- vation suggests that porcupines may be selective in terms of where they cross rivers and streams, avoid- ing deep, turbulent water in favour of more placid and shallow sections. Although the porcupine swam across the stream with apparent ease, its head and body were quite low in the water; thus, waves and rif- fles may pose a substantial risk of drowning. A swift current could also quickly take a porcupine down- stream during a crossing into hazards, such as rough water or waterfalls.
2019
Acknowledgements
Dwayne Lepitzki, Garth Mowat, and an anonym- ous reviewer kindly provided comments that im- proved this manuscript.
Literature Cited
Cott, P.A., and N.J. Mochnacz. 2007. Bull trout, Sa/velinus confluentus, and North American porcupine, Erethizon dorsatum, interaction in the Mackenzie Mountains, Northwest Territories. Canadian Field-Naturalist 121: 438-439. https://doi.org/10.22621/cfn.v12114.523
Dean, H.J. 1950. Porcupine swims for food. Journal of Mammalogy 31: 94.
Murie, O.J. 1926. The porcupine in northern Alaska. Jour-
JUNG: SWIMMING PORCUPINE 27
nal of Mammalogy 7: 109-113.
Roze, U. 2009. The North American Porcupine. Second Edi- tion. Cornell University Press, Ithaca, New York, USA.
Roze, U., and L.M. Ilse. 2003. Porcupine, Erethizon dors- atum. Pages 371-380 in Wild Mammals of North Amer- ica: Biology, Management, and Conservation. Second Edition. Edited by G.A. Feldhamer, B.C. Thompson, and J.A. Chapman. The John Hopkins University Press, Baltimore, Maryland, USA.
Woods, C.A. 1973. Erethizon dorsatum. Mammalian Spe- cies 29: 1-6,
Received 16 July 2018 Accepted 7 February 2019
The Canadian Field-Naturalist
More Mountain Chickadees (Poecile gambelt) sing atypical songs in urban than in rural areas
STEFANIE E. LAZERTE!”", KRISTEN L.D. MARINI, HANS SLABBEKOORN‘*, MATTHEW W. REUDINK?, and KEN A. OTTER!
'Natural Resources and Environmental Studies, University of Northern British Columbia, 3333 University Way, Prince George, British Columbia V2N 4Z9 Canada
?Current address: Department of Biology, Brandon University, 270- 18th Street, Brandon, Manitoba R7A 6A9 Canada
>Department of Biological Sciences, Thompson Rivers University, 805 TRU Way, Kamloops, British Columbia V2C 0C8 Canada
“Institute of Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, the Netherlands
“Corresponding author: sel@steffilazerte.ca
LaZerte, S.E., K.L.D. Marini, H. Slabbekoorn, M.W. Reudink, and K.A. Otter. 2019. More Mountain Chickadees (Poecile gambeli) sing atypical songs in urban than in rural areas. Canadian Field-Naturalist 133(1): 28-33. http://doi.org/ 10.22621/cfn.v13311.1994
Abstract
Urbanization results in novel ecosystems with unique challenges. These may lead to problems during song learning or development and could result in the singing of atypical songs. During studies of Mountain Chickadees (Poecile gambeli) and urbanization in British Columbia, Canada, we observed males singing atypical songs along an urbanization gradient. We found that eight of 78 males consistently sang atypical songs and the odds of singing atypical songs increased with urbanization. We explored several explanations including habitat quality, population density, and bioacoustics. Future stud- ies investigating causes and consequences of atypical singing will clarify effects of urbanization on Mountain Chickadees.
Key words: Mountain Chickadee; Poecile gambeli, Paridae; communication; atypical songs; urbanization; urbanization
index
Introduction
Among songbirds, unusual songs are those that differ from species-specific local song types. These unusual songs may be (a) rarely heard ‘special’ songs (such as whisper songs), (b) juvenile songs, the result of early song development, (c) uncommon mimicry of other species, or (d) dialectal songs in an abnormal geographic location (Borror 1968). Unusual songs that do not fit these four categories are considered atypical (e) and may be the consequence of errors in learning or developmental problems (Borror 1968).
Occasionally, young males make ‘mistakes’ when learning their songs. Perhaps they have few tutors, or cannot hear their tutors well, or perhaps their tu- tors are a closely related species (e.g., Black-capped Chickadees [Poecile atricapillus| and Carolina Chickadees [P. carolinensis] learn each other’s songs; Sattler et al. 2007). There may also be developmen- tal problems, as poor-quality habitat can lead to poor- quality songs (e.g., poor-quality Black-capped Chick- adee songs appear less dominant to both males and females; Grava et al. 2012, 2013a), which, in extreme cases, could be considered atypical. Alternatively,
©The Ottawa Field-Naturalists’ Club
changes to habitat acoustics may result in young males incorrectly hearing their tutors’ songs or act- ively modifying their own song to reduce interfer- ence and increase transmission (e.g., Slabbekoorn and den Boer-Visser 2006).
Many situations leading to atypical songs may occur as a result of urbanization. Urbanization cre- ates a novel ecosystem with unique challenges for many species. Among birds, urbanization can lead to changes in habitat quality that may be positive (e.g., increased food availability from bird feeders; Robb et al. 2008) or negative (e.g., habitat loss, competi- tion with invasive species, or environmental pollut- ants; McKinney 2002), and may influence population dynamics. Urbanization can also lead to altered habi- tat acoustics (e.g., echoes and reverberation from buildings and pavement; Warren et a/. 2006) and anthropogenic noise pollution, which can interfere with vocal communication through masking of lower frequencies (Patricelli and Blickley 2006; Shannon et al. 2015).
Mountain Chickadees (Poecile gambeli) live in montane forests in western North America. They are
2019
found in urban areas, although they occur at lower densities than they do in rural areas (LaZerte 2015; S.E.L. and K.L.D.M. pers. obs.) and may thus be less urban-adapted than Black-capped Chickadees. Here we present a short exploration of the relationship between atypical songs and urbanization in Mountain Chickadees using the combined data from Marini (2016) and LaZerte (2015).
Methods
We analyzed recordings of 78 adult male Moun- tain Chickadees vocalizing at dawn in the spring dur- ing nest-building and egg-laying (2012 through 2015). These recordings were obtained from two studies in- vestigating effects of urbanization: communication and individual condition (Marini et al. 2017a, n = 42), and vocal plasticity (LaZerte et al. 2017, n = 36). Recordings were made in and around the cit- ies of Williams Lake (n = 12; 52.129°N, 122.138°W), Kamloops (n = 60; 50.676°N, 120.341°W), and Ke- lowna (n = 6; 49.884°N, 119.493°W), British Colum- bia (BC), Canada. Each male was recorded a max- imum of once per year. We used site territoriality to distinguish among males within a year, but sites in Kamloops were revisited between years. Known duplicate recordings of males (if the male was banded or identified by distinctive atypical singing) were omitted. Habitat urbanization was evaluated as a con- tinuous index (low = rural, high = urban) by compar- ing satellite Google Earth images (Google Inc. 2012) of territories (defined as a circular area 150 m in diam- eter around the recording location of the focal male) and scoring the amount of natural vegetation (natural grass or trees) versus urban ground cover (pavement, buildings, or lawn; for more details see LaZerte et al. 2017; for scripts and tutorial see https://github.com/ steffilazerte/urbanization-index). The lowest habitat urbanization value (—0.95) reflected sites with 100% natural vegetation (no pavement, no buildings, no lawns). The highest value (2.01) reflected sites with only 11% natural vegetation cover, and 89% pave- ment, buildings, or lawn.
We only included samples with a minimum of five minutes of vocalization and 25 songs (as Mountain Chickadees use both songs and calls during the dawn chorus; McCallum et al. 1999; Grava et al. 2013b). Part of LaZerte et al.’s (2017) experimental protocol involved exposing males to five minutes of experi- mental noise. Although they found no effect of this exposure on song variation, we excluded all songs recorded during the noise exposure period and in the five minutes following.
Mountain Chickadees in BC typically sing songs with 3—5 notes in descending order (Grava eral. 2013b; Figure la). We therefore defined songs as atypical if
LAZERTE ET AL... ATYPICAL URBAN MOUNTAIN CHICKADEE SONGS 29
they were monotone (multiple notes sung on a sin- gle frequency; Figure 1b top), contained a reverse frequency change (ascending note[s] as opposed to descending; Figure 1b middle), or contained novel notes (e.g., anote with an extreme upwards frequency sweep; Figure 1b bottom). We used categorical desig- nations for songs as opposed to measuring song char- acteristics because our data were obtained from two prior studies. In one study, songs had been categor- ized, but there were no compiled data on individual songs. Although atypical songs are unusual, it is not uncommon for an individual to occasionally sing a few atypical songs. Therefore, we classified males as atypical singers only if they consistently sang atyp- ical songs (>80% of all songs recorded were atypical, most males sang <5% atypical songs).
To determine whether the odds of being an atyp- ical singer increased with urbanization, we performed a logistic regression of male singer type (atypical/typ- ical) against the urbanization index using R statis- tical software (version 3.3.2; R Core Team 2016). We calculated bias-corrected and adjusted (BCa) boot- strap 95% CI for coefficients. We performed 10000 replicates using the boot package for R (version 1.3- 20; Angelo and Ripley 2017). Figures were created using the R package ggplot2 (version 2.2.1; Wickham 2009). Spectrograms were created with Hanning window lengths of 1024 using the R packages ggplot2 and seewave (version 2.0.5; Sueur et al. 2008).
Results
Eight of 78 individuals consistently sang atyp- ical songs. Roughly categorizing urban areas as those with an urbanization index greater than the mean (0) showed that 21% of urban males consistently sang atypical songs whereas only 2% of rural males did (Figure 2a).
The odds of a male consistently singing atyp- ical songs increased significantly with the continu- ous urbanization index (Log odds = 1.10, 95% CI = 0.28—2.30, SE = 0.42, z=2.61, P = 0.009; Figure 2b); expressed as an odds ratio, for every 1 unit increase in the urbanization index, males were 3.00 (95% CI = 1.32—9.95) times as likely to be atypical singers. The probability of individuals in the most rural habi- tats being atypical singers was 2.4% (95% CI = 0.3— 11.2%). In the most urban habitats, the probability was 39.0% (95% CI = 11.6—68.0%).
Discussion
Consistently singing atypical songs was not com- mon; however, the odds of doing so increased with in- creasing urbanization. Because these recordings were collected during the breeding period before juveniles were present, it is highly unlikely that atypical songs
30
Kelowna
Williams Lake
ol 1
1 | Rese; » ——_) —_
Frequency (kHz) b
w i
THE CANADIAN FIELD-NATURALIST
Vol. 133
b. Atypical
Monotone
cee fm amt: pass?
Reverse frequency drop
Ga a
Kamloops Novel note: Freq. sweep & reverse freq. drop / & 44 SS t atl | =a exes) T T T T T T T T 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 2.0 Time (s)
FiGurE 1. Variation in Mountain Chickadee (Poecile gambeli) songs in British Columbia, Canada. a. Typical regional variation; all songs show descending frequencies. b. Some examples of atypical songs include monotone songs (top), songs with a reverse frequency drop (middle), and songs with novel notes (bottom).
a.
2% atypical
21% atypical
Number of individuals
Rural Urban
Habitat type
b. Atypical 4 @) Oo @® O00 0 o 5 a 2 5 Typical 4 een GD O@ anes ce T T T T
-1 0 1 2 Urbanization Index
Singer type [] Typical || Atypical
FiGuRE 2. Male Mountain Chickadees (Poecile gambeli) are more likely to consistently sing atypical songs in urban areas. a. By categorizing urban sites as those with an urbanization index > 0 and rural sites as those with an urbanization index <0, urban sites show 21% of males singing atypical songs versus 2% in rural areas. b. As urbanization increases, the like- lihood of being an atypical singer increases. The line represents the predicted logistic regression, the grey area shows the 95% CI interval around the predicted model. Each point represents a male Mountain Chickadee. The outlier (top left panel b) was recorded in a rural area on the outskirts of Kamloops. There were no sources of water, nor any other obvious sources of noise. It is possibly it could have been a windy location as it was on the side of a hill, but excessive wind was not noted. It was up slope of the train tracks, ~1.5 km away, a distance unlikely to have had an effect. Possibly this individual
migrated to the area from an urban area.
represent early song development. Further, as these cities are relatively small (the largest, Kamloops, has a population of 90280; Statistics Canada 2017) and are surrounded by rural habitat, it seems unlikely that birds from different populations (and with dif- ferent song types) would have exclusively settled in urban areas, or that these urban habitats are iso- lated enough to facilitate cultural evolution of song
(cf. Gammon and Baker 2004; Luther and Derryberry 2012). Consequently, atypical singers in urban areas may result from differences in habitat quality, popula- tion density, or environmental acoustics. Poor-quality habitat may be associated with poor- quality males, either because males in urban habitats do not get enough resources or because only poor- quality males will settle in urban habitats. This, in
2019
turn, may lead to poor-quality song (e.g., nutritional stress hypothesis; Nowicki et a/. 2002; male quality; Grava et al. 2012) which could explain the increase in atypical singers. However, our previous studies of Mountain Chickadees in Kamloops suggest that urban habitat seems to be of at least equivalent qual- ity to rural habitat (Marini et a/. 2017b). Thus, poor- quality habitat may not fully explain the presence of atypical singers we found.
Mountain Chickadees are less abundant in ur- ban than in rural areas (LaZerte 2015; S.E.L. and K.L.D.M. pers. obs.). In some species, greater urban population densities affect song variation, by influen- cing male-male interactions (e.g., Eurasian Blackbird [Turdus merula], Ripmeester et al. 2010; Great Tits [Parus major], Hamao et al. 2011). However, it is unclear how reduced competition could lead to singing atypical songs in Mountain Chickadees. Alternatively, low population density may result in fewer tutors or tutors that are farther away, making it difficult for young chickadees to learn songs correctly (similar to Laiolo and Tella 2005). Further, low dens- ities may also result in the direct introduction of un- usual song types by juveniles and less social pressure to conform to local song types (Gammon ef al. 2005; Gammon 2007).
Urban areas are often noisy (LaZerte et al. 2015) and more pavement and concrete leads to altered acoustics (Warren eft al. 2006). These changes may interfere with vocal communication leading to ad- justed songs and/or calls. Male Mountain Chickadees are known to adjust their vocalizations in noisy habi- tats and in response to noise exposure (LaZerte et al. 2017). In a study on closely related Great Tits, Slabbekoorn and den Boer-Visser (2006) found that, throughout Europe, urban males sang more atyp- ical song types (songs with fewer or more notes than the typical 2—4) than rural males, and suggested this could be due to noise interference. If, during song learning, only un-masked and well transmitted as- pects of tutor songs are learned properly, changes in bioacoustics could result in atypical songs (Rabin and Greene 2002; Slabbekoorn and den Boer-Visser 2006). Depending on the situation, these atypical songs could be beneficial or detrimental. Atypical songs, which are the result of learning only the least- masked aspects of a normal song (e.g., Mountain Chickadee monotone songs may represent songs which have lost low-frequency notes), could result in less noise-interference and better transmission, and could thus be an adaptation to urban environments. Alternatively, atypical songs may be a symptom of poor learning in urban areas wherein young males settling in urban areas are learning songs incorrectly from tutors that results in poor quality songs.
LAZERTE ET AL... ATYPICAL URBAN MOUNTAIN CHICKADEE SONGS 3]
While atypical songs were uncommon overall, urban Mountain Chickadees in BC were more likely to consistently sing atypical songs than rural males. However, it is not clear whether these songs repre- sent a response to the urban acoustic environment, or a symptom of low population densities. Studies in progress suggest that atypical songs may transmit bet- ter in noisier conditions than typical songs (S.E.L. un- publ. data). However, Gammon et al. (2005) observed more atypical songs in Black-capped Chickadees in quiet, rural populations as opposed to presumably noisier, urban populations, suggesting a stronger role for population density than urban noise. There are fewer studies on Mountain Chickadees and it is thus less clear how prevalent atypical songs are in more natural landscapes. Possibly, they might be more common than in Black-capped Chickadees, simply because their song varies more among populations than do Black-capped Chickadees (e.g., Grava et al. 2013a). Further studies exploring the interaction be- tween noise and population densities (such as ina 2x2 factorial design, varying density of birds and levels of urban noise) could help clarify the potential mech- anism. The research could be an observational study or a manipulative experiment (e.g., alter population density through removing birds, use audio speakers to vary the amount of urban noise). It is also unclear what consequences these changes may have on com- munication or reproductive success, which further studies may also help to clarify.
Author Contributions
S.E.L., K.A.O., and H.S. contributed to the de- velopment and design of the LaZerte (2015) study, and K.L.D.M., K.A.O., and M.W.R. contributed to the development and design of the Marini (2016) study. S.E.L. and K.L.D.M. collected data and conducted data cleaning and preparation. S.E.L. conducted the analysis and wrote the manuscript. All authors con- tributed to development of ideas and commented on draft versions of the manuscript.
Acknowledgements
The assistance of technicians from Thompson Rivers University and University of Northern British Columbia (UNBC) was greatly appreciated. We wish to thank: BC Parks; the cities of Williams Lake, Kel- owna, and Kamloops; Regional District of the Cen- tral Okanagan; Thompson Rivers University; and University of British Columbia Okanagan for al- lowing access to their parks and grounds. An anonym- ous reviewer and David Gammon provided helpful comments on the manuscript. Financial support was provided by The James L. Baillie Memorial Fund of Bird Studies Canada (S.E.L.); Natural Sciences and
32 THE CANADIAN FIELD-NATURALIST
Engineering Research Council of Canada through Post Graduate doctoral scholarship (S.E.L.), Indus- trial Postgraduate Scholarship (K.L.D.M.), and Dis- covery grants (K.A.O. and MW.R.); and UNBC through Graduate Entrance Research Awards and a Research Project Award (S.E.L.).
Literature Cited
Angelo, C., and B. Ripley. 2017. boot: Bootstrap R (S-Plus) Functions. Version 1.3-20. Accessed 30 July 2017. http:// CRAN.R-project.org/package=boot.
Borror, D.J. 1968. Unusual songs in passerine birds. The Ohio Journal of Science 68: 129-138.
Gammon, D.E. 2007. How postdispersal social environ- ment may influence acoustic variation in birdsong. Pages 183-197 in Ecology and Behavior of Chickadees and Titmice: an Integrated Approach. Edited by K.A. Otter. Oxford University Press, Oxford, United Kingdom.
Gammon, D.E., and M.C. Baker. 2004. Song reper- toire evolution and acoustic divergence in a popula- tion of Black-capped Chickadees, Poecile atricapillus. Animal Behaviour 68: 903-913. https://doi.org/10.1016/j. anbehav.2003.10.030
Gammon, D.E., M.C. Baker, and J.R. Tipton. 2005. Cultural divergence within novel song in the Black- capped Chickadee (Poecile atricapillus). Auk 122: 853— 871. https://doi.org/10.1642/0004-8038(2005)122[0853: cdwnsi|2.0.co;2
Google Inc. 2012. Google Earth. Accessed 26 August 2014. http://google.com/earth/.
Grava, T., A. Grava, and K.A. Otter. 2012. Vocal per- formance varies with habitat quality in Black-capped Chickadees (Poecile atricapillus). Behaviour 149: 35— 50. https://doi.org/10.1163/156853912x625854
Grava, T., A. Grava, and K.A. Otter. 2013a. Habitat- induced changes in song consistency affect perception of social status in male chickadees. Behavioral Ecology and Sociobiology 67: 1699-1707. https://doi.org/10.1007/ s00265-013-1580-z
Grava, A., K.A. Otter, T. Grava, S.E. LaZerte, A. Poesel, and A.C. Rush. 2013b. Character displacement in dawn chorusing behaviour of sympatric Mountain and Black- capped Chickadees. Animal Behaviour 86: 177-187. https://doi.org/10.1016/j.anbehav.2013.05.009
Hamao, S., M. Watanabe, and Y. Mori. 2011. Urban noise and male density affect songs in the Great Tit Parus ma- Jor. Ethology Ecology & Evolution 23: 111-119. https:// doi.org/10.1080/03949370.2011.554881
Laiolo, P., and J.L. Tella. 2005. Habitat fragmentation af- fects culture transmission: patterns of song matching in Dupont’s Lark. Journal of Applied Ecology 42: 1183— 1193. https://doi.org/10.1111/j.1365-2664.2005.01093.x
LaZerte, S.E. 2015. Sounds of the city: the effects of urban- ization and noise on Mountain and Black-capped Chick- adee communication. Ph.D. thesis, University of Nor- thern British Columbia, Prince George, British Colum- bia, Canada. https://do1.org/10.24124/2015/bpgub1059
LaZerte, S.E., K.A. Otter, and H. Slabbekoorn. 2015. Relative effects of ambient noise and habitat openness
Vol. 133
on signal transfer for chickadee vocalizations in rural and urban green-spaces. Bioacoustics 24: 233-252. https://doi.org/10.1080/09524622.2015.1060531
LaZerte, S.E., K.A. Otter, and H. Slabbekoorn. 2017. Mountain Chickadees adjust songs, calls and chorus composition with increasing ambient and experimental anthropogenic noise. Urban Ecosystems 20: 989-1000. https://doi.org/10.1007/s11252-017-0652-7
Luther, D.A., and E.P. Derryberry. 2012. Birdsongs keep pace with city life: changes in song over time in an urban songbird affects communication. Animal Be- haviour 83: 1059-1066. https://do1.org/10.1016/j.anbehav. 2012.01.034
Marini, K.L. 2016. City life and chickadees: effects of ur- banization on vocal output and reproductive success of the Mountain Chickadee (Poecile gambeli). M.Sc. thesis, Thompson Rivers University, Kamloops, British Columbia, Canada.
Marini, K.L., K.A. Otter, S.E. LaZerte, and M.W. Reu- dink. 2017b. Urban environments are associated with earlier clutches and faster nestling feather growth com- pared to natural habitats. Urban Ecosystems 20: 1291— 1300. https://doi.org/10.1007/s11252-017-0681-2
Marini, K.L., M.W. Reudink, S.E. LaZerte, and K.A. Otter. 2017a. Urban Mountain Chickadees (Poecile gambeli) begin vocalizing earlier, and have greater dawn chorus output than rural males. Behaviour 154: 1197-1214. https://do1.org/10.1163/1568539x-00003464
McCallum, D.A., R. Grundel, and D.L. Dahlsten. 1999. Mountain Chickadee (Poecile gambeli). In The Birds of North America Online. Edited by A. Poole. Cornell Laboratory of Ornithology, Ithaca, New York, USA. https://doi.org/10.2173/bna.453
McKinney, M.L. 2002. Urbanization, biodiversity, and conservation. BioScience 52: 883-890. https://doi.org/ 10.1641 /0006-3568(2002)052[0883:ubac]2.0.co;2
Nowicki, S., W.A. Searcy, and S. Peters. 2002. Brain de- velopment, song learning and mate choice in birds: a review and experimental test of the “nutritional stress hypothesis.” Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology 188: 1003-1014. https://doi.org/10.1007/s00 359-002-0361-3
Patricelli, G.L., and J.L. Blickley. 2006. Avian com- munication in urban noise: causes and consequences of vocal adjustment. Auk 123: 639-649. https://doi.org/ 10.1642/0004-8038(2006)123[639:aciunc]2.0.co;2
R Core Team. 2016. R: a Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria.
Rabin, L.A., and C.M. Greene. 2002. Changes to acous- tic communication systems in human-altered environ- ments. Journal of Comparative Psychology 116: 137— 141. https://doi.org/10.1037/0735-7036.116.2.137
Ripmeester, E.A.P., J.S. Kok, J.C. van Rijssel, and H. Slabbekoorn. 2010. Habitat-related birdsong diver- gence: a multi-level study on the influence of territory density and ambient noise in European Blackbirds. Behavioral Ecology and Sociobiology 64: 409-418. https://doi.org/10.1007/s00265-009-0857-8
Robb, G.N., R.A. McDonald, D.E. Chamberlain, and S.
2019
Bearhop. 2008. Food for thought: supplementary feed- ing as a driver of ecological change in avian popula- tions. Frontiers in Ecology and the Environment 6: 476— 484. https://doi.org/10.1890/060152
Sattler, G.D., P. Sawaya, and M.J. Braun. 2007. An assess- ment of song admixture as an indicator of hybridization in Black-capped Chickadees (Poecile atricapillus) and Carolina Chickadees (P. carolinensis). Auk 124: 926— 944. https://doi.org/10.1642/0004-8038(2007)124[926:aa osaa]2.0.co;2
Shannon, G., M.F. McKenna, L.M. Angeloni, K.R. Crooks, K.M. Fristrup, E. Brown, K.A. Warner, M.D. Nelson, C. White, J. Briggs, S. McFarland, and G. Wittemyer. 2015. A synthesis of two decades of research documenting the effects of noise on wildlife. Biological Reviews 91: 982-1005. https://do1.org/ 10.1111/brv.12207
Slabbekoorn, H., and A. den Boer-Visser. 2006. Cities change the songs of birds. Current Biology 16: 2326— 2331. https://doi.org/10.1016/j.cub.2006.10.008
LAZERTE ET AL... ATYPICAL URBAN MOUNTAIN CHICKADEE SONGS 33
Statistics Canada. 2017. Kamloops, British Columbia and British Columbia (table). Census Profile. 2016 Census. Statistics Canada Catalogue 98-316-X2016001. Ottawa. Released 29 November 2017. Accessed 22 January 2019. https://www1l2.statcan.gc.ca/census-recensement/2016/ dp-pd/prof/index.cfm?Lang=E.
Sueur, J., T. Aubin, and C. Simonis. 2008. Seewave: a free modular tool for sound analysis and synthesis. Bioacoustics 18: 213-226. https://doi.org/10.1080/0952 4622.2008.9753600
Warren, P.S., M. Katti, M. Ermann, and A. Brazel. 2006. Urban bioacoustics: it’s not just noise. Animal Behaviour 71: 491-502. https://doi.org/10.1016/j.anbehav. 2005.07.014
Wickham, H. 2009. ggplot2: elegant graphics for data an- alysis. Springer, New York, New York, USA.
Received 27 October 2017 Accepted 3 January 2018
The Canadian Field-Naturalist
Body mass as an estimate of female body condition in a hibernating small mammal
CAITLIN P. WELLS", JAMES A. WILSON’, DoUGLAS A. KELT', and Dirk H. VAN VUREN!
'Department of Wildlife, Fish, and Conservation Biology, University of California, 1 Shields Avenue, Davis, California 95616 USA
?Department of Biology, University of Nebraska, 6001 Dodge Street, Omaha, Nebraska 68182 USA
“Corresponding author: cpwells@ucdavis.edu
Wells, C.P., J.A. Wilson, D.A. Kelt, and D.H. Van Vuren. 2019. Body mass as an estimate of female body condition in a hibernating small mammal. Canadian Field-Naturalist 133(1): 34—42. https://doi.org/10.22621/cfn.v13311.2073
Abstract
In hibernating squirrels, the amount of energy stored as fat may influence several important demographic traits, but 1s dif- ficult to quantify in living animals. Thus, several non-destructive indices of body condition are used, including simple indi- ces that use body mass and scaled indices that correct body mass for structural size. However, the accuracy of these indices for hibernating squirrels is poorly known. We used measurements of total body electrical conductivity (TOBEC) from adult female Golden-mantled Ground Squirrels (Callospermophilus lateralis) to characterize body composition (lean mass versus fat mass) and condition (fat stores) at multiple stages in the circannual cycle. Body mass explained a high proportion of the variation in fat mass during the emergence and pre-hibernation stages, but less during the reproduction stage. Contrary to expectation, correcting for structural size did not markedly improve the condition index. Our results suggest that body mass is a good estimate of body condition during the periods of emergence and pre-hibernation fattening, and therefore may be useful to predict important components of fitness such as reproductive success and overwinter survival.
Key words: Body mass; body condition; condition index; mass-length residuals; fat; ground squirrel; Callospermophilus
lateralis
Introduction
Seasonal variation in energy supply is a central problem for many mammals, which may respond to periods of environmental energy shortage by storing energy, reducing energy expenditure, or both (Hum- phries et a/. 2003). Hibernation, which reduces meta- bolic demands during winter, is one life-history adaptation to seasonal energy scarcity, but sufficient energy stores are essential to its success (Pulawa and Florant 2000).
In hibernating squirrels, the amount of energy stored as fat may influence several important demo- graphic traits such as overwinter survival (Murie and Boag 1984; Lenihan and Van Vuren 1996), timing of reproductive maturity (Barnes 1984), male breeding effort (Delehanty and Boonstra 2011), female repro- ductive success (Dobson and Michener 1995; Rieger 1996), offspring sex allocation (Allainé et al. 2000), and natal dispersal (Nunes and Holekamp 1996; Neuhaus 2006). Additionally, estimating fat stores is essential for bioenergetic models of hibernation, which can be used to project distribution changes of hibernating species under changing climatic condi- tions (Humphries et a/. 2002). However, quantifying
©The Ottawa Field-Naturalists’ Club
body condition (defined here as fat stores, in grams; Kiell and Millar 1980; Dark et al. 1989) is difficult to do non-destructively. Because determining the effects of body condition on future life-history out- comes requires that the animal survive measure- ment, several non-destructive indices for estimating condition have been developed (Schulte-Hostedde er al. 2005; Peig and Green 2010). These include sim- ple condition indices that use body mass (e.g., Hock 1960), and scaled condition indices that attempt to correct body mass for structural size (e.g., Reid 1988). Many studies use total body mass as a simple condi- tion index, with the implicit assumption that greater mass reflects greater relative fat stores (Barnes 1984; Sauer and Slade 1987; Lenihan and Van Vuren 1996; Neuhaus 2003; Lane et a/. 2011). However, larger ani- mals may have greater mass due to larger structural size (skeleton and associated lean tissue) instead of greater fat stores (Dobson 1992). Thus, some stud- ies use a scaled condition index based on residuals derived from a regression of body mass on structural size, with the expectation that correcting body mass by the structural size of an individual improves the estimate of its condition (Bachman 1993; Dobson
2019
and Michener 1995; Dobson et al. 1999; Allainé et al. 2000). Positive residuals suggest the animal con- tains more tissue (presumably fat) than predicted for a given structural size, while negative residuals sug- gest the animal contains less tissue than predicted for a given structural size.
Scaled indices are appealing because they cor- rect for variance in body mass that is unrelated to energy stores, but available evidence indicates that size-corrected measures do not necessarily improve estimates of body condition compared to use of body mass alone (Krebs and Singleton 1993; Green 2001; Schamber ef al. 2009). However, most evaluations of condition indices have focussed on mammals that do not store fat for hibernation or energy reserves, and the poor relationship between the scaled condition index and measured fat content may occur because residuals of these relatively lean species primarily reflect differences in protein or water content rather than fat (Schulte-Hostedde et al. 2001). Scaled indi- ces might be more appropriate for species in which fat content is a greater proportion of body mass, such as hibernators (Schulte-Hostedde et a/. 2001), but the predictive ability of simple versus scaled condition indices for hibernating squirrels is poorly known.
Fat storage in hibernating squirrels follows circ- annual cycles of accumulation and depletion (Buck and Barnes 1999), reflecting seasonal changes in the balance between energy acquisition and expenditure (Kenagy ef al. 1989). For an index to be an appropri- ate estimate of body condition, it should explain a high proportion of the variation in fat storage, prefer- ably across multiple stages of the circannual cycle. Adult females are often excluded from condition index validation because of the confounding effect of fetal lean tissue elaboration during gestation (Krebs and Singleton 1993; Schulte-Hostedde et a/. 2005), yet energetic costs associated with hibernation and reproduction deplete fat stores, and therefore affect body condition, in adult females as well as males (Kenagy 1989; Michener and Locklear 1990; Buck and Barnes 1999). In this paper we use measurements from adult female Golden-mantled Ground Squirrels (Callospermophilus lateralis) to evaluate fat stores during four major stages (emergence, reproduction, post-reproduction, and pre-hibernation) in their cir- cannual cycle. Our goal is to assess body mass as a simple index of body condition in each stage, and determine if using a scaled index improves estimates of body condition.
Methods
We studied Golden-mantled Ground Squirrels over three years (2003-2005) in the northern Sierra Nevada mountains of California. These squirrels are
WELLS ET AL.: GROUND SQUIRREL BODY CONDITION 35
locally abundant, medium-sized (200-300 g), and relatively well-known both ecologically and physio- logically (Bartels and Thompson 1993).
Our study was conducted in the Plumas National Forest (40.004012°N, 120.810829°W) near Quincy, California, at an elevation of ~2100 m. In this area, adults emerge from hibernation in May and pups are weaned in late July; all squirrels gain weight dur- ing September before immerging into hibernation in October. Gestation in Golden-mantled Ground Squirrels is 28 days (Cameron 1967) and weaning occurs when pups reach 30 days old (Phillips 1981). We divided the active season into four circannual stages, defined broadly to encompass individual vari- ation in circannual timing: emergence, 15 May—15 June (emergence from hibernation through mating and early gestation); reproduction, 16 June—31 July (late gestation through lactation); post-reproduction, 1 August-31 August (after lactation but before late summer fattening becomes pronounced); and pre- hibernation, 1 September—early October (when pre- hibernation fattening occurs). Because we did not determine reproductive status for all females in this study, our sample may have included non- reproductive females.
We captured adult female squirrels with Toma- hawk live traps (Model 201, Tomahawk Live Trap Co., Hazelhurst, Wisconsin, USA) baited with rolled oats and black oil sunflower seeds coated with pea- nut butter. Traps were set in the early morning and checked mid-morning. Our methods were conducted according to a protocol approved by the Animal Care and Use Committee of the University of Cali- fornia, Davis, and followed guidelines approved by the American Society of Mammalogists (Sikes et al. 2016). At first capture, squirrels were fitted with a uniquely numbered metal tag (Self-piercing fish tag, Style 1005-1, National Band & Tag Company, Newport, Kentucky, USA) in each ear for perma- nent identification. We attempted to capture all squir- rels monthly, but due to differential trapping success not all squirrels were captured each month. We transported captured squirrels to a laboratory near Quincy, where we anesthetized them with an intra- muscular injection of ketamine hydrochloride (100 mg/ml). We recorded body mass to the nearest 0.1 g using a portable electronic balance and body length (measured as tip of nose to anus) to the nearest 0.1 cm (Pulawa and Florant 2000). We used body length as a measure of structural size (Bachman 1993; Allainé et al. 2000); our measurements of body length showed good repeatability for individuals recaptured in the same stage (Pearson correlation r = 0.83, n = 5). We quantified body fat using an EM-SCAN SA-3000 body composition analyzer (EM-SCAN, Springfield,
36 THE CANADIAN FIELD-NATURALIST
Illinois, USA; no longer available from the manufac- turer) to measure total body electrical conductivity. Total body electrical conductivity (TOBEC) is a non- destructive method to analyze the body composition of animals (Scott et a/. 2001) that has been used to obtain estimates of lean and fat mass from free-liv- ing small mammals (Walsberg 1988; Koteja 1996), including ground squirrels (Nunes and Holekamp 1996; Buck and Barnes 1999; Pulawa and Florant 2000). The TOBEC method uses electrical cur- rent, which travels differentially through fat versus lean tissue, to generate measures of electrical resist- ance; resistance measures are then converted to fat mass using species-specific calibration equations (Bachman 1994; Koteja 1996; Walsberg 1998; Scott et al. 2001).
EM-SCAN readings are known to vary with ani- mal movement during measurement, differences in gut contents, changes in ambient temperature, and changes in body temperature greater than 4°C (Wals- berg 1988; Scott et al. 2001). To minimize variation due to movement, we placed immobilized squirrels on a plastic sample tray and lightly restrained them with rubber bands to maintain each squirrel in the same position (dorsoventrally, ventral side down, with the tail tucked under the body). To minimize variation due to gut contents, we only trapped squirrels early in the morning (as foraging began) and did not pro- vide food or water until after TOBEC measurement. To minimize variation due to ambient temperature, we performed measurements in a laboratory at a field station. Anesthesia often causes a drop in body tem- perature; throughout our study, however, the mean change in body temperature was —1.6 + 0.3°C (SE), and no individuals lowered their body temperatures more than 4°C. Body composition was calculated as the mean of five replicate measurements; we recorded seven replicate measurements and then discarded the highest and lowest values, though variation in meas- urements was minimal (coefficient of variation = 0.03). We determined lean mass (V,) using the cali- bration curve for Golden-mantled Ground Squirrels:
M,, = 18.0 + 0.3M, + 1.2VL, x EM
where M, is body mass, L, is body length, and EM is the EM Scan measurement (r? = 0.98; Pulawa and Florant 2000). We calculated fat mass by subtracting lean mass from body mass.
We characterized the body composition (lean mass versus fat mass) and condition (fat mass) of adult fe- male ground squirrels during emergence, reproduc- tion, post-reproduction, and pre-hibernation stages. Because female energetic needs shift throughout the active season from expenditure on reproduction to acquisition before hibernation (Kenagy ef al. 1989),
Vol. 133
potentially changing the relationship between body mass and fat mass, we considered each circannual stage separately. We assessed fat stores of 23 adult fe- male Golden-mantled Ground Squirrels; seven were measured in a single circannual stage, six were meas- ured in two circannual stages, eight were measured in three circannual stages, and two were measured in all four stages. Sample size varied by stage, and each female was included only once per stage. If females were measured more than once within the same stage, we randomly selected a single measurement from those taken in the same year (” = 5 females), and we considered measures to be independent if taken in different years (n = 2 females; Broussard et al. 2005). We also tried averaging measurements for the same female within a year, but the results were similar whether we averaged or chose measurements at random. We used analysis of variance (ANOVA) with Tukey’s HSD post-hoc tests to test for signifi- cant differences in mean body length and mean body composition among circannual stages. We used linear regression to examine the relationship between body length and mass by each circannual stage.
Next, we used bivariate linear regression to evalu- ate the relationship between body mass and fat mass for each circannual stage, and also the relationship between mass-length residuals, calculated from re- gressing body mass on body length, and fat mass. In addition, because percent fat (fat mass/total body mass) is sometimes used as a measure of body con- dition in hibernating squirrels (Barnes 1984; Nunes and Holekamp 1996; Neuhaus 2003) we performed the same regressions for percent fat as we did for fat mass. The use of body mass as a variable in both the TOBEC calibration equation and as a predictor of fat mass may introduce some underlying structure to the data, with the potential to inflate the r? values. While this is unavoidable, we therefore report 7” values asso- ciated with linear regressions for comparison among stages and indexes, and without associated signifi- cance tests (Wasserstein and Lazar 2016).
Finally, because our data contained substantial individual and annual variation in percent fat, which may confound relationships between condition indi- ces and percent fat inferred through linear regres- sion, we fitted linear mixed models with individual female identity and year as random effects, and circ- annual stage and condition index specified as fixed effects. Models were estimated with Bayesian infer- ence. We used a Bayesian, mixed-effects approach for two reasons: 1) the hierarchical structure of our data suggested the use of mixed effects models that produce more accurate estimates of all parameters, and 2) Bayesian approaches more accurately parti- tion variance among mixed effect parameters than
2019
likelihood-only approaches (McElreath 2016). We developed four models: two with fat mass (in grams) as the response variable, predicted by either mass or mass-length residuals, and two with percent fat as the response variable, predicted by either mass or mass- length residuals. We included all measurements (” = 61) of the 23 adult females in this analysis.
We used a model comparison approach to evalu- ate the ability of each index to predict fat mass and percent fat. Specifically, we used the Watanabe- Akaike Information Criterion (WAIC) to rank mod- els, based on WAIC differences (AWAIC) and Akaike weights. Such values are analogous to other informa- tion criteria, where low AWAIC values indicate pre- ferred model, and high weight indicates increased probability that the model will successfully predict new data (Gelman ef al. 2014; McElreath 2016). All analyses were run in R version 3.5.2 (R Development Core Team 2016); we used the packages RStan (Stan Development Team 2016) and rethinking (McElreath 2016) to fit and compare mixed models, and ggplot2 (Wickham and Chang 2013) to plot figures.
Results
Lean mass of adult female Golden-mantled Ground Squirrels varied among circannual stages (F353; = 3.52, P = 0.02; Table 1), and was lowest at emergence from hibernation and highest before immergence. Estimated fat mass also varied among circannual stages (F3;,; = 7.35, P < 0.001), and was lowest at emergence from hibernation and highest before immergence. Percent fat varied among circ- annual stages (F3;, = 5.90, P = 0.002), and appeared stable throughout the first three stages before show- ing a sharp increase in the pre-hibernation stage. Additionally, mixed models revealed a generally positive effect of the pre-hibernation stage on fat mass, after controlling for year, individual, and mass or mass-length residual (Table 2).
The relationship between body mass and body length was positive during emergence (r? = 0.55, n = 12, P < 0.01), reproduction (7? = 0.41, n = 15, P< 0.01), and post-reproduction stages (r? = 0.33, n = 16,
WELLS ET AL.: GROUND SQUIRREL BODY CONDITION ov,
P =0.02), but was no longer apparent during the pre- hibernation stage (77= 0.00, n= 12, P=0.98; Figure 1).
Body mass explained a very high proportion of the variation (93-96%) in fat mass during the emergence, post-reproduction, and pre-hibernation stages, but a lower proportion (84%) during the reproduction stage (Figure 2). Correcting for structural size, as measured by head and body length, did not improve fit within any stage: the proportion of variation explained by mass-length residuals was less than that for the sim- ple index based on body mass during the emergence, reproduction, and post-reproduction stages (57-70%), and equivalent to that explained by body mass during the pre-hibernation stage (96%).
Overall, a similar pattern was evident for the analysis based on percent fat. Body mass explained a moderate to high proportion of the variation in per- cent fat during the emergence (77 = 0.79), post-repro- duction (7? = 0.69), and pre-hibernation stages (7? = 0.91), but a lower proportion during the reproduction stage (7? = 0.56). Correcting for structural size did not markedly improve fit within most stages, though mass-length residuals did explain a significant pro- portion of the variation in percent fat (emergence r? = 0.61, post-reproduction r? = 0.46, pre-hiberna- tion r?= 0.91). Correcting body mass by body length improved model fit only in the reproduction stage (r? = 0.86). While both mass and mass-length residuals showed strong positive effects on fat mass and per- cent fat, WAIC metrics showed a clear preference for the mass models (w; =1, AWAIC=0.0; AWAIC for the second model >69 for fat grams and >20 for percent fat; Table 2).
Discussion
Our results suggest that body mass is a useful esti- mate of body condition during the critical periods of emergence from hibernation and pre-hibernation fat- tening, and perhaps during the post-reproductive per- iod, supporting the use of body mass as a simple index to predict important components of fitness such as female reproductive success (Rieger 1996) and over- winter survival (Murie and Boag 1984). Body mass
TABLE 1. Mean length and body composition (+ 1 SE) of adult female Golden-mantled Ground squirrels (Callospermophilus lateralis) near Quincy, California, from 2003 to 2005, by circannual stage.
Emergence Reproduction Post-reproduction Pre-hibernation 15 May-—15 June 16 June—31 July 1-31 August 1 September—1 October
n 12 15 16 12
Mean length (cm) 17404 18+ 0.3 1740.3 18+0.3
Mean total mass (g) 158 + 8.5” IIS 3:3 1675.9" 198+ 9.4%! Mean lean mass (g) 124448” 135+3.4 130°: 3:6 142 + 4.5” Mean fat mass (g) Chiao keg 39°23 Sete Dole Mean percent fat Pwr BS im 22 EOS 2D 8% 28 + 1.4°4
“Statistically different value(s) from °* across circannual stages for that variable, according to Tukey HSD post-hoc test.
133 Vol.
IST
FIELD-NATURAL
IAN
CANAD
THE
e, when roduc tive ie d ring t ir rep 1S ass d lable during their tatus mp an s reliab ried in Clive s Holeka ant, was les likely ni ea en ee cae ae les like tion com ductive, elati fema aria in body epro the r n ev of ter sires Neri Anite ae ee this ae e299 ened Gumlestiike nd fat ition was de ass Bale s=- Nunes ating fem Te conditio ponies Ss ZeE 8.53 |< d lact body hen s, Inc fat ma g ES 3 n BS y am between ounced w t female sida of oO vary & a RY Ss 2 ex Dh = ship more ey aaa tissue ae EES pees >a 3 ge es as fat. n fe ive eta 235 Z| Bo See i - eee acetal Reproduce ones srs EBs a|- 15538 eee eee ge tite smpling EC 252 ela le rare Ro in lit dy e di tructi he T d gee §| a |< +l 2 OS ur stu First, w hdes gh t antle S28 Bla 15 a eea ue es. hroug Ithou den-m id o 4 (Es SO os le siz irrels t ond, a Gol we di Bez H| 6 ly S samp fsquirre Sec for 000), we « n Fas alate . tent o action. lidated ant 2 ulatio a a 2 an conte! 1 extr va d Flor r pop ne = 20 Ica been a and | for ou mo aoe 2 OS chem has Pulaw. hine for ¢ ed fro Ww 322 Bale | SS thod irrels ( C mack derivec to ne See 5 : pated ae Stee state ula- ee Sh 2 acres ot ca 1es. nN suc gcle Beep £550 Qs S| pecs — lation in anot of T n. Co nly. 4m = 2 o | 7 ro! Tk AS popul Is ina curacy known. imates ol Is BES ae 8 gra iadivada the ac Is is un e estim Squirre oS Sc S|Sk = ind but irre nt ar nd Sq n- Se 5 2 =| st S oo 4H = 2001), d squ conte Grou ition co 6.2 es 5/ a on S HOH ao al. roun of fat tled ositi th 2 so ° 2) nN N 1 Wa NS f ns of g ents n-man comp . ing bo Pa 2 © se) ay 4 SEDER Bs lo urem olde in body ain n Egse Fa a ae Ss meas ale G s in irrels, ga seaso 22 Sa seam lass eo 79 our It fem changes | squi active tud- & ¢ 22 S|c Adu onal ch nating s the her s Ee22 eas ber ing Ot ig Eb 22 ee ee ee ramen Tiber. oy 2s ia cA ee istent w d fa : Ric squ 1 hi = = = = 2% — peat and Mi trated t d fat tissu getative an ee te ° x ie ons an e ve 64; g mS 5 s 29 eg ( s have d e both | ese once d Mead 00). A ns poss 3 | & nel x ataboliz store th Sena rant 20 hibernat ss EQ Z| 59 S ste sain but eine es and eee es 1999; Bas ah | Sole w n ason 0; Pula is charac d Bar is stage 2808 215 SAGE ing sea r 1980; assris,ol uck and | this oo 8 5 2 |S a a Milla in fat m 98; B during z 3 ge 5 A = ¥F q a M me = pa gain ates et Aan It Eyboee Poe ee ar) ezlls a 4 aot s sea ies ( 000), ar d by S ex is easy ele SA Ss cle iD icte mas SS 1 26823 Ra é ace ing spe et a red dy t ma q 5 & a] 3 5 =) ile rand best p hat bo ale fa om- E 3 = 5 |" = + ee BLESSES r finding BA in pan that sited sehr: = that fa ral, ow keen ae s expla sv o) ne 2 n 10 S nd OS 2 oreo) ge atio rev ma rou Beas ae | Ser i ntial vari those of p rels: body Iding’s G hout 2835 Role gy a ubsta ith Bs Aa rae hroug f 5 es = Pola Se cons male and tion in fa dingi) coll 971), and 8 Feral ao E g SralECee = bined f the ee bet nd Tung | round Stee n cn x E ae : Sg 2 S a ete (Ur ne Sasa tas Arctic Te et al. using mee us nl oa a hb Squi ae seaso ercent fat captivity ural size ah var eG e/ 5 Sark he ac ion inp ') held in truct body ; £832 : ae lae if hess eye el a tes of for esti- a5: mys ee Eon the vat lus pa djusting estima tage Ss a EO S| 6 aa 29 AS (Urocite isingly, a t improve Sees body a gi pant z am 4 ive) oo — Aa rpr i no TO n ence, = S35 D + et Su did ; € rep th a erg Ess a 5 ae ody length Lduring "Body ae eed a < = S a ami Ss atin eee a in our eae eae age 2 Zs tes of f cota exetace toratees es on 5 sz 5S ma inearly mis in part, & ss 2 2 OS 2 ere lin the pre st in p Rae 252% orting e, at lea 5 SS 2 ae ene supp as due, eRe5 2 Bo 2 Y es W eS a5 43 sabato Stag & led aa = — 1 1 Ec eS) S ees aes = SOs s Sod oS 2 <I aaee pgeg83 N a) epee = BES 9 7 | oO mS ct <F oo = WN
2019
size. However, the relationship between body length and mass almost disappeared by the pre-hibernation stage (Figure 1). Because the regression of body mass on length had a slope of zero in the pre-hibernation stage, and the magnitude of residuals was equal to relative body mass, the fit of mass-length residuals was identical to that of body mass in this stage.
We suggest three reasons why the scaled index may have performed poorly. First, measures of struc- tural size may be particularly susceptible to meas- urement error (Yezerinac et al. 1992; Blackwell et
WELLS ET AL.: GROUND SQUIRREL BODY CONDITION 39
al. 2006; Martin et al. 2013). Although we reduced this error by measuring body length on anesthetized squirrels, which are more amenable to measurement than active, unanesthetized squirrels, and this meas- urement displayed high repeatability within stage, some measurement error remained. Second, meas- ures of structural size such as body length may some- times be a poor indicator of lean mass that is not associated with energy storage. As with the relation- ship between body length and total mass noted above, the strength of the relationship between body length
Body mass (g) No S
— on f=)
100
15 16 17 18 Body length (cm)
Stage
—* Emergence
-#- Reproduction -m&- Post-reproduction
+ Pre-hibernation
19 20
Figure 1. Linear relationships between adult female Golden-mantled Ground Squirrel (Callospermophilus lateralis) body
mass and body length, by circannual stage.
a. Emergence b. Reproduction
y =-36+045-x 7? =0.93
y =-25+0.37-x r= 0.84
Fat mass (g)
100 125 150 175 200
c. Post-reproduction d. Pre-hibernation
100 100 y =-30+0.41-x r= 0.94
y =-50+0.53-x ?=0.96
75
50
120 140 160 180 200 120 160 200 240
Body mass (g)
y =35+0.52-x P=0.57
y =39+0.44-x P=07
Fat mass (g)}
40 -20 0 20 40 -40 -20 0 20 Mass-length residuals
100 y =564+0.53-x r=0,96
75
50
-40 — -20 0 20 -0 -25 0 25 50
FiGcure 2. Linear relationships between adult female Golden-mantled Ground Squirrel (Ca/llospermophilus lateralis) total body mass and fat mass (top row), and mass-length residuals and fat mass (bottom row), by circannual stage (columns).
Dotted lines represent a 95% CI (two standard errors).
40 THE CANADIAN FIELD-NATURALIST
and lean mass declined over the active season (from r’= 0.64 at emergence to r?= 0.01 before hibernation). Some individuals that emerged from hibernation with lower body mass than expected for their body size still had substantial fat stores; perhaps these individ- uals preferentially lost lean mass during hibernation (Pulawa and Florant 2000) to retain fat stores neces- sary for initiating reproduction. Finally, although body length commonly has been used in ground squirrel studies (Morton et a/. 1974; Kiell and Millar 1980; Pulawa and Florant 2000), it may simply be a poor measure of structural size. Other studies have used breadth across the zygomatic arches as a meas- ure of structural size (Dobson et al. 1999; Viblanc et al. 2010). Zygomatic arch breadth has a significant but not especially strong linear relationship with body length for adult females of this species (7? = 0.44, P < 0.01, n = 18; C.P.W. unpubl. data), however, high- lighting the uncertainty of using a single measure to quantify as complex a trait as structural size.
Body condition is an important trait in the life his- tory of ground squirrels, but measuring condition directly requires sacrificing the animal. Our results suggest that the simple measure of body mass is a useful indicator of body condition, especially early and late in the active season, and that scaled indices do not improve on mass estimates during most stages in the circannual cycle.
Acknowledgements
We thank the Joint Fire Sciences Program and the United States Department of Agriculture (USDA), Forest Service (Region 5), and the USDA National Institute of Food and Agriculture (Hatch project CA-D-WFB-6126-H to D.A.K.; CA-D-WFB-5245-H to D.H.V.V.) for funding the project, C. Conroy (Uni- versity of California Berkeley, Museum of Vertebrate Zoology) for access to Callospermophilus lateralis skeletons, and FS. Dobson, D. Kramer, W. Halliday, and three anonymous reviewers for comments that greatly improved this manuscript.
Literature Cited
Allainé, D., F. Brondex, L. Graziani, J. Coulon, and I. Till-Bottraud. 2000. Male-biased sex ratio in litters of Alpine marmots supports the helper repayment hypoth- esis. Behavioral Ecology 11: 507-514. https://doi.org/10. 1093/beheco/11.5.507
Bachman, G.C. 1993. The effect of body condition on the trade-off between vigilance and foraging in Belding’s ground squirrels. Animal Behaviour 46: 233-244. https:// doi.org/10.1006/anbe.1993.1185
Bachman, G.C. 1994. Food restriction effects on the body composition of free-living ground squirrels, Spermo- Philus beldingi. Physiological Zoology 67: 756-770. https://doi.org/10.1086/physzool.67.3.30163769
Barnes, B.M. 1984. Influence of energy stores on activa-
Vol. 133
tion of reproductive function in male golden-mantled ground squirrels. Journal of Comparative Physiology, B 154: 421-425. https://doi.org/10.1007/bf00684449
Bartels, M.A., and D.P. Thompson. 1993. Spermophilus lateralis. Mammalian Species 440: 1-8. https://doi.org/ 10.2307/3504114
Blackwell, G.L., S.M. Bassett, and C.R. Dickman. 2006. Measurement error associated with external measure- ments commonly used in small-mammal studies. Jour- nal of Mammalogy 87: 216-223. https://doi.org/10.1644/ 05-mamm-a-215r1.1
Boswell, T., S.C. Woods, and G.J. Kenagy. 1994. Seasonal changes in body mass, insulin, and glucocorticoids of free-living golden-mantled ground squirrels. General and Comparative Endocrinology 96: 339-346. https:// doi.org/10.1006/gcen.1994.1189
Broussard, D.R., F.S. Dobson, and J.O. Murie. 2005. The effects of capital on an income breeder: evidence from female Columbian ground squirrels. Canadian Journal of Zoology 83: 546-552. https://doi.org/10.1139/z05-044
Buck, C.L., and B.M. Barnes. 1999. Annual cycle of body composition and hibernation in free-living arctic ground squirrels. Journal of Mammalogy 80: 430-442. https://doi.org/10.2307/1383291
Cameron, D.M. 1967. Gestation period of the golden-man- tled ground squirrel (Cite//us lateralis). Journal of Mam- malogy 48: 492—493. https://doi.org/10.2307/1377799
Dark, J., J.S. Stern, and I. Zucker. 1989. Adipose tissue dynamics during cyclic weight loss and weight gain of ground squirrels. American Journal of Physiology —Regulatory, Integrative and Comparative Physiolo- gy 256: R1286—R1292. https://doi.org/10.1152/ajpregu. 1989.256.6.r1286
Delehanty, B., and R. Boonstra. 2011. Coping with intense reproductive aggression in male arctic ground squirrels: the stress axis and its signature tell divergent stories. Physiological and Biochemical Zoology 84: 417-428. https://doi.org/10.1086/660809
Dickinson, K., T.J. North, G. Telford, S. Smith, R. Brammer, R.B. Jones, and D.J. Heal. 2001. Deter- mination of body composition in conscious adult fe- male Wistar utilizing total body electrical conductivity. Physiology & Behavior 74: 425-433. https://do1.org/ 10.1016/s0031-9384(01)00535-2
Dobson, F.S. 1992. Body mass, structural size, and life- history patterns of the Columbian ground squirrel. American Naturalist 140: 109-125. https://doi.org/10. 1086/285405
Dobson, F.S., and G.R. Michener. 1995. Maternal traits and reproduction in Richardson’s ground squirrels. Eco- logy 76: 851-862. https://doi.org/10.2307/1939350
Dobson, F.S., T.S. Risch, and J.O. Murie. 1999. In- creasing returns in the life history of Columbian ground squirrels. Journal of Animal Ecology 68: 73-86. https:// dot.org/10.1046/j.1365-2656.1999.00268.x
Gelman, A., J. Hwang, and A. Vehtari. 2014. Understand- ing predictive information criteria for Bayesian mod- els. Statistics and Computing 24: 997-1016. https://doi. org/10.1007/s11222-013-9416-2
Green, A.J. 2001. Mass/length residuals: measures of body condition or generators of spurious results? Eco-
2019
logy 82: 1473-1483. https://doi.org/10.1890/0012-9658 (2001)082[1473:mlrmob]2.0.co;2
Hilderbrand, G.V., C.C. Schwartz, C.T. Robbins, and T.A. Hanley. 2000. Effect of hibernation and reproduct- ive status on body mass and condition of coastal brown bears. Journal of Wildlife Management 64: 178-183. https://doi.org/10.2307/3802988
Hock, R.J. 1960. Seasonal variations in physiologic func- tions of arctic ground squirrels and black bears. Bulletin of the Museum of Comparative Zoology 124: 155-171.
Holekamp, K.E., and S. Nunes. 1989. Seasonal variation in body weight, fat, and behavior of California ground squirrels (Spermophilus beecheyi). Canadian Journal of Zoology 67: 1425-1433. https://doi.org/10.1139/z89-202
Humphries, M.M., D.W. Thomas, and D.L. Kramer. 2003. The role of energy availability in mammalian hibernation: a cost-benefit approach. Physiological and Biochemical Zoology 76: 165-179. https://doi.org/ 10.1086/367950
Humphries, M.M., D.W. Thomas, and J.R. Speakman. 2002. Climate-mediated energetic constraints on the distribution of hibernating mammals. Nature 418: 313— 316. https://doi.org/10.1038/nature00828
Jameson, E.W., and R.A. Mead. 1964. Seasonal chan- ges in body fat, water and basic weight in Cite/lus lat- erdlis, Eutamius speciosus and E. amoenus. Journal of Mammalogy 45: 359-365. https://doi.org/10.2307/ 1377407
Kenagy, G.J. 1989. Daily and seasonal uses of energy stores in torpor and hibernation. Pages 17—24 in Living in the Cold, Volume Hl. Edited by A. Malan and B. Canguilhem. John Libbey Eurotext Ltd., Montrouge, France:
Kenagy, G.J., S.M. Sharbaugh, and K.A. Nagy. 1989. Annual cycle of energy and time expenditure in a golden-mantled ground squirrel population. Oecologia 78: 269-282. https://doi.org/10.1007/bf00377166
Kiell, D.J., and J.S. Millar. 1980. Reproduction and nutrient reserves of arctic ground squirrels. Canadian Journal of Zoology 58: 416—421. https://doi.org/10.1139/ 280-055
Koteja, P. 1996. The usefulness of a new TOBEC instru- ment (ACAN) for investigating body composition in small mammals. Acta Theriologica 41: 107—112. https:// doi.org/10.4098/at.arch.96-10
Krebs, C.J., and G.R. Singleton. 1993. Indices of condi- tion for small mammals. Australian Journal of Zoology 41: 317-323. https://doi.org/10.1071/z09930317
Kunz, T.H., J.A. Wrazen, and C.D. Burnett. 1998. Changes in body mass and fat reserves in pre-hibernat- ing little brown bats (Myotis lucifugus). Ecoscience 5: 8-17. https://doi.org/10.1080/11956860.1998 11682443
Lane, J.E., L.E.B. Kruuk, A. Charmantier, J.O. Murie, D.W. Coltman, M. Buoro, S. Raveh, and F.S. Dobson. 2011. A quantitative genetic analysis of hibernation emer- gence date in a wild population of Columbian ground squirrels. Journal of Evolutionary Biology 24: 1949— 1959. https://doi.org/10.1111/j.1420-9101.2011.02334.x
Lee, T.N., R.W. Fridinger, B.M. Barnes, C.L. Buck, and D.M. O’Brien. 2011. Estimating lean mass over a wide range of body composition: a calibration of deu-
WELLS ET AL.: GROUND SQUIRREL BODY CONDITION 4]
terium dilution in the arctic ground squirrel. Rapid Communications in Mass Spectrometry 25: 3491-3496. https://doi.org/10.1002/rem.5253
Lenihan, C., and D. Van Vuren. 1996. Growth and sur- vival of juvenile yellow-bellied marmots (Marmota flaviventris). Canadian Journal of Zoology 74: 297-302. https://doi.org/10.1139/z96-037
Martin, J.G.A., M. Festa-Bianchet, S.D. Coté, and D.T. Blumstein. 2013. Detecting between-individual differ- ences in hind-foot length in populations of wild mam- mals. Canadian Journal of Zoology 91: 118-123. https:// doi.org/10.1139/cjz-2012-0210
McElreath, R. 2016. Statistical Rethinking: a Bayesian Course with Examples in R and Stan. CRC Press, Boca Raton, Florida, USA.
McKeever, S. 1964. The biology of the golden-mantled ground squirrel, Citellus lateralis. Ecological Mono- graphs 34: 383-401. https://doi.org/10.2307/2937069
Michener, G.R., and L. Locklear. 1990. Differential costs of reproductive effort for male and female Richardson’s ground squirrels. Ecology 71: 855—868. https://doi.org/ 10.2307/1937357
Morton, M.L., C.S. Maxwell, and C.E. Wade. 1974. Body size, body composition, and behavior of juven- ile Belding ground squirrels. Great Basin Naturalist 34: 121-134.
Morton, M.L., and H.L. Tung. 1971. The relationship of total body lipid to fat depot weight and body weight in the Belding ground squirrel. Journal of Mammalogy 52: 839-842. https://doi.org/10.2307/1378942
Murie, J.O., and D.A. Boag. 1984. The relationship of body weight to overwinter survival in Columbian ground squirrels. Journal of Mammalogy 65: 688-690. https://doi.org/10.2307/1380854
Neuhaus, P. 2003. Parasite removal and its impact on litter size and body condition in Columbian ground squirrels (Spermophilus columbianus). Proceedings of the Royal Society London, Series B 270: S213—S215. https://doi. org/10.1098/rsbl.2003.0073
Neuhaus, P. 2006. Causes and consequences of sex-biased dispersal in Columbian ground squirrel, Spermophilus columbianus. Behaviour 143: 1013-1031. https://doi.org/ 10.1163/156853906778623653
Nunes, S., and K.E. Holekamp. 1996. Mass and fat influ- ence the timing of natal dispersal in Belding’s ground squirrels. Journal of Mammalogy 77: 807-817. https:// doi.org/10.2307/1382686
Peig, J., and A.J. Green. 2010. The paradigm of body con- dition: a critical reappraisal of current methods based on mass and length. Functional Ecology 24: 1323-1332. https://doi.org/10.1111/j.1365-2435.2010.01751.x
Phillips, J.A. 1981. Growth and its relationship to the in- itial annual cycle of the golden-mantled ground squirrel, Spermophilus lateralis. Canadian Journal of Zoology 59: 865-871. https://doi.org/10.1139/z81-124
Pulawa, L.K., and G.L. Florant. 2000. The effects of ca- loric restriction on the body composition and hiberna- tion of the golden-mantled ground squirrel (Spermophi- lus lateralis). Physiological and Biochemical Zoology 73: 538-546. https://doi.org/10.1086/317752
R Development Core Team. 2016. R: a language and en-
42 THE CANADIAN FIELD-NATURALIST
vironment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria.
Reid, W.V. 1988. Age-specific patterns of reproduction in the Glaucous-winged gull: increased effort with age? Ecology 69: 1454-1465. https://doi.org/10.2307/1941642
Rickart, E.A. 1982. Annual cycles of activity and body composition in Spermophilus townsendii mollis. Cana- dian Journal of Zoology 60: 3298-3306. https://do1.org/ 10.1139/z82-418
Rieger, J.F. 1996. Body size, litter size, timing of reproduc- tion, and juvenile survival in the Uinta ground squir- rel, Spermophilus armatus. Oecologia 107: 463-468. https://doi.org/10.1007/bf00333936
Sauer, J.R., and N.A. Slade. 1987. Uinta ground squir- rel demography: is body mass a better categorical vari- able than age? Ecology 68: 642-650. https://doi.org/ 10.2307/1938469
Schamber, J.L., D. Esler, and P.L. Flint. 2009. Evaluating the validity of using unverified indices of body condi- tion. Journal of Avian Biology 40: 49-56. https://doi.org/ 10.1111/j.1600-048X.2008.04462.x
Schulte-Hostedde, A.I., J.S. Millar, and G.J. Hickling. 2001. Evaluating body condition in small mammals. Canadian Journal of Zoology 79: 1021-1029. https://doi. org/10.1139/z01-073
Schulte-Hostedde, A.I., B. Zinner, J.S. Millar, and G.J. Hickling. 2005. Restitution of mass-size residuals: vali- dating body condition indices. Ecology 86: 155-163. https://doi.org/10.1890/04-0232
Scott, I., C. Selman, P.I. Mitchell, and P.R. Evans. 2001. The use of total body electrical conductivity (TOBEC) to determine body composition in vertebrates. Pages 127-160 in Body Composition Analysis of Animals: a Handbook of Non-Destructive Methods. Edited by J.R.
Vol. 133
Speakman. Cambridge University Press, Cambridge, Massachusetts, USA.
Sikes, R.S., and the Animal Care and Use Committee of the American Society of Mammalogists. 2016. Guide- lines of the American Society of Mammalogists for the use of wild mammals in research. Journal of Mam- malogy 97: 663-688. https://do1.org/10.1093/jmammal/ gyw078
Stan Development Team. 2016. Stan Version 2.18. Ac- cessed 23 January 2019. https://mc-stan.org.
Viblanc, V.A., C.M. Arnaud, F.S. Dobson, and J.O. Murie. 2010. Kin selection in Columbian ground squir- rels (Urocitellus columbianus): littermate kin provide individual fitness benefits. Proceedings of the Royal Society London, Series B 277: 989-994. https://doi.org/ 10.1098/rspb.2009.1960
Walsberg, G.E. 1988. Evaluation of a nondestructive method for determining fat stores in small birds and mammals. Physiological Zoology 61: 153-159. https:// doi.org/10.1086/physzool.61.2.30156146
Wasserstein, R.L., and N.A. Lazar. 2016. The ASA’s statement on p-values: context, process, and purpose. American Statistician 70: 129-133. https://doi.org/10. 1080/00031305.2016.1154108
Wickham, H., and W. Chang. 2013. ggplot2: an imple- mentation of the Grammar of Graphics. Accessed 23 January 2019. https://ggplot2.tidyverse.org.
Yezerinac, S.M., S.C. Lougheed, and P. Handford. 1992. Measurement error and morphometric studies: statis- tical power and observer experience. Systematic Biology 41: 471-482. https://doi.org/10.1093/sysbio0/41.4.471
Received 16 March 2018 Accepted 17 February 2019
The Canadian Field-Naturalist
Desiccation of herpetofauna on roadway exclusion fencing SEAN P. Boy.e!*, RACHEL DILLON!, JACQUELINE D. LitzGcus', and DAvip LESBARRERES!
‘Biology Department, Laurentian University, 935 Ramsey Lake Road, Sudbury, Ontario P3E 2C6 Canada *Corresponding author: sboyle@laurentian.ca
Boyle, S.P., R. Dillon, J.D. Litzgus, and D. Lesbarréres. 2019. Desiccation of herpetofauna on roadway exclusion fencing. Canadian Field-Naturalist 133(1): 43—48. https://doi.org/10.22621/cfn.v13311.2076
Abstract
Significant advances have been made to minimize the detrimental effects of roads on wildlife, but little is known about unintended negative consequences of mitigation strategies. Here, we present observations of adverse effects on herpeto- fauna of exclusion fencing at Presqu’ile Provincial Park, Ontario. A total of 15 individuals (one salamander, nine anurans, and five snakes) were found dead on unburied fencing, apparent victims of desiccation and/or heat exposure. Air temper- atures did not differ between days when dead herpetofauna were and were not found on the fence; however, the fence sur- face was significantly warmer than the air. Our study shows that fence temperature and design may hinder animals escaping from the road to cooler refugia, and we discuss possible solutions.
Key words: Road ecology; road-effect mitigation; snakes; frogs; Presqu’ile Provincial Park; protected areas; southern Ontario
Introduction
Although herpetofauna are often overlooked com- pared with other taxa (Andrews ef al. 2008, 2015; Popp and Boyle 2017), the negative effects of roads on these species are becoming increasingly clear and well documented (Gibbs and Shriver 2002; Andrews et al. 2008, 2015; Baxter-Gilbert et al. 2015). As a countermeasure, wildlife exclusion fencing (WEF), typically combined with crossing structures, is an increasingly common tool employed by biologists and conservation practitioners to mitigate the effects of road mortality on herpetofauna (Glista et al. 2009; Beebee 2013; van der Ree ef al. 2015). In several instances, WEF has been shown to reduce the number of amphibians and reptiles killed in wildlife—vehicle collisions (Dodd et al. 2004; Aresco 2005; Colley et al. 2017; Markle et al. 2017). However, negative con- sequences associated with factors other than spatial ecology or road mortality have rarely been attributed to WEF (see Boarman et al. 1994; Ferronato et al. 2014; Eye et al. 2018). Because reducing road mor- tality is critical to maintaining population viability, WEF has important implications for conservation (Jaeger and Fahrig 2004). As such, documenting and understanding unintended negative consequences of WEF is an important step in conservation efforts.
Although road mortality is a major threat to her- petofauna, care must be taken to ensure that miti- gation techniques used to address this threat do not produce undesirable side effects. Unfortunately,
potential negative side effects of WEF on individ- uals and populations are somewhat difficult to pre- dict and may include fence by-catch (Ferronato ef al. 2014), an increase in the barrier effect (Jaeger and Fahrig 2004), disruption of important movement pat- terns (Clark et a/. 2010; Rouse ef al. 2011), hyper- thermia from excessive sun exposure (Peaden et al. 2017; Eye et al. 2018), and increased road mortality rates resulting from improperly installed or main- tained fencing (Baxter-Gilbert et a/. 2015; Markle et al. 2017). Further complicating the matter is the variety of WEF materials, installation methods, ter- rain, and management regimes, with each combina- tion presenting a unique set of potential side effects (e.g., solid versus mesh WEF; OMNREF 2016; Peaden et al. 2017).
In 2013, a six-year project was undertaken in Presqu ile Provincial Park, Ontario, Canada (43.9944°N, 77.7201°W) to identify the local road-crossing pat- terns of herpetofauna (Boyle et a/. 2017) and to test the effectiveness of various strategies to mitigate road mortality and habitat fragmentation. While complet- ing road mortality surveys for this project, we noticed several desiccated herpetofauna on portions of a WEF during its installation. This prompted an investiga- tion to determine whether the installation of the WEF, specifically the possibility that it could expose wild- life to extended periods of heat, was causing mor- tality of reptiles and amphibians. We hypothesized that if the WEF contributed to mortality associated
A contribution towards the cost of this publication has been provided by the Thomas Manning Memorial Fund of the Ottawa
Field-Naturalists’ Club.
©The Ottawa Field-Naturalists’ Club
44 THE CANADIAN FIELD-NATURALIST
with desiccation, then the fence’s bottom lip would be warmer than the air on days when we found dead animals. Second, if desiccation was a result of high temperatures, we expected that either the day or the day before we found desiccated animals on the fence would be warmer than days when no desiccated her- petofauna were found. To inform other road ecology practitioners and to contribute to the improvement of techniques, it is important to document negative sec- ondary effects of various types of WEF and investigate potential solutions.
Methods
The main road of Presqu’ile has a posted speed limit of 40 km/h and an average daily traffic volume of ~3000 vehicles during July and August; thus, this is a high-impact roadway for wildlife (S.P.B. unpubl. data).
Installation of ~1000 m of exclusion fencing (Ani- mex vertical above-ground black exclusion fencing, Knowle, Hampshire, England) began in June 2016 and was completed in August 2016. Fencing was installed ~1 m from the road’s edge. The fencing was 0.865 m high and composed of solid, high-density polyethylene (HDPE) sheets, each 16.7 m long. At both the top and bottom of the fence, a lip (0.15 m) was folded over in opposite directions. The bottom lip, folded at a 90° angle toward the road, increased stability of the fence once buried, and the upper lip, also folded at 90° but facing away from the road, was intended to reduce the ability of animals to climb over the fence onto the road. The fencing was installed in two phases: in phase one, the entire fence was fas- tened against plastic support stakes for stability, with sheets zip-tied together through small holes drilled at either end (20 June to 15 August 2016); in phase two, the bottom lip was buried under 0.10 m of mixed ageregate (mid-August 2016). The addition of aggre- gate on the road side of the fence precluded the need to bury the fence in a trench, which is costly, labour intensive, and potentially ecologically destructive. On completion, the fence was contiguous except at three intersections (two roads and a bicycle path), where it was curved in on itself away from the road, to create a minimum 5 m turn-around.
We report here observations made during the mid- construction phase (i.e., from the time when the fence was installed until its bottom lip was covered with aggregate) when small vertebrates could move under the fence. Visual encounter surveys were conducted daily by foot beginning at ~0915 along the 1250 m fenced portion of the road from 1 May to 30 August 2016. During surveys, either S.P.B. or R.D. searched the road and roadside for live and dead herpetofauna. No effort was made to detect herpetofauna on the
Vol. 133
habitat (non-road) side of the fence.
Shaded air temperature at waist height was meas- ured daily along the road at the start of each survey. In addition, we measured air and fence lip surface temperatures using a digital thermometer (Marathon, BA080008, + 2.0°C, San Leandro, California, USA) each time an animal (alive or dead) was found on the fence. Maximum air temperatures recorded at the nearest weather station, Trenton A, ~20 km northeast of Presqu’ile were also referred to (Environment and Natural Resources 2016).
We completed all analyses in R v3.4.1 (R Development Core Team 2014). We used Wilcoxon signed rank tests to make three comparisons: (1) air temperature on days in July and August when we found dead herpetofauna versus days on which we found no dead herpetofauna on the fence’s bottom lip, (2) maximum temperature of the previous day (Environment and Natural Resources 2016) on days when we found dead herpetofauna versus days when we found no herpetofauna on the fence’s bottom lip, and (3) fence temperature versus air temperature when we observed dead herpetofauna.
Results
On 14 July 2016, a dead, desiccated, but undam- aged Wood Frog (Lithobates sylvaticus) was dis- covered on the unburied bottom lip (road side) of the WEF. Typically, amphibians that are struck by vehicles sustain moderate to severe visible damage; thus, an apparently undamaged individual was note- worthy. Over the course of surveys, 12 amphibians (10 dead; one salamander and five species of frog; Table 1) and 10 snakes, all Common Gartersnakes (Thamnophis sirtalis, five dead; Table 1) were found on the bottom lip of the fencing. Additional individ- uals were observed before 14 July but no detailed notes were taken. Dead animals all appeared to be mostly intact, but had undergone various levels of desiccation (Table 1). Although not the main goal of our study, it is noteworthy that all of the desiccated herpetofauna were found at previously identified road mortality hotspots (Boyle et al. 2017). Of the 10 dead amphib- ians, all but two were fully desiccated (Figure 1a). The two live frogs detected on the fence behaved nor- mally but appeared to be unable to find a way through the fence, despite the bottom lip being unburied. In addition, one of the live snakes was coiled on the bottom lip of the fence, possibly basking, while the others demonstrated signs of stress (i.e., erratic move- ments, sluggishness, mouth gaping) possibly because of dehydration.
We did not find differences in air temperature between days we did or did not find deceased her- petofauna (W = 155, P = 0.30), nor between the
2019
BOYLE ET AL.: DESICCATED HERPETOFAUNA ON FENCES 45
TABLE 1. Reptiles and amphibians observed dead or alive on Animex exclusion fencing in Presqwile Provincial Park, Ontario, from 14 July to 30 August 2016, along with demographic and climatic information for each sighting.
Date Time Weather Species*
9Aug. 0935 Sunny Blue-spotted Salamander 12 Aug. 0927 Overcast Gray Treefrog
12 Aug. 0932 Overcast Gray Treefrog
12 Aug. 0939 Overcast Gray Treefrog
5Aug. 0900 Light rain American Bullfrog 12Aug. 1339 Overcast Green Frog
12Aug. 1039 Overcast Northern Leopard Frog 5 Aug. 0927 Overcast Northern Leopard Frog 14 Jul. 0940 Overcast Wood Frog
9Aug. 0935 Sunny Wood Frog
12Aug. 1139 Overcast Wood Frog
12 Aug. 1239 Overcast Wood Frog
22 Jul. 0925 Sunny Common Gartersnake 15 Aug. 1002 Mostly cloudy Common Gartersnake 22 Aug. 1120 Overcast Common Gartersnake 2Aug. 0926 Sunny Common Gartersnake 23 Aug. 1004 Sunny Common Gartersnake 17 Jul. 0924 Sunny Common Gartersnake 29 Jul. 0941 Partly cloudy Common Gartersnake 2Aug. 0940 Sunny Common Gartersnake 2Aug. 1024 Sunny Common Gartersnake 5 Aug. 0930 Sunny Common Gartersnake
Sex/lifestaget Air Fence Dead or temperature, °C temperature,°C alive Juvenile 27.6 31.8 Dead Juvenile 28.5 32.1 Dead Juvenile 25.1 35.4 Dead Juvenile 25.1 35.4 Dead Female 26.7 29.1 Alive Adult 25.1 35.4 Dead Adult 251 35.4 Dead Juvenile 27.3 29.2 Dead Juvenile 24.3 27.1 Alive Juvenile 27.6 31.8 Dead Juvenile 25.1 35.4 Dead Juvenile 25.1 35.4 Dead Adult 24.0 27D Alive Adult 23.6 DTD Dead Adult 21 29.3 Alive Female 23.9 25.6 Alive Female 24.4 26.9 Alive Juvenile 21.6 22.6 Alive Juvenile 26.3 32.1 Dead Juvenile 23.9 25.6 Dead Juvenile 28.7 31.9 Dead Juvenile 26.7 31.2 Dead
Note: Although all individuals demonstrated some desiccation, this was not quantified in situ. *Blue-spotted Salamander (Ambystoma laterale), Gray Treefrog (Hyla versicolor), American Bullfrog (Lithobates catesbe- ianus), Green Frog (Lithobates clamitans), Northern Leopard Frog (Lithobates pipiens), Wood Frog (Lithobates sylvaticus),
and Common Gartersnake (Thamnophis sirtalis).
+Snakes designated as “adult” were either not captured or not sexed to minimize additional stress on the animal.
maximum temperatures of days previous to detec- tions versus those without detections (W =156, P = 0.91). However, the fence was significantly warmer than the air (W =96, P =0.002; Table 2) on days when dead herpetofauna were observed on the fence.
Discussion
Contrary to our expectations, air temperature was a poor predictor of the presence of dead animals. However, the fence itself was warmer than the air when we found dead herpetofauna, supporting our hy- pothesis that the fence contributed to the desiccation and mortality. Individuals that moved to the edge of the fence in an attempt to exit the road’s right of way would have bypassed the exit path available under- neath the fence because of the folded lip. Thus, we conclude that the fence contributed to the observed mortality, likely by reducing the ability of animals to return to cooler refugia.
Consequences of fencing and thermal exposure Although negative interactions between herpeto- fauna and exclusion fencing have been previously acknowledged (Boarman ef al. 1994; Clark et al. 2010; Rouse et a/. 2011; Ferronato et a/. 2014; Baxter-
Gilbert et al. 2015; OMNRF 2016), we are unaware of any reports of herpetofauna being found dead or desiccated on the fencing surface. Peaden et al. (2017) suggested mesh exclusion fencing may sub- ject herpetofauna to an increased level of sun expos- ure because of time they spend trying to bypass it. Similarly, Eye et a/. (2018) suggested increased time spent navigating WEF could be detrimental because of increased heat exposure. We witnessed animals that had breached the fence line, but were unable to return to the habitat side and spent much time walk- ing the length of the fencing trying to find a breach. However, we suspect that solid fencing may partly alleviate the threat of sun exposure (especially in heavily vegetated conditions or on the habitat side). It seems likely that the mortality documented here is the result of extended heat stress leading to hyper- thermia and desiccation.
Roads constitute an ecological trap for rep- tiles because they are attractive for thermoregula- tion (Andrews et a/. 2015) and are used as nesting sites by some freshwater turtle species (Steen and Gibbs 2004). Furthermore, if animals that are initially attracted to the road’s heat for thermoregu- lation or nesting opportunities cannot avoid extreme
46 THE CANADIAN FIELD-NATURALIST
Vol. 133
Provincial Park, Ontario. a. Heavily desiccated adult Wood Frog (Lithobates sylvaticus) with ants scavenging the carcass. b. Partly desiccated adult female Common Gartersnake (Thamnophis sirtalis). Note: The unburied bottom lip of the fence is visible in photo b. c. Exclusion fencing buried by approximately 0.1 m of mixed aggregate. The completion of the fence may have contributed to fewer frogs on the road. Photos: Rachel Dillon (a,b), 2016; Sean Boyle (c), 2017.
temperatures by returning to cooler refugia, they risk desiccation and possibly death (Heatwole and Taylor 1987). Although air and fence temperatures were below the thermal maxima of 7° sirtalis (vol- untary = 35°C, critical = 38—41°C; Brattstrom 1965), on some days, these maxima were approached, and the thermal tolerance of snakes decreases if they are dehydrated (i.e., because of prolonged exposure; Ladyman and Bradshaw 2003). Particularly at risk may be amphibians and juvenile snakes because of their higher surface area to volume ratio. Although we cannot estimate how long the individuals we detected were exposed to extreme heat, even a short
time could cause heat stress, especially if the indi- viduals were already compromised or dehydrated quickly once on the fence’s bottom lip.
Potential sources of bias
We considered alternative causes of mortality. Because we did not observe obvious wounds on the carcasses, mortality from failed depredation is un- likely. Although it is possible that individuals were struck by traffic and subsequently ricocheted onto the fence, this also seems unlikely for multiple rea- sons. First, individuals were largely undamaged and roughly maintained their shape (Figure 1a,b);
TABLE 2. Average shaded air and fence temperatures recorded on detecting live and dead herpetofauna along Animex exclusion fencing in Presqu’ile Provincial Park, Ontario, in July and August 2016.
Herpetofauna Living animals
Air temperature, °C + SE
Fence temperature, °C + SE
Amphibians (” = 2) 2S Dele 28.1 + 1.0
Snakes (n = 5) 23.0 + 0.7 Ds oe we ot (a Dead animals
Amphibians (n = 10) 26.16 + 0.4 33.73 0.7
Snakes (n = 5) 2578+ 0:9 29.6 + 1.3
2019
typically, when snakes and amphibians are struck by cars, they suffer major injuries and are often flattened (S.P.B. pers. obs.). Second, we did not find individ- uals in the same desiccated condition on the grass or gravel between the fence and the road surface. Third, we saw live frogs and snakes on the bottom lip of the fencing (where we also found the dead individuals), indicating that they used, or at least travelled along the fence, possibly looking for a way to bypass it. Although our detection rates for dead individuals were likely not 100% (because of scavengers, deteri- oration, and camouflage), we assumed that the detec- tion probability was equal among all surveys and that detection rate was high because of the slow and methodical nature required for walking surveys spe- cifically targetting small-bodied and often heavily damaged carcasses (Baxter-Gilbert et al. 2017). Given that the number of animals we found on surveys (Boyle et al. 2017) generally was much higher than the number we found on the fence (reported here), it is also likely that many individuals visited the fence but were able to escape before our surveys and, as such, the risk of thermal exposure and desiccation affects a relatively small proportion of the population.
Precautions and solutions
Although the number of dead animals observed on the mitigation fencing may be inconsequential com- pared with the road mortality that the fence prevents (1.e., thousands versus dozens; S.P.B. unpubl. data), this likely heat-related source of mortality should be addressed. Exclusion fencing is often installed in areas with at-risk species, where losing even a sin- gle individual could have significant consequences for population persistence (Steen and Gibbs 2004). A white version of this fencing, which has a lower heat capacity (Animex International 2016), could be used to limit hyperthermia risk for animals. In many mitigation scenarios, however, white fencing would not be appropriate because of its conspicuousness and increased rate of photo-degradation and conse- quent reduced lifespan (D. Swensson pers. comm. 8 March 2017).
Although fence temperature may have played a role in the observed mortality, it may be less import- ant than the inability of animals to seek cooler loca- tions. In the summer following our study, several animals were detected along the now back-filled fence line, but none were found dead. Three main differences were apparent between 2016 and 2017: (1) the road side of the fencing had now been back- filled with gravel, reducing access to the road; (2) the weather was much drier in 2016 than in 2017; and (3) vegetation was cut during fence installation in 2016, whereas, in 2017, it had recovered thus providing shade (Figure Ic).
BOYLE ET AL.: DESICCATED HERPETOFAUNA ON FENCES 47
Therefore, to reduce the risk of desiccation of her- petofauna, we recommend that backfilling the fence with gravel be viewed as a time sensitive priority and, when logistically possible, backfilling take place as the fence is installed. In addition, removal of vege- tation should not occur during dry periods with high temperatures. Ramps (i.e., one-way jump-outs) built at frequent intervals in the fence to allow animals to exit the road and avoid prolonged heat exposure may also mitigate this issue; however, further investiga- tion is required. Although mortality caused by over- heating on fences is not likely to be a major source of population decline, especially when compared to the threat the fence mitigates (1.e., road mortality), it is an example of a conservation action that reduces one threat while potentially creating another and, thus, an additional issue to be considered when planning and installing road mortality mitigation devices.
Author Contributions
Writing — Original Draft: S.P.B., R.D., J.D.L., and D.L.; Writing — Review & Editing: S.P.B., R.D., J.D.L., and D.L.; Conceptualization: S.P.B. and R.D.; Investigation: S.P.B. and R.D.; Formal Analysis: S.P.B. and R.D.
Acknowledgements
Funding for this project was provided by Laur- entian University, Presqu’ile Provincial Park, On- tario Ministry of Natural Resources and Forestry (OMNRF) Species at Risk Stewardship Fund, On- tario Parks, and Friends of Presqu’ile Provincial Park. Opinions expressed in this paper are those of the au- thors and may not necessarily reflect the views and policies of the OMNRF. We thank Dean Swensson of Animex fencing for his expert opinion on white fenc- ing. All observations and handling of live animals were done ethically, under approval by the Laurentian University Animal Care Committee. Research was conducted under animal care and use permits ac- quired by J.D.L. and D.L. The authors declare no con- flicts of interest.
Literature Cited
Andrews, K.M., J.W. Gibbons, and D.M. Jochimsen. 2008. Ecological effects of roads on amphibians and rep- tiles: a literature review. Pages 121-143 in Urban Her- petology. Edited by J.C. Mitchell, R.E. Jung Brown, and B. Bartholomew. Society for the Study of Amphibians and Reptiles, Salt Lake City, Utah, USA.
Andrews, K., T.A. Langen, and R.P.J.H. Struijk. 2015. Reptiles: overlooked but often at risk from roads. Pages 271-280 in Handbook of Road Ecology. Edited by R. van der Ree, D.J. Smith, and C. Grilo. John Wiley and Sons, Chichester, United Kingdom.
Animex International. 2016. Fencing specifications and installation guides. Version 2.0. Knowle, Hampshire,
48 THE CANADIAN FIELD-NATURALIST
England. Accessed 25 July 2019. https://animexfencing. com/assets/images/Animex-Wildlife-Fencing- Specifications-Version-2.pdf.
Aresco, M.J. 2005. Mitigation measures to reduce highway mortality of turtles and other herpetofauna at a North Florida lake. Journal of Wildlife Management 69: 549— 560. https://doi.org/10.2193/0022-541x(2005)069[0549: mmtrhm]2.0.co;2
Baxter-Gilbert, J.H., J.L. Riley, S.P. Boyle, D. Lesbar- réres, and J.D. Litzgus. 2017. Turning the threat into a solution: using roadways to survey cryptic species and identify locations for conservation. Australian Journal of Zoology 66: 50-56. https://doi.org/10.1071/z017047
Baxter-Gilbert, J.H., J.L. Riley, D. Lesbarréres, and J.D. Litzgus. 2015. Mitigating reptile road mortality: fence failures compromise ecopassages effectiveness. PLoS One 10: e0120537. https://doi.org/10.1371/journal. pone.0120537
Beebee, T. 2013. Effects of road mortality and mitigation measures on amphibian populations. Conservation Biology 27: 657—668. https://do1.org/10.1111/cobi.12063
Boarman, W.I., M. Sazaki, K.H. Berry, G.O. Goodlett, W.B. Jennings, and A.P. Woodman. 1994. Measuring the effectiveness of a tortoise-proof fence and cul- verts: status report from first field season. Pages 126— 142 in Proceedings of the 1992 Desert Tortoise Council Symposium. Desert Tortoise Council, Palm Desert, California, USA.
Boyle, S.P., J.D. Litzgus, and D. Lesbarréres. 2017. Comparison of road surveys and circuit theory to pre- dict hotspot locations for implementing road-effect miti- gation. Biodiversity and Conservation 26: 3445-3463. https://doi.org/10.1007/s10531-017-1414-9
Brattstrom, B.H. 1965. Body temperature of reptiles. Amer- ican Midland Naturalist 73: 376—422.
Clark, R.W., W.S. Brown, R. Stechert, and K.R. Zamu- dio. 2010. Roads, interrupted dispersal, and genetic di- versity in timber rattlesnakes. Conservation Biology 24: 1059-1069. https://doi.org/10.1111/j.1523-1739.2009. 01439.x
Colley, M., S.C. Lougheed, K. Otterbein, and J.D. Litz- gus. 2017. Mitigation reduces road mortality of a threat- ened rattlesnake. Wildlife Research 44: 48-59. https:// doi.org/10.1071/WR16130
Dodd, Jr., C. k., W.J. Barichivich, and L.L. Smith. 2004. Effectiveness of a barrier wall and culverts in reducing wildlife mortality on a heavily traveled highway in Flo- rida. Biological Conservation 118: 619-631. https://doi. org/10.1016/j.biocon.2003.10.011
Environment and Natural Resources. 2016. Historical data: Trenton A Ontario. Government of Canada, Ottawa, Ontario, Canada. Accessed January 2019. July: https:// tinyurl.com/ yx9prbho; August: https://tinyurl.com/yxfv 6asn.
Eye, D.M, J.R. Maida, O.M. McKibban, K.W. Larson, and C.A. Bishop. 2018. Snake mortality and cover board effectiveness along exclusion fencing in British Columbia, Canada. Canadian Field-Naturalist 132: 30— 35. https://doi.org/10.22621/cfn.v132i1.2031
Ferronato, B.O., J.H. Roe, and A. Georges. 2014. Reptile bycatch in a pest-exclusion fence established for wild- life reintroductions. Journal for Nature Conservation
Vol. 133
22: 577-585. https://doi.org/10.1016/j.jnc.2014.08.014
Gibbs, J.P., and W.G. Shriver. 2002. Estimating the effects of road mortality on turtle populations. Conservation Biology 16: 1647-1652. https://doi.org/10.1046/j.1523-17 39.2002. 01215.x
Glista, D.J., T.L. DeVault, and J.A. DeWoody. 2009. A re- view of mitigation measures for reducing wildlife mor- tality on roadways. Landscape and Urban Planning 91: 1—7. https://doi.org/10.1016/j.landurbplan.2008.11.001
Heatwole, H., and J.A. Taylor. 1987. Ecology of Reptiles. Second Edition. Surrey Beatty & Sons, Chipping Nor- ton, New South Wales, Australia.
Jaeger, J.A.G., and L. Fahrig. 2004. Effects of road fen- cing on population persistence. Conservation Biology 18: 1651-1657. https://doi.org/10.1111/).1523-1739.2004. 00304.x
Ladyman, M., and D. Bradshaw. 2003. The influence of dehydration on the thermal preferences of the Western tiger snake, Notechis scutatus. Journal of Comparative Physiology B 173: 239-246. https://doi.org/10.1007/s00 360-003-0328-x
Markle, C.E., S.D. Gillingwater, R. Levick, and P. Chow- Fraser. 2017. The true cost of partial fencing. Wildlife Society Bulletin 41: 342-350. https://doi.org/ 10.1002/ wsb.767
OMNRF (Ontario Ministry of Natural Resources and Forestry). 2016. Best management practices for miti- gating the effects of roads on amphibians and reptile species at risk in Ontario. OMNRF, Toronto, Ontario, Canada.
Peaden, J.M., A.J. Nowakowski, T.D. Tuberville, K.A. BuhlImann, and B.D. Todd. 2017. Effects of roads and roadside fencing on movements, space use, and cara- pace temperatures of a threatened tortoise. Biological Conservation 214: 13—22. https://doi.org/10.1016/j.biocon. 2017.07.022
Popp, J.N., and S.P. Boyle. 2017. Railroad ecology: under- represented in science? Basic and Applied Ecology 19: 84-93. https://doi.org/10.1016/j.baae.2016.11.006
R Development Core Team. 2014. R: a language and en- vironment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria.
Rouse, J.D., R.J. Willson, R. Black, and R.J. Brooks. 2011. Movement and spatial dispersion of Sistrurus catenatus and Heterodon platirhinos: implications for interactions with roads. Copeia 2011: 443-456. https:// doi.org/10.1643/CE-09-036
Steen, D.A., and J.P. Gibbs. 2004. Effects of roads on the structure of freshwater turtle populations. Con- servation Biology 18: 1143-1148. https://doi.org/10.1111/ j.1523-1739.2004.00240.x
van der Ree, R., J.W. Gagnon, and D.J. Smith. 2015. Fencing: a valuable tool for reducing wildlife—vehicle collisions and funnelling fauna to crossing structures. Pages 159-171 in Handbook of Road Ecology. Edited by R. van der Ree, D.J. Smith, and C. Grilo. John Wiley and Sons, Chichester, United Kingdom.
Received 6 April 2018 Accepted 8 February 2019
The Canadian Field-Naturalist
Monitoring Rock Ptarmigan (Lagopus muta) populations in the Western Aleutian Islands, Alaska
Cait E. BRAUN!*, WILLIAM P. TAYLOR”, STEVEN M. EBBERT**, and Lisa M. SPITLER*
‘Grouse Inc., 5572 North Ventana Vista Road, Tucson, Arizona 85750 USA
212841 Nora Drive, Anchorage, Alaska 99515 USA
3Alaska Maritime National Wildlife Refuge, 95 Sterling Highway, Suite 101, Homer, Alaska 99603 USA ‘Current Address: P.O. Box 457, Anchor Point, Alaska 99556 USA
‘Alaska Maritime National Wildlife Refuge, Aleutian Islands Unit, P.O. Box 5251, Adak, Alaska 99546 USA “Corresponding author: sgwtp66@gmail.com
Braun, C.E., W.P. Taylor, S.M. Ebbert, and L.M. Spitler. 2019. Monitoring Rock Ptarmigan populations in the Western Aleutian Islands, Alaska. Canadian Field-Naturalist 133(1): 49-55. https:doi.org/10.22621/cfn.v13311.1948
Abstract
Knowledge of population fluctuations of Aleutian Islands Rock Ptarmigan (Lagopus muta) is limited because of isolation and access. We reviewed the available but limited data on ptarmigan counts on islands in North America and evaluated the use of point counts to estimate changes in apparent numbers of Rock Ptarmigan on three islands (Adak, Amchitka, and Attu) in the Western Aleutian Islands in Alaska. We developed a standardized protocol to count numbers of Rock Ptarmigan (males and females) seen and/or heard on 5-minute point counts at 0.8 km intervals along marked global pos- itioning system routes on Adak (2015-2017), Amchitka (2015), and Attu (2015) islands. Apparent densities based on Rock Ptarmigan seen and/or heard at 98 stops on 10 routes varied and were highest (1.9 birds per stop in 2015, 1.4 in 2016, and 1.0 in 2017) on Adak, lower (0.4 birds per stop) on Amchitka, and lowest (0.0 birds per stop) on Attu in late May—early June 2015. These island populations represent three subspecies and unique conservation units. Continuation of point-count sur- veys of these three subspecies in future years will provide baseline data over time and lead to a better understanding of any fluctuations in and synchrony among Rock Ptarmigan populations on these islands. This information is necessary for both theoretical (how are ptarmigan breeding populations regulated on islands) and practical reasons (identifying the optimal period for possible translocation to islands where ptarmigan were extirpated by introduced Arctic Fox [Vulpes lagopus]).
Key words: Rock Ptarmigan; Lagopus muta, Adak; Amchitka; Attu; Aleutian Islands; point counts; Alaska; USA
Introduction
Animal population fluctuations have long been of interest (Elton 1924), especially in insular areas that have no obvious corridors or where populations are otherwise isolated. Rock Ptarmigan (Lagopus muta) has a circumpolar distribution in northern latitudes with multiple subspecies: up to 14 in North America alone (AOU 1957; the last time subspecies were listed by the American Ornithologists’ Union). Populations of Rock Ptarmigan occupy remote areas and their distribution can be highly fragmented including on islands. Thus, documentation of population fluctua- tions over time can be difficult. It is important to moni- tor the status and population changes of species, such as Rock Ptarmigan, and to investigate any un- derlying factors affecting long-term changes (Peder- sen et al. 2005; Tesar et al. 2016). Measuring changes over time can be problematic in isolated areas such as in the Arctic and substantial efforts to learn how to ef- fectively monitor population status of ptarmigan have
been made (Pelletier and Krebs 1997; Bart et a/. 2011).
There is some evidence that Rock Ptarmigan are cyclic on islands (Iceland; Magnusson ef al. 2004), but population trends are poorly documented in North America (Weeden 1965; Cotter 1999; Taylor 2013). Peaks in Rock Ptarmigan cycles may repre- sent a 10-fold increase from lows as discussed by Holder and Montgomerie (1993: 15), who cited stud- ies in Scotland (Watson 1965) and Canada (Cotter 1991). Grouse cycles may be correlated with changes in their predator numbers or parasites and not only immigration or emigration from the local popula- tion (Dobson and Hudson 1992; Hudson et al. 1992; Cattadori et al. 2005).
As many as seven to eight subspecies of Rock Ptarmigan have been described from the Aleutian Archipelago, Alaska (AOU 1957). This number has been condensed into four groups (L. m. evermanni, L. m. townsendi, L. m. atkhensis, and L. m. nelsoni) of which ne/soni also occur on mainland Alaska to
A contribution towards the cost of this publication has been provided by the Thomas Manning Memorial Fund of the Ottawa
Field-Naturalists’ Club.
©This work is made available under the Creative Commons CCO 1.0 Universal Public Domain Dedication (CCO 1.0).
50 THE CANADIAN FIELD-NATURALIST
the east (Gibson and Kessel 1997; Montgomerie and Holder 2008). The evermanni subspecies occurs in the Near Islands (Attu and Agattu); townsendi occurs in the Rat Islands, including Amchitka and Kiska islands, while atkhensis occurs in the Andreanof Islands group including Adak, Tanaga to Atka, and possibly other islands. We studied three subspecies (atkhensis, evermanni, and townsend), all of which are considered endemic groups or unique conserva- tion units (Pruett et al. 2010).
Pelletier and Krebs (1997) tested line transect methods to estimate densities of breeding male ptar- migan and concluded they cannot be censused in small areas alone (size of their multiple study sites ranged from 3.0 to 13.5 km?) as the results were too variable. Others (Brodsky and Montgomerie 1987; Cotter 1999; Watson et al. 2000; Favaron et al. 2006; Pedersen et a/. 2012) used methods such as marking and reobservation, point transects, and distance sam- pling to estimate changes in population size. Bart et al. (2011) experimented with use of helicopter and fixed-wing aircraft to survey ptarmigan (and other Species) over large areas in northern Canada and Alaska. All of these methods are either labour inten- sive and/or costly.
The Breeding Bird Survey protocol was developed in the early 1960s to estimate population trends in bird populations over time across large areas and variable habitats in North America (Bystrak 1981; Robbins et al. 1986; Droege 1990). It initially used 3-minute count intervals along routes with 50 stops at 0.8 km
i—«&— Attu ei Bering Sea mae een et ye > cpt, “Zaee— Adak Sp Nee 300 km “a 25 ae Oe “4
Pacific Ocean
Vol. 133
intervals with routes being surveyed once each year, during the breeding period. More recently 5-minute point counts have been used to better represent popu- lation indices of selected species (Ralph et al. 1995). All birds (males and females) both seen and heard are recorded at point-count stops.
Male Rock Ptarmigan during the breeding period (late April to early June) are conspicuous (they can range in colour from white to mottled shades of light brown to almost black [Attu] with white bellies and wings), perch up, and make flights from conspicuous sites while calling as they advertise and defend terri- tories (Holder and Montgomerie 1993; Pelletier and Krebs 1997). Males in late May and early June can be solitary or paired with females, which are drab brown (in flight they have white wings) or mottled and in- conspicuous in many, if not most, situations (some may be on nests).
Our objectives were to review the available liter- ature on surveys of Rock Ptarmigan on three islands in the Western Aleutian Islands and develop and im- plement a 5-minute point count protocol to estimate trends in breeding populations of Rock Ptarmigan on Adak, Amchitka, and Attu islands in the Western Aleutian Islands (Figure 1).
Study Area
We reviewed the published and other available lit- erature on Rock Ptarmigan (no other species of ptar- migan occur on these islands) on Adak (51.883°N, 176.65°W), Amchitka (51.35°-51.65°N, 178.617°—
Figure 1. Aleutian Archipelago, Alaska showing Adak, Amchitka, and Attu islands.
2019
179.483°E), and Attu (52.85°N, 173.183°E) in the Western Aleutian Islands, Alaska (Appendix S1). Areas surveyed on the three islands by us and others were similar low elevation sites (i.e., marine and stream terraces) adjacent to rarely-used trails (Am- chitka and Attu) and occasionally used roads (Adak) that tended to follow coastal areas. The islands vary in size from ~300 km? (Amchitka) to 711 km? (Adak) and 894 km? (Attu). Adak is in the Andréanof group while Amchitka is in the Rat Island group and Attu is in the Near Islands. All are bounded by the North Pacific Ocean to the south and west and the Bering Sea to the north and east. The three islands are dis- tant from each other with Amchitka being 301 km southwest of Adak that is 720 km east of Attu. There are no human residents on Amchitka and Attu and the resident population on Adak is variable and <100 people.
The geology of the three islands is complex with multiple inactive volcanos and volcanic flows as well as past glacial and marine erosion (Coats 1956; Fraser and Snyder 1959; Powers etal. 1960). Topography var- ies from gently sloping marine terraces to undulating tundra ranging to rugged mountains. We surveyed ptarmigan at an elevation of 10 to 300 m on all three islands. Lower and well-drained sites are occupied by grasses and sedges (Calamagrostis spp., Leymus spp., Carex spp.), and low-growing forbs including Caltha spp., Ranunculus spp., and Lupinus spp. with higher slopes dominated by crowberry (Empetrum spp.), Empetrum-Cladonia tundra, Cladina spp. lichens, and other mosses with some low-growing heather
BRAUN ET AL.: ROCK PTARMIGAN IN THE WESTERN ALEUTIAN ISLANDS 51
(Cassiope spp., Phyllodoce spp.), willow (Salix spp.), and Kamchatka Rhododendron (Rhododendron cam- tschaticum Pallas) shrubs (Amundsen and Clebsch 1971; Everett 1971; White et al. 1977).
The climate on all three islands is moist marine with frequent high velocity winds, rain, and fog (Gates etal. 1971). Mean daily average temperatures vary seasonally ranging from 0.4°C in January to 11°C in August. Daily (3.9°C in all seasons) and sea- sonal (9.4°C) ranges in temperature are limited (Arm- strong 1971, 1977). Wind speeds are highly variable, and the mean annual precipitation ranges from 83 to 139 cm, depending on the island, with June and July being the months with lowest precipitation (Weather- base 2015).
Methods
We established and conducted 5-minute point stations (protocol in Table 1) in 2015 following Ralph et al. (1995) at 0.8 km intervals along trails and roads on all three islands (dates in Table 2). All routes were conducted using an all-terrain vehicle. Starting points were at trail junctions or easily rec- ognized local features and were recorded as global positioning system coordinates (on file with Alaska Maritime National Wildlife Refuge, Homer, Alaska, USA). Point-count routes were in areas where at least four stops at 0.8 km intervals could be established. There were four routes on Adak with from six to 17 stops, three routes on Amchitka with from four to 21 stops, and three routes with from four to seven stops on Attu (Table 2).
TABLE 1. Protocol for Rock Ptarmigan (Lagopus muta) surveys on Adak, Amchitka, and Attu islands, Western Aleutians,
Alaska.
5-minute point counts
Count and record all Rock Ptarmigan seen (as male or female) or heard at each point stop. Rarely, the vehicle stopped near a ptarmigan which did not call or flush during the 5-minute count but flushed when the vehicle
departed. These birds were included in the count.
Use of two counters is best (one front and one back). A central spot should be chosen. Consolidate and record totals at end of each point count before returning to the vehicle.
Conduct point-count route prior to 10:00 AM.
Try to avoid high winds (>30 km per hr) and heavy rain.
Adak (use GPS locations at >0.8 km points)
Old Loran Road (10 stops).
Finger Cove (six stops).
Navfac Creek to past Clam Cove (17 stops). Lake Andrew (six stops).
Amchitka (use GPS locations at >0.8 km points) Jones Lake/Engineer Road (17 stops). Charlie-Baker Taxiway south (four stops). Infantry Road (21 stops).
Attu (use GPS locations at >0.8 km points) Casco Cove to old airstrips (four stops).
Engineer Hill (top towards Peace monument) from Massacre Creek Beach Trail (seven stops).
Navytown (two stops) to Quonset Valley (four stops).
52
THE CANADIAN FIELD-NATURALIST
Vol. 133
TABLE 2. Point-count (5-minute) surveys of Rock Ptarmigan (Lagopus muta, RP) on Adak, Amchitka, and Attu islands, Alaska, 2015-2017.
Island Routes Date
Adak 2015 Finger Bay 29 May 2015 Navfac Creek-Clam Lagoon 29 May 2015 Old Loran Station Road 30 May 2015 Andrew Lake 30 May 2015
Mean
Adak 2016 Finger Bay 18 May 2016 Navfac Creek-Clam Lagoon 3 June 2016 Old Loran Station Road 27 May 2016 Andrew Lake 20 May 2016
Mean
Adak 2017 Finger Bay 1 June 2017 Navfac Creek-Clam Lagoon 29 May 2017 Old Loran Station Road 30 May 2017 Andrew Lake 3 June 2017
Mean
Amchitka Infantry Road 9 June 2015 Jones Lake-Engineer Road 9 June 2015 Charlie to Baker Taxiway 9 June 2015
Mean
Attu Old Loran/Old Runways 3 June 2015 Massacre to Top Engineer 4 June 2015 Navytown to Quonset Valley 4 June 2015
Mean
n points RP seen/heard Birds/Stop 6 6 1.0 17 12 0.7 10 49 49 6 6 1.0 1:9 3 0.5 17 16 1.4 10 10 21 6 10 17 1.4 6 0 0.0 17 16 0.9 10 16 1.6 a 4 1.3 1.0 21 12 0.6 17 3 0.2 4 0 0.0 0.4 4 0 0.0 7 0 0.0 6 0 0.0 0.0
*High winds did not allow completion or resurveys of three of six routes.
Results
Rock Ptarmigan were heard or seen on all but one (2017 only) point-count routes on Adak and two of three on Amchitka but none was recorded on any of the three point-count routes on Attu (Table 2). However, one ptarmigan pair was seen and four males were heard prior to establishment of point- count routes but not near any of the point-count stops on Attu. Numbers of ptarmigan per stop recorded on point-count routes were highest (1.9, 1.4, 1.0; 2015— 2017, respectively) on Adak, lower (0.4) on Amchitka, and non-existent (0.0) on Attu.
Discussion
A literature review of surveys and reports of Rock Ptarmigan on Adak, Amchitka, and Attu Islands re- vealed that Rock Ptarmigan were mentioned but that few surveys occurred over time with the exception of Amchitka with less information for Attu and Adak (Appendix S1). Large populations were documented for Amchitka (White et al. 1977) and Attu (Braun ef al. 2014) over short periods. Overall, the literature suggests populations of Rock Ptarmigan on the three islands were historically low, especially on Attu.
Our point counts indicate the Rock Ptarmigan population was highest on Adak (2015-2017), lower in 2015 on Amchitka, and very low on Attu in 2015. Our point-count survey data on Attu in 2015 con-
firmed the ongoing decline on this island reported by Braun ef al. (2014) from an intensive survey area con- ducted in 2003-2009. No effort was made to quantify ptarmigan numbers on Attu at higher elevations but ptarmigan were common at lower elevations in 2003-— 2005 (Braun et al. 2014).
The areas that we surveyed on all three islands had similar relief (low marine and stream terraces), were highly disturbed in the mid 1940s and 1950s (Amchitka and Attu) to the late 1990s (Adak), but are now well vegetated with low to non-existent re- cent human occupation. The three islands have simi- lar predator assemblages (no ground mammals except rats, but with eagles, falcons, gulls, jaegers, owls, and ravens), but we have no estimate of densities. We have no basis to expect that predators (Gilg et al. 2003; Therrien et al. 2014) affected ptarmigan numbers on the three islands in 2015. We also detected no evi- dence that male aggressive behaviour was a factor at the densities we observed (Mougeot ef al. 2003). The possibility that herbivory (Sinclair et a/. 1988) could affect populations of ptarmigan across islands at substantial distances from each other through plant compounds was considered but was deemed unlikely because of isolation, few deciduous shrubs, and dis- tances involved.
We documented three different levels of abun- dance of Rock Ptarmigan on Adak (high), Amchitka
2019
(lower), and Attu (very low) in 2015. The apparent, long-term decline on Attu since 2003 (Braun ef al. 2014) appears to have stabilized from 2009 to 2014 (Braun et al. 2014). We agree with the hypothesis of Sandercock et al. (2005) that animal cycles in Arctic marine and terrestrial environments are most likely affected by latitudinal gradients in the north and alti- tudinal gradients elsewhere. The islands we studied are surrounded by the North Pacific Ocean and the Bering Sea and we worked at or below 300 m, thus the birds on these high latitude islands are mostly af- fected by the marine environment. We further agree that systematic surveys (Tesar et al. 2016) to detect trends in breeding populations (Nichols and Williams 2006) of different populations of Rock Ptarmigan are needed at least at 3-5 year intervals for both theor- etical and practical reasons and should be able to de- tect population changes. It is possible that further translocations, similar to the one from Attu to Agattu in 2003-2005 (Kaler et al. 2010), may be considered to re-establish populations where they were extirpated by introduced Arctic Fox (Vulpes lagopus). Braun et al. (2014) documented the immediate recovery of ptarmigan after removal of Arctic Fox. But before such future translocations can be considered, a better survey protocol was needed to determine population status and trends of ptarmigan on these other islands. Knowing when ptarmigan populations may be ‘high’, especially if they cycle, also would be important so ad- equate numbers can be captured for immediate release on islands currently unoccupied by Rock Ptarmigan. This should reduce costs and improve chances for suc- cess of the transplants. Understanding fluctuations of Rock Ptarmigan populations, if they occur, is also important in the Arctic as the results from studies on islands may have relevance to ‘cycles’ and manage- ment of species of ptarmigan in mainland areas. Point counts may be the most efficient and least expensive method to obtain standardized data (all birds seen and/or heard) for Rock Ptarmigan in areas with road or trail systems because large areas can be surveyed with few personnel. Early counts (May) should provide an opportunity to record more fe- males than counts in early to mid June when females will be nesting. The three islands of Adak, Amchitka, and Attu each have different Rock Ptarmigan sub- species of conservation importance (Pruett ef al. 2010) and their population dynamics deserve further study. There is a continuing need for population data to provide insight into whether cycles exist and their periodicity and synchronicity among islands.
Author Contributions Conceptualization: C.E.B., W.PT., and S.M.E.; Funding Acquisition: S.M.E.; Investigation: C.E.B.,
BRAUN ET AL.: ROCK PTARMIGAN IN THE WESTERN ALEUTIAN ISLANDS 53
W.P.T., S.M.E., and L.M.S.; Writing — Original Draft: C.E.B; Writing — Review & Editing: C.E.B., W.PT., S.M.E., and L.M.S.
Acknowledgements
We thank the crew of U.S. Fish and Wildlife Ser- vice research ship Tiglax for safe transit along the North Pacific Ocean and the Bering Sea and espe- cially the administrators of the Alaska Maritime National Wildlife Refuge for support of our efforts over a period of years. We acknowledge the help of the reviewers and the Editor for improvements in the manuscript. The findings and conclusions in this arti- cle are those of the author(s) and do not necessar- ily represent the views of the U.S. Fish and Wildlife Service.
Literature Cited
Amundsen, C.C., and E.E.C. Clebsch. 1971. Dynamics of the terrestrial ecosystem vegetation of Amchitka Island, Alaska. Bioscience 21: 619-623. https://doi.org/ 10.2307/1295734
AOU (American Ornithologists’ Union). 1957. Check- list of North American birds. Fifth Edition. American Ornithologists’ Union, Washington, DC, USA.
Armstrong, R.H. 1971. Physical climatology of Amchitka Island, Alaska. Bioscience 21: 607—609. https://do1.org/ 10.2307/1295730
Armstrong, R.H. 1977. Weather and climate. Pages 53— 58 in The Environment of Amchitka Island. Edited by M.L. Merritt and R.G. Fuller. U.S. Energy Research and Development Administration, TID-26712. U.S. De- partment of Energy, Washington, DC, USA.
Bart, J., M. Fuller, P. Smith, and L. Dunn. 2011. Use of large-scale, multi-species surveys to monitor Gyr- falcon and ptarmigan populations. Pages 263-271 in Gyrfalcons and Ptarmigan in a Changing World. Edited by R.T. Watson, T.J. Cade, M. Fuller, G. Hunt, and E. Potapov. The Peregrine Fund, Boise, Idaho, USA. Accessed 2 March 2018. http://www.peregrinefund.org/ subsites/conference-gyr/proceedings/.