Snow track counts for density estimation of mammalian predators in the boreal forest
Mark O’Donoghue
A * , Brian G. Slough B , Kim Poole C , Stan Boutin D , Elizabeth J. Hofer E , Garth Mowat F G , Dennis Murray H and Charles J. Krebs E
+ Author Affiliations
- Author Affiliations
A Environment Yukon, Fish and Wildlife Branch, Box 310, Mayo, YT Y0B 1M0, Canada.
B 37-71 Aksala Drive, Whitehorse, YT Y1A 0M5, Canada.
C Aurora Wildlife Research, 1918 Shannon Point Road, Nelson, BC V1L 6K1, Canada.
D Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.
E Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
F B.C. Ministry of Forests, Fish and Wildlife Branch, Suite 401, 333 Victoria Street, Nelson, BC V1L 4K3, Canada.
G Department of Earth, Environmental and Geographic Sciences, University of British Columbia, Kelowna, BC V1V 1V7, Canada.
H Department of Biology, Trent University, 1600 West Bank Drive, Peterborough, ON K9L 0G2, Canada.
Wildlife Research - https://doi.org/10.1071/WR21159
Submitted: 30 October 2021 Accepted: 13 September 2022 Published online: 4 October 2022
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing
Abstract
Context: Methods for estimating density of meso-carnivores in northern ecosystems are labour intensive and expensive to implement if mark–recapture and radio collaring are used. One alternative is to count tracks in the snow along transects as an index of density, but this method has been criticised as imprecise and lacking validation.
Aims: We aimed to examine the utility of track counts along snowmobile trails in the snow for measuring changes in populations of Canada lynx and coyotes in the boreal forest of north-western Canada.
Methods: We compared winter track counts of Canada lynx at three study sites and of coyotes at one site with concurrent estimates of density based on locations of radio-collared animals and estimates of numbers of uncollared animals from three 7–9-year studies in the Yukon and Northwest Territories, during a period of cyclical population fluctuations.
Key results: Snow track counts were positively correlated (r2 = 0.83) with density of Canada lynx, estimated by live trapping and radio collaring in the three survey areas. Coyotes also showed a clear relationship (r2 = 0.80) between known density and snow track counts, but track counts were strongly affected by season, with much higher counts in the early winter when snow was shallower. This indicates the need to control for season or snow depth when using track counts as indices of coyote abundance. We recommend sample sizes of at least 10 track counts per winter along a 25-km transect to maximise precision.
Conclusions: Snow track counts are a relatively simple, inexpensive method of concurrently tracking abundance of multiple species of meso-carnivores. These data indicate that track counts may be reliably used to monitor trends in numbers, but we suggest site-specific validation of the regressions reported here between tracks and animal abundance are required to translate these indices into estimates of density.
Implications: Track counts have the potential to be an affordable alternative to more intensive methods of monitoring trends in abundance of medium-sized mammals, for purposes such as management of harvest or to measure the success of programs to increase or reduce population abundance.
Keywords: abundance indices, Canada lynx, census methods, coyote, Kluane Lake, mammalian meso-predators, snow tracking, Yukon.
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