Multiscale wolf predation risk for elk does migra

Authors: Mark Hebblewhite Evelyn H Merrill

Publish Date: 2007/02/08

Volume: 152, Issue: 2, Pages: 377-387

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Abstract

While migration is hypothesized to reduce predation risk for ungulates there have been few direct empirical tests of this hypothesis Furthermore few studies examined multiscale predation risk avoidance by migrant ungulates yet recent research reveals that predator–prey interactions occur at multiple scales We test the predation risk reduction hypothesis at two spatial scales in a partially migratory elk Cervus elaphus population by comparing exposure of migrant and resident elk to wolf Canis lupus predation risk We used GPS and VHF telemetry data collected from 67 migrant and 44 resident elk over the summers of 2002–2004 in and adjacent to Banff National Park BNP Canada We used wolf GPS and VHF telemetry data to estimate predation risk as a function of the relative probability of wolf occurrence weighted by a spatial density model that adjusted for varying pack sizes We validated the predation risk model using independent data on wolfkilled elk and showed that combining wolf presence and spatial density best predicted where an elk was likely to be killed Predation risk on summer ranges of migrant elk was reduced by 70 compared to within resident elk summer ranges Because wolves avoided areas near high human activity however finescale selection by resident elk for areas near high human activity reduced their predation risk exposure to only 15 higher than migrants a difference significant in only one of three summers Finally during actual migration elk were exposed to 17 times more predation risk than residents even though migration was rapid Our results support the hypothesis that largescale migrations can reduce predation However we also show that where smallscale spatial variation in predation risk exists nonmigratory elk may equally reduce predation risk as effectively as migrants under some circumstancesFunding was provided by the Alberta Conservation Association Alberta Cooperative Conservation Research Unit Alberta Enhanced Career Development Alberta Sustainable Resource Development the Canon National Parks Science Scholarship for the Americas MH Centre for Mathematical Biology Challenge Grants in Biodiversity Foothills Model Forest Foundation for North American Wild Sheep Marmot Mountain Equipment Coop Environment Fund National Sciences and Engineering Research Council NSERC CRO grant 26109102 Parks Canada Patagonia Rocky Mountain Elk Foundation Sundre Forest Products Limited Weyerhauser Inc and the University of Alberta We thank the staff and biologists of the Ya Ha Tinda ranch Parks Canada and Alberta Fish and Wildlife For animal capture services we thank T Shury DVM and C Wilson and T Vandenbrink and M Dupuis for fixedwing telemetry monitoring We thank the numerous field assistants for invaluable help during this study especially C Mueller L Thurston H Spaedtke and H Keta Finally we thank H Beyer S Boutin C CassadySt Clair J Frair C Gates C Jerde F Messier L Morgantini M Musiani D Simader and C White for helpful discussion and reviews of past drafts of this manuscript All research was conducted in accordance with and obtained authorization from appropriate University Provincial and Federal legislation and policies

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