Capture-based studies of the Western Hudson Bay (WH) polar bear population in Canada have reported declines in abundance, survival, and body condition, but these findings are inconsistent with the perceptions of local people. To address this uncertainty about current status, we conducted a comprehensive aerial survey of this population during August, 2011, when the region was ice-free and bears were on shore. We flew a combination of overland transects oriented perpendicular to the coastline, coastal transects parallel to shore, and transects across small islands. We used distance sampling and sight-resight protocols to estimate abundance. Bears were concentrated along the coast in central and southern Manitoba and Ontario portions of the population, although sightings >10. km inland were not uncommon in central Manitoba. We analyzed 2 combinations of data and derived an abundance estimate of 1030 bears (95% CI: ~754-1406). This figure is similar to a 2004 mark-recapture estimate but higher than projections indicating declining abundance since then. Our results suggest that mark-recapture estimates may have been negatively biased due to limited spatial sampling. We observed large numbers of bears summering in southeastern WH, an area not regularly sampled by mark-recapture. Consequently, previous mark-recapture estimates are not directly comparable to our aerial survey of the entire population. Whereas our results do not necessarily contradict the reported declines in this population, we believe that improvements are needed in monitoring, and methodological limitations and inconsistencies must be resolved to accurately assess status and the impacts of climate change.
Bibliographical noteFunding Information:
We thank Mitch Campbell (Government of Nunavut, Department Of Environment), Leah Muckpah, Leo Ikakhik and Peter Mikeeuneak (Arviat Hunting and Trapping Organization), Norman Ford, Tommy Kabuitok and Ralph Nukitut (Rankin HTO), Joe Savikataaq, Jack Batstone (Manitoba Conservation), Rodney Redhead (Parks Canada) and Jonathan Talon (Hudson Bay Helicopters) for their work as observers and data collectors during the survey. Input on survey design was provided by members of the Arviat, Rankin Inlet, Whale Cove Hunting and Trapping Organizations during a July, 2010 workshop in Churchill and at the Kivalliq Wildlife Board in June, 2011. D. Lee and B. Dean (Nunavut Tunngavik Incorporated) also contributed to survey design. J. Laake and T. Arnold provided valuable statistical advice. T. Arnold, I. Stirling and 4 anonymous reviewers provided useful comments on earlier drafts of this manuscript. Financial support was provided by the Government of Nunavut (Department of Environment), Environment Canada, the Nunavut Wildlife Management Board, and Indian and Northern Affairs Canada. In-kind support was received from Manitoba Conservation, Parks Canada, and the Ontario Ministry of Natural Resources. S. Stapleton received additional support from the University of Minnesota. This study was conducted under research permits from Parks Canada (Wapusk National Park Research and Collection Permit Number WAP-2011-8340) and the Government of Nunavut (Wildlife Research Permit Number 2011-040). Field protocols were approved by the Institutional Animal Care and Use Committee at the University of Minnesota (Permit Number 0907A68891).
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- Abundance estimation
- Aerial survey
- Distance sampling
- Hudson Bay
- Marine mammal