Novel range overlap of three ursids in the Canadian subarctic

Douglas Andrew Clark,Kiva Olson,Chelsea Oliphant-Reskanski,Michel P Laforge,Ryan Brook,Danielle Rivet

doi:10.1139/as-2018-0013

Abstract

We describe for the first time in the peer-reviewed literature observations of American black bear (Ursus americanus Pallas, 1780), grizzly bear (Ursus arctos Linnaeus, 1758), and polar bear (Ursus maritimus Phipps, 1774) at the same locations. Using remote cameras we documented 401 bear-visits of all three species at three camps in Wapusk National Park, Canada, from 2011–2017. These observations add to a growing body of evidence that grizzlies are undergoing a substantial range increase in northern Canada and the timing of our observations suggests denning locally. Polar and grizzly bears are of conservation concern regionally and internationally, so from the literature we assessed the potential effects on conservation efforts from interactions between these three species. In aggregate, those effects are likely to be positive for grizzlies and weakly negative for black and polar bears; further research is needed. Range overlap of these three species in this dynamic ecotonal region should not be viewed as a threat to any of them, but rather as an ecological response to environmental change that needs to be better understood.

Highlights

This paper describes, for the first time, observations of North America’s three ursid species — American black bears (Ursus americanus Pallas, 1780), grizzly bears (Ursus arctos Linnaeus, 1758), and polar bears (Ursus maritimus Phipps, 1774) — co-occurring in the same locations
Wapusk National Park has long been known as important seasonal polar bear habitat so it is unsurprising they were commonly observed all three camps, or that their observed camp visitation pattern is consistent with previous studies of their terrestrial distribution on the west coast of Hudson Bay (Stirling et al 1977; Latour 1981; Derocher and Stirling 1990; Clark and Stirling 1998; Towns et al 2010)
The distribution and ecology of the other two species in Wapusk — grizzlies — are far less well understood. These species appeared to differ in their behavioural responses to the camps, they are unlikely to have been sampled at different intensities as our cameras were fixed and had a constant detection radius (Laforge et al 2017)

Summary

Introduction

This paper describes, for the first time, observations of North America’s three ursid species — American black bears (Ursus americanus Pallas, 1780), grizzly bears (Ursus arctos Linnaeus, 1758), and polar bears (Ursus maritimus Phipps, 1774) — co-occurring in the same locations These observations were made during an ongoing study focusing on polar bear– human interactions in Wapusk National Park, MB, Canada. A large, but varying, proportion of polar bears from the Western Hudson Bay subpopulation spend summer and autumn (typically July–November) ashore in Wapusk due to complete annual melting of the sea ice (Stirling et al 1977, 2004) On shore those bears segregate by age and sex classes, with most bears remaining on the coast and pregnant females traveling inland to a maternity denning area where they will overwinter and give birth (Clark et al 1997; Clark and Stirling 1998). Polar bears are provincially listed as threatened and are highly vulnerable to a warming Arctic climate, the Western Hudson Bay subpopulation is considered temporarily stable (Lunn et al 2016)

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Conclusion