title: Demography of an apex predator at the edge of its range: impacts of changing sea ice on polar bears in Hudson Bay.
abstract: Changes in the abundance and distribution of wildlife populations are common consequences of historic and contemporary climate change. Some Arctic marine mammals, such as the polar bear (Ursus maritimus), may be particularly vulnerable to such changes due to the loss of Arctic sea ice. We evaluated the impacts of environmental variation on demographic rates for the Western Hudson Bay (WH), polar bear subpopulation from 1984 to 2011 using live-recapture and dead-recovery data in a Bayesian implementation of multistate capture-recapture models. We found that survival of female polar bears was related to the annual timing of sea ice break-up and formation. Using estimated vital rates (e.g., survival and reproduction) in matrix projection models, we calculated the growth rate of the WH subpopulation and projected population responses under different environmental scenarios while accounting for parametric uncertainty, temporal variation, and demographic stochasticity. Our analysis suggested a long-term decline in the number of bears from 1185 (95% Bayesian credible interval [BCI] = 993-1411) in 1987 to 806 (95% BCI = 653-984) in 2011. In the last 10 yr of the study, the number of bears appeared stable due to temporary stability in sea ice conditions (mean population growth rate for the period 2001-2010 = 1.02, 95% BCI = 0.98-1.06). Looking forward, we estimated long-term growth rates for the WH subpopulation of ~1.02 (95% BCI = 1.00-1.05) and 0.97 (95% BCI = 0.92-1.01) under hypothetical high and low sea ice conditions, respectively. Our findings support previous evidence for a demographic linkage between sea ice conditions and polar bear population dynamics. Furthermore, we present a robust framework for sensitivity analysis with respect to continued climate change (e.g., to inform scenario planning) and for evaluating the combined effects of climate change and management actions on the status of wildlife populations.
authors.affiliation: Wildlife Research Division, Science & Technology Branch, Environment and Climate Change Canada, CW405 Biological Sciences Centre, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Lunn
authors.affiliation: Colorado Cooperative Fish and Wildlife Research Unit, Colorado State University, Fort Collins, Colorado, 80523, USA.|Patuxent Wildlife Research Center, US Geological Survey, 12100 Beech Forest Road, Laurel, Maryland, 20708, USA.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Servanty
authors.affiliation: Marine Mammals Management, US Fish and Wildlife Service, 1011 East Tudor Road, Anchorage, Alaska, 99503, USA.
authors.forename: Eric V
authors.initials: EV
authors.lastname: Regehr
authors.affiliation: Patuxent Wildlife Research Center, US Geological Survey, 12100 Beech Forest Road, Laurel, Maryland, 20708, USA.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Converse
authors.affiliation: Wildlife Research Division, Science & Technology Branch, Environment and Climate Change Canada, CW405 Biological Sciences Centre, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.
authors.forename: Evan
authors.initials: E
authors.lastname: Richardson
authors.affiliation: Wildlife Research Division, Science & Technology Branch, Environment and Climate Change Canada, CW405 Biological Sciences Centre, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.|Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.
authors.forename: Ian
authors.initials: I
authors.lastname: Stirling
mesh_terms: D000818:Animals; D001110:Arctic Regions; D061006:Bays; D057231:Climate Change; D017753:Ecosystem; D005260:Female; D046448:Ice Cover; D008297:Male; D008954:Models, Biological; D011157:Population Dynamics; D013997:Time Factors; D001503:Ursidae / Q000502:physiology*
keywords: 
  Ursus maritimus
  ; Bayesian; Hudson Bay, Canada; abundance; climate change; multistate capture-recapture; polar bear (Ursus maritimus); population growth rate; reproduction; sea ice; survival