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Evan S. Richardson

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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)...
Categories: Publication; Types: Citation; Tags: Ecological Applications
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In the southern Beaufort Sea of the United States and Canada, prior investigations have linked declines in summer sea ice to reduced physical condition, growth, and survival of polar bears (Ursus maritimus). Combined with projections of population decline due to continued climate warming and the ensuing loss of sea ice habitat, those findings contributed to the 2008 decision to list the species as threatened under the U.S. Endangered Species Act. Here, we used mark–recapture models to investigate the population dynamics of polar bears in the southern Beaufort Sea from 2001 to 2010, years during which the spatial and temporal extent of summer sea ice generally declined. Low survival from 2004 through 2006 led to...
Categories: Publication; Types: Citation; Tags: Ecological Applications
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The Southern Hudson Bay (SH) population of polar bears (Ursus maritimus) resides in a seasonal sea ice environment and is the most southerly population in the species’ range. Therefore, SH polar bears may be among the first to show negative effects associated with climate warming and consequent loss of sea ice. Polar bears in the neighboring Western Hudson Bay (WH) population have declined significantly in body condition since the mid-1980s, and a recent study indicated that the size of the WH population declined by about 22% between 1987 and 2004. Similarly, SH bears have shown a significant decline in body condition since the mid-1980s, and an assessment of the current status of the SH population was therefore...
Categories: Publication; Types: Citation; Tags: Administrative Report
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We evaluated the demography and population status of the Western Hudson Bay (WH) polar bear subpopulation for the period 1984-2011, using live-recapture data from research studies and management actions, and dead-recovery data from polar bears harvested for subsistence purposes or removed during human-bear conflicts. We used a Bayesian implementation of multistate capture-recapture models, coupled with a matrix-based demographic projection model, to integrate several types of data and to incorporate sampling uncertainty, and demographic and environmental stochasticity across the polar bear life cycle. This approach allowed for estimation of a suite of vital rates, including survival and reproduction. These vital...
Categories: Publication; Types: Citation
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