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Ware JV, Rode KD, Bromaghin JF, Douglas DC, Wilson RR, Regehr EV, Amstrup SC, Durner GM, Pagano AM, Olson J, Robbins CT, Jansen HT. Habitat degradation affects the summer activity of polar bears. Oecologia 2017; 184:87-99. [PMID: 28247129 DOI: 10.1007/s00442-017-3839-y] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 02/09/2017] [Indexed: 01/24/2023]
Abstract
Understanding behavioral responses of species to environmental change is critical to forecasting population-level effects. Although climate change is significantly impacting species' distributions, few studies have examined associated changes in behavior. Polar bear (Ursus maritimus) subpopulations have varied in their near-term responses to sea ice decline. We examined behavioral responses of two adjacent subpopulations to changes in habitat availability during the annual sea ice minimum using activity data. Location and activity sensor data collected from 1989 to 2014 for 202 adult female polar bears in the Southern Beaufort Sea (SB) and Chukchi Sea (CS) subpopulations were used to compare activity in three habitat types varying in prey availability: (1) land; (2) ice over shallow, biologically productive waters; and (3) ice over deeper, less productive waters. Bears varied activity across and within habitats with the highest activity at 50-75% sea ice concentration over shallow waters. On land, SB bears exhibited variable but relatively high activity associated with the use of subsistence-harvested bowhead whale carcasses, whereas CS bears exhibited low activity consistent with minimal feeding. Both subpopulations had fewer observations in their preferred shallow-water sea ice habitats in recent years, corresponding with declines in availability of this substrate. The substantially higher use of marginal habitats by SB bears is an additional mechanism potentially explaining why this subpopulation has experienced negative effects of sea ice loss compared to the still-productive CS subpopulation. Variability in activity among, and within, habitats suggests that bears alter their behavior in response to habitat conditions, presumably in an attempt to balance prey availability with energy costs.
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Affiliation(s)
- Jasmine V Ware
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, 99164-7620, USA.
| | - Karyn D Rode
- Alaska Science Center, U.S. Geological Survey, 4210 University Dr., Anchorage, AK, 99508, USA
| | - Jeffrey F Bromaghin
- Alaska Science Center, U.S. Geological Survey, 4210 University Dr., Anchorage, AK, 99508, USA
| | - David C Douglas
- Alaska Science Center, U.S. Geological Survey, 250 Egan Drive, Juneau, AK, 99801, USA
| | - Ryan R Wilson
- U.S. Fish and Wildlife Service, 1011 East Tudor Road, MS 341, Anchorage, AK, 99503, USA
| | - Eric V Regehr
- U.S. Fish and Wildlife Service, 1011 East Tudor Road, MS 341, Anchorage, AK, 99503, USA
| | | | - George M Durner
- Alaska Science Center, U.S. Geological Survey, 4210 University Dr., Anchorage, AK, 99508, USA
| | - Anthony M Pagano
- Alaska Science Center, U.S. Geological Survey, 4210 University Dr., Anchorage, AK, 99508, USA
| | - Jay Olson
- Department of Plant and Wildlife Sciences, Brigham Young University, 5049 LSB, Provo, UT, 84602, USA
| | - Charles T Robbins
- School of the Environment and School of Biological Sciences, Washington State University, Pullman, WA, 99164-4236, USA
| | - Heiko T Jansen
- Department of Integrative Physiology and Neuroscience, Washington State University, Pullman, WA, 99164-7620, USA
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Malenfant RM, Davis CS, Cullingham CI, Coltman DW. Circumpolar Genetic Structure and Recent Gene Flow of Polar Bears: A Reanalysis. PLoS One 2016; 11:e0148967. [PMID: 26974333 PMCID: PMC4790856 DOI: 10.1371/journal.pone.0148967] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Accepted: 01/21/2016] [Indexed: 12/26/2022] Open
Abstract
Recently, an extensive study of 2,748 polar bears (Ursus maritimus) from across their circumpolar range was published in PLOS ONE, which used microsatellites and mitochondrial haplotypes to apparently show altered population structure and a dramatic change in directional gene flow towards the Canadian Archipelago-an area believed to be a future refugium for polar bears as their southernmost habitats decline under climate change. Although this study represents a major international collaborative effort and promised to be a baseline for future genetics work, methodological shortcomings and errors of interpretation undermine some of the study's main conclusions. Here, we present a reanalysis of this data in which we address some of these issues, including: (1) highly unbalanced sample sizes and large amounts of systematically missing data; (2) incorrect calculation of FST and of significance levels; (3) misleading estimates of recent gene flow resulting from non-convergence of the program BayesAss. In contrast to the original findings, in our reanalysis we find six genetic clusters of polar bears worldwide: the Hudson Bay Complex, the Western and Eastern Canadian Arctic Archipelago, the Western and Eastern Polar Basin, and-importantly-we reconfirm the presence of a unique and possibly endangered cluster of bears in Norwegian Bay near Canada's expected last sea-ice refugium. Although polar bears' abundance, distribution, and population structure will certainly be negatively affected by ongoing-and increasingly rapid-loss of Arctic sea ice, these genetic data provide no evidence of strong directional gene flow in response to recent climate change.
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Affiliation(s)
- René M. Malenfant
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Corey S. Davis
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | | | - David W. Coltman
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
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