Habitat degradation affects the summer activity of polar bears
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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.
KeywordsActivity Behavioral plasticity Climate change Sea ice loss Ursus maritimus
This work was supported by U.S. Geological Survey’s Changing Arctic Ecosystems Initiative and the U.S. Fish and Wildlife Service. Additional support was provided by the Detroit Zoological Association; a Coastal Impact Assessment Program grant through the State of Alaska (Grant No. M11AF00060); and the National Fish and Wildlife Foundation. Teck Alaska Inc, BP Exploration Alaska, Inc.; ARCO Alaska Inc.; Conoco-Phillips, Inc.; and the ExxonMobil Production Company provided in-kind support. We would like to thank the reviewers for their time and comments on this manuscript. This paper was reviewed and approved by USGS under their Fundamental Science Practices policy (http://www.usgs.gov/fsp). The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the U.S. Fish and Wildlife Service. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Author contribution statement
KDR, EVR, RRW, SCA, GMD, and AMP conducted the fieldwork, KDR developed original idea for manuscript, DCD, RRW, JO, and JVW compiled, organized, and coded aspects of the data, JFB, KDR, and JVW designed statistical models and analyzed the data, CTR, HTJ, and KDR provided mentorship, project guidance and manuscript feedback to JVW, and JVW, KDR, and JFB wrote the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare there are no conflicts of interest.
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