Habitat degradation affects the summer activity of polar bears
- 952 Downloads
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.
- Amstrup SC (1995) Movements, distribution, and population dynamics of polar bears in the Beaufort Sea. PhD dissertation, University of Alaska, Fairbanks, AK, USAGoogle Scholar
- Amstrup SC, Marcot BG, Douglas DC (2008) A Bayesian network modeling approach to forecasting the 21st century worldwide status of polar bears. American Geophysical Union Geophysical Monograph Series, Washington, pp 213–268Google Scholar
- Atwood TC, Marcot BG, Douglas DC, Amstrup SC, Rode KD, Durner GM, Bromaghin JF (2015a) Evaluating and ranking threats to the long-term persistence of polar bears. US Geological Survey open-file report. doi: 10.3133/ofr20141254
- Atwood TC, Peacock E, McKinney MA, Lillie K, Wilson R, Miller S (2015b) Demographic composition and behavior of polar bears summering on shore in Alaska. US Geological Survey, administrative reportGoogle Scholar
- Bates D, Maechler M, Bolker B, Walker S, Christensen RHB, Singmann H, Dai B, Grothendieck G, Eigen C, Rcpp L (2015) Package ‘lme4’. R Foundation for Statistical Computing, Vienna Google Scholar
- Burnham KP, Anderson DR (2002) Model selection and multimodel inference: a practical information-theoretic approach, 2nd edn. Springer, New YorkGoogle Scholar
- Cavalieri D, Parkinson C, Gloersen P, Zwally H (1996) Sea ice concentrations from Nimbus-7 SMMR and DMSP SSM/I passive microwave data. Digital Media, National Snow and Ice Data Center, Boulder (updated 2006) Google Scholar
- Durner GM, Douglas DC, Nielson RM, Amstrup SC, McDonald TL, Stirling I, Mauritzen M, Born EW, Wiig Ø, DeWeaver E, Serreze MC, Belikov SE, Holland MM, Maslanik J, Aars J, Bailey DA, Derocher AE (2009) Predicting 21st-century polar bear habitat distribution from global climate models. Ecol Monogr 79:25–58. doi: 10.1890/07-2089.1 CrossRefGoogle Scholar
- Johnson DS (2013) Crawl: fit continuous-time correlated random walk models to animal movement data. R package version 3.1.4. http://cran.r-project.org/package=crawl
- Kochnev A (2002) Autumn aggregations of polar bears on Wrangel Island and their importance to the population. In: Proceedings of the marine mammals of the holarctic 2002, Moscow, RussiaGoogle Scholar
- Laidre KL, Stern H, Kovacs KM, Lowry L, Moore SE, Regehr EV, Ferguson SH, Wiig Ø, Boveng P, Angliss RP (2015) Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century. Conserv Biol 29:724–737. doi: 10.1111/cobi.12474 CrossRefPubMedPubMedCentralGoogle Scholar
- Obbard ME, Thiemann GW, Peacock E, Debruyn TD (2010) Polar bears: proceedings of the 15th working meeting of the Iucn/Ssc Polar Bear Specialist Group, Copenhagen, Denmark: IUCN. 29 June–3 July 2009. Gland, Switzerland and Cambridge, UK. IUCNGoogle Scholar
- Olson J (2015) Identifying maternal denning of polar bears using temperature: denning distribution in relation to sea ice in the southern Beaufort Sea. M.S. thesis, Department of Plant and Wildlife Sciences, Brigham Young University, Provo, Utah, USAGoogle Scholar
- Ovsyanikov N, Menyushina I (2010) Number, condition, and activity of polar bears on Wrangel Island during ice free autumn seasons of 2005–2009. In: Proceedings of the marine mammals of the holarctic meeting, Oct. 11–15, 2010, Kaliningrad, Russia, pp 445–450Google Scholar
- Peacock E, Sonsthagen SA, Obbard ME, Boltunov A, Regehr EV, Ovsyanikov N, Aars J, Atkinson SN, Sage GK, Hope AG (2015) Implications of the circumpolar genetic structure of polar bears for their conservation in a rapidly warming Arctic. PLoS ONE 10:e0136126. doi: 10.1371/journal.pone.0112021 CrossRefPubMedPubMedCentralGoogle Scholar
- R Core Team (2014) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna. http://www.R-project.org
- Rode KD, Regehr EV, Douglas DC, Durner G, Derocher AE, Thiemann GW, Budge SM (2014b) Variation in the response of an Arctic top predator experiencing habitat loss: feeding and reproductive ecology of two polar bear populations. Glob Change Biol 20:76–88. doi: 10.1111/gcb.12339 CrossRefGoogle Scholar
- Schliebe S, Rode K, Gleason J, Wilder J, Proffitt K, Evans T, Miller S (2008) Effects of sea ice extent and food availability on spatial and temporal distribution of polar bears during the fall open-water period in the Southern Beaufort Sea. Polar Biol 31:999–1010. doi: 10.1007/s00300-008-0439-7 CrossRefGoogle Scholar
- Suydam RS, George JC (2004) Subsistence harvest of bowhead whales (Balaena mysticetus) by Alaskan Eskimos, 1974–2003. Presented to the 56th International Whaling Commission. SC/56/BRG12Google Scholar
- Ware J, Rode K, Pagano A, Bromaghin J, Robbins C, Erlenbach J, Jensen S, Cutting A, Nicassio-Hiskey N, Hash A, Owen M, Jansen H (2015) Validation of mercury tip-switch and accelerometer activity sensors for identifying resting and active behavior in bears. Ursus 26:86–96. doi: 10.2192/ursus-d-14-00031.1 CrossRefGoogle Scholar