Abstract
The phenology and habitat selection of polar bear (Ursus maritimus) maternity dens may shift over time in response to changing environmental conditions. We compared maternity den phenology and habitat characteristics using satellite telemetry data from adult female polar bears from the Baffin Bay (BB) (n = 16 dens; 2009–2015) and Kane Basin (KB) subpopulations (n = 3 dens; 2012–2015) to previously published maternity den data from 1991 to 1997 (BB n = 8 dens; KB n = 3 dens). BB maternity denning duration decreased from a mean of 194.1 days (SD = 21.0 days, n = 8) in the 1990s, to a mean of 167.1 days (SD = 27.6 days, n = 16; p = 0.017) in the 2000s. Delayed den entry accounted for shorter denning durations (1990s entry date \(\bar{x}\) = 7 September; 2000s entry date \(\bar{x}\) = 5 October; p = 0.018). For dens habitat characteristics of which could be measured, BB maternity dens in the 2000s occurred at higher elevations (\(\bar{x}\) = 707.0 m, SD = 284.9 m, n = 15; p = 0.003) and greater slopes (\(\bar{x}\) = 23.1°, SD = 7.4°; p = 0.003) than the 1990s (elevation \(\bar{x}\) ± SD = 351.3 ± 194.5 m, n = 8; slope \(\bar{x}\) ± SD = 11.9 ± 6.4°). Aspect also significantly differed between the 1990s (\(\bar{x}\) = 51.3°) and 2000s BB maternity dens (\(\bar{x}\) = 199.7°; Watson’s U 2 p = 0.042). KB dens were not statistically compared due to low sample size (n = 3 dens in both periods). Shifts in sea ice phenology and snow availability may explain the observed changes.
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Acknowledgements
The authors wish to offer their thanks to the Scientific Working Group of the Canada-Greenland Joint Commission on Baffin Bay and Kane Basin Polar Bears for providing the 2000s satellite telemetry data. Thanks are also due to A. Hornof, M. Logsdon, H. Stern, and R. McGovern for their assistance with analyses and GIS, and to the local hunters and technicians from Greenland and Canada for their assistance in the field. Funding for the polar bear fieldwork was provided by the Greenland Institute of Natural Resources, the Government of Greenland; the Danish Ministry of Environment (Miljøstøtte til Arktis); Environment Canada; the Government of Nunavut, and the Vetlessen Foundation. The Nunavut Wildlife Management Board and the Polar Continental Shelf Program provided key logistical and financial supports for the KB collaring effort. This material is based on the project supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1256082; the University of Washington’s School of Aquatic and Fishery Sciences; and the US National Aeronautics and Space Administration’s (NASA) Biodiversity Program Grant No. NNX11A063G (PI: K. Laidre). Three anonymous reviewers helped to improve the manuscript.
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Escajeda, E., Laidre, K.L., Born, E.W. et al. Identifying shifts in maternity den phenology and habitat characteristics of polar bears (Ursus maritimus) in Baffin Bay and Kane Basin. Polar Biol 41, 87–100 (2018). https://doi.org/10.1007/s00300-017-2172-6
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DOI: https://doi.org/10.1007/s00300-017-2172-6