Abstract
We examined the use of the ratio of serum urea to serum creatinine as a physiological biomarker of fasting to monitor temporal patterns in the feeding ecology of polar bears (Ursus maritimus). Blood was collected from 436 polar bears in the eastern Beaufort Sea during April and May of 1985–1986 and 2005–2006. The proportions of polar bears fasting were 9.6% in 1985, 10.5% in 1986, 21.4% in 2005, and 29.3% in 2006. We used stepwise logistic regression analysis to evaluate factors that could influence the binary response variable of fasting or not fasting. Significant predictor variables of fasting were: the 2005 and 2006 capture years, solitary adult male bears, and adult male bears that were accompanying an estrous female. The increased number of polar bears in a physiological fasting state from all sex, age, and reproductive classes in 2005 and 2006 corresponded with broad scale changes in Arctic sea ice composition, which may have affected prey availability. The higher proportion of adult males fasting from all years was attributed to spring breeding behavior.
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Acknowledgments
We especially thank Dennis Andriashek and Greg Thiemann for assistance with field work and collection of specimens. We gratefully acknowledge financial and logistic support from Canadian Wildlife Federation, Canadian Wildlife Service, Circumpolar/Boreal Alberta Research, Inuvialuit Game Council, Natural Sciences and Engineering Research Council of Canada, Northern Scientific Training Program, Northwest Territories Department of Environment and Natural Resources, Polar Continental Shelf Project, Polar Bears International, United States Geological Survey, and World Wildlife Fund (Canada).
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Cherry, S.G., Derocher, A.E., Stirling, I. et al. Fasting physiology of polar bears in relation to environmental change and breeding behavior in the Beaufort Sea. Polar Biol 32, 383–391 (2009). https://doi.org/10.1007/s00300-008-0530-0
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DOI: https://doi.org/10.1007/s00300-008-0530-0