Fasting physiology of polar bears in relation to environmental change and breeding behavior in the Beaufort Sea

Cherry, Seth G.; Derocher, Andrew E.; Stirling, Ian; Richardson, Evan S.

doi:10.1007/s00300-008-0530-0

Cited by 70 publications

(76 citation statements)

References 75 publications

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“…Reductions in sea ice extent and/or duration have been associated with shifts toward more land-based denning, evidence of nutritional stress, reduced body condition, reproduction, survival, and body size for polar bears in parts of their range (Stirling et al 1999, Obbard et al 2006, Stirling and Parkinson 2006, Fischbach et al 2007, Cherry et al 2008. In recent years in the southern Beaufort Sea there have also been more numerous observations of unusual predation attempts and of drowned, emaciated, and cannibalized polar bears , Monnett and Gleason 2006.…”

Section: Polar Bears and Sea Icementioning

confidence: 99%

Climate change threatens polar bear populations: a stochastic demographic analysis

Hunter

Caswell

Runge

et al. 2010

Ecology

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Abstract. The polar bear (Ursus maritimus) depends on sea ice for feeding, breeding, and movement. Significant reductions in Arctic sea ice are forecast to continue because of climate warming. We evaluated the impacts of climate change on polar bears in the southern Beaufort Sea by means of a demographic analysis, combining deterministic, stochastic, environmentdependent matrix population models with forecasts of future sea ice conditions from IPCC general circulation models (GCMs). The matrix population models classified individuals by age and breeding status; mothers and dependent cubs were treated as units. Parameter estimates were obtained from a capture-recapture study conducted from 2001 to 2006. Candidate statistical models allowed vital rates to vary with time and as functions of a sea ice covariate. Model averaging was used to produce the vital rate estimates, and a parametric bootstrap procedure was used to quantify model selection and parameter estimation uncertainty. Deterministic models projected population growth in years with more extensive ice coverage (2001)(2002)(2003) and population decline in years with less ice coverage (2004)(2005). LTRE (life table response experiment) analysis showed that the reduction in k in years with low sea ice was due primarily to reduced adult female survival, and secondarily to reduced breeding. A stochastic model with two environmental states, good and poor sea ice conditions, projected a declining stochastic growth rate, log k s , as the frequency of poor ice years increased. The observed frequency of poor ice years since 1979 would imply log k s ' À 0.01, which agrees with available (albeit crude) observations of population size. The stochastic model was linked to a set of 10 GCMs compiled by the IPCC; the models were chosen for their ability to reproduce historical observations of sea ice and were forced with ''business as usual'' (A1B) greenhouse gas emissions. The resulting stochastic population projections showed drastic declines in the polar bear population by the end of the 21st century. These projections were instrumental in the decision to list the polar bear as a threatened species under the U.S. Endangered Species Act.

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Section: Polar Bears and Sea Icementioning

confidence: 99%

Climate change threatens polar bear populations: a stochastic demographic analysis

Hunter

Caswell

Runge

et al. 2010

Ecology

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229

218

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“…During these periods they fast and rely on body lipid reserves for energy (Cherry et al, 2009). Climate warming causes earlier break-up of sea-ice and thus prolongs this fasting period in polar bears, resulting in increased mortality rates due to emaciation and starvation (Gagnon and Gough, 2005;Molnar et al, , 2014Stirling and Derocher, 2012).…”

Section: Combined Effects On Energetic Processesmentioning

confidence: 99%

Anthropogenic flank attack on polar bears: interacting consequences of climate warming and pollutant exposure

et al. 2015

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Polar bears (Ursus maritimus) are subjected to several anthropogenic threats, climate warming and exposure to pollutants being two of these. For polar bears, one of the main effects of climate warming is limited access to prey, due to loss of their sea ice habitat. This will result in prolonged fasting periods and emaciation and condition related negative effects on survival and reproduction success. Prolonged fasting will result in increases of the tissue concentrations of persistent organic pollutants (POPs) in polar bears, and thus increase the probability for POP levels to exceed threshold levels for effects on health, and thus on reproductive success and survival. There are clear potentials for interactions between impacts of climate warming and impacts of pollutant exposure on polar bears. It is likely that that fasting-induced increases of POPs will add to mortality rates and decrease reproductive success beyond effects caused by loss of habitat alone. However, there is a lack of studies that have addressed this. Thus, there is a need to focus on population effects of POP exposure in polar bears, and to consider such effects in relation to the effects of climate induced habitat loss.

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“…However, we examined the potential for previous thawing of samples during long-term storage to affect UC ratios by comparing paired previously thawed and not thawed samples collected from five individuals on the same capture date (Appendix S1). Levels of blood urea nitrogen (BUN) and creatinine were measured in serum using comprehensive rotors with an Abaxis vetscan (Abaxis, Inc., Union City, CA, USA) or via methods described in Cherry et al (2009). Serum urea was calculated by multiplying BUN 9 0.466 (Nelson, Beck, & Steiger, 1984) and divided by serum creatinine to determine a urea:creatinine ratio (hereafter UC ratio); a metric that is commonly used to identify fasting status in polar bears (Cherry et al, 2009;Derocher, Nelson, Stirling, & Ramsay, 1990;Nelson et al, 1984).…”

Section: Sample Collection and Analysismentioning

confidence: 99%

“…Although much attention has been placed on the loss of summer sea ice as a platform for hunting seals (Derocher, Lunn, & Stirling, 2004;Rode et al, 2015;Whiteman et al, 2015), studies in the Beaufort Sea suggest that reductions in polar bear foraging efficiency are occurring during seasons when sea ice loss has been less dramatic. Cherry, Derocher, Stirling, and Richardson (2009) documented reduced spring (i.e., March-April) foraging success evidenced by a greater frequency of fasting over the previous 7 days or more in compared to 1985-1986. Furthermore, Rode, Pagano, Bromaghin, et al (2014 and Rode, Regehr, Douglas, et al (2014) documented that frequencies of fasting in the southern Beaufort Sea (SB) were much higher than those observed in the adjacent CS in recent years.…”

Section: Introductionmentioning

confidence: 99%

Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity

Rode

Wilson

Douglas

et al. 2017

Global Change Biology

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The effects of declining Arctic sea ice on local ecosystem productivity are not well understood but have been shown to vary inter-specifically, spatially, and temporally.Because marine mammals occupy upper trophic levels in Arctic food webs, they may be useful indicators for understanding variation in ecosystem productivity. Polar bears (Ursus maritimus) are apex predators that primarily consume benthic and pelagic-feeding ice-associated seals. As such, their productivity integrates sea ice conditions and the ecosystem supporting them. Declining sea ice availability has been linked to negative population effects for polar bears but does not fully explain observed population changes. We examined relationships between spring foraging success of polar bears and sea ice conditions, prey productivity, and general patterns of ecosystem productivity in the Beaufort and Chukchi Seas (CSs). Fasting status (≥7 days) was estimated using serum urea and creatinine levels of 1,448 samples collected from 1,177 adult and subadult bears across three subpopulations. Fasting increased in the Beaufort Sea between 1983-1999 and 2000-2016 and was related to an index of ringed seal body condition.This change was concurrent with declines in body condition of polar bears and observed changes in the diet, condition and/or reproduction of four other vertebrate consumers within the food chain. In contrast, fasting declined in CS polar bears between periods and was less common than in the two Beaufort Sea subpopulations consistent with studies demonstrating higher primary productivity and maintenance or improved body condition in polar bears, ringed seals, and bearded seals despite recent sea ice loss in this region. Consistency between regional and temporal variation in spring polar bear fasting and food web productivity suggests that polar bears may be a useful indicator species. Furthermore, our results suggest that spatial and temporal ecological variation is important in affecting upper trophic-level productivity in these marine ecosystems.

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Fasting physiology of polar bears in relation to environmental change and breeding behavior in the Beaufort Sea

Cited by 70 publications

References 75 publications

Climate change threatens polar bear populations: a stochastic demographic analysis

Climate change threatens polar bear populations: a stochastic demographic analysis

Anthropogenic flank attack on polar bears: interacting consequences of climate warming and pollutant exposure

Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity

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