Fasting season length sets temporal limits for global polar bear persistence
1.
Amstrup, S. C. et al. Greenhouse gas mitigation can reduce sea-ice loss and increase polar bear persistence. Nature 468, 955–958 (2010).
CAS Google Scholar
2.
Regehr, E. V. et al. Conservation status of polar bears (Ursus maritimus) in relation to projected sea-ice declines. Biol. Lett. 12, 20160556 (2016).
Google Scholar
3.
Molnár, P. K., Derocher, A. E., Thiemann, G. W. & Lewis, M. A. Predicting survival, reproduction and abundance of polar bears under climate change. Biol. Conserv. 143, 1612–1622 (2010); corrigendum 177, 230–231 (2014).
4.
Kay, J. E. et al. The Community Earth System Model (CESM) Large Ensemble Project: a community resource for studying climate change in the presence of internal climate variability. Bull. Am. Meteorol. Soc. 96, 1333–1349 (2015).
Google Scholar
5.
Rode, K. D., Robbins, C. T., Nelson, L. & Amstrup, S. C. Can polar bears use terrestrial foods to offset lost ice-based hunting opportunities? Front. Ecol. Environ. 13, 138–145 (2015).
Google Scholar
6.
Stern, H. S. & Laidre, K. L. Sea-ice indicators of polar bear habitat. Cryosphere 10, 2027–2041 (2016).
Google Scholar
7.
Stirling, I. & Derocher, A. E. Effects of climate warming on polar bears: a review of the evidence. Glob. Change Biol. 18, 2694–2706 (2012).
Google Scholar
8.
Regehr, E. V., Lunn, N. J., Amstrup, S. C. & Stirling, I. Effects of earlier sea ice breakup on survival and population size of polar bears in Western Hudson Bay. J. Wildl. Manag. 71, 2673–2683 (2007).
Google Scholar
9.
Rode, K. D., Amstrup, S. C. & Regehr, E. V. Reduced body size and cub recruitment in polar bears associated with sea ice decline. Ecol. Appl. 20, 768–782 (2010).
Google Scholar
10.
Rode, K. D. et al. A tale of two polar bear populations: ice habitat, harvest, and body condition. Popul. Ecol. 54, 3–18 (2012).
Google Scholar
11.
Bromaghin, J. F. et al. Polar bear population dynamics in the Southern Beaufort Sea during a period of sea ice decline. Ecol. Appl. 25, 634–651 (2016).
Google Scholar
12.
Lunn, N. J. et al. Demography of an apex predator at the edge of its range: impacts of changing sea ice on polar bears in Hudson Bay. Ecol. Appl. 26, 1302–1320 (2016).
Google Scholar
13.
Obbard, M. E. et al. Trends in body condition in polar bears (Ursus maritimus) from the Southern Hudson Bay subpopulation in relation to changes in sea ice. Arctic Sci. 2, 15–32 (2016).
Google Scholar
14.
Hunter, C. M. et al. Climate change threatens polar bear populations: a stochastic demographic analysis. Ecology 91, 2883–2897 (2010).
Google Scholar
15.
Molnár, P. K., Derocher, A. E., Klanjscek, T. & Lewis, M. A. Predicting climate change impacts on polar bear litter size. Nat. Commun. 2, 186 (2011).
Google Scholar
16.
De la Guardia, L. C., Derocher, A. E., Myers, P. G., van Scheltinga, A. D. T. & Lunn, N. J. Future sea ice conditions in Western Hudson Bay and consequences for polar bears in the 21st century. Glob. Change Biol. 19, 2675–2687 (2013).
Google Scholar
17.
Hamilton, S. G. et al. Projected polar bear sea ice habitat in the Canadian Arctic Archipelago. PLoS ONE 9, e113746 (2014).
Google Scholar
18.
Cavalieri, D., Parkinson, C., Gloersen, P. & Zwally, H. J. Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data Version 1 (1979–2016) (NASA DAAC at the National Snow and Ice Data Center, accessed 7 June 2017).
19.
Arnould, J. P. Y. & Ramsay, M. A. Milk production and milk consumption in polar bears during the ice-free period in western Hudson Bay. Can. J. Zool. 72, 1365–1370 (1994).
Google Scholar
20.
Dyck, M., Campbell, M., Lee, D. S., Boulanger, J. & Hedman, D. Aerial Survey of the Western Hudson Bay Polar Bear Sub-Population 2016. 2017 Final Report (Wildlife Research Section, Department of Environment, Government of Nunavut, 2017).
21.
Manning, T. H. Geographical Variation in the Polar Bear Ursus Maritimus Phipps. Rep. Ser. No. 13 (Canadian Wildlife Service, 1971).
22.
Derocher, A. E. & Stirling, I. Geographic variation in growth of polar bears (Ursus maritimus). J. Zool. Lond. 245, 65–72 (1998).
Google Scholar
23.
Derocher, A. E. & Wiig, Ø. Postnatal growth in body length and mass of polar bears (Ursus maritimus) at Svalbard. J. Zool. Lond. 256, 343–349 (2002).
Google Scholar
24.
Obbard, M. E. et al. Re-assessing abundance of Southern Hudson Bay polar bears by aerial survey: effects of climate change at the southern edge of the range. Arctic Sci. 4, 634–655 (2018).
Google Scholar
25.
Peacock, E., Taylor, M. K., Laake, J. & Stirling, I. Population ecology of polar bears in Davis Strait, Canada and Greenland. J. Wildl. Manag. 77, 463–476 (2013).
Google Scholar
26.
Galicia, M. P., Thiemann, G. W., Dyck, M. G. & Ferguson, S. H. Characterization of polar bear (Ursus maritimus) diets in the Canadian high arctic. Polar Biol. 38, 1983–1992 (2015).
Google Scholar
27.
Laidre, K. L. et al. Interrelated ecological impacts of climate change on an apex predator. Ecol. Appl. 30, e02071 (2020).
Google Scholar
28.
Stapleton, S., Peacock, E. & Garshelis, D. Aerial surveys suggest long-term stability in the seasonally ice-free Foxe Basin (Nunavut) polar bear population. Mar. Mammal Sci. 32, 181–201 (2016).
Google Scholar
29.
Regehr, E. V. et al. Integrated population modeling provides the first empirical estimates of vital rates and abundance for polar bears in the Chukchi Sea. Sci. Rep. 8, 16780 (2018).
Google Scholar
30.
Stirling, I., McDonald, T. L., Richardson, E. S., Regehr, E. V. & Amstrup, S. C. Polar bear population status in the Northern Beaufort Sea, Canada, 1971–2006. Ecol. Appl. 21, 859–876 (2011).
Google Scholar
31.
Pagano, A. M. et al. High-energy, high-fat lifestyle challenges an Arctic apex predator, the polar bear. Science 359, 568–572 (2018).
CAS Google Scholar
32.
Aars, J. et al. The number and distribution of polar bears in the western Barents Sea. Polar Res. 36, 1374125 (2017).
Google Scholar
33.
Moss, R. et al. Towards New Scenarios for Analysis of Emissions, Climate Change, Impacts, and Response Strategies (IPCC, 2008).
34.
Molnár, P. K., Derocher, A. E., Lewis, M. A. & Taylor, M. K. Modelling the mating system of polar bears: a mechanistic approach to the Allee effect. Proc. R. Soc. B 275, 217–226 (2008).
Google Scholar
35.
Ingolfsson, O. & Wiig, Ø. Late Pleistocene fossil find in Svalbard: the oldest remains of a polar bear (Ursus maritimus Phipps, 1744) ever discovered. Polar Res. 28, 455–462 (2008).
Google Scholar
36.
Notz, D. & Stroeve, J. Observed Arctic sea-ice loss directly follows anthropogenic CO2 emission. Science 354, 747–750 (2016).
CAS Google Scholar
37.
Durner, G. M. et al. Predicting 21st century polar bear habitat distribution from global climate models. Ecol. Monogr. 79, 25–58 (2009).
Google Scholar
38.
Cherry, S. G., Derocher, A. E., Thiemann, G. W. & Lunn, N. J. Migration phenology and seasonal fidelity of an Arctic marine predator in relation to sea ice dynamics. J. Anim. Ecol. 82, 912–921 (2013).
Google Scholar
39.
Smith, R. D., Kortas, S. & Meltz, B. J. A. Curvilinear Coordinates for Global Ocean Models. Tech. Note LA-UR-95-1146 (Los Alamos National Laboratory, 1997).
40.
Amstrup, S. C., Marcot, B. G. & Douglas, D. C. in Arctic Sea Ice Decline: Observations, Projections, Mechanisms, and Implications (eds DeWeaver, E. T. et al.) 213–268 (American Geophysical Union, 2008).
41.
Regehr, E. V., Hunter, C. M., Caswell, H., Amstrup, S. C. & Stirling, I. Survival and breeding of polar bears in the Southern Beaufort Sea in relation to sea ice. J. Anim. Ecol. 79, 117–127 (2009).
Google Scholar
42.
Whiteman, J. P. et al. Summer declines in activity and body temperature offer polar bears limited energy savings. Science 349, 295–298 (2015).
CAS Google Scholar
43.
Whiteman, J. P. et al. Phenotypic plasticity and climate change: can polar bears respond to longer Arctic summers with an adaptive fast? Oecologia 186, 369–381 (2018).
Google Scholar
44.
Fetterer, F., Knowles, K., Meier, W. & Savoie, M. Sea Ice Index (National Snow and Ice Data Center, 2002).
45.
Furnell, D. J. & Oolooyuk, D. Polar bear predation on ringed seals in ice-free water. Can. Field-Nat. 94, 88–89 (1980).
Google Scholar
46.
Stirling, I., Lunn, N. J. & Iacozza, J. Long-term trends in the population ecology of polar bears in western Hudson Bay in relation to climate change. Arctic 52, 294–306 (1999).
Google Scholar
47.
Cavalieri, D. J., Parkinson, C. L., Gloersen, P., Comiso, J. C. & Zwally, H. J. Deriving long-term time series of ice cover from satellite passive-microwave multisensor data sets. J. Geophys. Res. 104, 15803–15814 (1999).
Google Scholar
48.
Meier, W. N. & Stewart, J. S. Assessing uncertainties in sea ice extent climate indicators. Environ. Res. Lett. 14, 035005 (2019).
Google Scholar
49.
Durner, G. M. et al. Increased Arctic sea ice drift alters adult female polar bear movements and energetics. Glob. Change Biol. 23, 3460–3473 (2017).
Google Scholar
50.
Durner, G. M. et al. Consequences of long-distance swimming and travel over deep-water pack ice for a female polar bear during a year of extreme sea ice retreat. Polar Biol. 34, 975–984 (2011).
Google Scholar
51.
Pagano, A. M., Durner, G. M., Amstrup, S. C., Simac, K. S. & York, G. S. Long-distance swimming by polar bears (Ursus maritimus) of the Southern Beaufort Sea during years of extensive open water. Can. J. Zool. 90, 663–676 (2012).
Google Scholar
52.
Derocher, A. E. & Stirling, I. Aspects of survival in juvenile polar bears. Can. J. Zool. 74, 1246–1252 (1996).
Google Scholar
53.
Molnár, P. K., Klanjscek, T., Derocher, A. E., Obbard, M. E. & Lewis, M. A. A body composition model to estimate mammalian energy stores and metabolic rates from body mass and body length, with application to polar bears. J. Exp. Biol. 212, 2313–2323 (2009).
Google Scholar
54.
Best, R. C. Thermoregulation in resting and active polar bears. J. Comp. Physiol. 146, 63–73 (1982).
Google Scholar
55.
Mathewson, P. D. & Porter, W. P. Simulating polar bear energetics during a seasonal fast using a mechanistic model. PLoS ONE 8, e72863 (2013).
CAS Google Scholar
56.
Pagano, A. M. et al. Energetic costs of locomotion in bears: is plantigrade locomotion energetically economical? J. Exp. Biol. 221, jeb175372 (2018).
Google Scholar
57.
Derocher, A. E. & Stirling, I. Distribution of polar bears (Ursus maritimus) during the ice-free period in Western Hudson Bay. Can. J. Zool. 68, 1395–1403 (1990).
Google Scholar
58.
Lunn, N. J., Stirling, I., Andriashek, D. & Richardson, E. Selection of maternity dens by female polar bears in western Hudson Bay, Canada and the effects of human disturbance. Polar Biol. 27, 350–356 (2004).
Google Scholar
59.
Parks, E. K., Derocher, A. E. & Lunn, N. J. Seasonal and annual movement patterns of polar bears on the sea ice of Hudson Bay. Can. J. Zool. 84, 1281–1294 (2006).
Google Scholar
60.
Derocher, A. E., Stirling, I. & Andriashek, D. Pregnancy rates and serum progesterone levels of polar bears in Western Hudson Bay. Can. J. Zool. 70, 561–566 (1992).
CAS Google Scholar
61.
Lee, P. C., Majluf, P. & Gordon, I. J. Growth, weaning and maternal investment from a comparative perspective. J. Zool. Lond. 225, 99–114 (1991).
Google Scholar
62.
Oftedal, O. T. The adaptation of milk secretion to the constraints of fasting in bears, seals, and baleen whales. J. Dairy Sci. 76, 3234–3246 (1993).
CAS Google Scholar
63.
Derocher, A. E., Andriashek, D. & Arnould, J. P. Y. Aspects of milk composition and lactation in polar bears. Can. J. Zool. 71, 561–567 (1993).
Google Scholar
64.
Stapleton, S., Atkinson, S., Hedman, D. & Garshelis, D. Revisiting Western Hudson Bay: using aerial surveys to update polar bear abundance in a sentinel population. Biol. Conserv. 170, 38–47 (2014).
Google Scholar
65.
Calvert, W. & Ramsay, M. A. Evaluation of age determination of polar bears by counts of cementum growth layer groups. Ursus 10, 449–453 (1998).
Google Scholar
66.
Regehr, E. V., Wilson, R. R., Rode, K. D. & Runge, M. C. Resilience and Risk—a Demographic Model to Inform Conservation Planning for Polar Bears Open-File Report 2015–1029 (US Geological Survey, 2015).
67.
Molnár, P. K., Lewis, M. A. & Derocher, A. E. Estimating Allee dynamics before they can be observed: polar bears as a case study. PLoS ONE 9, e85410 (2014).
Google Scholar
68.
Rode, K. D. et al. 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 (2014).
Google Scholar
69.
Laliberté, F., Howell, S. E. L. & Kushner, P. J. Regional variability of a projected sea ice‐free Arctic during the summer months. Geophys. Res. Lett. 43, 256–263 (2016).
Google Scholar
70.
Massonnet, F. et al. Constraining projections of summer Arctic sea ice. Cryosphere 6, 1383–1394 (2012).
Google Scholar
71.
McNab, B. K. Geographic and temporal correlations of mammalian size reconsidered: a resource rule. Oecologia 164, 13–23 (2010).
Google Scholar
72.
McNutt, J. W. & Gusset, M. Declining body size in an endangered large mammal. Biol. J. Linn. Soc. 105, 8–12 (2012).
Google Scholar
73.
Amstrup, S. C. & Durner, G. M. Survival rates of radio-collared female polar bears and their dependent young. Can. J. Zool. 73, 1312–1322 (1995).
Google Scholar More