Parmesan, C. & Yohe, G. A globally coherent fingerprint of climate change impacts across natural systems. Nature 421, 37–42 (2003).
Pecl, G. T. et al. Biodiversity redistribution under climate change: impacts on ecosystems and human well-being. Science 355, eaai9214 (2017).
Walsh, J. E. Intensified warming of the arctic: causes and impacts on middle latitudes. Glob. Planet. Change 117, 52–63 (2014).
Jansen, E. et al. Past perspectives on the present era of abrupt Arctic climate change. Nat. Clim. Change 10, 714–721 (2020).
Previdi, M., Janoski, T. P., Chiodo, G., Smith, K. L. & Polvani, L. M. Arctic amplification: a rapid response to radiative forcing. Geophys. Res. Lett. 47, e2020GL089933 (2020).
Rantanen, M. et al. The Arctic has warmed nearly four times faster than the Globe since 1979. Commun. Earth Environ. 3, 168 (2022).
Post, E. et al. Ecological dynamics across the Arctic associated with recent climate change. Science 325, 1355–1358 (2009).
Kovacs, K. M., Lydersen, C., Overland, J. E. & Moore, S. E. Impacts of changing sea-ice conditions on Arctic marine mammals. Mar. Biodivers. 41, 181–194 (2010).
Laidre, K. L. et al. Arctic marine mammal population status, sea ice habitat loss, and conservation recommendations for the 21st century. Conserv. Biol. 29, 724–737 (2015).
Isaksen, K. et al. Exceptional warming over the Barents area. Sci. Rep. 12, 13568 (2022).
Stern, H. & Laidre, K. L. Sea-ice indicators of Polar bear habitat. Cryosphere 10, 1–15 (2016).
Regehr, E. V. et al. Conservation status of Polar bears (Ursus maritimus) in relation to projected sea-ice declines. Biol. Lett. 12, 20160556 (2016).
Mauritzen, M., Derocher, A. E. & Wiig, Ø. Space-use strategies of female Polar bears in a dynamic sea ice habitat. Can. J. Zool. 79, 1704–1713 (2001).
Derocher, A. E. Population ecology of Polar bears at Svalbard, Norway. Popul. Ecol. 47, 267–275 (2005).
Aars, J. et al. Estimating the Barents sea Polar bear subpopulation size. Mar. Mamm. Sci. 25, 35–52 (2009).
Aars, J. et al. Polar bear population structure and trend in the Western Barents sea. Polar Res. 36, 1374125 (2017).
Naciri, M., Aars, J., Blanchet, M. A., Gimenez, O. & Cubaynes, S. Reproductive senescence in Polar bears in a variable environment. Front. Ecol. Evol. 10, 960435 (2022).
Derocher, A. E. et al. Sea ice and Polar bear Den ecology at Hopen Island, Svalbard. Mar. Ecol. Prog. Ser. 441, 273–279 (2011).
Blanchet, M.-A., Aars, J., Andersen, M. & Routti, H. Space-use strategy affects energy requirements in Barents sea Polar bears. Mar. Ecol. Prog. Ser. 639, 1–19 (2020).
Lone, K., Merkel, B., Lydersen, C., Kovacs, K. M. & Aars, J. Sea ice resource selection models for Polar bears of the Barents sea subpopulation. Ecography 41, 567–578 (2018a).
Griffen, B. D. Modeling the metabolic costs of swimming in Polar bears (Ursus maritimus). Polar Biol. 41, 491–503 (2018).
Tartu, S. et al. Geographical area and life history traits influence diet in an Arctic marine predator. PLoS One 11, e0155980 (2016).
Lippold, A. et al. Temporal trends of persistent organic pollutants in Barents sea Polar bears (Ursus maritimus) in relation to changes in feeding habits and body condition. Environ. Sci. Technol. 53, 984–995 (2019).
Prop, J. et al. Climate change and the increasing impact of Polar bears on bird populations. Front. Ecol. Evol. 3, 33 (2015).
Hamilton, C. D., Kovacs, K. M., Ims, R. A., Aars, J. & Lydersen, C. An Arctic predator-prey system in flux: climate change impacts on coastal space use by Polar bears and ringed seals. J. Anim. Ecol. 86, 1054–1064 (2017).
Atwood, T. C. et al. Rapid environmental change drives increased land use by an Arctic marine predator. PLoS One 11, e0155932 (2016).
Castro de la Guardia, L., Myers, P. G., Derocher, A. E., Lunn, N. J. & Terwisscha Van Scheltinga, A. D. Sea ice cycle in Western Hudson Bay, Canada, from a Polar bear perspective. Mar. Ecol. Prog. Ser. 564, 225–233 (2017).
Ware, J. V. et al. Habitat degradation affects the summer activity of Polar bears. Oecologia 184, 87–99 (2017).
Laidre, K. L. et al. Interrelated ecological impacts of climate change on an apex predator. Ecol. Appl. 30, e02044 (2020).
Molnar, 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).
Molnar, P. K. et al. Fasting season length sets Temporal limits for global Polar bear persistence. Nat. Clim. Change 10, 732–738 (2020).
Wilder, S. M., Raubenheimer, D. & Simpson, S. J. Moving beyond body condition indices as an estimate of fitness in ecological and evolutionary studies. Funct. Ecol. 30, 108–117 (2016).
Cerini, F., Childs, D. Z. & Clements, C. F. A predictive timeline of wildlife population collapse. Nat. Ecol. Evol. 7, 320–331 (2023).
Stirling, I., Lunn, N. J. & Iacozza, J. Long-term trends in the population ecology of Polar bears in Western Hudson Bay in relation to Climatic change. Arctic 52, 294–306 (1999).
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).
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).
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).
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 (2010).
Rode, K. D. et al. Seal body condition and atmospheric circulation patterns influence Polar bear body condition, recruitment, and feeding ecology in the Chukchi sea. Glob. Change Biol. 27, 2684–2701 (2021).
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).
Penk, S. R. et al. A body composition model with multiple storage compartments for Polar bears (Ursus maritimus). Conserv. Physiol. 11, coad043 (2023).
Pagano, A. M. et al. Polar bear energetic and behavioral strategies on land with implications for surviving the ice-free period. Nat. Commun. 15, 44682 (2024).
Ramsay, M. A. & Stirling, I. Reproductive biology and ecology of female Polar bears (Ursus maritimus). J. Zool. 214, 601–634 (1988).
Atkinson, S. N. & Ramsay, M. A. The effects of prolonged fasting of the body-composition and reproductive success of female Polar bears (Ursus maritimus). Funct. Ecol. 9, 559–567 (1995).
Derocher, A. E. & Stirling, I. The population dynamics of polar bears in western Hudson Bay. In Wildlife 2001: Populations (eds. McCullough, D. & Barrett, R.) 1150–1159 (Elsevier, 1992).
Rode, K. D. et al. Diet energy density estimated from isotopes in predator hair associated with survival, habitat, and population dynamics. Ecol. Appl. 33, e02751 (2023).
Stirling, I., Spencer, C. & Andriashek, D. Immobilization of Polar bears (Ursus maritimus) with Telazol in the Canadian Arctic. J. Wildl. Dis. 25, 159–168 (1989).
Christensen-Dalsgaard, S. N., Aars, J., Andersen, M., Lockyer, C. & Yoccoz, N. G. Accuracy and precision in Estimation of age of Norwegian Arctic Polar bears (Ursus maritimus) using dental cementum layers from known-age individuals. Polar Biol. 33, 589–597 (2010).
Derocher, A. E. & Wiig, Ø. Postnatal growth in body length and mass of Polar bears (Ursus maritimus) at Svalbard. J. Zool. 256, 343–349 (2002).
Cattet, M., Caulkett, N. A., Obbard, M. E. & Stenhouse, G. B. A body-condition index for ursids. Can. J. Zool. 80, 1156–1161 (2002).
Thompson, D. W. J. & Wallace, J. M. The Arctic Oscillation signature in the wintertime geopotential height and temperature fields. Geophys. Res. Lett. 25, 1297–1300 (1998).
Rigor, I. G., Wallace, J. M. & Colony, R. L. Response of sea ice to the Arctic Oscillation. J. Clim. 15, 2648–2663 (2002).
Galicia, M. P., Thiemann, G. W. & Dyck, M. G. Correlates of seasonal change in the body condition of an Arctic top predator. Glob. Change Biol. 26, 840–850 (2019).
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. (2013).82, 912–21.
Wood, S. N. Generalized Additive Models: an Introduction with R, 2nd edn. (CRC Press, 2017).
Simpson, D., Rue, H., Riebler, A., Martins, T. G. & Sørbye, S. H. Penalising model component complexity: a principled, practical approach to constructing priors. Stat. Sci. 32, 1–28 (2017).
Dambly, L. I., Isaac, N. J. B., Jones, K. E., Boughey, K. L. & O’Hara, R. B. Integrated species distribution models fitted in INLA are sensitive to mesh parameterisation. Ecography 7, doi:https://doi.org/10.1111/ecog.06391 (2023).
Burnham, K. P. & Anderson, D. R. Model Selection and Multimodel Inference: A Practical information-theoretic Approach. 2nd edn, (Springer, 2002).
Hartig, F. DHARMa: Residual Diagnostics for Hierarchical (Multi-Level / Mixed) Regression Models. R package version 0.4.7. http://florianhartig.github.io/DHARMa/ (2024). Massicotte, P, & South, A. rnaturalearth: World Map Data from Natural Earth_. doi:https://doi.org/10.32614/CRAN.package.rnaturalearth (2023).
Massicotte, P, & South, A. rnaturalearth: World Map Data from Natural Earth. 10.32614/CRAN.package.rnaturalearth (2023).
Stirling, I. & Derocher, A. E. Effects of climate warming on Polar bears: a review of the evidence. Glob. Change Biol. 18, 2694–2706 (2012).
Aars, J. Polar bear Ursus maritimus Phipps, 1774. In Handbook of the Mammals of Europe (eds. Hackländer, K. & Zachos, F. E.) 1–24 (Springer, Cham, 2024).
Maduna, S. N. et al. Sea ice reduction drives genetic differentiation among Barents Sea polar bears. Proc. R. Soc. B 288, 20211741 (2021).
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 (2015).
Archer, L. C., Atkinson, S. N., Lunn, N., Penk, S. R. & Molnar, P. K. Energetic constraints drive the decline of a Sentinel Polar bear population. Science 387, 516–521 (2025).
Freitas, C. et al. Importance of fast ice and glacier fronts for female Polar bears and their Cubs during spring in Svalbard, Norway. Mar. Ecol. Prog. Ser. 447, 289–304 (2012).
Kovacs, K. M., Liston, G. E., Reinking, A. K., Gerland, S. & Lydersen, C. Climate warming impacts on ringed seal breeding habitat in Svalbard. Ecol. Model. 495, 110790 (2024).
Smedsrud, L. H. et al. Nordic Seas heat loss, Atlantic inflow, and Arctic sea ice cover over the last century. Rev. Geophys. 60, e2021RG000762 (2022).
Stirling, I. Polar Bears: the Natural History of a Threatened Species. (Fitzhenry & Whiteside, 2011).
Iversen, M. et al. The diet of Polar bears (Ursus maritimus) from Svalbard, Norway, inferred from scat analysis. Polar Biol. 36, 561–571 (2013).
Lydersen, C. Status and biology of ringed seals (Phoca hispida) in Svalbard. In Ringed Seals in the North Atlantic (eds. Heide-Jørgensen, M. P. & Lydersen, C.) 46–62 (NAMMCO, 1998).
Carlens, H., Lydersen, C., Krafft, B. A. & Kovacs, K. M. Spring haul-out behavior of ringed seals (Pusa hispida) in Kongsfjorden, Svalbard. Mar. Mamm. Sci. 22, 379–393 (2006).
Derocher, A. E., Andersen, M., Wiig, Ø. & Aars, J. Sexual dimorphism and the mating ecology of Polar bears (Ursus maritimus) at Svalbard. Behav. Ecol. Sociobiol. 64, 939–946 (2010).
Laidre, K. L. et al. Females roam while males patrol: divergence in breeding season movements of pack-ice polar bears (Ursus maritimus). Proc. R. Soc. B 280, 1752 (2013).
Ims, R. A. Spatial clumping of sexually receptive females induces space sharing among male voles. Nature 335, 541–543 (1988).
Rosing-Asvid, A. The influence of climate variability on Polar bear (Ursus maritimus) and ringed seal (Pusa hispida) population dynamics. Can. J. Zool. 84, 357–364 (2006).
Rode, K. D., Reist, J. D., Peacock, E. & Stirling, I. Comments in response to “Estimating the energetic contribution of polar bear (Ursus maritimus) summer diets to the total energy budget” by Dyck and Kebreab (2009). J. Mammal. 91, 1517–1523 (2010).
Derocher, A. E., Wiig, Ø. & Andersen, M. Diet composition of Polar bears in Svalbard and the Western Barents sea. Polar Biol. 25, 448–452 (2002).
Laidre, K. L., Stirling, I., Estes, J. A., Kochnev, A. & Roberts, J. Historical and potential future importance of large whales as food for Polar bears. Front. Ecol. Environ. 16, 515–524 (2018).
Le Moullec, M., Pedersen, A. Ø., Stien, A., Rosvold, J. & Hansen, B. B. A century of conservation: the ongoing recovery of Svalbard reindeer. J. Wildl. Manag. 83, 1676–1686 (2019).
Stempniewicz, L., Kulaszewicz, I. & Aars, J. Yes, they can: Polar bears (Ursus maritimus) successfully Hunt Svalbard reindeer (Rangifer Tarandus platyrhynchus). Polar Biol. 44, 2199–2206 (2021).
Kovacs, K. M., Aars, J. & Lydersen, C. Walruses recovering after 60 + years of protection at Svalbard, Norway. Polar Res. 33, 26034 (2014).
Lønø, O. The Polar bear (Ursus maritimus Phipps) in the Svalbard area. Norsk Polarinstitutt Skrifter 149, 103 (1970).
Merkel, B., Lydersen, C., Yoccoz, N. G. & Kovacs, K. M. The world’s northernmost harbour seal population—how many are there? PLoS One 8, e67576 (2013).
Wiig, Ø., Aars, J. & Born, E. W. Effects of climate change on Polar bears. Sci. Prog. 91, 151–173 (2008).
Hamilton, S. G. & Derocher, A. E. Assessment of global Polar bear abundance and vulnerability. Anim. Conserv. 22, 83–95 (2019).
Laidre, K. L. et al. Transient benefits of climate change for a high-Arctic Polar bear (Ursus maritimus) subpopulation. Glob. Change Biol. 26, 6251–6265 (2020).
Durner, G. M. et al. Predicting 21st-century Polar bear habitat distribution from global climate models. Ecol. Monogr. 79, 25–58 (2009).
Lone, K. et al. Aquatic behaviour of Polar bears (Ursus maritimus) in an increasingly ice-free Arctic. Sci. Rep. 8, 9677 (2018b).
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).
Rode, K. D. et al. Spring fasting behavior in a marine apex predator provides an index of ecosystem productivity. Glob. Change Biol. 24, 410–423 (2018).