Chukchi Sea (CS)

Unknown population size. The subpopulation thought to be declining based on reductions in sea-ice and unknown rates of illegal harvest.

Status table outtake

Size Sea ice metrics Human-caused removals 2010–2014
Estimate /
95% CI
Year Method Change in spring ice retreat / Change in fall ice advance (days per decade) Change in summer sea ice area (percent change per decade) 5-yr mean Last year
Potential Actual Potential Actual
Unknown  -3.4/4.2-18.85829 (U.S.) + approx. 32 (Russia)589 (U.S.) + approx. 32 (Russia)
See also the complete table (all subpopulations)

Comments, vulnerabilities and concerns

Indices of good body condition and recruitment during springtime research, although autumn observations suggest declining cub survival.  Longer ice-free periods are increasing land use. Subsistence harvest is legal and monitored in US. Harvest remains illegal in Russia. Updated estimates of subpopulation size anticipated in 2017.

Status and delineation

Chukchi Sea subpopulation mapThe Chukchi Sea area. See also the complete map (all subpopulations).

Studies in the late 1980s and early 1990s revealed that polar bears in the Chukchi Sea (CS) subpopulation, also known as the Alaska-Chukotka subpopulation, are widely distributed on the pack ice of the northern Bering, Chukchi, and eastern portions of the East Siberian seas (Garner et al. 1990, 1994, 1995). Based upon these telemetry studies, the western boundary of the subpopulation was set near Chaunskaya Bay in northeastern Russia. The eastern boundary was set at Icy Cape, Alaska, which is also the western boundary of the Southern Beaufort Sea (SB) subpopulation (Amstrup and DeMaster 1988, Garner et al. 1990, Amstrup et al. 1986, 2004a, 2005).

Precise estimates of subpopulation size or status are not available. An approximate estimate of 2,000-5,000 animals was based on the number of maternity dens observed on Wrangel and Herald islands and the Chukotkan coast, and the assumed proportion of females in the subpopulation (Belikov 1993). In recent years the range occupied by the CS subpopulation has experienced longer ice-retreat seasons and more ice-free days over the biologically productive waters of the continental shelf (Durner et al. 2009; Rode et al. 2013). Sea ice loss is expected to continue (Douglas 2010). Rode et al. 2013 documented stable or improving body condition and reproduction for polar bears captured in the U.S. between 1986-1994 and 2008-2011, a period during which substantial sea ice loss occurred, suggesting the capacity for positive population growth. Autumn-based observations on Wrangel Island for the period 2004-2010, however, suggest relatively low cub production and reduced maternity denning (Ovsyanikov 2012).

Estimates of illegal take of polar bears in Russia are based on village interviews conducted 2010-2012, and the current level appears to be significantly lower than in the 1990s (Kochnev and Zdor 2016). Combined with legal subsistence harvest in the U.S., the overall level of human-caused removals for the CS subpopulation may exceed sustainable limits. Uncertainty in the level of human-caused removals, current population size, and population growth rate result in a designation of “Data deficient” for the status relative to historic abundance and the current trend of the CS subpopulation.

New studies have found that polar bears in the CS have been increasingly using land during the summer, both in Russia, on Wrangel Island and the Chukotkan peninsula, and on the northwest Alaskan coast of the United States (Rode et al. 2015). However, Wilson et al. (2014, 2016) have found that despite large reductions in sea ice, particularly in summer, polar bears have not changed their habitat selection preferences in the Chukchi Sea.

References

Amstrup, S. C., Stirling, I. and Lentfer, J. W. 1986. Past and present status of polar bears in Alaska. Wildl. Soc. Bull. 14: 241-254.

Amstrup, S. C. and DeMaster, D. P. 1988. Polar bear Ursus maritimus. Pp. 39-56 In Lentfer, J. W. (ed.). Selected Marine Mammals of Alaska: Species Accounts with Research and Management Recommendations. Marine Mammal Commission, Washington, DC, USA.

Amstrup, S. C., Durner, G. M., Stirling, I. and McDonald, T. L. 2005. Allocating harvests among polar bear stocks in the Beaufort Sea. Arctic 58:247-259.

Amstrup, S. C., McDonald, T. L. and Durner, G. M. 2004. Using satellite radiotelemetry data to delineate and manage wildlife populations. Wildl. Soc. Bull. 32:661-679.

Belikov 1993. The polar bear. pp 420-475 in Vaysfeld, M. A. and I.E. Chestin (eds.) Bears. Moscow, Nauka (In Russian with English summary)

Douglas, D. C. (2010) Arctic sea ice decline: Projected changes in timing and extent of sea ice in the Chukchi and Bering Seas. U.S. Geological Survey Open-File Report 2010-1176:32 pp.

Durner, G. M., D. C. Douglas, R. M. Nielson, S. C. Amstrup, T. L. McDonald, I. Stirling, M. Mauritzen, E. W. Born, O. Wiig, E. DeWeaver, M. C. Serreze, S. Belikov, M. Holland, J. A. Maslanik, J. Aars, D. A. Bailey, and A. E. Derocher. (2009) Predicting 21st-century polar bear habitat distribution from global climate models. Ecological Monographs 79:25-58.

Garner, G. W., Belikov, S. E., Stishov, M. S. and Arthur, S. M. 1995. Research on polar bears in western Alaska and eastern Russia 1998-92. Pp.155-165 In Wiig,Ø., Born, E. W. and G. W. Garner, (eds.). Polar Bears: Proceedings of the Eleventh Working Meeting of the IUCN/SSC Polar Bear Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK.

Garner, G. W., Belikov, S. E., Stishov, M. S., Barnes Jr., V. G. and Arthur, S. M. 1994. Dispersal patterns of maternal polar bears from the denning concentration on Wrangel Island. Internat.Conf. Bear Res.Manage. 9:401-410.

Garner, G. W., Knick, S. T. and Douglas, D. C. 1990. Seasonal movements of adult female bears in the Bering and Chukchi seas. Internat. Conf. Bear Res. Manage. 8:219-226.

Kochnev A. and E. Zdor. 2016. Harvest and use of polar bears in Chukotka: Results of 1999-2012 studies.  Moscow: Pi Kvadra. 2014. 148 pp. ISBN 978-5-9904685-7-3.

Ovsyanikov, N.G. 2012. Occurrence of family groups and litters size of polar bears on Wrangel Island in the autumns of 2004-2010 as an indication of population status. In: Marine Mammals of the Holarctic, Suzdal, 2012.

Rode, K.D., E.V. Regehr, D.C. Douglas, G. Durner, A.E. Derocher, G.W. Thiemann, and S. Budge. 2014. Variation in the response of an Arctic top predator experiencing habitat loss: feeding and reproductive ecology of two polar bear populations. Global Change Biology 20: 76-88. Doi: 10.111/gcb.12339.

Rode, K. D., R. R. Wilson, E. V. Regehr, M. S. Martin, D. C. Douglas, and J. Olson. 2015. Increased land use by Chukchi sea polar bears in relation to changing sea ice conditions. PLoS ONE 10:1–18.

Wilson, R. R., E. V Regehr, K. D. Rode, and M. St Martin. 2016. Invariant polar bear habitat selection during a period of sea ice loss. Proceedings of the Royal Society B: Biological Sciences 283.