Reposted from Dr. Susan Crockford’s Polar Bear Science.
Wrangel Island analysis crew counted a report variety of Chukchi Sea polar bears in 2020
Posted on September 21, 2021 | Feedback Offon Wrangel Island analysis crew counted a report variety of Chukchi Sea polar bears in 2020
Many Chukchi Sea polar bears spend the summer season on Wrangel Island and a survey there performed by Russian researchers in 2020 reportedly collected knowledge on a report 747 bears, nicely up from the 589 reportedly counted in 2017 by the identical crew (photograph under is from 2015).
Notice the newest survey of the Chukchi Sea estimated about 3,000 bears inhabit the area (AC SWG 2018; Regehr et al. 2018), not less than 1,000 extra that the determine of two,000 utilized in current IUCN assessments and survival predictions (Amstrup et al. 2007; Regehr et al. 2016; Wiig et al. 2015). Wrangel Island is the first terrestrial denning space within the Chukchi Sea (Garner et al. 1984; Rode et al. 2014) and a lately printed examine confirmed that the physique situation (i.e. fatness) and litter measurement of Chukchi Sea polar bears has not been negatively affected by low summer season sea ice (Rode et al. 2021).
In keeping with a brief venture report final week from polar bear specialist Eric Regehr (previously on the US Wildlife Service, now College of Washington), filed on 14 September 2021 (‘Polar bears on Wrangel Island‘), Russian researchers on the Wrangel Island State Nature Reserve have been capable of proceed work that started in 2016 as a joint American/Russian venture. Covid-19 restrictions stored US researchers from taking part in 2020 and once more this 12 months.
There have been no particulars offered on the methodology of the examine and no report on the work is but accessible. However relaxation assured that if any indicators of a inhabitants collapse or ravenous bears had been noticed, it could have been headline information world wide as a substitute of a ‘excellent news’ story on the Polar Bears Worldwide web site. Quite the opposite, the photograph that accompanies Regehr’s article (under) seems to point out a feminine with 4 cubs-of-the-year, a uncommon phenomenon additionally reported in 2017. In actual fact, it sounds just like the Chukchi Sea subpopulation remains to be ‘productive and heathly’ as Regehr instructed the Day by day Mail they have been in 2017, regardless of markedly diminished summer season sea ice since 2007.
Polar bear numbers on Wrangel Island since 2007
Though strategies of counting and quantity of the island surveyed won’t be comparable between years (unimaginable to know at this level), here’s what the reported counts have been 12 months to 12 months:
2020 747 bears (Regehr 2021)
2017 589 bears (Regehr, quoted within the Day by day Mail 2017)
2012 ~200-300 bears (Ovsyanikov and Menyushina 2015)
2013 ~200-300 bears (Ovsyanikov and Menyushina 2015)
2007 ~550-600 bears (Ovsyanikov 2010)
Sea ice circumstances
The variety of bears taking refuge on Wrangel Island through the summer season clearly varies 12 months to 12 months. This variability could also be a perform of native sea ice circumstances, which additionally fluctuate 12 months to 12 months, slightly than reflecting the general numbers of bears within the subpopulation. Nonetheless, opposite to predictions that lack of ice 12 months after 12 months ought to trigger inhabitants stress, counts of bears on Wrangel Island in ‘high-bear’ years have clearly elevated since 2007 regardless of a corresponding decline in summer season sea ice.
This 12 months (at 19 September 2021), Wrangel Island remains to be virtually surrounded by ice, because it was earlier this month, which can imply that fewer bears have spent the summer season on the island. We gained’t know till subsequent 12 months, when this summer season’s survey outcomes are launched, if that has been the case or not.
In 2020 when the survey mentioned above discovered report numbers of polar bears, the pack ice was nicely away from Wrangel Island on the identical date (19 September), as proven under.
Equally in 2017, when 589 bears have been discovered on Wrangel, sea ice extent within the Chukchi Sea at mid-September (under) was extra like 2020: far, far-off.
In distinction, in 2012 (at 13 September, see closeup under) there was a patch of ice round Wrangel regardless that Chukchi Sea ice on the whole was at a really low extent, with solely about 200-300 bears counted on the island. That is what suggests counts for 2021 could also be comparable: most likely not as little as 2012 however decrease than 2020. In high-ice years like 2021, pregnant females might make up the majority of bears that spend the summer season on Wrangel. Time will inform if that’s the case.
AC SWG 2018. Chukchi-Alaska polar bear inhabitants demographic parameter estimation. Eric Regehr, Scientific Working Group (SWG. Report of the Proceedings of the tenth assembly of the Russian-American Fee on Polar Bears, 27-28 July 2018), pg. 5. Revealed 30 July 2018. US Fish and Wildlife Service. https://www.fws.gov/alaska/fisheries/mmm/polarbear/bilateral.htm pdf right here.
Amstrup, S.C., Marcot, B.G. & Douglas, D.C. 2007. Forecasting the rangewide standing of polar bears at chosen instances within the twenty first century. US Geological Survey. Reston, VA. Pdf right here
Garner, G.W., Belikov, S.E., Stishov, M.S., Barnes Jr., V.G. and Arthur, S.M. 1984. Dispersal sample of maternal polar bears from the denning focus on Wrangel Island. Worldwide Convention on Bear Analysis and Administration (now URSUS) 9(1):401-410.
Regehr, E.V., Hostetter, N.J., Wilson, R.R., Rode, Okay.D., St. Martin, M., Converse, S.J. 2018. Built-in inhabitants modeling supplies the primary empirical estimates of important charges and abundance for polar bears within the Chukchi Sea. Scientific Studies 8 (1) DOI: 10.1038/s41598-018-34824-7 https://www.nature.com/articles/s41598-018-34824-7
Regehr, E.V., Laidre, Okay.L, Akçakaya, H.R., Amstrup, S.C., Atwood, T.C., Lunn, N.J., Obbard, M., Stern, H., Thiemann, G.W., & Wiig, Ø. 2016. Conservation standing of polar bears (Ursus maritimus) in relation to projected sea-ice declines. Biology Letters 12: 20160556. http://rsbl.royalsocietypublishing.org/content material/12/12/20160556
Rode, Okay.D., Regehr, E.V., Douglas, D., Durner, G., Derocher, A.E., Thiemann, G.W., and Budge, S. 2014. Variation within the response of an Arctic high predator experiencing habitat loss: feeding and reproductive ecology of two polar bear populations. International Change Biology 20:76-88. http://onlinelibrary.wiley.com/doi/10.1111/gcb.12339/summary
Rode, Okay.D., Regehr, E.V., Bromaghin, J.F., Wilson, R.R., Martin, M.S., Crawford, J.A. and Quakenbush, L.T. 2021. Seal physique situation and atmospheric circulation patterns affect polar bear physique situation, recruitment, and feeding ecology within the Chukchi Sea. International Change Biology 27:2684-2701.
Ovsyanikov, N. 2010. Polar bear analysis on Wrangel Island and within the central Arctic Basin. In, Proceedings of the fifteenth assembly of the Polar Bear Specialists Group IUCN/SSC, 29 June-3 July, 2009, edited by Obbard, M.E., Theimann, G.W., Peacock, E. and DeBryn, T.D., pp. 171-178. Gland, Switzerland and Cambridge UK, IUCN. pdf right here.
Ovsyanikov, N.G. and Menyushina, I. E. 2015. Demographic processes in Chukchi-Alaskan polar bear inhabitants as noticed in Wrangel Island area. pg. 37-55, In: Marine Mammals of the Holarctic, Assortment of Scientific Papers. Vol. 2. Moscow. pdf right here.
Wiig, Ø., Amstrup, S., Atwood, T., Laidre, Okay., Lunn, N., Obbard, M., et al. 2015. Ursus maritimus. The IUCN Pink Record of Threatened Species 2015: e.T22823A14871490. Out there from http://www.iucnredlist.org/particulars/22823/0 [accessed Nov. 28, 2015]. See the complement for inhabitants figures.
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