Tag Archives: cub survival

Chukchi Sea polar bears number almost 3000 according to new survey results

The Chukchi Sea finally has a polar bear population estimate! According to survey results from 2016 only recently made public, about 2937 bears (1522-5944) currently inhabit the region, making this the largest subpopulation in the Arctic. This is exciting news — and a huge accomplishment — but the US Fish and Wildlife Service responsible for the work has been oddly mum on the topic.

beaufort-bears_-suzanne-miller-usfws-3-af-2c-on-spit-1.jpg

Not only that, but an extrapolation of that estimate calculated by USFWS researchers for Chukchi plus Alaska (the US portion of the Southern Beaufort Sea subpopulation) was estimated at 4437 (2283-9527), although with “significant uncertainty.” Nevertheless, it means the 2016 estimate for Alaska could be roughly three times what it was in 2010: a whopping 1500 or so, up from about 450 (or about 225-650) for the same area estimated during the last survey (Bromaghin et al. 2015: Fig. 5a).

Even if the real number for Alaska is only twice as large (~1000), that’s still a huge improvement. It would eliminate the Southern Beaufort as the only polar bear subpopulation in the Arctic to have shown a significant decline blamed on human-caused global warming (Crockford 2018). If the recovery is real, it means the 2004-2006 decline was a temporary fluctuation after all, just like previous declines in the region. I expect, however, that it will take a dedicated SB population survey for officials to concede that point.

There is not yet a detailed report to cite (Regehr et al. in prep), but the numbers were announced at the 10th meeting of the Russian-American Commission on Polar Bears held at the end of July this year (AC SWG 2018) by Eric Regehr (formerly of the US Fish & Wildlife Service, as of 2017 at the University of Washington). [h/t to G.H.] This was the same report that raised the quota for subsistence hunting in the Chukchi from 58 to 85, based on these new figures, as I discussed last week.

Wrangel Island polar bear with cubs 2015 news story

From “Military bases to open on Wrangel Island and Chukotka” 22 October 2015.

Regehr was quoted as saying:

“Chukchi bears remain larger and fatter and have not seen downward trends in cub production and survival, according to new preliminary information on the health and numbers of bears.”

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Facts contradict predictions that Chukchi Sea polar bears should be in trouble

Last fall, there were persistent alarms raised about low levels of sea ice in the Chukchi Sea that were echoed this spring. But these low ice levels are not really a serious concern for these polar bears: a 2018 assessment found the bears were in excellent health with no declines in cub production or survival. Funny how little we hear about that.

Wrangel Island polar bear with cubs 2015 news story

From “Military bases to open on Wrangel Island and Chukotka” 22 October 2015.

See a photo essay of Wrangel Island here and of the islands polar bears here and here.

You also don’t hear about the fact that sea ice has declined by about the same amount in the Chukchi Sea as in Western Hudson Bay. Since 1979, sea ice in the Chukchi Sea has declined at a rate similar to Western Hudson Bay (-0.90 days per year vs. -0.86 days per year, respectively), see graphs below from Regehr et al. (2016, Fig. 2):

Regher et al. 2016 fig 2 Barents and Chukchi Sea ice declineRegher et al. 2016 fig 2 Wh Bay ice decline

While Western Hudson Bay bear numbers have declined slightly in number (by a non-statistically significant amount) and appear to have suffered some recent declines in cub survival (Dyck et al. 2017) (with unsubstantiated claims of declines in adult body condition), Chukchi Sea bears have not (Rode and Regehr 2010; Rode et al. 2013, 2014, 2018).

The fact that Chukchi bears are thriving while Western Hudson Bay bears appear to be struggling, given almost identical trends in sea ice decline, is a connundrum that polar bear specialist are loath to explain.

Only last week, it was announced that the quota for subsistence hunting of Chukchi Sea polar bears had been raised from 58 to 85 due to the excellent status of the population. Polar bear biologist Eric Regehr was quoted as saying:

“Chukchi bears remain larger and fatter and have not seen downward trends in cub production and survival, according to new preliminary information on the health and numbers of bears.”

So, despite warnings from the polar bear and sea ice “experts” that Chukchi Sea bears may be in dire straits due to recent sea ice declines (see below), it appears that the bears themselves are more resilient to changing conditions than the experts give them credit.

NSIDC sea ice experts cruising the Chukchi Sea took this photo of a polar bear in excellent condition a couple of weeks ago (early August 2018, A. Khan), despite the scary-looking melt ponds:

Chukchi Sea polar bear Arctic_early August 2018_A Khan NSIDC

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Chukchi polar bear status contradicts the “message” – new details

Previously, I summarized preliminary results of polar bear research in the Chukchi Sea undertaken between 2008 and 2011 by US Fish & Wildlife biologist Eric Regehr and US Geological Survey researcher Karyn Rode. At the time, a peer-reviewed paper on this study was promised shortly.

It now appears this paper is indeed on the way. I’m sure of that because a few weeks ago, I came across a conference presentation given by Karyn Rode that is a summary of the upcoming Chukchi research paper. The title of both presentation and ‘in review’ paper is:

“Variation in the response of an Arctic top predator experiencing habitat loss: feeding and reproductive ecology of two polar bear populations.

Rode’s slide presentation (given at the annual Lowell Wakefield Fisheries Symposium at the end of March, in Anchorage, Alaska) was posted online by the symposium organizers. It provides some very interesting details on the status of Chukchi Sea bears compared to bears in the Southern Beaufort, and contains some mighty “inconvenient” conclusions that should raise some eyebrows.

I’ve summarized these details and conclusions below in point form, below the maps.

Figure 1. Chukchi and Beaufort Seas (from Wikipedia), upper. ‘Chukchi Sea’ polar bears are shared between the USA and Russia; ‘Southern Beaufort’ bears are shared between the US and Canada, lower (from PBSG, with labels added). Pink dots are the subpopulations featured in the Rode et al. presentation and upcoming paper.

Figure 1. Chukchi and Beaufort Seas (from Wikipedia), upper. ‘Chukchi Sea’ polar bears are shared between the USA and Russia; ‘Southern Beaufort’ bears are shared between the US and Canada, lower (from PBSG, with labels added). Pink dots are the subpopulations featured in the Rode et al. presentation and upcoming paper.

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