Scientific study finds polar bears excel at diving, contradicting previous expert opinion

A recent study by Norwegian biologist Karen Lone and colleagues, who tagged 57 polar bear females with sensors around Svalbard, discovered that polar bears can dive to a maximum depth of 13.9m and can swim long distances across open water without rest. Contrary to previous claims, polar bears are excellent divers and their breath-holding ability did not seem to limit how deep they could dive.

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From the abstract of the new paper by Lone and colleagues (Lone et al. 2018):

“Some bears undertook notable long-distance-swims. Dive depths up to 13.9 m were recorded, with dives ≥5 m being common. The considerable swimming and diving capacities of polar bears might provide them with tools to exploit aquatic environments previously not utilized.”

Compare the above statement to one made by Stirling and van Meurs (2015), after describing a 3 minute dive video-taped during an aquatic stalk of a bearded seal, also in the Svalbard area:

“…increased diving ability cannot evolve rapidly enough to compensate for the increasing difficulty of hunting seals because of the rapidly declining availability of sea ice during the open-water period resulting from climate warming.” [my bold]

These two papers really show the difference between using anecdotal accounts as if they were evidence of species-wide physical abilities and doing a scientific study on the physical ability of interest.

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New paper provides no evidence that polar bears ate whale carcasses to survive Eemian interglacial

Contrary to what the misleading press release implies, an entirely speculative new paper by polar bear specialists Kristin Laidre and Ian Stirling (among others) presents zero evidence that polar bear consumed whale carcasses during the last warm Interglacial (Eemian, ca. 115-130kya). And contrary to the impression that Eemian conditions were very challenging for polar bears, simulations from the single paleo sea ice simulation paper these authors cite show the ice-free season over most of the Eemian was less severe than today in the polar basin, with no reason for polar bears to scavenge extensively on large whale carcasses.

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Polar bears are shown scavenging on the carcass of a dead bowhead whale that washed ashore on Wrangel Island, Russia. Credit: Chris Collins/Heritage Expeditions

This is yet another paper posing as science co-authored by Stirling that uses anecdotal accounts of behaviour to send a message about evolutionary capabilities of polar bears (Stirling and van Meurs 2015). With little or nothing to back it up, the paper’s real purpose is to convey Stirling’s opinion that past polar bear survival is irrelevant to understanding future polar bear survival — and that all the bears are gonna die unless we do something about carbon dioxide emissions generated by fossil fuel use.

Is it a coincidence that the Summary for Policy Makers was issued by the IPCC over the weekend (not the report with the science in it but the document that all politicians agreed were acceptable)? Look no further than the last sentence of National Geographic’s article on this story, which includes a quote from lead author Laidre and a link to the magazine’s interpretation of the new IPCC report:

“Laidre put it even more bluntly: “If you want polar bears around we need sea ice, and loss of sea ice closely tied to our activities and our fossil fuel emissions.” (Learn about the IPCC’s dire new climate report.)” 

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Now at least 10 years with sea ice at 2050-like levels yet polar bears are still abundant

We’ve hit the seasonal Arctic sea ice minimum for this year, called this morning by US NSIDC for 19th and 23rd of Septmeber: 4.59 mkm2, the same extent as 2008 and 2010. This is not a “ho-hum” year for polar bears: it means that since 2007, they have triumphed through 10 or 11 years1 with summer ice coverage below 5.0 mkm2 —  levels that in 2007 were expected to cause catastrophic declines in numbers.

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Summer sea ice below 5.0 mkm2 were not expected to occur until about 2050, according to 2005/2006 sea ice models and polar bear specialists at the US Geological Survey (USGS). Polar bear survival models predicted 2/3 of the world’s polar bears would disappear when ice levels reached this threshold for 8 out of 10 years (Amstrup et al. 2007, 2008; Hunter 2007) but polar bears have been more resilient than expected (Crockford 2017, 2018; Crockford and Geist 2018). In fact, in many areas (like the Chukchi Sea, Barents Sea and Foxe Basin) polar bears are thriving despite dramatic declines in summer sea ice coverage (Aars et al. 2017; ACSWG 2018; Peacock et al. 2013; Regehr et al. 2016; Stapleton et al. 2016).

The sea ice models used to support the addition of polar bears to the US Endangered Species List as ‘threatened’ with extinction suggested sea ice levels from 3-5 mkm2 would not occur unti mid-century, yet they dropped before the ink was dry on the 2007 USGS Reports (ACIA 2005; Hassol 2004; Holland et al. 2006; Solomon et al. 2007; Zhang and Walsh 2006).

The ice extent charts from the University of Bremen (below) show ice that’s 50% concentration or greater at the date of the seasonal minimum (19th September): what polar bear specialists define as preferred habitat (Amstrup et al. 2007).

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Compare the minimum shown above to the coverage predicted for 2050 and to coverage at the minimum in 2012 (the NSIDC image is here):

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Inuit hunters frustrated by polar bear conservation rules that put their lives at risk

‘The rules are taking over Inuit tradition and the bears are taking over Inuit. We’re just watching in the distance, afraid of these bears because they’re free to do whatever they want.’ says Brian Aglukark, after two fatal polar bear attacks this summer (CBC,  24 September 2018).

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Here’s an excerpt (my bold): continue reading

Polar bears that killed Foxe Basin hunter in August were in good condition, say officials

Just in from NunatsiaqNews (6 September 2018): The polar bears that killed Foxe Basin resident Darryl Kaunak were in good condition, as were the bears who approached the group of hunters after the fact. And the bear that mauled Arviat resident Aaron Gibbons in early July was an adult male in “fair” condition, according to necropsy results.

Foxe Basin polar_bears_rowley_island_Stapleton 2012 press photo labeled sm

In all, no evidence that lack of sea ice was to blame. Quotes below.

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The politics of starving polar bears: my op-ed in the National Post last week

In case you missed it: The real story behind the famous starving polar-bear video reveals more manipulation (29 August 2018).

Chukchi Sea polar bear Arctic_early August 2018_A Khan NSIDC

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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.

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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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