Tag Archives: seals

USGS ‘treadmill’ paper repeats bogus claim that ice loss harmed polar bears

The newest polar bear science paper making the rounds courtesy the US Geological Survey, is a perfect example of a statistically-significant result with no biological significance. While the results are rather lame, the paper is dangerous because it repeats the disingenuous claim (see Crockford 2017) that Southern Beaufort Sea polar bear numbers declined in recent years due to summer sea ice loss.

polar_bear_rubble_ice_Mike Lockhart USGS_8 April 2011

The USGS authors (Durner et al. 2017) know this harm-from-summer-ice-loss assertion is not true for the Southern Beaufort subpopulation but the more papers they can get into print that say so, the more likely it will be believed — and the less likely readers will check older literature that documents the recent decline in polar bear numbers was due to a three year period (2004-2006) when thick ice conditions in spring made seal hunting a challenge, a repeat of a well-known phenomenon (e.g. Stirling et al. 1980; Stirling 2002) unique to this region that has been documented since the 1960s.

The Durner paper (USGS press releaseIncreased Sea Ice Drift Puts Polar Bears on Faster Moving Treadmill” published online 6 June ahead of print) spins the research results as potentially significant bad news but in so doing reveals how desperate they have become to make the public and their biology colleagues believe that Southern Beaufort polar bears, among others, are being negatively affected by summer sea ice loss (as per Stirling and Derocher 2012).

Durner, G.M., Douglas, D.C., Albeke, S.E., Whiteman, J.P., Amstrup, S.C., Richardson, E., Wilson, R.R. and Ben-David, M. 2017. Increased Arctic sea ice drift alters adult female polar bear movements and energetics. Global Change Biology. DOI: 10.1111/gcb.13746 http://onlinelibrary.wiley.com/doi/10.1111/gcb.13746/abstract [paywalled]

In fact, the Durner et al. paper does not document any harm to polar bears from the proposed ‘treadmill’ effect of more rapidly moving ice for the period 1999-2013 compared to 1987-1998, but instead uses models to suggest bears might have to eat one to three more seals per year to compensate for the extra energy needed to walk against the moving ice. That’s right: perhaps only 1 more seal per year out of the 50 or so they would usually consume (see Stirling and Øritsland 1995). In my opinion, that’s a pretty lame result for what one of the co-authors described as an immense amount of work.

News outlets have essentially used the USGS press release as a click-bait lede for another round of Trump-bashing with respect to the Paris climate change agreement, see here and here: the stories are hardly about polar bears at all. And predictably, polar bear activist and co-author Steven Amstrup (paid spokesperson for Polar Bears International, famous for their “Save Our Sea Ice” campaign) appears to be using the same approach: an up-coming call-in talk radio program at NPR’s Anchorage affiliate KSKA for Tuesday 13 June at 10:00 (Alaska time, see “Talk of Alaska”) is being billed as a discussion of “polar bears, climate change, and the Paris Accord” (h/t AK geologist). Continue reading

An El Niño year late start to freeze-up on Hudson Bay: bears gearing up to hunt

There is no serious ice on the west shore of Hudson Bay yet (as the map below shows) but the winds have just shifted – instead of coming from the south, they are now blowing in from the north.

Freeze-up and a resumption of seal hunting for Western and Southern Hudson Bay polar bears looks imminent. The bears get out on the ice as soon as they are physically able, when the ice is about 3-4 inches thick (about 10 cm).


I’m going to let Kelsey Eliasson from PolarBearAlley, on shore at Churchill, convey the gist of the freeze-up situation on the Bay.

Recall that freeze-up was late in both 1998 and 1999 – during the height of that strong El Niño warmth as well as the year following. Continue reading

Polar bear habitat this fall shaping up fast – more like 2010 than 2007

Arctic sea ice tied 2007 for extent at the September minimum less than 3 weeks ago but with the refreeze proceeding much faster than 2007, seals will soon be returning to the ice edge and polar bears will be back to feeding like they did in 2010.


Sea ice extent less than 5.0 mkm2 lasted less than 6 weeks (23 August – 28 September), according to NSIDC.

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Polar bears seldom catch seals they stalk in summer – it’s why they fast

This short BBC video shows why polar bears are so often unsuccessful in their summer hunts – adult bearded seals are the species most often available on the ice. These seals are not only predator-savvy but there are lots of escape routes in the melting ice, and this has always been so.

“Hungry polar bear surprises a seal – The Hunt: Episode 2 Preview – BBC One”

Melting ice in summer is not a new phenomenon (e.g. NASA photo below from mid-July 2016) – Thomas Grenfell and Gary Maykut described the process of melt pond development back in the 1970s:

“Melt ponds reach the maximum extent shortly after the disappearance of the snow, when they may cover upwards of 50% of the ice.”


Melting summer ice has always made it challenging for polar bears to catch seals, as this quote from Ian Stirling (1974) show, based on his work in the Central Canadian Arctic in the summer of 1973 (July and August):

There is a great abundance of natural holes in the ice during summer, anyone of which a seal could surface through.

This is still true in areas like the Southern Beaufort Sea today (e.g. Whiteman et al. 2015): the ice melts and in some areas, disappears completely in summer.

It’s why polar bears – unlike other species of bears in summer – depend on their stored fat to see them through until the ice reforms in the fall.

The meme “If there’s no ice, there’s no ice bear” is political-style rhetoric, not science.

[When polar bear scientists say “sea ice” or “ice” – they mean summer sea ice. Sea ice in winter and spring are not predicted to decline by 2100 to any appreciable degree and that has been true since sea ice predictions began]

Polar bears in Hudson Bay and Davis Strait routinely go 4-5 months without sea ice in the summer and have done since studies on them began. Yet, all of the polar bear subpopulations in Hudson Bay and Davis Strait are stable or increasing.

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Five years of polar bear habitat at June 20 around the Arctic

Five years worth of sea ice maps for the same date is hard to come by in this country, since the Canadian Ice Service does not archive their daily sea ice maps. However, due to some forethought, I have at hand ice maps going back to 2012 for the longest day of the year for Canada and archives for other regions provide similar perspective at the solstice.

Polar_Bear_male on sea ice_Regehr photo_March 21 2010_lg

Few photos of polar bears in June likely exist – too early for most bears to come ashore and the ice too unstable for humans to be offshore [photo above is dated March].

Compare the five maps for Canada and eastern Alaska below. Notice the differences for Hudson Bay: it may seem ironic, but 2012 (which had the lowest September minimum since 1979 due to an August storm) had the most typical Hudson Bay breakup/melt pattern compared to previous years. [Keep in mind this recent post about how much ice can remain even when almost none is visible on the ice maps]

In many regions, polar bear hunting efforts are seldom successful after early June because young-of-the-year seal pups have taken to the water to feed, which means the only prey still on the ice are predator-savvy adults and subadults that have an easy time escaping in the rapidly breaking up ice fields. Bears that come ashore in June likely are not missing much – a little less ice than usual at this time of year is not going to make much difference.

Overall, despite doom and gloom predictions we heard in March 2016 (“wintertime extent hits another record low”), sea ice extent (courtesy NSIDC) at 20 June 2016 was the same at this date as it was in 2010 and 2012 at this time of year – which essentially marks the end of the primary feeding period for polar bears (except for those that live in the Canadian Arctic Archipelago, where seals give birth a bit later in the spring).

Sea ice at 20 June_2016 vs 2012 and 2010_NSIDC interactive

And did polar bears die in droves due to conditions in 2010 or 2012, in any subpopulation around the Arctic affected by low sea ice levels? No, they did not. In fact, the subpopulation that had the most recent survey done (Svalbard portion of the Barents Sea – 2015) was not only found to be thriving but numbers had increased markedly (42%) over 2004 levels. Now that’s resilience!

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More polar bear habitat in Hudson Bay region at mid-May than in 2006 & 2011

What a difference a bit of historical perspective can make to one’s attitude on the annual Arctic sea ice breakup.


The usual recent pattern (since 1979) has been for breakup to begin on the east side. However, this year and last (below), it has begun in the NW (as it did in 1990 and a few other years).

Not all of the open water is due to melt, of course. As I discussed last week in relation to the Southern Beaufort Sea, winds and prevailing currents at this time of year start to fracture the ice and move it around well before much significant melt has begun.

Compare 2016 (above) to 2006 (below), when there was 0.1 mkm2 less overall – with much less ice in Hudson Strait and in the east of Hudson Bay than this year:

Compare to 2011, when there was also 0.1 mkm2 less overall than this year:

It’s important to keep in mind that the intensive feeding season for polar bears is drawing to a close – within another two weeks, most young-of-the-year seals will be in the water feeding and inaccessible to bears.

The only seals on the ice during June and July are predator-savvy adults and subadults that have hauled out to moult and for these seals the rapidly disintegrating ice creates many escape routes. That means that as long as the ice breakup sequence allows polar bears to get their fill of young seals before the end of May, even during early breakup years most bears should be fat enough to survive the coming summer and winter fasts (see more here). So we should expect to see some bears coming ashore within the next two weeks.

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Tracking polar bears in the Beaufort Sea in April 2016 and early polynya formation


Here’s the update on the polar bears fitted with satellite collars or ear tags in the Beaufort by USGS biologists over the last two years. Five new bears were added last month, which means there are now thirteen bears being tracked. Ice conditions are somewhat different than they have been in the past but concluding that such a situation means trouble is premature, I think (see here). Continue reading