Tag Archives: spring feeding

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

Breakup of sea ice on track in Canada as critical feeding period for polar bears ends

Relative to recent years and potential impacts on polar bear health and survival in Canada, there is nothing alarming in the pattern or speed of sea ice breakup for 2017, either over Hudson Bay, the southern Beaufort, or the eastern high Arctic.

Sea ice Canada 2017 June 8

Last year at this time (see map below), there was more open water in Hudson Bay and in the Southern Beaufort yet the polar bears came ashore in fine shape that summer and there was no hue-and-cry of dying bears anywhere. Breakup this year is on track to be about 3 weeks earlier than it was in the 1980s, as it has been since at least 2001, a conclusion reached by polar bear specialists (Castro de la Guardia et al. 2017; Lunn et al. 2016), who examined sea ice breakup to 2015.

Sea ice extent Canada 2016 June 8 CIS

Here are critical words to remember (more details here) from biologist Martin Obbard and colleagues (2016:29) on the relationship between body condition and sea ice for Southern Hudson Bay (SH) polar bears, which apply equally well to bears in other regions:

Date of freeze-up had a stronger influence on subsequent body condition than date of break-up in our study. Though models with date of freeze-up were supported over models with other ice covariates, we acknowledge that lower variability in freeze-up dates than in ice duration or break-up dates could have influenced the model selection process. Nevertheless, we suggest that a stronger effect of date of freeze-up may be because even though break-up has advanced by up to 3-4 weeks in portions of Hudson Bay it still occurs no earlier than late June or early July so does not yet interfere with opportunities to feed on neonate ringed seal pups that are born in March-April in eastern Hudson Bay (Chambellant 2010). Therefore, losing days or weeks of hunting opportunities during June and July deprives polar bears of the opportunity to feed on adult seals, but does not deprive them of the critical spring period (Watts and Hansen 1987) when they are truly hyperphagic. No doubt, the loss of hunting opportunities to kill adult seals has a negative effect on body condition, but it appears that for bears in SH a forced extension of the fast in late fall has a greater negative effect on subsequent body condition.” [my bold]

In other words, by mid-June at least (maybe earlier), polar bears have largely finished their intensive feeding that’s so critical to their survival over the rest of the year.

That’s why the latest count of SH polar bears (Obbard et al. 2015) showed a stable population (and see this recent post on WHB polar population estimates). But freeze-up was late last year and that’s what will make the difference to polar bears over the coming year.

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Another fat bear onshore in late winter, along Gulf of St. Lawrence north coast

Another fat bear onshore in late winter, this time along the Quebec shore of the Gulf of St. Lawrence (22 March 2017) – and this time, one of the witnesses to the sighting took some great photos. Courtesy CBC News (Polar bear makes rare appearance on Quebec’s Lower North Shore 24 March 2017).

Gulf St Lawrence North shore PB visit 22 March 2017_CBC headline

Quotes, location map, and sea ice charts below.

Continue reading

Report of Hudson Bay polar bear onshore in winter is rare indeed – here’s why

Late February is still the dead of winter in the Arctic, a time when most polar bears are at their leanest and out on the sea ice trying to find seals – and that means yesterday’s report of a “very fat” polar bear onshore outside Inukjuak is unusual at face value – but my followup inquiry revealed details that make it even more startling.

bear-onshore-end-feb-2017_cbc-photo-facebook

CBC North facebook entry 27 Feb 2017

At my request, CBC North reporter Priscilla Hwang reached out to the hunter involved, who is the mayor of the community. She was told the incident took place on Saturday 25 February 2017 and the very fat bear in the story was actually a young, subadult female.

Subadults are more likely to be in poorer condition than adults at any time of year, due to their lack of hunting experience and competition with adult males. So to see a young bear that’s very fat before the feeding begins is quite astonishing: it suggests that feeding opportunities out on Hudson Bay have been very good over the winter and/or this bear was a savvy hunter despite her youth.

According to the mayor’s report, this community hasn’t had a bear onshore in nearly 30 years. Polar bears in Hudson Bay travel with the retreating ice to the western and southern shores, so with some exceptions, bears usually only have access to the east coast during winter through spring.

Last winter saw an extraordinary number of reports of bears on shore in winter, most of them causing trouble (see summary here). This Inukjuak sighting is the second I’ve come across this year – the other was in Svalbard (a female with cubs). Whether this new pattern is due to more bears or lack of hunting leading to bears having less fear of people – or a bit of both – it’s not yet possible to say.

So under the circumstances, the mayor of Inukjuak’s decision to kill this bear for the protection of the community seems quite reasonable (given the extensive resources required in Svalbard to drive their problem bears away rather than kill them).

Excerpts from the CBC story, and some maps and charts, are below.
Continue reading

Ice formation in W Hudson Bay slower than 2015 but not likely as slow as 1983

After a great start this year for Churchill-area polar bears of Western Hudson Bay – who came off the ice in better than usual condition after what must have been a good spring hunting season – ice maps suggest that freeze-up will be later than last year, an impression confirmed by on-the-ground observers.

Ice coverage this year at 7 November (2016):

sea-ice-extent-canada-2016-nov-7_cis

Ice coverage last year at this date (7 November 2015), see this post for details:
Continue reading

Tracking polar bears in the Beaufort Sea – all bears on the ice in June

The recent open water in the Southern Beaufort didn’t seem to change what polar bears were doing – bears tracked by USGS show them on the ice, likely trying to hunt. More ice edge means more hunting habitat at this time of year.

Beaufort tracking USGS bear-movements-June 2016 lg closeup

However, few hunts are likely successful at this time of year – because only older seals are on the ice and the broken ice makes escape so much easier for the seals (see previous post here). Fat bears on shore this summer (like the ones seen at Kaktovik in September) will tell us that they got enough to eat earlier in the season. Note that bears in good condition that appear at the whaling bone piles in September are there by choice (not stranding) and they got fat by feeding in the spring (March-May), not by picking at leftover whale scraps. Calories from terrestrial sources (for most bears) just reduce the amount of weight they lose over the summer.

More maps below. Continue reading

Critical spring feeding for polar bears is over – sea ice levels are now irrelevant

Polar bears in virtually all regions will now have finished their intensive spring feeding, which means sea ice levels are no longer an issue. A few additional seals won’t make much difference to a bear’s condition at this point.

Relative importance of seasons polar bear graphic_PolarBearScience_June2016

The only seals available on the ice for polar bears to hunt in early July are predator-savvy adults and subadults but since the condition of the sea ice makes escape so much easier for the seals, most bears that continue to hunt are unsuccessful – and that’s been true since the 1970s. So much for the public hand-wringing over the loss of summer sea ice on behalf of polar bear survival! Continue reading