Monthly Archives: March 2016

Late winter surge in sea ice habitat and the resilience of Svalbard polar bears

The Barents Sea – and Svalbard in particular – has had very little sea ice this winter but recent evidence suggests pregnant females adapted by moving east to Franz Josef Land to have their cubs. The surge in ice that’s come over the last few weeks will, however, be welcome habitat for the critical hunt of fat newborn seals that takes place primarily in April and May.

Svalbard polar bear_NP015991-isbjorn-JA

It was only last fall that Norwegian biologist Jon Aars (photo above taken by him in August 2015) was touting the fat condition of Svalbard-area polar bears he and his team saw in August and admitted the population had increased by a whopping 42% since 2004 – despite dire predictions of a drastic decline. In fact, 2014/2015 was a great year for the area’s polar bears.

However, in the fall of 2015 sea ice was so late forming around Svalbard that it seemed impossible that any females would get to traditional denning grounds on the east coast in time to give birth. There was no sea ice to speak of until late December, so it seemed virtually certain that all females had gone to Franz Josef Land further east (in Russia) – as they are known to do – to utilized its alternative denning sites.

It’s called resilience – the ability to shift behaviour in response to changing conditions. In this case, all indications are that shifting den locations to Franz Josef Land is a long-standing response of Svalbard area polar bears to low ice conditions. This shift does not even require a movement outside their subpopulation boundaries, let alone a movement outside the ill-defined “sea ice ecoregions” originally defined by Steven Amstrup and colleagues (2008) to support their prediction that polar bears will likely be extinct by 2100, taken up later by others since.

Some polar bear specialists appear to believe that if Barents Sea conditions are not precisely what they were in the 1980s (examples here and here), polar bears cannot possibly survive. But the bears are showing them otherwise – and demonstrating how they likely survived previous warm periods like the Holocene Optimum ~9,000 years ago and the Eemian Interglacial ~115,000-130,000 years ago (CERQA 2014:66) without population numbers getting anywhere near extinction levels.
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2016 record low maximum will make headlines but unlikely to affect polar bears

Never mind that the sea ice maximum this year came almost a month later than last year (and close to latest since 1979) – and was lower by only .02 – the US National Sea Ice Data Center (NSIDC) today trumpeted a new record low.  What this means to polar bears, if anything, remains to be seen.

Sea ice extent 2016 March 24 NSIDC_max 14_52mkm2 sm

2015: maximum set February 25 (day 56), at 14.54 mkm2

2016: maximum set March 24 (day 84), at 14.52 mkm2

[The difference in area? Smaller than the Islands of the Bahamas]

Latest maximum extent (since 1979) occurred in 2010 on April 2 (Day 92).

The average date for maximum extent is March 12.

I note, however, that given the lateness of the winter sea ice surge meant that the amount of ice present at 24 March 2016 (see NSIDC Interactive) was more than was present on the same date in 2006, 2007 and 2015.

Clearly, there was plenty enough sea ice in the spring of those years for most polar bears to hunt seals successfully and put on the weight they needed to survive the summer fast ahead. I see no reason to expect 2016 to be different.

Polar_Bear_male_Regehr photo_March 21 2010_labeled
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Both sides now: New paper critiques Canadian polar bear population status

Demographic and traditional knowledge perspectives on the current status of Canadian polar bear subpopulations. 2016 (in press). Jordan York, Martha Dowsley, Adam Cornwell, Miroslaw Kuc and Mitchell Taylor. Ecology and Evolution 6(9):2897-2924. DOI: 10.1002/ece3.2030

York et al 2016 fig 1_numbers 2013

Take home quote:

“We see reason for concern, but find no reliable evidence to support the contention that polar bears are currently experiencing a climate crisis. We suggest that the qualitative projections for dramatic reductions in population numbers and range are overly pessimistic given the response of polar bears, climate, and sea ice to the present.”

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Condition of S Hudson Bay polar bears varies with freeze-up only says new study

Despite the fact that the polar bears of Southern Hudson Bay (SHB) live further south year round than any others, a recent study found their average body weight has declined relatively little since the 1980s. There has been no decline in the size of the population over that time either. Perhaps that’s why there was neither a press release nor a massive media blitz when this paper came out earlier this month.

James Bay female and cub_Ontaro Govt

Remarkably – despite what we are told about how critical breakup dates are to polar bear health and survival in Hudson Bay – this study found that for SHB bears, the small decline in body condition index correlated only with freeze-up dates, not breakup dates or length of the ice-free season. They also found that regional breakup and freeze-up dates relevant to polar bears in this area was the day when ice cover reached 5% (not 50%).

In other words, SHB polar bears left the ice (or returned to it) when the average ice  cover near the coast was about 5%. This finding is yet more evidence that the meteorological definition of “breakup” (date of 50% ice cover) used by many researchers (see discussion here) is not appropriate for describing the seasonal movements of polar bears on and off shore.

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Polar bears onshore in winter – will more bears mean more deadly attacks?

Incidents of polar bears causing problems onshore this winter (January & February) – including one that killed a horse in Greenland and another that threatened a resident in western Hudson Bay (only weeks after several incidents in southern Labrador) may be the tip of a very scary iceberg. I’ve taken a look at what records exist of this phenomenon, which in the past often involved deadly attacks. The large number of reports this winter appears to be a real increase, which is a rather terrifying prospect indeed.

Doug Clark photo polar bears onshore in Feb 2013 Wapusk NP

In winter, all polar bears except females in dens nursing newborn cubs are presumed by biologists to be on the sea ice hunting but it turns out that is not quite true. Although relatively rare over the last twenty years or so, it appears that in some areas, bears are now coming ashore in winter.

The photo above shows a polar bear photographed by a remote camera installed at Broad River Camp, Wapusk National Park, western Hudson Bay on 7 February 2013. It was visible to the camera for 40 minutes but apparently caused no trouble (camera installed and maintained by associate professor Doug Clark from the University of Saskatchewan and colleagues).

Given the fact that there are now many more polar bears than there were in the 1970s as well as more people living in many coastal Arctic communities, problems with bears in winter are likely to increase, as this winter’s events show. More bears out on the ice in winter (January-March) will almost certainly create more competition for the little bit of food that’s available (seals are hard to catch in winter), which means some bears might increasingly be looking for alternate sources of food onshore.

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Challenging Alaska polar bear research sound bites and bewildering ESA status

Beaufort Sea male polar bear USGS_2005 Amstrup photo

It’s easy to take polar bear research papers at face value but it’s not very scientific. The snappy sound bites provided for the benefit of the media – whether they’re embedded in press releases or in published abstracts – don’t cut it with trained scientists. Trained scientists read the whole report, critically examine the evidence it contains and assess that evidence within the context of previous knowledge. That’s what they are trained to do.

I challenge the superficial summary on the status of Alaskan polar bear populations provided by journalist Vanessa Schipani.  Schipani disputed a comment made by Alaska Senator Lisa Murkowski that, according to the latest research Alaskan polar bear population numbers are strong and healthy. I’m not especially interested in the political context of the statement, only Schipani’s bald claim that Murkowski’s declaration is false.

I’ve read all the relevant papers in full and I contend that the evidence supports Murkowski’s statement. Schipani is confusing the issue by regurgitating ‘facts’ that don’t tell the truth of the matter. By the sum of accounts, Alaskan polar bear populations are indeed healthy and strong – whether or not this status will continue is an entirely different question. Continue reading

A new count planned for Southern Beaufort polar bears

I know I was not the only one that thought the last polar bear count conducted by the US Geological Survey (USGS) in the Southern Beaufort generated an untenable result but it appears that some of those challengers are in a position to demand a recount.

polar_bear_usfws_no date_sm

CBC News ran a story late last week announcing a plan is in the works to do an aerial survey of Southern Beaufort Sea polar bears across their entire range over two years starting in 2017 (11 March 2016, “Joint U.S.-Canada Beaufort Sea polar bear survey planned“).

With luck, this period will not include another bout of the same thick spring ice conditions that decimated the population in the mid-2000s (which many reporters concluded was due to reduced summer sea ice because that’s what leading biologists implied). Even if it does, lucky timing will not negate the fact that this population is routinely subjected to devastating population declines caused by natural changes to spring sea ice conditions from which they have recovered on numerous occasions. Continue reading