Tag Archives: survival

Tracking polar bears in the Beaufort Sea in July & sea ice comparison with 2007/2012

Only four Alaskan polar bear females had USGS satellite collars left transmitting locations in the Beaufort Sea and all four of these bears were on the ice during July, 2016. The same was true in June and May.

Beaufort tracking USGS bear-movements-July 2016 sm

Original caption: “Movements of 4 satellite-tagged polar bears for the month of July, 2016. Polar bears were tagged in 2015 and 2016 on the spring-time sea ice of the southern Beaufort Sea. All 4 of these bears have satellite collar transmitters. Polar bear satellite telemetry data are shown with AMSR2 remotely-sensed ice coverage from 31 July, 2016.” Original here.


There looks like a lot of open water for this time of year but in terms of absolute extent there is somewhat less ice than there was in 2007 and only slightly less than 2012, according to NSIDC Masie charts. And of course, what we know is that polar bears of the Chukchi Sea and the Southern Beaufort not only survived the low ice summers of 2007 and 2012, they thrived: CS bears were in great condition and reproducing well, and BS bears were recovering from the devastating thick ice conditions of the 2004-2006. Have a look at the maps below. Continue reading

Polar bear survival: habitat 2013 vs. 2016 for 22 January

Using sea ice maps issued by the National Sea Ice Data Center (NSIDC), it’s interesting to compare these two years with respect to polar bear health and survival (keeping in mind that no polar bears live in what I like to call the armpits of the Arctic – the Sea of Okhotsk, the Baltic Sea or in the Gulf of St. Lawrence)1:

22 January 2016

Sea ice extent 2016 Jan 22 NSIDC

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Summer polar bear habitat then & now – little impact from 2007 record-breaking sea ice low

Sea ice looks low for this time of year but how does it compare to 2007, when summer ice habitat for polar bears hit a record-breaking low?  What can the impact of 2007 ice levels on polar bears tell us about what to expect this year?

Sea ice at 2015 Aug 8 vs pb status map_Aug 9 2015 sm

By this date in 2007 (8 August, Day 220, NSIDC Masie map below), there was almost 1 million km2 less ice than there is this year (map above). However, look which polar bear subpopulations not only survived, but thrived, through the 2007 low ice summer: Chukchi Sea, Southern Beaufort, Barents Sea, Davis Strait, Foxe Basin, Western Hudson Bay, and Southern Hudson Bay. That’s all of the subpopulations for which we have recent data.

There is more than a month left in the melt season, of course. However, while 2012 finished with a lower minimum ice extent due to a massive mid-August storm that broke up a lot of ice (Simmonds and Rudeva 2012), by the end of the first week of August (i.e, the 8th), there was more  ice in 2012 than in 2007 and a bit less than this year (2012, 6.3 mkm2; 2007, 5.6 mkm2; 2015, 6.5 mkm2).

This means if less summer ice for a longer period of time impacts polar bear health and survival, conditions in 2007 should have had a noticeable impact on polar bears around the world. They didn’t. That suggests even if this September sea ice minimum is as low as 2007, it won’t have any negative impact on polar bear health or survival. The most profoundly negative documented impacts have come from thick sea ice in spring or  suboptimal spring snow levels (Crockford 2015) and the evidence shows that variation in the extent of summer ice is simply irrelevant to polar bears.

Sea ice at 2007 Aug 8_polarbearscience
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IUCN Polar Bear Specialist Group out-lived its usefulness 20 years ago

The IUCN Polar Bear Specialist Group (PBSG) should have been disbanded in 1996, the year polar bears were down-graded from a status of ‘vulnerable to extinction’ to ‘lower risk – conservation dependent’ (now called ‘least concern’) on the IUCN Red List.

Bumpersticker from Cambridge Bay, Nunavut, courtesy Joe Prins.

Bumpersticker from Cambridge Bay, Nunavut, courtesy Joe Prins.

Polar bears had recovered from previous decades of wanton over-hunting — by all measures used by the International Union for the Conservation of Nature, they were a conservation success story.

Why did the IUCN and Arctic governments not break up the PBSG back in 1996? Leaving the group intact once polar bears were down-graded to ‘least concern’ simply made its members desperate to justify their existence. That’s precisely what we’ve seen over the last 20 years — PBSG members working tirelessly to ensure the organization didn’t go extinct.

pbsg logo

In fact, polar bears are in no more danger of extinction now than they were in 1996, despite dedicated efforts of the PBSG to convince the world otherwise. Take a look at the history and see if you come to a different conclusion.
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Polar bears in winter – a seasonal review of insights and research

Here are summaries of my “Polar bears in winter” series. It’s an interesting recap of what polar bears do over the unimaginably cold and dark months of an Arctic winter.

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Labrador polar bears face a longer ice-free season than Hudson Bay bears, but do well

Pretty typical ice levels in both regions for this time of year – Davis Strait polar bears (especially those in Labrador) are still onshore while Hudson Bay bears (even those in the south) have their sea ice hunting platform back.

Davis Strait Hudson Bay freeze-up at Nov 25 2014_PolarBearScience

Funny thing is, the Davis Strait subpopulation may still be increasing despite a longer ice-free season than Western Hudson Bay. And bears in the south of that region – who spend the summer onshore in Labrador – have the longest ice-free season of all1 yet according to the latest survey they were even doing better than bears in northern Davis Strait.

That apparent paradox has an easy explanation – sea ice extent in late summer/early fall (length of the ice-free season) has much less of an impact on polar bear health and abundance than the state of the food supply in the spring. More seals in spring, polar bears do well; few seals in spring, polar bears starve.

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Natural selection helps polar bears adapt to sea ice variability – which means some bears die

Evolution is not just for the long-term – natural selection also goes on over short time periods. In the case of polar bears, this adaptation is almost certainly critical for its long-term survival.

Hudson Bay female with cub_Wapusk_Thorsten Milse_Gov CA

Hudson Bay female with cub Wapusk National Park, Thorsten Milse, Government of Canada

Not all polar bears are identical — that is the reality that allows natural selection to operate.

I will argue that early breakup years in Western Hudson Bay weed out individual polar bears that do not have the physiological or behavioral characteristics necessary to be useful members of the population – and that this is a good thing for the entire population.

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Andrew Derocher raises the “starving polar bears” issue in DailyMail interview

In what looks like a follow-up to last week’s CBC documentary, The Politics of Polar Bears, the London (UK) based DailyMail published interviews with polar bear biologists Mitch Taylor and Andrew Derocher (September 9, 2014).

The CBC film did have a one scientist vs. another” flavor about it and this article definitely echoes that approach. My comments below on Derocher’s insinuations and questions about starving bears and global warming.
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New genetic study confirms polar bears survived several warm Interglacials

There is a new polar bear genetics paper out in the Journal of Heredity, by University of Alaska Fairbanks genetics professor Matt Cronin and colleagues. Matt Cronin, in case you didn’t know, was the first to pick up the close genetic relationship between polar bears and grizzlies, as a result of research he and colleagues did back in the early 1990s (Cronin et al. 1991).

Figure1 from Cronin et al. 2014 (in press) showing the locations of bear samples used in their genetic study. MT, Montana; AK, Alaska; Polar bear samples were from the Chukchi, Beaufort and Barents Sea populations.

Figure 1 from Cronin et al. 2014 (in press) showing the locations of bear samples used in their genetic study. MT, Montana; AK, Alaska; Polar bear samples were taken from the Chukchi, Beaufort and Barents Sea populations.

While no earth-shattering new information was revealed in this new study, reported over the weekend by the Alaska paper SitNews (March 15), it used a more detailed method to confirm the results of previous work – that polar bears have been around long enough to have survived several past Interglacial periods that were warmer than today (with less ice in the Arctic) and are genetically distinct from grizzlies.

A feature that really set this work apart was how it was promoted.
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Guest post: How ‘science’ counts bears

This essay by Dr. Jim Steele, professor emeritus, San Francisco State University, is reblogged from a July 3 2013 post at WUWT post, with Dr. Steele’s permission. I am not a field biologist and have never done a mark-recapture study but Dr. Steele has. His perspective on the way polar bear biologists count bears and estimate survival in the Southern Beaufort is a perfect companion to yesterday’s post, a related post that I’ll put up later this week, and this one from December, among others. I’ve added links to the references cited in this essay where they are available, as is my custom. See the original post for Jim’s responses to comments and questions.

Guest post by Jim Steele   “How ‘science’ counts bears”

The Inuit claim “it is the time of the most polar bears.” By synthesizing their community’s observations they have demonstrated a greater accuracy counting Bowhead whales and polar bears than the models of credentialed scientists. To estimate correctly, it takes a village. In contrast the “mark and recapture” study, which claimed the polar bears along South Beaufort Sea were victims of catastrophic global warming and threatened with extinction, relied on the subjective decisions of a handful of modelers.

In mark and recapture studies, the estimate of population abundance is skewed by the estimate of survival. For example, acknowledging the great uncertainty in his calculations of survival, in his earlier studies polar beat expert Steven Amstrup reported three different population estimates for bears along the South Beaufort Sea. If he assumed the adult bears had an 82% chance of surviving into the next year, the models calculated there were 1301 bears. If survivorship was 88%, the abundance climbed to 1776 bears. If he estimated survivorship at a more robust 94%, then polar bear abundance climbed to 2490.1 Thus depending on estimated survival rates, a mark-and-recapture study may conclude that the population has doubled, or that it has suddenly crashed.

Here are the simplified basics of estimating survival.

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