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.
Posted in Life History, Sea ice habitat
Tagged bearded seals, Davis Strait, facts, Hudson Bay, hunting, no ice, no ice bear, platform, polar bear, sea ice, seals, summer
The traditional gift for a 4th anniversary is flowers, so to celebrate 4 years of blogging at PolarBearScience, I’m highlighting a CBC article from last year that featured the work of photographer Dennis Fast, who captured some fantastic images of polar bears cavorting in a field of fireweed near Churchill (see screencap below from the 2015 CBC feature, more at the DailyMail for 21 August 2015). Great photography – it deserves another look.
Hard to imagine that four years have passed! Cheers to Hilary Ostrov (who blogs at The view from here) for getting me over my initial frustrations with WordPress – without which I’d never have made it this far – and for her much-appreciated typo alerts [Hilary is still dealing with on-going health issues but we talk on the phone from time to time.]
And thanks of course to my readers, who’ve made it all worthwhile. I truly appreciate all your tips and feedback. The word is getting out, via tweets and retweets, reblogging, personal blog and Facebook discussions, as well as links back to particular posts in the comments of news articles and other internet content, and straight up media mentions. The sum of it all has brought us to this point: 495 posts, over 764,000 views, and more than 411,000 visitors. Not too shabby for a single issue science blog, eh?
I thought of adding a Tip Jar button for next year, but decided against it – instead, if you’d like to support my efforts here, you can buy my polar bear attack novel (give it as a gift if you’re not keen on this type of fiction). I’d be just as grateful. See the sidebar for the link.
But back to business – below find sea ice maps of polar bear habitat at 25 July (‘Christmas in July’), this year as well as some previous years.
Posted in Polar bear attacks, Sea ice habitat, Uncategorized
Tagged anniversary, blogging, Christmas in July, Churchill, Dennis Fast, facts, Hudson Bay, ice extent, media, polar bear, posts, sea ice, stats, views, visitors
There is slightly less ice this year in Hudson Bay than last year but it is hugging tight against the western shore, which means polar bears in Western and Southern Hudson Bay will be able to stay out on the ice (if they want to) until August.
The latest weekly ice graph from the Canadian Ice Service (for 9 July) below shows average ice coverage this year (and more than there was in 1976 and 1977):
[By the way, the IUCN Polar Bear Specialist Group website is still “under construction” allowing them to avoid mentioning the less-than-dire conclusions contained in the 2015 IUCN Red List assessment]
More ice maps below, comparing previous years.
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.
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).
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!
Posted in Life History, Sea ice habitat
Tagged Barents Sea, breakup, Canada, facts, Hudson Bay, polar bear, record low, resilience, sea ice, seals, solstice, Svalbard
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.
Recent media hype over swimming polar bears in the Southern Beaufort has been quite spectacular (still going strong today at the Washington Post here) but a close look at relevant data shows the message is bogus. Researchers admit (in their methods section) they couldn’t tell if bears said to have swum “non-stop” actually hauled out for half a day or more to rest on small ice flows invisible to satellites and astonishingly, the bear getting all the media attention – who swam the longest of any bear – lost less weight than a bear would have done simply sitting on shore for the same length of time.
Posted in Advocacy, Conservation Status, Life History, Sea ice habitat
Tagged Beaufort Sea, claims, facts, Hudson Bay, longest swim, media hype, melting ice, misinformation, non-stop swims, polar bear, sea ice, swimming, weight loss, without rest
You may have seen the headlines in Canadian news outlets over the last 2 days.
“Polar bears swimming farther as sea ice recedes, study shows”
“Melting sea ice forces polar bears to swim longer, farther: study” [“Bear biologist Andrew Derocher says the forced swims are particularly hard on mothers with young cubs”]
“Polar bears swimming longer, farther because of melting sea ice, study finds”
Oddly, none of the above news reports said where the paper was published or mentioned the name of the lead author – only University of Alberta co-author Andrew Derocher was interviewed (see the only press release I could find here, issued by the San Diego Zoo where the lead author is now employed).[update: CBC ran another story a day later that corrected these omissions]
But what did the study actually say?
Significantly, no bears died while swimming during the two lowest sea ice extent summers since 1979 and no evidence was presented that swims were “particularly hard on mothers with young cubs.” The quotes from the paper below sum it up for Beaufort Sea (BS) bears (the inclusion of Hudson Bay (HB) bears in this study seems gratuitous and potentially misleading, since only a few swam anyway – only 15 out of 59):
“….91% (91/100) of the swims in the BS occurred before the annual September minimum sea ice extent had been reached. …In the BS, 81% (29/36) of swims started and ended in pack ice…”
So, despite what may be implied during media moments, Beaufort Sea polar bears were not frantically trying to reach the sea ice from land so that they could attempt to keep feeding over the summer – most of their swimming was done during breakup in July and August from one bit of pack ice to another and they showed no evidence of harm from doing so. Map from the study and more quotes below.
Posted in Life History, Sea ice habitat
Tagged Beaufort, Derocher, forced swims, Hudson Bay, mothers with young cubs, Pilfold, polar bear, receding sea ice, sea ice, summer, swim longer, swimming, swimming further