Category Archives: Life History

Arctic Basin polar bears – researchers spot fat pregnant female from icebreaker

Researchers in the Arctic Basin yesterday spotted a hugely fat pregnant polar bear female on broken ice over water about 2,500 meters deep. Some people seem to find this surprising but it’s what I discussed last week.

Healy Aug 24 2015 Polar-Bear VI Tim Kenna

Photo above by Tim Kenna from aboard the Coast Guard cutter Healy. Researchers are in the area as part of the TRACES of Change in the Arctic” program. Another perspective on the bear and the location it was spotted on 24 August 2015 below, as well as some background on Arctic Basin bears.
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In 1999, climate change apparently threatened Western Hudson Bay polar bears

Now, not so much. Here is a 16- year old CBC TV special on Churchill polar bears – listen to Ian Stirling and reporter Eve Savory use the early breakup of sea ice on Hudson Bay in 1999 to hype the alarm about Western Hudson Bay polar bears. Watch Stirling in action darting and measuring bears and bemoaning the good old days of the 1980s, claiming the “bears are sending a signal from the ecosystem.

Watch this archived copy of “The Shrinking Bears of Hudson Bay and compare his claims to what has actually happened in the 16 years since then. It runs just over 15 minutes.

Climate change threatens polar bears 2_CBC 1999

“Just as the ice is shrinking in Hudson Bay, so are its polar bears. Climate change has shortened the season for winter ice, a crucial period for the bears to feast on seals and build up their fat reserves. And so, over the 18 years that wildlife biologist Ian Stirling has been studying them, the polar bears have become skinnier and their offspring fewer. In this 1999 report for CBC-TV’s The National, Stirling says once their habitat is gone, there’s nowhere else the Hudson Bay polar bears can go.” [my bold – see notes below]

Program: The National [Canadian Broadcasting Company, CBC]
Broadcast Date: Sept. 23, 1999
Duration: 16:39

Stirling has continue to make these claims since 1999, yet no updated evidence has been provided. There is no plausible evidence that the decline of polar bear numbers in Western Hudson Bay was due to sea ice changes caused by human-caused global warming (Crockford 2015) or that continued declines in condition of bears or litter size have  occurred. Note that the latest survey of Western Hudson Bay polar bears found no trend in either breakup or freeze-up dates since 2001 (Lunn et al. 2013) and that the population is now stable.

Ice coverage charts and breakup dates graph below, for context.
UPDATE ADDED – see below
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Summer habitat for most polar bears is either shoreline or sea ice in the Arctic Basin

At this time of year, sea ice extent numbers are meaningless for polar bears.  The extreme low September minimum of 2012 – when masses of polar bears didn’t die – showed rational people that this is true. Even the low 2007 summer extent, which hit earlier in the season than 2012, had little to no negative impact.

Greenland W coast_Female w cubs_2006_Mads Heide-Jorgensen_NOAA sm

In late summer, bears outside the Canadian Archipelago either retreat to shore or stay on the sea ice as it retreats north into the Arctic Basin (see image below, click to enlarge).  Most bears in the Archipelago have ice year round, so life doesn’t change much. This means that it does not matter to polar bears how much area the Arctic Basin ice covers in September – for their needs, 1.0 mkm2 would be plenty.

Sea ice and summer refuges for polar bears_17 Aug 2015

Still, Southern Hudson Bay polar bears had extended hunting opportunities in July this year (whether or not they hunted successfully) and for this date, Hudson Bay had more ice remaining than any year on record. Yes, more than even 1992 but only by a few percent. See charts and maps below.

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2nd highest ice coverage for Hudson Bay since 1971 at mid-August – only 1992 higher

Since 1971, there has been no year when there was as much ice left on Hudson Bay as there is this year at August 13th, except 1992 – the year when Mt. Pinatubo seemingly affected Hudson Bay ice levels but not any other region in Eastern Canada or the Beaufort Sea. Odd, that – see the graphs below.

Hudson Bay same week 13 Aug 1971-2015

Doesn’t mean that much to polar bears, since they will mostly be fasting whether they are onshore for the summer or riding the ice – they primarily live off their fat this time of year. Still, the relative ice levels are interesting because it could impact freeze-up dates later this fall, which will influence the bears’ ability to hunt before the winter fast sets in.

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Hudson Bay ice update – researchers awfully quiet about what polar bears are doing

This year 225 thousand km2 of sea ice remained on Hudson Bay at 10 August compared to 96 thousand km2 in 2009, the last late breakup year for which there are detailed ice maps and polar bear data.

Hudson Bay breakup Aug 10 2015_CIS

In 2009, most Western Hudson Bay polar bears were onshore by 22 August, just after the very last remnants of ice disappeared (see map below). This year? The remaining ice is further east, in Southern Hudson Bay territory.  Last report from a few weeks ago showed some Southern Hudson Bay bears came ashore early but past behavior suggests some bears will wait until the bitter end before they come ashore – until the very last remnants of ice disappear (Cherry et al. 2013).
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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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Pacific walrus sob stories begin again

Now we have poor hunting conditions in the Bering Strait touted as evidence that “walrus migration patterns have changed” with the implication that this is because “…the past eight years have had the eight lowest amounts of summer sea ice on record” due to man-made global warming.

Walrus 2012 July USGS

A subsistence lifestyle is hard, particularly so if it depends on a highly mobile, migratory herd animal. Think Barren-ground Inuit caribou hunters, who often starved because herd sizes declined for a few years or moved unpredictably.

Many factors – seasonal weather, last year’s winter conditions, size of the herd, food supply – all affect where and when a migratory herd will move and the likelihood it will be positioned for optimal harvesting by hunters. Add another highly variable factor into that – Bering Sea ice – and you have a highly unpredictable food supply, especially if you sit in one spot (like on St. Lawrence Island) and expect that migratory herd animal to come within reach.

Hunting walrus from St. Lawrence Island depends on just the right combination of ice and winds. Too much ice is not good, too much open water is not good, and too much wind is not good.

Alaska Dispatch, courtesy the Associated Press, reports St. Lawrence natives are again short of walrus meat because of “warm temperatures”: “Warming temps push walrus north, leaving Alaska villages without traditional food source” (Rachel D’Oro, The Associated Press, August 6, 2015). And the caption of the above USGS (A. Sonsthagen) photo predictably implies all current hunting troubles can be blamed on climate channge:

“The walruses in this July 2012 file photo are hauled out in the Eastern Chukchi Sea. Walrus migration patterns have changed as sea ice and other environmental factors have shifted — and that’s spelled trouble for Alaska Native communities who hunt them for subsistence.”

The people of St. Lawrence Island and the Bering Strait that depend on walrus for subsistence have my sympathy, they indeed have a hard life – but this is not a tale of woe about the status of Pacific walrus and changing summer sea ice.

Bering Strait natives hunt walrus in spring, from mid-April to early June (Huntington et al. 2013). All indications are that walrus are moving differently than they used to in summer because the population is now very large.  As far as I know, there is no new population information on walrus that wasn’t available last year, when I covered this topic extensively (Crockford 2014; video below).

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