Summer sea ice melt and polar bear maternity dens

The yearly sea ice minimum extent is almost upon us, which has recently been the seasonal signal for excitable biologists and their activist groupies to resume their breathless rants about what sea ice loss could mean for polar bears.

Polar bear den_CreditUSFWS_labeled

Never mind that the summer minimum extent reached in September, no matter how low it goes, is pretty much irrelevant to polar bear health and survival. As I’ve discussed before, what’s really important is the presence of not-too-thick ice during the spring, so they can catch lots of young seals and put on lots of fat.

But to a lesser degree, the extent at mid-to-late summer is important because this is when pregnant females that prefer to make their maternity dens on shore are looking for good places to spend the winter.

So the topic for today is this: how much does the extent of ice at the height of summer dictate where polar bear females make their winter dens?
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Foxe Basin and Hudson Bay have more than average polar bear hunting habitat

This is shaping up to be a banner year for polar bears in Foxe Basin (central Canada), with more ice in this region than there’s been since 1992. Hudson Bay still has a large patch of thick first year ice, more than there has been at this date since 2009, which was a late breakup year.

Hudson Bay Foxe Basin ice map Aug 7 2014 labeled_sm

Ice maps and charts below tell the story.
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Dodgy new clarification of global polar bear population estimate (yes, another)

In an attempt to get themselves out of a mess of their own making, the IUCN Polar Bear Specialist Group (PBSG) has just dug their hole even deeper.

pbsg logo

Although the minutes of their 2014 June meeting (pdf here) contained this statement…

K. Laidre summarized the need for the PBSG to do a better job of communicating accurate and balanced science about polar bears.” Pg. 28

…you might conclude, after reading the rest of this post, that polar bear specialists don’t really understand what these terms mean.

Due to the flack they have been catching over their global polar bear population estimates, the PBSG determined that another clarification was in order. [As opposed to the first clarification, a footnote the group planned to insert in an upcoming report, which PBSG chairman Dag Vongraven sent to me in May)]

The new clarification, apparently co-authored by Steve Amstrup and Andy Derocher (PBSG 17 minutes, pg. 33 – copied below), makes an astonishingly bold claim that I can easily show is untrue.

PBSG 17 minutes_global pop estimate explanation action p33 to post Continue reading

Global population estimate footnote causes problems for polar bear specialists

Apparently, the IUCN Polar Bear Specialist Group (PBSG) are catching flack over their global polar bear population estimates.

pbsg logo

Global Population Footnote [its own section, Pg. 32-33, of the minutes of the June 2014 meeting (pdf here). Recall my post on the issue here]

Over the years, the global population estimate found in the Proceedings status table has been used and misused by the general public and self-interest groups. Often the global estimate is taken out of context, without reading all the accompanying text, and used to suggest that the numbers of polar bears have been slightly increasing or at least stable over a period in which much has been made of the loss of sea ice habitat.

In an attempt to clarify this, a footnote to the website status table was drafted. This footnote has subsequently been used to suggest that the PBSG does not really know how many polar bears there are and certainly cannot defend the notion that the loss of sea ice has been a threat to the species.

As a result, the global estimate of 20,000-25,000 polar bears is back in the news and has caused problems for the PBSG. The Group should probably reconsider population estimates for data deficient subpopulations for the next status table.

In the meantime, there was considered to be value in drafting an explanation for the global population estimate of 20,000-25,000 for the online status table. It was thought that this would be a better approach than to directly engage those who have been misusing the information.” [my bold]

[As I showed in my post, the text accompanying the PBSG status tables for 2005 and 2009 did not include a clarification of this kind – the only mention of this uncertainty was found in the drafted press release published at the end of the document]

Another statement in the June 2014 minutes caught my eye:

K. Laidre summarized the need for the PBSG to do a better job of communicating accurate and balanced science about polar bears.” Pg. 28

In my next post, I’ll show you how they did on this assignment.

 

Tracking polar bears in the Beaufort Sea – July 2014 map and subpopulation boundary issues

Here is the July 2014 follow-up to my post on the July 2013 track map for female polar bears being followed by satellite in the Beaufort Sea by the US Geological Survey (USGS) – “Ten out of ten polar bears being tracked this summer in the Beaufort Sea are on the ice.”

See that post for methods and other background on this topic, and some track maps from 2012 (also available at the USGS website here).

The USGS track map July 2004 is copied below (Fig. 1).

Compare this to June’s map (Fig. 4). The 20 bears from May (down to 14 in June) are now down to 13. All seven of the bears outfitted with glue-on satellite transmitters in April [either males or subadult animals] have either moved out of the area or their tags have fallen off or stopped transmitting. This means that all of the bears shown on the June and July maps below are females.

One bear has moved into Canadian territory and another is well into the Chukchi Sea. This is now known to be a typical rather than unusual phenomenon, and is pertinent to the bigger picture of what constitutes a discrete geographic subpopulation for polar bears.
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Up to 20% of collared polar bears located on ice that officially does not exist, says the PBSG

Here are two more priceless quotes from the minutes of the last meeting of the IUCN Polar Bear Specialist Group (PBSG) – on issues with sea ice percentages used to define “ice-free” and the problem of bears with collars showing up on sea ice that, according to ice data, does not exist. These quotes are in addition to the ones I posted earlier this week (here and here).

Polar bear with collar and tag_USGS_labeled

See the original document for the context here.
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PBSG determined to see polar bears listed as threatened by the IUCN in 2015

IUCN Polar Bear Specialist Group conservation biologists are determined to have polar bears listed as ‘threatened with extinction’ by the International Union for Conservation of Nature (IUCN) in 2015 – even though the bears would not meet that classification if assessed today.

According to the minutes of their last meeting (in addition to the astonishing admissions from sea ice experts I reported yesterday), PBSG members are busy planning their strategy. They have thrown objectivity to the wind and are certain they can find a way to mask overcome the inadequacies of their case and see polar bears remain listed as ‘vulnerable’ (IUCN-equivalent to ‘threatened’ in the US) on the 2015 IUCN Red List update.

polar-bear_USFWS labeled

Along with some other priceless quotes, the minutes reveal their plan. See the original document for the context of these quotes here and an excerpt of “the plan” (pgs. 12-17) here. Continue reading