Tag Archives: Southern Beaufort

Status of Canadian polar bear populations has been changed – more good news

According to maps dated June 2014, Environment Canada (EC) has changed the trend status of several Canadian subpopulations — without any announcement or publicly-available documents explaining the basis of the changes.

Figure 3. "Series of Circumpolar Polar Bear Subpopulation and Status Trend Maps 2010, 2013 & 2014" Note the asterisk below the 2014 map, which is dated "June 2014" and is different in its status assessment from the one released in February 2013 by the PBSG. Original here.

Figure 1. Environment Canada’s “Map 4: Series of Circumpolar Polar Bear Subpopulation and Status Trend Maps 2010, 2013 & 2014.” Original here.

And would it surprise you to learn that virtually all of these status changes reveal more good news about polar bears?
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Beaufort Sea polar bear subpopulation boundary has been changed

Environment Canada recently posted a set of maps on its website that show it has moved the boundary between the polar bear subpopulation it shares with the USA — without a word to the media or a note anywhere.

EC S_N Beaufort boundary change Sept 8 2014_cropped PolarBearScience

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Tracking polar bears in the Beaufort Sea – September 2014 map

Here is the September 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 for September 2014 is copied below (Fig. 1).

At the end of September, with sea ice starting to rebuild, it appears there were 8 bears on the ice and three on land.

The situation for September was not very much different from August, except that two of the 11 bears (up from one) were on the ice in the Chukchi Sea in September, a phenomenon that was recently acknowledged to have affected the last population estimate for the Southern Beaufort subpopulation.

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Tracking polar bears in the Beaufort Sea – August 2014 map

Here is the August 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 for August 2014 is copied below (Fig. 1).

Compare this to July’s map (Fig. 4). The 20 bears from May (down to 13 in June) are now down to 11. 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 maps below are females.

At the end of August, nearing the minimum extent of ice for this year, seven bears were on the ice and only four were on land.
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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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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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W Hudson Bay mark-recapture studies of polar bears were invalid, says peer-reviewed study

“Our results suggest that mark–recapture estimates may have been negatively biased due to limited spatial sampling. We observed large numbers of bears summering in southeastern WH, an area not regularly sampled by mark–recapture.” Stapleton et al. 2014.

Polar bear at Wapusk National Park (just south of Churchill) in August 2011. Courtesy Parks Canada.

Polar bear at Wapusk National Park in August 2011. Courtesy Parks Canada.

We’ve seen the results of this 2011 study before, in government report format. But now it’s been revamped, peer-reviewed and published in a respected scientific journal – it actually came out in February, without fanfare, but I’ve only just come across it.

Some excerpts below, with conclusions that should raise some eyebrows.

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