Category Archives: Life History

Polar bear counts for W Hudson Bay: ‘core’ area numbers are not comparable

Polar bear population estimates for Western Hudson Bay have recently become contentious because one specialist has been making statements that confuse the issue. As we all wait for the release of the report on the WHB aerial survey of 2016, it’s worth going over the recent history of these counts and what they have revealed.

Churchill_Polar_Bear_2004-11-15 Wikipedia

The official count for bears in WHB (used by the IUCN Polar Bear Specialist Group, the IUCN Red List, and Environment Canada) is 1030, based on an aerial survey of the entire region conducted in 2011 (Stapleton et al. 2014).

Since last year, Andrew Derocher (University of Alberta) has been telling any media pundit who will listen that WHB polar bears have declined from about 1200 bears in the 1980s to only 800 or so bears today (one example here) — a statement that is clearly not true.  In recent months, however, whether due to complaints from the public or from his colleagues, he’s qualified that statement by saying it’s the number of bears in the “core” area of WHB that has declined.

But is Derocher’s revised statement a clear scientific interpretation of the facts? Have a look at the details below and see if you come to the same decision I have: that it’s not possible to compare WHB ‘core’ area polar bear population estimates over time.

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Much more sea ice in NW Hudson Bay this year than 2016 or 2015 at 27 May

In recent years, sea ice loss over Hudson Bay has begun with open water in the NW corner (which is just as likely due to prevailing offshore winds as ice melt) rather than along the east coast but this year that patch of ice is smaller than its been for the last two years. In addition, despite two patches of open water at either end of the Beaufort Sea, most of the coast of Alaska is still covered in thick ice — much more than existed last year, yet masses of polar bears did not die as far as I know (actually, WHB bears came ashore in excellent condition last year).

Sea ice Canada 2017 May 27

Compare to previous years:

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Southern Beaufort sea ice melt in May: good news for polar bears or catastrophe?

Last week biologist Andrew Derocher recently implied via twitter that less sea ice in the eastern portion of the Southern Beaufort (SB) this year at mid-May is harmful to polar bears (calling it “a hole in the ice where polar bears used to live“), but both long-term and short-term data don’t support such a glass-half-empty interpretation.

Not only does spring breakup of sea ice in the SB normally begin with such open patches of water (see the video above from last year) — driven by the powerful currents of the Beaufort Gyre, not ice melt (explained in detail here) — it may actually be necessary for the survival of local seals, polar bears and whales in spring and early summer (Citta et al. 2015; Crawford et al. 2015; Harwood et al. 2015; Stirling et al. 1981).

As I’ve pointed out before, the biggest threat to SB bears is thick sea ice in spring and its associated late breakup, a 2-3 year-long phenomenon unique to this region known to have occurred about every 10 years since the early 1960s (well documented in the scientific literature) but which has not (as far as I know) happened since 2004-2006.

In other words, a considerable patch of open water and less concentrated ice in the eastern SB around Cape Bathurst is almost certainly a good thing for this particular subpopulation (see previous post here for an in-depth discussion) because historically, when a polynya of some extent has not formed by April or May it has been devastating for local marine mammals.

The fact that an extensive patch of open water existed at mid-May in this region last year and the year before (2015 and 2016) — with no public hue-and-cry about a great dying of SB bears from Derocher or anyone else — suggests that open water in the eastern SB this year is likely to be beneficial for SB polar bears, or at least benign. Continue reading

Polar bear mating season winds down with lots of sea ice habitat available

Habitat for polar bears is abundant worldwide as the prime feeding season passes its peak and mating season for sexually mature bears winds down.

JR1_1266.tif

Battle among polar bear males for the right to mate, from this 2011 DailyMail story here.

There is much more ice than usual around Svalbard in the Barents Sea and off Newfoundland and southern Labrador, home to ‘Davis Strait’ bears. There have been no media reports of polar bears onshore anywhere (since the third week of April in Newfoundland and late January in Svalbard).

Sea ice map below for 12 May 2017:

Svalbard ice extent 2017 May 12_NIS

Compare the extent and concentration of ice around Svalbard above (at 12 May 2017) to conditions that prevailed on the same date in 2015 (below), considered a “good ice” year for local polar bears (and the year of the last population size count which registered an increase over the 2004 count):

Svalbard ice extent 2015 May 12_NIS

There hasn’t been this much ice in the area at this point in the season for many years, especially to the north of Svalbard, and levels since late April have been above even the long-term average (disregard the huge downward blip, which is clearly a sensor malfunction of some kind):

Svalbard ice extent 2017 May 12 graph_NIS

In fact, ice is pretty solid throughout the Barents Sea and East Greenland at this time:

Barents Sea ice extent 2017 May 12_NIS

Across the Atlantic, the situation is similar, with unseasonably heavy sea ice off eastern North America and the Southern Beaufort Sea.

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East Coast crawling with polar bears since early March thanks to the pack ice

The  hot polar bear news right now is the large number of sightings of bears onshore in Newfoundland and Labrador – even the CBC is impressed.

Melrose nfld Polar Bear 02_2017 April 3_Brandon Collins shared photo The Packet

Photo taken by Brandon Collins in Melrose (on the Trinity Bay side of the peninsula) Monday 3 April 2017

All the bears have been brought to land by the abundant pack ice that’s been present off Labrador and northern Newfoundland (the territory of Davis Strait polar bears), which also killed a humpback whale that got trapped against the north shore (a not unusual event, apparently).

Mapping the reports of polar bear sightings since early March helped me get a handle on the total number of encounters: more than a dozen, it turns out.  There have been a few bear sightings in this region every year recently but such high numbers are remarkable, especially so early in the season. When will it end?

Increased numbers of bears in the population is one explanation for increased numbers of encounters onshore at this time of year, although recent storms may have encouraged more bears than usual to come ashore in Newfoundland.

My picture annotated map and a list of sighting reports, with links, is below but stay tuned: this story may not be over yet.

UPDATE 4 April: more photos and sea ice maps added below.

UPDATE 5 April: another sighting, in St. Brendan’s (west of Bonavista), added to the map below and quotes from one witness. The map is now Version 2. A sea ice map for 5 April has also been added at the end of the post.

UPDATE 9 April: another sighting and a bear casualty, see below. Map revised again.

UPDATE 14 April: CBC Newfoundland article (12 April: Highway of ice: Easy route for polar bears chasing food, prof says) based on my radio interview that aired 11 April.

UPDATE 22 April: Another sighting west of St. Anthony on Wednesday, 19 April has been added to the map (now Version 4) and an alert that I’ve added a new post (21 April) about the claim by one vocal polar bear specialist that all of these sightings are the result of “failed” sea ice conditions off Newfoundland and Labrador this year (seriously, I’m not making this up). I’ve added the most recent ice map at the end of this post.
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Another fat bear onshore in late winter, along Gulf of St. Lawrence north coast

Another fat bear onshore in late winter, this time along the Quebec shore of the Gulf of St. Lawrence (22 March 2017) – and this time, one of the witnesses to the sighting took some great photos. Courtesy CBC News (Polar bear makes rare appearance on Quebec’s Lower North Shore 24 March 2017).

Gulf St Lawrence North shore PB visit 22 March 2017_CBC headline

Quotes, location map, and sea ice charts below.

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Prehistoric polar bear find has elongated body type Inuit know as a ‘weasel bear’

A story that broke in Alaska newspapers a month ago made the UK press this weekend about the archaeological discovery of 1,300 year old polar bear skull that may be associated with an unusual body type known to Inuit hunters. See the Mail Online cropped headline below, full story here – and some quotes and critical background below.

Weasel bear headline with skull graphic 18 March 2017

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