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.
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.
Posted in Life History, Population, Sea ice habitat
Tagged breakup dates, Churchill, counting polar bears, Derocher, early breakup, estimates, Ontario, polar bear, population numbers, Wapusk National Park, western hudson bay
I knew it was coming up and then forgot to check, but sometime about 2 weeks ago blog views here at PolarBearScience passed the one million mark — more than two months ahead of my 5th anniversary.
Over 1 million views, four polar bear books (including my first novel, the polar bear attack thriller EATEN), several white-paper type publications (here, here, and here), several magazine articles (one here), two videos (see below), and a scientific paper on polar bear conservation that was peer reviewed before it’s publication at PeerJ Preprints.
Not bad for a five year stint on a blog with a single species focus. Continue reading
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
Posted in Life History, Population, Sea ice habitat
Tagged bearded seals, Beaufort Gyre, Cape Bathurst, Derocher, hole in the ice, polar bear, polynya, ringed seals, sea ice, shore leads, Southern Beaufort, thick spring ice
Habitat for polar bears is abundant worldwide as the prime feeding season passes its peak and mating season for sexually mature bears winds down.
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:
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):
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):
In fact, ice is pretty solid throughout the Barents Sea and East Greenland at this time:
Across the Atlantic, the situation is similar, with unseasonably heavy sea ice off eastern North America and the Southern Beaufort Sea.
Posted in Life History, Sea ice habitat
Tagged body condition, Churchill, fighting, Hudson Bay, mating, polar bear, problem bears, ringed seals, sea ice, snow depth, Svalbard
Similar to the spin on the 2013 Baffin Bay/Kane Basin polar bear population survey, the IUCN Polar Bear Specialist Group now insists the latest count of the Barents Sea subpopulation is not evidence of an increase in numbers since 2004, as the leader of the study announced in 2015.
This is Part 2 of the big surprises in the latest version of the polar bear status table published by the IUCN Polar Bear Specialist Group (PBSG) on 30 March 2017. See last post here regarding the PBSG population size estimates that no longer concur with the 2015 Red List assessment, including the global total — even though PBSG members wrote the report (Wiig et al. 2015, and its Supplement).
Here I want to focus on the results of subpopulation surveys that were made public after the 2015 Red List assessment was published, particularly the Barents Sea estimate.
While the 2013 Baffin Bay and Kane Basin estimates (SWG 2016) have been added to the new PBSG table, any suggestion that these might indicate population increases are strong discounted. Similarly, contrary to initial reports by the principal investigators of the survey, the PBSG insist that the Barents Sea population has not actually increased since 2004, which you may or many not find convincing.
Posted in Advocacy, Conservation Status, Population
Tagged Barents Sea, body condition, counting polar bears, cubs, declining population, increasing numbers, IUCN, PBSG, polar bear, population, size, survey, Svalbard
Davis Strait polar bears around Newfoundland and Labrador are currently experiencing what one polar bear specialist refers to as “failed” sea ice conditions, causing bears to come ashore in droves. I’m not making this up.
The ice was so thick in the Strait of Belle Isle between Newfoundland and southern Labrador last week that a ferry was stuck for 24 hours and had to be rescued by an icebreaker.
The boats of fisherman on the north shore of Newfoundland are stuck in thick ice that’s not expected to clear until mid-May at the earliest and they can’t get out to fish.
See this video posted on Twitter two days ago.
The same thing (perhaps even worse) happened in 2007, see Twillingate in the spring of 2007 below:
Yet, in 2007 there was not a single polar bear reported onshore in Newfoundland (as far as I am aware) but this year there were almost a dozen. And the photos show fat, healthy bears – not animals struggling to survive.
According to Andrew Derocher, that’s proof “failed” sea ice is the reason that polar bears came ashore this year but not last year (when there was also lots of ice in late March/early April, see additional maps and graphs below). Last year there were sightings in the middle of winter (January/February) in Labrador and Newfoundland (which I reported here) and one bear was shot in Newfoundland in early May when he advanced on local RCMP officers.
I think Derocher believes he’s set the record straight by offering an interview of his own to refute the things I said to the CBC last week (I talked on two Newfoundland radio stations, which generated a print CBC article). But Newfoundlanders have to deal with used car salesmen just like the everyone else, so I expect they are having a good laugh right now at the expert who’s blaming their polar bear troubles on a lack of sea ice.
Polar bear numbers have risen since 2005, no matter how you look at it:
USGS estimated 24,500 (average) polar bears in 2005.
IUCN estimated 26,500 (average of 22,000-31,000) in 2015
(assessment completed in July, released in November).
Subpopulation surveys completed or reported after July 2015 (Baffin Bay, Kane Basin, Barents Sea) added ~2,000 bears.
This brings the adjusted average total at 2015 to ~28,500.
Explained in full in this published paper, pgs 20-21:
Crockford, S.J. 2017 V3. Testing the hypothesis that routine sea ice coverage of 3-5 mkm2 results in a greater than 30% decline in population size of polar bears (Ursus maritimus). PeerJ Preprints 2 March 2017. Doi: 10.7287/peerj.preprints.2737v3 Open access. https://doi.org/10.7287/peerj.preprints.2737v3