Leading polar bear biologists knew by November 2013 that mark-recapture studies showed the Western Hudson Bay subpopulation had not changed appreciably since 2004 but none said so. This includes Steven Amstrup and Ian Stirling at Polar Bears International, Andrew Derocher (University of Alberta), and Nick Lunn (Canadian Wildlife Service), all of whom are (or have been) extensively involved in Western Hudson Bay polar bear research and have made recent statements to the media on this topic.
The story reveals that there are two Canadian Wildlife Service (Environment Canada) reports containing population estimates of Western Hudson Bay polar bears – one produced in 2011 and another in November 2013 (reversing the 2011 conclusion) – that have not been made public.
[In contrast, Nunavut Government reports on their 2011 population estimate, based on aerial surveys, were made public in both draft and final report formats (and have since been peer-reviewed and published)]
The conclusion of the 2013 report, quoted in this mornings article, suggests that some of our most vocal polar bear specialists have been misleading the public about the status of the Western Hudson Bay population for the last year.
From this morning’s news report:
An oft-quoted study done by researchers with the federal government’s Canadian Wildlife Service claimed the subpopulation’s numbers declined by 22 per cent between 1984 and 2004, from about 1,200 bears to about 935.
And they said that because of global warming, the later formation of sea ice in the fall was making it harder for bears to hunt seals on the ice, decreasing their chances of survival.
And they claimed the Western Hudson Bay subpopulation would continue to decline in the future.
Around the same time , the CWS did another study, claiming the subpopulation had fallen to 806.
“The 2011 population estimate for Western Hudson Bay subpopulation based on capture-recapture analysis is 806 bears with 95% confidence intervals of 653-984,” Environment Canada said at the time, producing more fear among people who believe that the demise of the polar bear is imminent, due to global warming.
And prior to the  NWMB [Nunavut Wildlife Management Board] public meeting, a group of CWS researchers put on their thinking caps and did more work on their projections for the future.
They describe their technique in a big, fat mouthful of statistical jargon.
“We used a Bayesian implementation of multistate capture-recapture models, coupled with a matrix-based demographic projection model, to integrate several types of data and to incorporate variation across the polar bear life cycle,” they said in a summary of a 50-page report they produced in November 2013.
“Bayesian implementation” means the use of a certain kind of logic to determine whether certain types of events are probable in the future, and how probable they might be.
And by doing that they found their earlier predictions were off — and that the population is now stable.
“This updated population assessment suggests that polar bear numbers in Western Hudson Bay have been relatively stable over approximately the past decade,” Environment Canada said.
Environment Canada put this “new information” into a submission to the NWMB they filed last November , in advance of last week’s public hearings.” [my bold]
Read the full story here.
Contrast that 2013 report conclusion, quoted above, with this: Andrew Derocher was interviewed last month (November 2014) by the BBC (“Will polar bears become extinct?”) in an article that included the following:
“In the Hudson Bay, when Derocher first started doing research in the region there were 1200 bears. Now there are barely 800. “The current status is the numbers have dropped by about a third,” Derocher says.” [my bold]
See also, from 27 November 2013 “Polar bear numbers in Hudson Bay of Canada on verge of collapse“
In short: It appears that Western Hudson Bay polar bears have not declined appreciably since 2004, according to mark-recapture studies as well as aerial surveys. An unpublished 2011 mark-recapture study concluding the population had declined since 2004 was apparently based on a statistical misconstruction that was corrected more than a year ago in another unpublished report. However, you wouldn’t have gathered any of that from comments made by prominent polar bear researchers to the media since 2013. The fact that these taxpayer-funded reports were not made public has allowed this deplorable situation to occur.
We won’t know any more details until we can see the reports. I submitted a request to Environment Canada for copies of both WHB reports first thing this morning – I’ll keep you posted.
Polar bear researchers still withholding Hudson Bay data November 28, 2013
Stapleton S., Atkinson, S., Hedman, D., and Garshelis, D. 2014. Revisiting Western Hudson Bay: using aerial surveys to update polar bear abundance in a sentinel population. Biological Conservation 170:38-47. http://www.sciencedirect.com/science/article/pii/S0006320713004618#