Ian Stirling’s howler update: contradicted by scientific data
Following up on my last post (Ian Stirling’s latest howler: “the polar bear who died of climate change”), I tracked down some details contained in the original Norwegian news report but which were left out of the articles that spread the story around the world. I also found some pertinent research posted online that appears to be the work of the researchers who captured this bear in April.
Figure 1. The Norwegian newspaper, The Local (Aug. 7, 2013), says the bear was found on “a small island near Texas Bar” (marked by the square on the above map) in the very north of Spitsbergen, and states it was found on July 7 – details other reports did not bother to include. [“Texas Bar” is a hut built by a Norwegian hunter in 1927]. To have been 250km south of that position in April (when he was tagged), he must have left the ice near the southern tip of Spitsbergen when there was still lots of ice further north.
Further details on the dead bear
The Norwegian newspaper, The Local (Aug. 7, 2013), included the following (which, among other things, explains why necropsy results were not given):
“[Ashley] Cooper, who runs the agency Global Warming Images, said that the eco-tourism expedition he was with, accompanied by renowned polar bear expert Dr Ian Stirling, had travelled [sic] deep into the Arctic before it found ice.
“We had to push up until 550 miles from the North Pole before we found any sea ice, which was kind of rotten. It was very patchy and broken up and thin, only just about holding the weight of a polar bear.”
The bear, a 16-year-old male, was found on a small island near Texas Bar. When it was tagged in April in southern Svalbard, some 250 kilometres from where it was found, it had been in a healthy condition.
Dr Ian Stirling, who works as an adjunct professor at the University of Alberta, told The Local that this spring’s record low levels of sea ice were the most likely reason for the bear’s death.
“The bear was extremely thin, no apparent fat at all, and based on all these pieces of information, I thought the most likely cause of death was starvation.”
Stirling stressed however that as he was not able to handle the carcass or take samples, this could not be known with certainty. He confirmed that Svalbard had seen unusually low levels of sea ice last winter, making it difficult for polar bears to find food. [my bold]
The cruise that Cooper and Stirling took appears to have been this one, operated by OneOcean Expeditions (pdf here). The only July trip on offer this year that spans the date the dead bear was found (July 7) is the one running 05 – 15 July. It seems then that both Cooper and Stirling were together, apparently fortuitously, when the bear was found and no pre-arrangement was necessary as I thought might have been the case. There is no indication, however, of who called the press.
Research on body condition of male Svalbard polar bears in 2013
I found research results posted at the website of the project for Environmental Monitoring of Svalbard and Jan Mayen (MOSJ) that appears to be the work of the Norwegian biologists who captured the now-famous dead bear when it was alive and healthy in April.
Polar bear researchers Jon Aars and Magnus Andersen (both at the Norwegian Polar Institute) discuss several aspects of their on-going research on this website, apparently adding results as they became available (Aars and Andersen 2013, here, pdf here). One of the topics discussed is “body condition of adult males,” which must have been added very recently, as the data include bears captured up to May 2013 — in other words, work completed this spring.
Figure 2. Body condition of adult males in Svalbard (the Barents Sea subpopulation). Original caption: “Body condition index of adult male polar bears caught in spring (Mar-May) in the period 1993-2013” (details below). There is no significant trend over time, according to the authors. Note that the data presented for 2013 contains no outliers (the black dots) and several years (e.g. 1998, 2000) had more bears that were in poorer condition than 2013. The “body condition index” values (not defined) appear to be anomalies (i.e. “0” is “normal”) – I’ll correct this if I find out otherwise.
This is how they describe the results:
“The lines in the middle of each box show the median value, and the box segments and lines above and below the median each cover ca 25% of the data points. Outliers are represented by small circles. There is no significant trend over time. [my bold]
However, a major part of the interannual variation can be explained by variation in the Arctic Oscillation (AO). High values of AO (milder weather) at the time of capture correlate with a lower body condition index (leaner animals).”
Significantly, 2013 contained no “outliers” (the black dots, indicating bears in much poorer condition than others that year) and several years (e.g. 1998, 2000) had more bears that were in poor condition than were found in 2013.
These results indicate that winter/spring ice conditions in 2013 did not result in an unusual number of bears in poor body condition compared to previous years, back to 1993, and adds further support to my conclusion that the sad fate of the bear featured by the media last week was unrelated to “low levels of sea ice,” as Ian Stirling proclaimed. Starvation is unfortunately the most common cause of death for old adult polar bears, which Stirling well knows.