Polar bear specialist Andrew Derocher reported that two of his 23 tagged polar bears were still on the sea ice, a phenomenon that’s been happening since at least 2015 at breakup. Instead of heading to shore when the sea ice concentration dwindles below 50% coverage, some bears are choosing to lounge around on decaying bits of ice, sometimes into late July or well into August, until they must finally swim ashore. There is no evidence that the bears continue to successfully hunt seals under these conditions but no evidence either that their choice to stay on the ice rather than move to land at this time of year has had any negative impact on their health or survival.
Posted onJuly 4, 2022|Comments Off on Polar bear evolution and recent genetic papers
Two scientific papers in June on polar bear evolution got a bit of media attention but not what the topic deserves. I’ve not written about them because I am currently working on a larger piece putting this conflicting genetic information into full context. Have patience, it’s coming.
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Posted onJune 2, 2022|Comments Off on Grizzly spotted on Western Hudson Bay shore but there are no polar bears on land for it to mate with
On 28 May last week a big grizzly (probably a male) was spotted on the shore of Wapusk National Park just south of Churchill, Manitoba but unless he heads out onto the sea ice, he has no chance of finding a polar bear female to mate with. Even if he does, he is unlikely to find a polar bear female willing to mate: most polar bears mate late March to early May (Smith and Aars 2015). Brown bears (called grizzlies across most of North America) mate later in the year, from late May to July, which means finding hybrids here is highly unlikely.
A few tundra grizzlies from the Northwest Territories have been spotted moving southeast into the Hudson Bay area since 2008. There was some media-and-expert-generated excitement back in 2016 when a hunter shot what he thought might have been a grizzly/polar bear hybrid near Arviat but it turned out to be a blonde grizzly, which are not uncommon in the tundra population from which it came. A similar result came from recent genetic study: samples from two pale blonde grizzlies from the North Slope of Alaska that looked remarkably like polar bear hybrids were not only unrelated to each other but showed no evidence of being hybrids (Lan et al. 2016 Supplementary data, pg. 3).
Contrary to some predictions, grizzly/polar bear hybrids are still quite rare (Crockford 2018:23).
Posted onMay 10, 2014|Comments Off on Evolution by geneticists again: yet another date for when polar bears arose
The latest addition to the never-ending story of when-and-why polar bear evolution took place according to geneticists (Liu et al. 2014 — the 8th such paper in less than 4 years, if you can believe it) is getting way, way more media attention than it deserves.
Liu et al. 2014 figure provided in the abstract.
This multi-member research team used a new data set (mostly Scandinavian brown bears and Greenland polar bears, for a change) to add not much of anything new on the evolutionary insight front except yet another estimate of when polar bears came to be.1
However, the real focus of the paper is the description of their finding of a few genetic differences between brown bears and polar bears that they identified. They found a few genes in polar bears were different than brown bears and made a boat load of assumptions about what these might mean.
Their discovery was not accompanied by any attempt to demonstrate that the changes in gene architecture they found also involved a change in the function of the genes or were associated with different effects on bear physiology. If a changed gene cannot be shown to act differently or to have a demonstrated new physiological effect on the animal in question, the changes themselves mean next to nothing – especially for evolution!
That’s my take – see what you think. It looks long but a lot of it is quotes. Continue reading
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Posted onMay 8, 2014|Comments Off on Ancestor of the polar bear by any name: grizzly vs. brown bear monikers explained
Apparently, all media outlets (exceptFox News) so confused the distinction between the two common names used for the ancestor of polar bears, Ursus arctos, that they got the point of a recent news story totally wrong. An Alaskan journalist explains.
Coastal brown bears from Admiralty Island, southeast Alaska (courtesy Jim Baichtal, US Forest Service, Alaska). See previous post here.
Tundra grizzly bear from the Yukon (courtesy Government of Yukon Territory). These bears also occur across the north slope of Alaska and are the bears that occasionally hybridize with polar bears this time of year, as explained here.
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