Polar Bear Blog – Walking Hibernationish Sort of

A recent study out of Alaska is gaining a fair bit of traction in the media, raising alarm bells that ‘polar bears are not able to adapt to climate change’ and the usual hub-bub.  It is a fairly comprehensive study of polar bear biology from spring to fall, measuring body temperature, locomotion and that sort of thing.  It is also a study that turns a few common polar bear facts on their head.

First of all, the study suggests that ‘walking hibernation’ is actually not that important an adaptation for polar bears, if it exists at all.  Walking hibernation was coined in the 1990s as the bears ability to slow their metabolism after 7-10 days without food.  The commonly held belief was that this adaptation allowed polar bears to survive periods of food deprivation that would otherwise be fatal to a black or brown bear.

As I stated earlier this year, experts have begun to shy away from this term but it really has been a fixture of polar bear biology for, say, 25 years now.  From what I can tell in this study, it might be a bit premature to make this claim…  bears go in and out of walking hibernation many times through a season, be it summer or the dead of winter.  So, I’m not sure that you would really see a general trend in body temperature, etc over the whole season, its hard to say.

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Another question I have is that most of the bears studied are female which are generally more active through the year than males, but I doubt that made a ton of difference.  As well, its a bit disappointing that the winter months, when walking hibernation is most relied upon, were not a focal point.  December through February are quite possibly the leanest and hardest times for bears as the ice is too thick to hunt seals and there are no other foraging/scavenging options.  Polar bears hit their lowest annual weights by March.

I’m sure more studies will come out as this looks like a preliminary analysis of the data so I for one am pretty excited to see if the polar bear world gets turned on its head or not.  Always fun stuff.

A couple other things worth noting in this study and not necessarily bad news.  The body temperature measurements indicate that bears are not the inefficient walkers that previous studies claim.  They do not see to use excessive energy or increase their body temperature from continued movement.  Northern guides and Inuit have long been suspicious of this claim (except of course for the giant males that overheat pretty quick…).

As well, swimming bears were found to lose much less heat and less energy while in the water.  Basically, reduce their skin temperature while swimming and heat the core of their body.  The similarity between skin and water temperature is believed to mitigate heat loss.  Bears use less energy walking and less energy swimming than we thought.  Neat.

To me, this study says walking hibernation is not as important to summer survival as we thought but bears also expend less energy so its a bit of a mixed bag of news.  And by no means does it provide definitive proof one way or the other…  So once again, a study that is full of interesting and complex ideas, gets reduced to ‘the bears are all going to die’.  But hey, that’s just the way we roll in the polar bear world.

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