While grizzly bears and black bears hibernate through long winters, the opposite was thought to be true for polar bears. When warmer weather comes, polar bears don't have access to as much food as they normally do. Up until now, it's been thought that polar bears could could enter a semi-hibernation state, what's called a "walking hibernation." The theory was that bears could drop their body temperatures, which would then send signals to the brain that there wasn't a need for as much food.
A recent study that was conducted over multiple years, monitoring the body temperatures of the bears, as well as other physiological factors has shown that this isn't actually the case.
Normally, in the winter, seals are on the icy land where the polar bears live. When the ice melts in the warmer weather the seals will swim away from the ice and that's when the food supply drops. The new study, published in the journal Science, was conducted by a team of biologists from the University of Wyoming lead by Dr. John P. Whiteman and his colleagues Merav Ben-David and Henry J. Harlow. In addition, there were researches from Polar Bears International, the US Fish and Wildlife Service. And the US Geological Survey. In a statement to the New York Times, Dr. Whiteman said,"We didn't find anything that looks like hibernation."
The data was collected by the team after spotting and tagging about two dozen bears in Beaufort Sea in Alaska. The bears were fitted with GPS collars to track their movements and also had devices implanted that could record their body temperatures. Researchers also took blood samples from the bears, measured body parts and collected fur samples.
To make the study as complete as possible, the team kept track of polar bears that are "ice bears" and who follow the ice all year long, even as it melts and seeps backwards as well as "shore bears" who stay in the same area all year, despite the lack of ice. For the hibernation theory to have been proven, the bears would have shown lower temperatures and decreased metabolism. In an interview with the Washington Post, Merav Ben-David stated, "If there was hibernation metabolism ... you would see all of them have a very steep, abrupt decline in body temperature to about 35 degrees [Celsius] and then remain like that the whole period, but we don't see that."
The team stressed that the study wasn't just about hibernation and body temperatures. The amount of data collected will be useful for scientists for years to come. The team was able to get a much clearer picture of what happens to the bears over the summer. Since climate change will mean that periods of warmer weather will get longer each year. The polar bears are already endangered and are under the protection of the Endangered Species Act, but that only deals with prohibitions against hunting the bears.
While the information gathered is significant, Dr. Whiteman told the Washington Post, "We're not looking at any quantitative predictions for what will happen to the bears in the future in terms of climate change. There still are some fundamental aspects of polar bear biology that we have yet to understand."
Check out the video below for more information on the study
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