Polar bears unable to adapt to lack of food in warmer Arctic
Polar bears are not able to adapt to their behavior to cope with the food losses associated with warmer summers in the Arctic.
Scientists had believed the animals would enter a type of ‘walking hibernation’ when deprived of prey.
However, new research says that the bears simply starve in hotter conditions when there is scarcity of food.
The authors say the implications for survival of the species in a world that is warmer are grim.
Back in 2008 polar bears were listed as a threatened species in the US. The Secretary of the Interior at that time noted that the dramatic decline in sea ice was the greatest threat the bears faced.
Mainly, polar bears survive on a diet of seals that they hunt on the sea ice-but the number of seals is reduced by melting in the summer and as a result, the bears have to struggle in order to find a meal.
There are some researchers who have argued that polar bears would deal with a reduced calorie intake by going into a low-activity state known as “walking hibernation’, similar to the way that many species of bear cope with winter.
Scientists, to test this idea, embarked on a dangerous and expensive trial where they attached satellite collars and surgically implanted logging devices to track the movement of bears and record physiological details.
They studied over 2 dozen bears in the Beaufort Sea, north Alaska.
The made the conclusion that during summer seasons, the bears didn’t slow down, they simply starved when food was short.
“Their metabolism is very much like a typical food limited mammal rather than a hibernating bear,” said John Whiteman from the University of Wyoming, the lead author of the paper.
“If you and I were to be food-limited for weeks on end we would look like the bears’ data”
Though the bears might not be able to change their behavior when it comes to food, they do seem to have a significant adjustment that helps them cope with swimming in cold water.
“They have this ability to temporarily allow the outermost portion of the core of the body to cool off substantially and this protects the innermost vital organs-there was not an expectation of that, it was very surprising,” said Whiteman.
The researchers also detailed extraordinary swimming ability of the bears in the study, with one female surviving a 9 day, 400 mile swim from shore to ice- http://www.bbc.com/news/science-environment-33551569 (follow this link for additional information).
Seven weeks later when she was recaptured, the bear had lost 22% of her body mass as well as her cub.
Scientists say, despite her strong performance in cold water, it does not compensate for the lack of food and inability of the bears to slow down their metabolism response.
“We’ve uncovered what seems to be a fascinating adaptation for swimming in cold artic waters, but I don’t think that is going to play a big role in determining their fate as the loss of hunting opportunities will,” said Whiteman.
“We think this data also points towards their eventual decline.
The paper has been published in the journal Science.