Melting sea ice forces polar bears to travel further for food – WSU Insider

Melting sea ice forces polar bears to travel further for food – WSU Insider

PULLMAN, Wash. — In recent years, polar bears in the Beaufort Sea have had to travel far beyond their traditional Arctic hunting grounds, contributing to a nearly 30% decline in their population.

The bears’ home range, or the amount of space they need for food and other resources, was about 64% larger from 1999-2016 than it was in 1986-1998, according to a recent study in the journal Ecosphere.

“Having to travel longer means these bears are using more energy, which could threaten their survival,” said Anthony Pagano, a postdoc researcher at Washington State University’s School of the Environment and lead author of the study. “If we want to preserve the habitat of these amazing mammals, then we need to focus on the root of the problem that is slowing down global climate change.”

For the study, Pagano and colleagues from the U.S. Geological Survey used satellite tracking data to analyze the movement patterns of female polar bears from 1986-2016 in the Beaufort Sea area north of Alaska.

Their work has shown over the last two decades that polar bears have to travel further north of their traditional hunting grounds on the continental shelf to remain on their receding sea ice habitat.

The continental shelf extends about 100 miles north of Alaska and Canada and is a shallow water habitat that contains plenty of fish for the bears’ favorite prey, seals.

During early summer, when seals wean their young and are most vulnerable to attack, polar bears will often double their body weight from eating the fatty meat.

Anthony Pagano

The researchers’ data show that as the sea ice over the continental shelf continues to retreat earlier and further back; the bears are displaced from this primary foraging habitat and travel further north into deeper waters where there are fewer seals to prey on.

“The combined effect of having to move further and further north with the ice in the summer and then having to move back in the fall and winter when the ice freezes takes a huge toll,” Pagano said. “Our work highlights the worrying impact of sea ice decline on the polar bear’s movement patterns.”

Another interesting finding of the study is that about 20% of the polar bear population in the Beaufort Sea completely abandons their traditional sea ice hunting areas in the summer and fall. These bears move inland along the coasts of Alaska and Canada in search of food such as carrion, berries and sometimes even bowhead whales, which are left on the coast by native residents hunting the large water mammals.

“Sometimes you want 50 to 100 polar bears gathering around these whale bodies and competing with each other for food,” Pagano said. “As more and more bears move ashore, I suspect there will be a lot more competition for these food resources, and we’ll probably start to see further declines in abundance and survival.”

Going forward, Pagano and his colleagues with the USGS plan to conduct further studies of polar bears moving into the country to get a better idea of ​​how they cope with their new terrestrial habitat.

He said the best thing humans can do to help conserve the Beaufort Sea’s 800 remaining polar bears is to focus on limiting global carbon emissions, which are the main cause of declining Arctic sea ice.

Recent modeling work has shown that adopting rules to reduce these emissions to avoid global warming of more than 2 ° C (3.6 ° F) could drastically slow down the decline of polar bear habitats in the Arctic. which in turn will help these animals survive.

“Encountering a polar bear while flying over the Arctic in a helicopter is a surreal experience,” Pagano said. “They are incredibly massive and impressive. It is amazing to observe this animal that is so uniquely adapted to exist in this harsh Arctic environment. They are worth the effort it will take to preserve them.”

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