As the planet continues to warm up, and the Arctic sea continues to retreat, researchers are becoming more and more concerned that polar bears will have less access to food they need to survive.

Scientists had thought that the bears would enter a kind of “walking hibernation” to survive when they do not have access to prey, BBC reports. The animals would stay awake, but they would significantly lower their metabolism in order to save their energy. This sort of hibernation would be useful during the warmer summer months, according to Washington Post.

A new study, published in Science Thursday, says that research conducted over 3 years and with more than 24 polar bears from the Arctic’s Beaufort sea turns that idea down. The new research says that polar bears will starve in warmer conditions when food-deprived.

The study monitored the temperatures of bears living on land and on ice. Researchers did not find any evidence concluding that temperatures dropped low enough to not need food in the summer months. In other words, the temperature patterns and activity recorded for polar bears were not comparable to the patterns of hibernating bears in winter.

Biologist at the University of Wyoming and lead author John Whiteman said, “We didn’t find anything that looks like hibernation,” New York Times reports.

“We haven’t known until now whether bears really reduce their metabolism in summer, which, if they did, may have offered a limited buffer from some of the negative effects of ice loss,” he added.

A scientific adviser to Polar Bears International and bear biologist at the University of Alberta Andrew Derocher said that the results put more concern on polar bears’ fate since food sources are more scarce on land than seals are on the ice (Polar bears use sea ice to hunt seals).

Though the bears do not have the ability to change their behavior when it comes to food, they do have the ability to adapt to 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,” Whiteman said.

Researchers said that a female bear survived a 9-day 400-mile swimming stretch from the shore to ice; however, the bear had lost 22 percent of her body mass and her baby after seven weeks. Though swimming in cold water is a great accomplishment, Whiteman does not believe it will play as big of a role “in determining their fate” as a lack of hunting options will.