Can't Sleep and Must Find Food... Why Polar Bears Lose 1kg a Day

Feeding Shortens Hibernation Period
Further Glacier Reduction Threatens Survival

As global warming causes Arctic sea ice to melt, the habitat of polar bears is also being threatened. A study has found that the number of polar bears entering hibernation each year is decreasing, leading to a rapid decline in their body weight. Fully grown polar bears weigh about 150?250 kg for females and around 450 kg for males.

On the 13th (local time), the international academic journal Nature Communications published the results of a study by the U.S. Geological Survey team tracking polar bears in Hudson Bay, Canada.

Polar bear. [Image source=Pixabay]

Sea ice is very important to the life of polar bears. When the sea freezes and sea ice forms, they go out to hunt for food, and when winter passes and the weather warms, causing the sea ice to melt, they enter hibernation. However, due to climate change reducing sea ice and thus food availability, polar bears have begun to venture onto land to hunt. As a result, they now spend about 130 days out of the year on land, reducing their hibernation period.

The researchers fitted GPS collars equipped with video recording functions on 20 polar bears and tracked them over about three years in western Hudson Bay, Canada. The investigation found that all the polar bears lost an average of 1 kg of body weight per day.

The weight loss is due to increased activity and reduced hibernation time. Only two of the observed bears entered hibernation during the sea ice period, while the other 18 moved their habitat to land. The researchers speculated that "the 18 active bears likely supplemented their nutrition by hunting various foods such as grass, berries, seagulls, rodents, and seal carcasses."

Anthony Pango, a wildlife biologist at the U.S. Geological Survey who led the study, explained, "Polar bears are creative and innovative animals. If they have the will, they will find ways to survive and seek food resources to replenish their energy needs."

However, the food obtained on land alone cannot provide the calories polar bears need. This is because the total energy expended during activity exceeds the total energy intake. The researchers expressed concern, stating, "Nineteen out of the 20 polar bears lost weight during this period," and warned that "the longer polar bears spend on land, the greater the risk of starvation."

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