CLIMATE CHANGE
During ice-free periods, polar bears lose an average of one kilo per day. This is evident from a new study with twenty polar bears in Canada. Ice-free periods in the polar regions are lasting longer, meaning polar bears have to survive on land for longer and longer periods of time.
Source: Nature Communications Today at 6:00 PM
In normal circumstances, polar bears mainly live on seals that they catch from ice floes off the coast, but in ice-free periods they are forced to survive on the mainland and search for food. Those periods without ice are getting longer. For example, the Hudson Bay area, an inland sea in northern Canada, now has 130 ice-free days per year, which is three ice-free weeks more than in 1979.
A research team led by biologist Anthony Pagano spent three summers studying the survival strategies of polar bears during ice-free periods in the Canadian province of Manitoba on Hudson Bay. With cameras and GPS trackers, they followed twenty polar bears for three weeks at a time during the summer months. They weighed the bears and took their blood.
The researchers wanted to gain insight into how the bears maintain their weight during periods without ice. That turned out to be impossible for 19 of the 20 polar bears. On average they lost one kilo per day.
However, the polar bears used different strategies to survive. Most bears appeared to rest a lot to save energy. They ate berries, grass, birds, rodents and bird eggs. A few bears were occasionally able to snare a larger seabird or deer as prey, but even that did not maintain their weight and energy levels. Those polar bears lost a lot of energy and calories while hunting. They are not used to this because they are mainly specialized in catching “inattentive” seals, the study explains.
Although the researchers show that polar bears are adaptable to changes, there is no single method by which they manage to maintain their weight and energy levels. The animals are unable to adapt their diet to life on land. Weight loss increases the risk of mortality. The researchers conclude that polar bears could be threatened with extinction during ice-free periods.
