Hunger threatens to make the polar bear extinct

Hunger threatens to make the polar bear extinct

«Polar bears are not brown bears in white coats; “They are very very different.” This is how exhaustive Charles Robbins, director of the Bear Center at Washington State University, is when he warns of the difficulties that this emblematic animal species is, and will continue to encounter, in a context of climate change and melting ice like the current one. So much so that they will not be able to adapt to the increasingly longer Arctic summers. The more time on land, the less chance of feeding as their nature requires. Thus, they may starve and disappear from the ecosystem.

This is the conclusion reached by a team of American researchers who, for the first time, have been able to monitor the activity of 20 polar bears in the Arctic area of ​​Hudson Bay, in Manitoba (Canada), with cameras and GPS. during the summer.

The conclusions of their work, published in Nature, debunk old theories about the hypothetical ability that these bears would have to adapt their diet to what the environment offered them during long periods of thaw, while they remained on land in coastal areas. .

The truth is that, by not having their main source of fat and protein available, that is, the seals, they lose weight at a rate of one kilo per day. The diet offered by the greened Arctic brought about by climate change is not enough to prevent them from dying of hunger.

First, because many of the adult male polar bears analyzed simply lie down to conserve energy, burning calories at a rate similar to that of hibernation. Others foraged and consumed bird and caribou carcasses, as well as berries, seaweed, and grasses.

Generally larger than grizzly bears (gray bears, a subspecies of the brown bear), adult male polar bears can reach three meters in length and weigh 680 kilos compared to the former’s two meters and 350 kilos. To maintain that large mass, polar bears rely on energy-rich seal blubber, which they capture best on ice.


Every day that polar bears spend on land, forced by the progressive melting of the Arctic, with increasingly longer summers, they lose this weight: one kilo.

“Terrestrial foods gave them some energetic benefit, but ultimately the bears had to expend more energy to access those resources,” explains Antony Pagano, a wildlife research biologist with the US Geological Survey’s Polar Bear Research Program. USA and lead author of the aforementioned study published in Nature. According to the data collected, some adult females spent up to 40% of their time searching for food without all that activity, and their energy expenditure, having any fruit.

Monitoring of the specimens has also managed to demonstrate that they are not capable of feeding on the corpses they find in the water. “Two found bodies in the water, a beluga and a seal, but no bear was able to eat them while swimming or bring them back to land,” the researchers say. Only one of the 20 bears gained weight after finding a dead marine mammal on land.

Still, polar bears across the Arctic are at risk of starvation as the ice-free period continues to lengthen. “As polar bears are forced to come ashore sooner, the period in which they normally acquire most of the energy they need to survive is shortened,” Pagano said.

“With increased land use, the expectation is that we will likely see an increase in starvation, particularly among adolescents and females with cubs.”

In this context, both Robbins and Pagano consider that they will not develop any adaptation strategy that allows polar bears to “exist beyond a certain period of time” on Earth.


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