This is the desperate struggle of polar bears to find food in a melting Arctic

In a world where climate change is altering natural habitats at a rapid pace, polar bears have become one of the symbols of the fight for survival.

Summers are lengthening, planet temperatures are increasing and there is less and less ice.

When the frozen blocks of the Arctic disappear, bears spend more time on land, where it is difficult to find food, as their traditional hunting strategies that take advantage of the sea ice are less effective.

A study published today in

Nature Communications

presents a portrait of the challenges that the 25,000 polar bears left on the planet face in order not to die of starvation.

In the period of late spring and early summer, polar bears use sea ice as a hunting platform.

They feed mainly on seals that are giving birth and weaning their pups in the same season.

When the ice melts, the Arctic giants have to slow down as much as possible to conserve energy.

A team of scientists, led by wildlife biologist Anthony Pagano of the United States Geological Survey, observed polar bears up close for three weeks over the summer.

To achieve this, they placed collars equipped with cameras and GPS on twenty bears in western Hudson Bay, Manitoba (Canada).

In this area the population has decreased by around 30% since 1987 and the ice-free period has increased by three weeks since 1979, keeping bears on land for approximately 130 days in the last decade.

After analyzing the images, they discovered that the bears tried different tactics to feed and maintain energy reserves, including scavenging and resting at similar levels as grizzly bears when they enter hibernation.

70% of those who were active ate terrestrial foods such as berries, herbs and bird carcasses.

Three bears ventured to swim long distances to find food in the water and although two of them found remains of belugas and seals, they were unable to eat while swimming or bring them to land.

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Regardless of their eating or rest strategy, there was a consistent decrease in body mass and 19 of the 20 lost an average of 1 kilogram per day.

“A continued increase in the length of summer on land will be associated with an increased risk of starvation,” says Pagano.

“Neither strategy will allow polar bears to exist on land beyond a certain amount of time.

Even those bears that were foraging lost weight at the same rate as those that were lying down,” adds Charles Robbins, director of the Bear Center at Washington State University and co-author of the study.

It has been speculated that polar bears could adapt to ice-free seasons by searching for terrestrial food, but the study shows that it is not so easy to find it and that it does not provide them with the nutrients or energy they need, so they end up suffering from famine.

David Nogués Bravo, a macroecologist at the Center for Macroecology, Evolution and Climate at the University of Copenhagen who has not participated in the study, explains that the lack of food “reduces the probability of maintaining generational replacement” and adds that “terrestrial foods gave them some energy benefit, but ultimately they had to spend more energy to access those resources.”

A polar bear in western Hudson Bay.David McGeachy

The ice that covers the Arctic reaches its minimum every September and each year is less than the previous.

According to NASA data, based on several of its satellites, the extent of the polar cap has decreased at a rate of 12.6% each decade since 1980. A 2023 study supported by observations from NASA and ESA satellites predicts that between 2030 and 2050 the first ice-free September will arrive.

And if greenhouse emissions are not reduced, by 2100 the Arctic region will spend up to half a year without ice.

The study's findings have important implications for the conservation of polar bears, but also invite us to investigate the repercussions it has for the marine and terrestrial ecosystems of the Arctic.

The presence of these animals hunting for longer in terrestrial areas has indirect impacts on other species such as birds, according to Nogués.

“Bears are capable of eating dozens of eggs in a short time and reduce the probability that these bird populations have to survive,” he adds.

That polar bears are in serious danger of extinction is nothing new.

What is surprising is the massive decline in hatchlings and the starvation faced by adults due to melting sea ice.

“I have seen polar bears in the Arctic and it is darkening to witness the path of this species towards its probable functional extinction in the not too distant future,” says Nogués, who emphasizes that it is important to take into account that “the biodiversity crisis and the climate crisis are not two different crises, but two sides of the same coin.”

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