Arctic polar bears are going hungry and losing weight thanks to climate change

A study published in the journal Nature Communications, yesterday, has come to the conclusion that polar bears in the Arctic are gradually starving to death because of global warming. That’s how I would characterise the findings of their study.

In essence, it goes like this. There is less sea ice because of global warming. Polar bears are accustomed to living on sea ice and hunting seals on sea ice. Because there is less sea ice they have to swim a lot more sometimes extreme distances to find a prey animal or they can hunt on dry land.

Polar bears are going hungry as ice melts from Arctic thanks to global warming
Polar bears are going hungry as ice melts from Arctic thanks to global warming
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But the clincher is this: when they hunt on dry land the amount of energy they expend in finding animals and things to eat is greater than the input of energy from the food they consume and therefore these animals lose weight.

Don’t adapt to behaving like grizzly bears

In short, they are starving to death no matter how they try and deal with the loss of sea ice caused by global warming. Conservationists were hoping that polar bears would adapt to hunting in a different way on dry land because that is the future for them. The first ice-free Arctic summer is projected to arrive between 2030 and 2050.

But, polar bears have demonstrated in the study that they are unable to adapt in the way the conservationists had hoped and so they will starve to death on the current assessment.

I’m told in a Times report that there are 26,000 polar bears left on the planet. Several populations spend extended periods on dry land. There was speculation that they could adapt to behave like grizzly bears that they can’t.

The researchers were based at the US Geological Survey and Washington State University. They put GPS trackers and cameras on 20 polar bears in the Canadian province of Manitoba. They recorded their movements and what they ate. And they recorded their body weight over three weeks.

Different methods to survive

Individual bears had different methods of dealing with the problems they faced. Some bears remained sedentary to try and save energy. Three bears made long swims totalling 54-175 km. Extraordinary distances.

Two of these bears found the carcasses of marine mammals in the water but based on video footage polar bears are not very good at eating carcasses in the water.

Of the 20 bears studied only one individual gained weight during the study. The others lost between 8 kg and 30 kg of weight over the three weeks.

The conclusion by the scientists is as follows:

“Our findings indicate that terrestrial foods are inadequate to extend the duration that polar bears can survive on land…We found they used as much energy to locate those foods as they gained from feeding on them.”

Anthony Pagano, lead author of this study cited below.

Do we care?

Do we care? Clearly, we don’t care enough because every time I research polar bear survival in the wild, I always come away depressed. For years they’ve been swimming massive distances to find an animal to eat and I’m sure that some of them drown in the attempt. Their evolution has made them reliant on sea ice and it’s disappearing pretty rapidly thanks to human behaviour.

Study citation

Pagano, A.M., Rode, K.D., Lunn, N.J. et al. Polar bear energetic and behavioral strategies on land with implications for surviving the ice-free period. Nat Commun 15, 947 (2024). https://doi.org/10.1038/s41467-023-44682-1

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