Scientists expect that longer time spent on land will increase the risk of starvation.
ADVERTISEMENTLong Arctic summers are putting polar bears at higher risk of extinction than ever before, according to new research.
The study, published in the journal Nature Communications, shows they are unlikely to adapt to spending more time on land as they face greater risk of starvation.
Scientists observed 20 polar bears over a three-week period during the Arctic summer, looking at the ways they tried to conserve energy. Despite resting, scavenging and foraging for alternative foods, all of them rapidly lost weight.
They weighed the bears before and after the study period and on average found that they lost almost a kilogram each day.
‘Polar bears are not grizzly bears wearing white coats’
As summers in the Arctic get longer due to climate change, some scientists thought that these animals could adapt to living on land for extended periods by acting like their grizzly bear relatives.
Many of the male polar bears laid down to conserve energy, burning similar calories to when they hibernate. Other bears went searching for food, eating bird and caribou carcasses, kelp, berries and grasses.
But neither resting nor adapting their diet would allow polar bears to exist on land for extended periods of time, the study’s authors say.
'Even those bears that were foraging lost body weight at the same rate as those that laid down,” explains Charles Robbins, director of the Washington State University Bear Center and co-author of the study.
'Polar bears are not grizzly bears wearing white coats.”
Polar bears don’t adapt well to time spent on land
Polar bears spend the majority of their time on the sea ice where they hunt for seals, catching one to eat every few days. On land, the foods they can find have a much lower calorific content - they don’t have the fat content needed to sustain the bears.
Scientists also found that the bears struggled to eat carcasses they scavenged while swimming out in the water.
“The terrestrial foods did give them some energetic benefit, but ultimately, the bears had to spend more energy to access those resources,” says lead author Anthony Pagano, research wildlife biologist with the US Geological Survey Polar Bear Research Programme.
As ice-free periods get longer, the study suggests polar bears across the Arctic are at risk of starvation. And polar bear numbers have already declined by an estimated 30 per cent since 1987.
“As polar bears are forced on land earlier, it cuts into the period that they normally acquire the majority of the energy they need to survive,” Pagano adds.
“With increased land use, the expectation is that we'll likely see increases in starvation, particularly with adolescents and females with cubs.”
