Some polar bears are facing starvation as the Arctic ice melts because they cannot adapt their diet to live on land, scientists have found. The iconic Arctic species normally feed on ringed seals, which they catch on offshore ice floes.
Polar bears face starvation due to climate change PHOTO Archive
But as ice disappears in a warming world, many bears are spending more time on shore, eating bird eggs, berries and grass. However, animals lose weight quickly on land, with an increased risk of death, notes BBC News.
The polar bear has made headlines for the growing threat of climate change in the Arctic, but the reality of the impact on this species is complicated.
Climate change, the main threat
Bear numbers declined by the 1980s, mainly due to unsustainable hunting. With greater legal protection, polar bear numbers have increased. But rising global temperatures are now seen as their biggest threat. That's because the frozen Arctic seas are key to their survival.
The animals use the sea ice as a platform to hunt ringed seals, which have high concentrations of blubber, especially in late spring and early summer. But during the warmer months, many parts of the Arctic are now increasingly ice-free.
In western Manitoba, where this study was conducted, the ice-free period increased by three weeks between 1979 and 2015. To understand how the animals survive as the ice disappears, the researchers tracked the activities of 20 polar bears during the months of summer for a period of three years. In addition to taking blood samples and weighing the bears, the animals were fitted with GPS-equipped video camera collars.
This allowed scientists to record the animals' movements, their activities and what they ate.
During the ice-free summer months, bears have adopted different strategies to survive, some conserving their energy. Most tried to look for vegetation or berries or swam to see if they could find food. Both approaches failed, with 19 of the 20 bears in the study losing body mass, up to 11 percent in some cases. On average, they lost a kilogram a day.
“No matter what strategy they were trying to use, none of the approaches had any real benefit in terms of being able to extend the time they could survive on land.”according to the study's lead author, Dr. Anthony Pagano of the US Geological Survey in Alaska.
“Polar bears are not grizzly bears wearing white coats”said co-author Charles Robbins of the Bear Center at Washington State University. “They are very, very different.”
Two of the three bears that went to the water found carcasses of dead animals, but spent only a short time eating because they were too tired from their efforts.
“A subadult female found a dead beluga whale, took a few bites from it, but mostly used it as a buoy to rest on. It really suggests to us that these bears can't eat and swim at the same time”said Dr. Pagano, for BBC News.
The adaptability of the species
An interesting finding of the study was that one bear gained 32 kg in weight. Researchers believe that this bear, which had spent much of its time resting and conserving its strength, was lucky enough to come across an animal carcass.
While previous research has highlighted the challenges the climate presents in the coming decades, this new work raises important questions about the species' ability to adapt.
However, other researchers say the impact of climate change on polar bears would be different depending on the location.
“Polar bears are likely to disappear from areas where sea ice is lost in the future, but it is difficult to say when and where”said Jon Aars of the Norwegian Polar Institute, who was not involved in the study.
“Some areas will have good bear conditions for many decades. The area of this study is one where conditions may be very difficult for bears in the short term if sea ice continues to disappear as predicted.”
PHOTO Profimedia Images
Key information about polar bears
– There are about 26,000 polar bears left in the world, most of them in Canada. Populations are also found in the USA, Russia, Greenland and Norway.
– Polar bears are listed as vulnerable to extinction by the International Union for Conservation of Nature (IUCN), with climate change being a key factor in their decline.
– Adult males can grow up to about 3 meters in length and weigh almost 600 kg. Polar bears can eat up to 45 kg of fat in one meal.
– These bears have a strong sense of smell and can sniff out prey from a distance of up to 16 km.
– They are strong swimmers and have been observed up to 100 kilometers out to sea, they can swim at speeds of around 10 km/h, in part due to their slightly webbed feet.
