Scientists expected the opposite, but polar bears in the Norwegian Arctic archipelago of Svalbard have become fatter and healthier since the early 1990s, all while sea ice has steadily declined due to climate change.
Polar bears rely on sea ice as a platform from which to hunt the seals that they rely on for blubber-rich meals. The bears' fat reserves provide energy and insulation and allow mothers to produce rich milk for cubs.
Researchers weighed and measured 770 adults in Svalbard between 1992 and 2019 and found that bears had become significantly fatter. They think that Svalbard bears have adapted to recent ice loss by eating more land-based prey, including reindeer and walruses.
The discovery, published in Scientific Reports, was particularly puzzling because of the impact of climate change in Svalbard. During the same period that this research was carried out, global temperature rise has reduced the number of ice-free days per year in the region by almost 100 - at a rate of about four days each year.
Lead researcher Dr Jon Aars from the Norwegian Polar Institute stated, The fatter a bear is the better it is, acknowledging he expected to see a decline in body condition given the profound loss of sea ice.
Walruses, which have been officially protected in Norway since the 1950s after being hunted to near extinction, have increased in number, providing a new source of food for polar bears. Dr. Aars noted, There are a lot more walruses around [for them to hunt] these days. He also suggested that if seals have smaller areas of sea ice, they may gather more closely together, giving bears easier access to them.
While this is unexpected good news for these Arctic predators, the researchers think it is unlikely to last as the sea ice continues to decline. As bears travel farther to access hunting grounds, they will expend more energy and deplete their fat reserves.
Experts believe the findings may be linked to a population recovery following heavy hunting until the 1970s, combined with increases in prey availability. However, Dr. John Whiteman from Polar Bears International warns that long-term, the need for sea ice remains critical for their survival, stating, If ice loss continues unchecked, we know the bears will eventually disappear. The results illustrate that while polar bears can adapt temporarily, their future is uncertain amid ongoing environmental change.
