Svalbard polar bears have proven themselves resourceful, but there are limits
9 April 2021
The Barents Sea is home to one of the world’s 19 recognized polar bear populations. But in recent decades, sea ice has been diminishing more quickly here than anywhere else in the Arctic. As Jon Aars explains, it hasn’t yet led to population declines, but it is affecting the bears’ lives in several ways.
The Barents Sea polar bears live in Svalbard, Norway and the western Russian Arctic. In Svalbard, in the century before the 1973 agreement to conserve polar bears, commercial hunters killed more than 30,000 of these bears. The population increased after the agreement was signed—only to face the rapidly accelerating loss of their sea-ice habitat in the ensuing years. Given scientists’ predictions that the ice will continue to recede in future decades, polar bears in the area are bound to face further challenges, and their numbers will likely decline. We just don’t know when.
Some 3,000 polar bears—a ninth of the world’s total stock—belong to the Barents Sea population. The majority depend on the ice edge to hunt for most of the year. However, all adult female polar bears build their dens on the Norwegian (Svalbard) or Russian (Franz Josef Land) islands. They give birth in midwinter to a couple of small cubs, generally every third year if the cubs live until they are weaned at the age of two.
The long trek to find a den
Female polar bears who live at the ice edge may have to travel hundreds of kilometres to reach their denning areas in Svalbard. This distance was easier to cover when the ice edge extended further south. The bears could walk on the ice to reach the islands in autumn. These days, they sometimes have to swim hundreds of kilometres to get there—a feat that is not only risky, but costs them considerable energy. We also suspect that more bears have begun going to Franz Josef Land than to Svalbard to den. This is a successful workaround for now, but in 10 to 20 years’ time, they may face a long swim to get to Franz Josef Land too.
About 300 polar bears remain in Svalbard year-round rather than hunting on the ice edge. We know more about the Svalbard bears than the ice-edge bears because we are usually working in Svalbard when we capture and mark bears for research purposes—and the challenges they face as temperatures climb are very different from those encountered by their ice-edge peers. For example, females do not need to travel as far to find dens, but the retreating sea ice is shortening their hunting season, which could leave them with less fat reserves to survive the winter and provide milk for fast-growing cubs. They may be in their dens without food for as long as half a year.
Predicting the future of Svalbard bears
So far, the Svalbard bears are not in poor condition, and they are still reproducing. The question is: why do they seem to be thriving despite having access to less sea ice? There are a few possible answers. It could be that the density of bears is still low compared to what it was before people started to hunt. That would mean less competition for food resources. Another relevant factor is that polar bears are good at adapting and using every resource they can find.
For example, we have seen a change in their feeding strategies. Hunting ringed seals in spring is still important. Polar bears also used to hunt seals near glaciers on the fjord ice in summer. Now that the sea ice is often lacking, they spend more time plundering bird colonies for eggs and chicks. We also see them hunting harbour seals, which are becoming more common in Svalbard even though they are not an Arctic species. The bears also take reindeer, something they were not known to do in decades past. Walrus—which are themselves quickly recovering from earlier unsustainable hunting—are also food for Svalbard polar bears.
It will be interesting to see how the local Svalbard bears do in future years as the sea ice continues to diminish. Unlike polar bears in some other Arctic areas, they have few competitors (such as brown bears, wolves or wolverines). But the fact that polar bears depend on sea ice in all the areas they occupy suggests there will be a threshold for this population too. They have proven resilient in the face of challenges so far, but to continue to thrive, they will need access to sea ice to hunt seals for at least a period in spring and early summer.
For now, polar bears in the Barents Sea area seem to be coping with their habitat loss. However, as the sea ice continues to disappear, it is likely they will be challenged at some point. Being a polar bear in Svalbard today is already a very different experience compared to 30 or 40 years ago, and the environment is changing swiftly.
JON AARS is a senior research scientist who leads the Norwegian polar bear program at the Norwegian Polar Institute.
Polar bears evolved from a brown, terrestrial omnivore to become a white, marine carnivore that has long thrived in the Arctic’s icy environment. But as Andrew Derocher explains, given the pace of change in the Arctic, evolution doesn’t favour this highly specialized bear of the ice.
Spring is a particularly important time for polar bears. Polar bear mothers emerge hungry from their snow dens with their young cubs after fasting for four months. They need to hunt and replenish their energy quickly so they can continue to nurse their cubs. But as climate change continues to warm the Arctic, sea ice melts earlier in the summer and forms later in the fall.