Melting Sea Ice Causing Hungry Polar Bears To Switch From Seals To Goose Nesting Sites

Melting sea ice is causing polar bears to shift from eating ringed seals to goose eggs, causing bird numbers to crash by up to 90 percent. critterbiz/Shutterstock

As the ice melts, polar bears are struggling to get enough to eat. Usually, they rely on ringed seals to make up the bulk of their diet, but they need sea ice to hunt. This major shift in the environment is driving the emergence of new behaviors, with polar bears in Svalbard turning instead to poaching eggs.

Researchers have been tracking the bears living on the Arctic island to see how they are responding to the shrinking sea ice. They have been monitoring the animals’ diet, noting how it is altering in response to the warming region, paying particular attention to before and after the dramatic melting of sea ice in 2006. And they’ve found some pretty striking changes.

Published in the Journal of Animal Ecology, the team report how they have tagged 60 ringed seals and 67 polar bears over their study period. They found that before the melting of the ice, the bears were remarkably successful in sneaking up on and devouring ringed seals as the marine mammals hauled themselves up onto the ice. But when the ice became thinner and broke up due to the warming Arctic, things changed.

The bears could no longer hunt the seals in this way, and were forced to swim stealthily up to ice floes before jumping out and catching seals, a technique that only a few male bears were able to master. Consequently, the researchers found that most bears had given up on hunting seals, and were instead retreating from the coast and hanging around goose nesting grounds instead.

Here, the bears would simply wander from nest to nest, hoovering up any and every egg they found, decimating the entire breeding site as the geese helplessly watched on. How this shift in diet will impact the bears, in the long run, is not known or understood. Seals are rich in fat, while the eggs are heavy in protein, something that could have implications later down the line.

But it is also, obviously, a disaster for the geese who now face a predator not previously experienced. The impacts of a drop in geese numbers may affect more than just the birds themselves. If the geese were to die off, for example, this could affect the fox populations, whose cubs rely heavily on the birds when growing up.

But it’s not only their predators that could feel the pinch. It’s easy to forget that geese are grazers, and traverse the tundra clipping the grass in their thousands. This, in turn, maintains the grasslands and aid reindeer as they too roam the tundra chomping on the grass. Ecosystems are complex webs, and the knockout of one species can have massive unforeseen consequences later down the line.

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