Unusual hunting and feeding behaviour of polar bears on Spitsbergen

Prolonged chasing of an adult reindeer ( Rangifer tarandus ) by a polar bear ( Ursus maritimus ) was observed both on land and in the sea, in Magdalenefjorden, northwest Spitsbergen. Polar bears were also observed catching black guillemot ( Cepphus grylle ) in the sea in northwest Spitsbergen and feeding on chicks in the arctic tern ( Sterna paradisea ) colony in Hornsund, southwest Spitsbergen. While feeding on seabird species is unsurprising, the prolonged chasing of adult reindeer is unusual for polar bear hunting behaviour. The few documented cases of polar bear hunting reindeer consist of either surprising and killing resting/sleeping prey or stalking and a short rapid chase of the reindeer. Our observations describe new feeding habits of polar bears that may be in response to decreasing seal availability due to shrinking sea-ice cover in the Arctic.