When polar bears hunt snow geese, hunger justifies the means

• Polar bears (Ursus maritimus) take advantage of the winter to build up their fat reserves.
• Intensive hunting of seals, a resource rich in fat, allows bears to store up enough energy to get through the summer.
• The adaptations that bears will have to make to meet the challenges brought about by climate change are numerous and unpredictable.

An unusual sighting – a polar bear in fresh water

• Some 80 km from the Inuit community of Mittimatalik, the Bylot Island field station was bustling with activity.
• Today, scientists from a variety of backgrounds scour the Quarliktuvik valley floor, which is generally flat, to study the soil, water, plants and wildlife.

• The image was foggy, but what I initially thought were two colleagues walking side by side, turned out to be the distinctive shape of a polar bear.
• Everyone in our group had the necessary protective equipment — bear spray, anti-bear cartridges and sometimes even a rifle — but I alerted them by radio and immediately returned to the field station.
• They waded in quickly enough to keep the bear, who was swimming on the surface, at a safe distance.
• 1:45 p.m. - 2:00 p.m.: the bear swims in the lake […], makes 4 dives to try to catch a goose.
• During the afternoon, the bear used this technique two more times, once failing and once with success.

What are the benefits of this behaviour for bears?

• Nowhere in the scientific literature is there any mention of such behaviour.
• At best, there are reports of attacks on murres in the ocean near the coasts, an environment very different from the calm, shallow ponds where we observed the bear’s attacks.
• the time the bear spent swimming and its success in hunting, allowed us to answer this question.

An energy boost, but far from sufficient

• First of all, a goose provides relatively little energy — around 200 times less than a ringed seal weighing 45 kilograms.
• Hunting geese could therefore be of benefit to certain bears from time to time, but on a population-wide scale, it will not alleviate the energy deficits caused by the melting ice pack.

David Bolduc received funding from the NSTP and the Canadian Association for Humane Trapping. Matthieu Weiss-Blais received funding from NSERC, FRQNT and NSTP.