Polar bears (Ursus maritimus) benefit from the winter to construct up their fats reserves. Intensive looking of seals, a useful resource wealthy in fats, permits bears to retailer up sufficient vitality to get by way of the summer season.
As the local weather warms, looking alternatives on the ice pack are diminishing. Experts consider that because of this, there may be not adequate meals assets on the land to permit bears to construct up the vitality reserves they require.
Faced with these adjustments, some polar bears are making the most of colonies of nesting birds and their eggs, one of many few assets available on land, to compensate for his or her vitality deficits. The variations that bears must make to satisfy the challenges caused by local weather change are quite a few and unpredictable.
As a scholar researcher in ecology, I used to be going to benefit from a brief journey north of Baffin Island, in Nunavut, to do some work on the small fauna of Bylot Island. One afternoon, a polar bear determined in any other case. Here we report on his exploits, which led to observations of unprecedented behaviour.
An uncommon sighting – a polar bear in contemporary water
It was Aug. 8, 2021. Some 80 km from the Inuit group of Mittimatalik, the Bylot Island subject station was bustling with exercise.
Established 30 years in the past, the sphere station is situated within the coronary heart of the breeding grounds of the most important recognized colony of snow geese (Anser caerulescens caerulescens). Today, scientists from quite a lot of backgrounds scour the Quarliktuvik valley ground, which is mostly flat, to check the soil, water, vegetation and wildlife.
(Tim Moser), Fourni par l’auteur
Coming out of a ravine, one of many few landforms within the space, I used to be scanning the valley with my binoculars when two pairs of legs within the distance caught my eye. The picture was foggy, however what I initially thought had been two colleagues strolling facet by facet, turned out to be the distinctive form of a polar bear. Everyone in our group had the required protecting tools — bear spray, anti-bear cartridges and generally even a rifle — however I alerted them by radio and instantly returned to the sphere station.
Several colleagues had gathered on a small hill to control the newcomer. In truth, by the point I’d lined the kilometre distance to the camp, the bear had walked three kilometres and was transferring round a pond the place geese had been gathered. At this time of yr, the geese are moulting — and due to this fact unable to fly — in order that they congregate close to ponds to keep away from the Arctic fox (Vulpes lagopus), which is reluctant to leap into the water. With a bear within the neighborhood, we ceased our subject actions and took benefit of the radiant afternoon to look at the king of the ice pack.
True to type, the geese took refuge within the nearest pond on the first sight of hazard. They waded in shortly sufficient to maintain the bear, who was swimming on the floor, at a protected distance.
But the bear was about to make use of a brand new looking method: he dove below the water, disappeared from the eyes of the geese who had stopped fleeing, and emerged from beneath one in all them.
My colleague Mathilde Poirier recorded the behaviour in her pocket book:
1:45 p.m. – 2:00 p.m.: the bear swims within the lake […], makes 4 dives to attempt to catch a goose. Succeeds in its 4th try (catches the goose from under, throughout a dive).
During the afternoon, the bear used this system two extra instances, as soon as failing and as soon as with success.
What are the advantages of this behaviour for bears?
Two months later, again at Laval University, we had been nonetheless fascinated by this commentary. Nowhere within the scientific literature is there any point out of such behaviour. At finest, there are experiences of assaults on murres within the ocean close to the coasts, an setting very totally different from the calm, shallow ponds the place we noticed the bear’s assaults.
Being conscious of the vitality challenges bears face through the summer season, our analysis group — led by Matthieu Weiss-Blais — wished to reply the next query: would this looking method permit polar bears to learn from consuming snow geese?
The info recorded within the subject, i.e. the time the bear spent swimming and its success in looking, allowed us to reply this query. By combining our observations with estimates of the vitality value of swimming in bears and the vitality contained in a snow goose, we had been capable of mannequin the vitality effectivity of the method.
These calculations reveal that this looking method may permit bears to accumulate extra vitality than they expend, significantly for smaller bears, and in the event that they handle to catch a goose shortly.
(Yannick Seyer), Fourni par l’auteur
An vitality increase, however removed from adequate
However, this vitality contribution can be very restricted in scope.
First of all, a goose supplies comparatively little vitality — round 200 instances lower than a ringed seal weighing 45 kilograms.
What’s extra, the geese are not often out there as prey: they lose the power to fly for less than three or 4 weeks every summer season and so they solely have colonies in a couple of locations within the Arctic.
Hunting geese may due to this fact be of profit to sure bears every now and then, however on a population-wide scale, it won’t alleviate the vitality deficits brought on by the melting ice pack.
Although our commentary highlights the vary of behaviours bears can undertake with the intention to exploit terrestrial assets, such a interplay between snow geese and polar bears shouldn’t have any influence on the populations of both species.
David Bolduc acquired funding from the NSTP and the Canadian Association for Humane Trapping.
Matthieu Weiss-Blais acquired funding from NSERC, FRQNT and NSTP.