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Polar bears (Ursus maritimus) reap the benefits of the winter to construct up their fats reserves. Intensive looking of seals, a useful resource wealthy in fats, permits bears to retailer up sufficient power to get via the summer time.
Because the local weather warms, looking alternatives on the ice pack are diminishing. Specialists consider that because of this, there may be not enough meals sources on the land to permit bears to construct up the power reserves they require.
Confronted with these modifications, some polar bears are benefiting from colonies of nesting birds and their eggs, one of many few sources available on land, to compensate for his or her power deficits. The diversifications that bears should make to fulfill the challenges led to by local weather change are quite a few and unpredictable.
As a pupil researcher in ecology, I used to be going to reap the benefits of 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. Right 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 neighborhood of Mittimatalik, the Bylot Island area station was bustling with exercise.
Established 30 years in the past, the sector station is positioned within the coronary heart of the breeding grounds of the most important identified colony of snow geese (Anser caerulescens caerulescens). Right this moment, scientists from quite a lot of backgrounds scour the Quarliktuvik valley flooring, which is mostly flat, to review the soil, water, crops and wildlife.
Popping 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. Everybody 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 sector station.
A number of colleagues had gathered on a small hill to regulate the newcomer. The truth is, by the point I’d coated 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 the moment of 12 months, 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 area actions and took benefit of the radiant afternoon to observe the king of the ice pack.
True to kind, the geese took refuge within the nearest pond on the first sight of hazard. They waded in rapidly sufficient to maintain the bear, who was swimming on the floor, at a secure distance.
However the bear was about to make use of a brand new looking method: he dove underneath the water, disappeared from the eyes of the geese who had stopped fleeing, and emerged from beneath one among 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 beneath, throughout a dive).
In the course of the afternoon, the bear used this method two extra occasions, 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 College, we had been nonetheless fascinated by this statement. Nowhere within the scientific literature is there any point out of such behaviour. At finest, there are reviews of assaults on murres within the ocean close to the coasts, an atmosphere very completely different from the calm, shallow ponds the place we noticed the bear’s assaults.
Being conscious of the power challenges bears face in the course of the summer time, our analysis group — led by Matthieu Weiss-Blais — needed to reply the next query: would this looking method enable polar bears to profit from consuming snow geese?
The data recorded within the area, 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 power value of swimming in bears and the power contained in a snow goose, we had been in a position to mannequin the power effectivity of the method.
These calculations reveal that this looking method may enable bears to amass extra power than they expend, significantly for smaller bears, and in the event that they handle to catch a goose rapidly.
An power enhance, however removed from enough
Nonetheless, this power contribution can be very restricted in scope.
Initially, a goose supplies comparatively little power — round 200 occasions lower than a ringed seal weighing 45 kilograms.
What’s extra, the geese are not often out there as prey: they lose the flexibility to fly for less than three or 4 weeks every summer time they usually solely have colonies in a couple of locations within the Arctic.
Looking geese may due to this fact be of profit to sure bears on occasion, however on a population-wide scale, it won’t alleviate the power deficits attributable to the melting ice pack.
Though our statement highlights the vary of behaviours bears can undertake with a purpose to exploit terrestrial sources, one of these interplay between snow geese and polar bears shouldn’t have any influence on the populations of both species.
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