In a single 12 months, one polar bear can depart roughly 300 kilograms of prey for different animals to dine on. Altogether, the carnivores present 7.6 million kilograms of carrion for scavengers all through the Arctic, researchers estimate.
The findings, reported October 28 in Oikos, spotlight the essential function these apex predators play in feeding an enormous array of species and hints on the manner that meals internet may be shaken as local weather change warms the Arctic, endangering polar bear populations.
Scientists have lengthy identified that polar bears usually eat the bladder of their prey — normally seals — then depart the remainder. Nonetheless, the biomass of these leftovers and their significance has been lengthy missed, says Nicholas Pilfold, a scientist on the San Diego Zoo Wildlife Alliance who labored for 15 years within the Arctic.
Pilfold and colleagues dove into research, observations and anecdotes of scavenging exercise round carcasses relationship way back to the Nineteen Thirties. The workforce additionally analyzed research on what number of energy seals can present and what number of seals polar bears devour annually.
Throughout its yearly looking peak, a polar bear kills roughly one seal each three to 5 days — normally ringed seals — which equates to about 1,000 kilograms of meals yearly. A bear eats a majority of that mass, leaving some 30 % up for grabs. Contemplating there are an estimated 26,000 polar bears within the Arctic, all these leftovers add as much as tens of millions of kilograms of meals for scavengers, together with arctic foxes, gulls, ravens and different polar bears. Sometimes even snowy owls, wolves and grizzly bears will feast on the stays.
These species wouldn’t be capable to entry this type of meals if the polar bears didn’t depart it behind, says research coauthor Holly Gamblin, a wildlife biologist on the College of Manitoba in Winnipeg, Canada.
Pilfold has seen a few of these interactions firsthand. “The foxes will comply with within the tracks of the place the polar bears have gone,” ready for the bears to desert the carrion. Birds would additionally fly overhead and wait their flip, he says. “There’s simply this cacophony of sound of gulls which are all swirling round, and so they’re all attempting to get a few of that seal.”
Jon Aars, a polar bear skilled on the Norwegian Polar Institute in Tromsø, says the findings come as no shock. The leftovers are in all probability a “somewhat essential,” meals supply for different species, “notably at a time of the 12 months when different meals isn’t really easy to get,” he says.
However the Arctic is warming, affecting polar bear populations and, in flip, their leftovers. “If we’re going to begin to see declines in polar bears, we’re seemingly going to see declines in that carrion biomass,” Pilfold says.
For instance, an estimated 323,000 kilograms of carrion per 12 months has been misplaced in two areas the place polar bear sub-populations have been declining, the workforce calculates. Melting ice may additionally make it tougher for some scavengers to achieve the bears’ leftovers.
It’s tough to foretell the impact that the lower of polar bears’ carrion might need on different species, Aars says. However “it can have [an] impression a method or one other,” relying on which species and which “a part of the Arctic we have a look at.”
