Local weather change is extending the period of time that components of the Far North go with out sea ice, which polar bears depend on to hunt their favourite prey: fats, calorie-rich seals. When the ice melts in the summertime, the bears transfer on land and face two choices. They’ll relaxation and decelerate to a state approaching hibernation, or they will forage for different meals similar to berries, chook eggs and small land animals.
Scientists who adopted 20 polar bears in Manitoba, beneath the Arctic Circle on the southern finish of the animal's vary, discovered that the choice the polar bears selected didn't make a lot distinction. Typically, foraging bears get sufficient energy from their small meals to replenish the vitality they spent discovering, however not sufficient to take care of their physique mass.
“Terrestrial meals aren’t appropriate for extending the interval that polar bears can survive on land,” stated Anthony Pagano, a wildlife biologist on the US Geological Survey and the lead writer of a examine based mostly on in regards to the analysis, revealed Tuesday in Nature Communications.
In western Hudson Bay, the ice-free interval is three weeks longer than within the Seventies, and polar bears now spend about 130 days on land throughout the yr. Scientists estimate that, going ahead, there will probably be 5 to 10 extra sea ice-free days every decade.
The query of whether or not polar bears can survive for longer durations on land has been politicized at occasions because the creatures have develop into an emblem of local weather change.
A 2015 evaluation by the Worldwide Union for Conservation of Nature discovered a excessive likelihood of the worldwide polar bear inhabitants declining by greater than 30 p.c by 2050. This native inhabitants in Hudson Bay could also be decreased by half already, from an estimated 1,200 bears in 2015. the Eighties to about 600 bears in 2021.
Virtually all of the bears tracked within the new examine misplaced weight, and two people have been on monitor to die of hunger earlier than the ocean ice returned.
Anecdotal observations of particular person polar bears consuming geese, geese, seabird eggs and even caribou on land have provided hope that the animals might adapt to a hotter world. However analysis documenting solely what polar bears eat isn't sufficient to grasp whether or not the bears are getting sufficient energy from that meals to assist them survive longer durations with out sea ice.
For this examine, Dr. Pagano and colleagues traveled to Wapusk Nationwide Park in northern Manitoba. Over three seasons, they captured 20 polar bears and geared up them with video cameras on collars to supply the bear's eye view of their days.
Scientists weigh the bears, take blood samples and measure their respiration to color detailed footage of their physique circumstances, exercise ranges and vitality expenditure. They recovered every bear after about three weeks, retrieving the cameras and repeating their measurements.
Placing cameras on polar bears is a brand new method, and passing the video was “wonderful,” stated Dr. Pagano. “Watching what a polar bear really does within the wild was actually rewarding.”
Six of the bears (fewer than the scientists had anticipated) appeared rested and quick, whereas the others have been straining and some even went for lengthy swims.
Foraging bears have been seen consuming principally grass, kelp and berries, with occasional chook carcasses, bones, caribou horn, eggs and small mammals. Two of the swimmers discovered seal and beluga whale carcasses, however they couldn't eat a lot whereas swimming in open water.
No matter whether or not the bears fasted or foraged, all however one misplaced related quantities of weight. The scientists calculated an “anticipated hunger date” for every bear based mostly on how a lot physique fats and muscle it had, and the way a lot vitality was estimated to be expended every day.
Most have been anticipated to be superb till the ocean ice returned in November, however two younger females, which are typically the smallest polar bears, had predicted hunger dates earlier than then, and some others have been shut. at the moment. (The researchers have to go away in September and have no idea what occurred to the bears).
Dr. Pagano famous that the examine didn’t embrace females with cubs, who burn way more vitality whereas nursing. The researchers included some pregnant bears, however they left earlier than giving delivery.
These findings are “what we feared and what we hoped to not see,” but additionally considerably anticipated, stated Melanie Lancaster, a conservation biologist who focuses on Arctic species on the World Wildlife Fund.
Dr. Lancaster, who was not concerned within the examine, cautioned that these 20 bears characterize just one inhabitants in a single area. “Polar bears aren’t experiencing the consequences of local weather change uniformly throughout the Arctic,” he stated. At greater latitudes the place the thickest sea ice persists for a few years, polar bears are nonetheless doing nicely.
However for this declining inhabitants in Hudson Bay, the person variability the researchers discovered is critical, stated Gregory Thiemann, an affiliate professor at York College in Toronto who research arctic carnivores however was not concerned on this analysis.
Every polar bear has tried its strategy to cope, however the variation exhibits that there isn’t any single profitable answer. “It paints a collective image that it is a group of bears stretched to their organic limits,” he stated.
