[ad_1]
Summer is not an easy time for polar bears.
They are apex predators and powerful hunters, and as Inuit and research scientists have long known, they prefer a diet of fatty seals captured from the sea ice.
However, during the period of the year when there is no sea ice, It’s getting longeryields are much lower due to anthropogenic climate change.
In a new study published Tuesday, nature communications Led by the United States Geological Survey (USGS), scientists used GPS tracking, video collars, blood chemistry and other data to track the lives of 20 polar bears near Churchill, Man., over three weeks in the summer. Did.
As expected, some bears remained on land, conserving energy and subsisting on stored fat, almost hibernating.
Others compete for food, scavenge for berries and plants, munch on antlers and birds, or, in the case of one 3-year-old female, swim a total of 175 kilometers through the cold waters of Hudson Bay and swim on sandy beaches. I took a break. A beluga carcass that she momentarily tried to eat.
Despite a surprising range of tactics, nearly all the bears lost weight, averaging about 1 kilogram per day.
“What we found was that they had all these different behaviors and many energy strategies, and none of them were able to prevent weight loss,” co-authors and U.S. Geological Survey said Karin Lord, a research wildlife biologist at the Alaska Science Center. I have been studying polar bears for over 25 years.
“What we really wanted to know in our study was: What are the limits of polar bears’ ability to adapt?”
WATCH | Collar footage shows how bears eat.
Risk of starvation on land
Polar bears have a reputation for being resilient, adaptable, and even opportunistic predators.
in 2022 report From Polar Knowledge Canada, Inuit knowledge keepers from the Panniltung and Kimilut communities in Nunavut shared how bear movement changes in the absence of ice.
“As sea ice forms, bears come out more onto the ice. Once the ice is gone, we don’t know where the bears are,” Kimilt’s Joe Aluktu said in the report. He said it depends on where the prey is.
The new study was partly inspired by observations in the Arctic region, Lord said. Following these observations, scientists from the USGS, Washington State University, and Environment and Climate Change Canada (ECCC) looked to quantify those movements in terms of energy and food intake.
The tracking lasted only about three weeks for each bear, spanning August and September in 2019, 2021, and 2022.
But the researchers also calculated what would happen next: how long the bear could stay alive if it didn’t find more calories somewhere else.
Some had stored up fat to survive, but figures showed some were close to starvation by the end of November. On average over the past 10 years, this is when sea ice in western Hudson Bay re-forms.
Only one of the 20 bears, a young male polar bear, gained weight during the study.
The video collar malfunctioned, but blood tests showed the 4-year-old was one of the high-fat food sources a polar bear might find on land. It was the washed-up carcass of a large marine mammal, likely a seal or beluga whale.
“Unless they encounter something like that, we wouldn’t expect the weight loss we observed to be any different from other times of the year when they’re on land,” Lord said.
Professor Andrew DeRocher of the University of Alberta, who did not participate in the study but reviewed the paper, has been studying polar bears across the Arctic for more than 40 years, and has researched how climate change will affect polar bears. I wrote it for the first time. 30 years ago.
He said the study takes an “elegant approach” and brings together many types of data to see what the ice-free period means for polar bears.
“There is little indication that there is enough food on land for polar bears to survive,” Desrochers said.
When he started working at Churchill in the 1980s, the bears were “fat and happy,” he says.
On land, bears killed birds, ate eggs, and scavenged plants while staining their teeth with blueberries. But unlike some of the more energetic or perhaps desperate foragers observed in the study, they didn’t need to worry, he said.
“The bears are doing what they’ve always done,” Desrochers said.
“What this…new research shows is that no matter what tricks they have up until now, and have probably been using them for thousands of years, it’s not enough.”
Limits of adaptation
Polar bears are classified as: Species of special concern It has been listed as vulnerable by the Commission on the Status of Endangered Wildlife in Canada (COSEWIC) and by the International Union for Conservation of Nature (IUCN) primarily due to sea ice loss.
There are 19 recognized polar bear subpopulations around the world. While some have recovered from hunting-related losses, there is evidence of sea ice-related declines already in two locations, including the western Hudson Bay group near Churchill, IUCN said.
“Another 20 to 30 years of warming may be enough to push the population to a breaking point, where the rate of decline accelerates and the population declines much more rapidly than it is now,” Desrochers said.
He predicts that by mid-century, polar bears may not be able to survive as far south as Churchill. in 2012 He co-authored a book review with legendary polar bear researcher Ian Stirling.
In addition to reducing emissions to slow global warming, humans can help polar bears survive by limiting other types of mortality, such as shooting problem bears, Desrochers said. Says.Several arctic community Following the example of Churchill, Massachusetts, they have secured trash and used non-lethal tactics to deter bears without killing them.
Further north, key hunting grounds for sea ice will remain for a long time, but will not be immune to the effects of climate change, Desrochers said.
“Ultimately, the entire Arctic is warming, and all populations will be affected by sea ice loss in the future.”
[ad_2]
Source link
