Not all polar bears are inwards the same dire province of affairs due to retreating sea ice, at to the lowest degree non correct now. Off the western coast of Alaska, the Chukchi Sea is rich inwards marine life, but the issue of polar bears inwards the expanse had never been counted. The get-go formal report of this population suggests that it's been salubrious as well as relatively abundant inwards recent years, numbering most 3,000 animals.
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| Hundreds of Chukchi Sea polar bears pass the ice-free months on Wrangel Island, including this female mortal and cub photographed inwards autumn 2017 [Credit: Eric Regehr/University of Washington] |
"This go represents a decade of query that gives us a get-go approximate of the abundance as well as status of the Chukchi Sea subpopulation," said get-go writer Eric Regehr, a researcher amongst the UW's Polar Science Center who started the projection equally a biologist inwards Alaska amongst the U.S. Fish as well as Wildlife Service. "Despite having most i calendar month less fourth dimension on preferred sea H2O ice habitats to hunt compared amongst 25 years ago, nosotros constitute that the Chukchi Sea subpopulation was doing good from 2008 to 2016.
"Sea-ice loss due to climate alter remains the primary threat to the species but, equally this report shows, in that place is variation inwards when as well as where the effects of sea-ice loss appear. Some subpopulations are already declining spell others are however doing OK."
Of the world's xix subpopulations of polar bears, the U.S. shares ii amongst neighboring countries. The other U.S. subpopulation -- the southern Beaufort Sea polar bears, whose territory overlaps amongst Canada -- is showing signs of stress.
"The southern Beaufort Sea subpopulation is well-studied, as well as a growing trunk of bear witness suggests it's doing poorly due to sea-ice loss," Regehr said.
Polar bears were listed equally threatened nether the U.S. Endangered Species Act inwards 2008 due to the threat of declining sea ice, which the animals depend on for hunting, breeding as well as traveling. But the novel report suggests that such effects are non yet visible for bears inwards the remote waters that split Alaska from Chukotka, Russia.
"It's a real rich area. Most of the Chukchi Sea is shallow, amongst nutrient-rich waters coming upwards from the Pacific. This translates into high biological productivity and, importantly for the polar bears, a lot of seals," Regehr said.
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| The striped expanse on the left shows the Chukchi Sea polar send subpopulation's range. Sea H2O ice reaches due south to the dotted line inwards winter, as well as retreats to the company dark occupation inwards summer. The correct shows a closeup of the report area off Alaska's coast. White circles demo where polar bears were tagged betwixt 2008 as well as 2016 [Credit: Regehr et al./Scientific Reports, 2018] |
"Just flight around, it's nighttime as well as 24-hour interval inwards damage of how many seals as well as other animals you lot see," Regehr said. "The Chukchi Sea is super productive as well as the Beaufort Sea is less so."
The expanse too has an abundance of whale traffic, as well as when carcasses launder upwards on shore the polar bears tin feed on them inwards summer, when the sea H2O ice melts as well as a component division of the Chukchi Sea subpopulation waits on the world for the bounding main to refreeze.
Recent ecological observations had suggested that Chukchi Sea bears are doing well. Influenza A virus subtype H5N1 report led past times co-author Karyn Rode, at the U.S. Geological Survey, showed the go past times predators accept like amounts of trunk fatty equally 25 years ago, a goodness indicator of their overall health.
The electrical current report is the get-go assessment of the subpopulation size using modern methods. It estimates only nether 3,000 animals, amongst to a greater extent than oftentimes than non goodness reproductive rates as well as cub survival.
As a federal wild animals biologist based inwards Alaska until 2017, Regehr as well as colleagues gathered the information past times tagging roughly sixty polar bears inwards most years from 2008 to 2016. He flew past times helicopter over the expanse only N of Alaska's Seward Peninsula, looking for tracks on the sea ice. The helicopter thus would follow tracks inwards the snowfall to locate the send as well as utilization a tranquilizer dart to sedate the animal. Over most an hour, researchers would weigh the bear, collect biological samples, apply private tags and, inwards only about cases, attach a GPS transmitter.
All the information were incorporated into a novel model designed to approximate population size for large carnivores that are highly mobile as well as whose territory spans a large region. The authors made the model publicly available inwards the promise that it volition live on used on other populations or species.
"Polar bears tin go thousands of miles inwards a year. But amongst the GPS tags, nosotros tin meet when a send leaves our report expanse but is however alive, because it's moving. This information is fundamental because in that place are bears that nosotros meet i time as well as never meet again, as well as to larn a goodness population approximate you lot demand to know if these animals died or only moved to a novel area," Regehr said.
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| A sub-adult polar send on the shore of Wrangel Island [Credit: Eric Regehr/University of Washington] |
"It was of import to convey our scientific discipline together amongst the observations as well as expertise of people who live on inwards polar send the world year-round as well as sympathise the animals inwards dissimilar ways," Regehr said.
Influenza A virus subtype H5N1 articulation U.S.-Russia committee is responsible for management as well as conservation of the Chukchi Sea subpopulation. In reply to the novel assessment, the committee raised the sustainable degree of subsistence harvest, which is nutritionally as well as culturally of import to Native people inwards Alaska as well as Chukotka.
"These polar bears deed dorsum as well as forth betwixt the U.S. as well as Russia, thus it's real much a shared resource," said Regehr, a longtime scientific advisor to that commission.
As utilization of his electrical current query at the UW, Regehr spends most ii months each yr working amongst Russian scientists on Wrangel Island inwards the Arctic Ocean, where hundreds of Chukchi Sea polar bears pass their summers.
"These findings are goodness intelligence for now, but it doesn't hateful that bears inwards the Chukchi Sea won't live on affected past times H2O ice loss eventually," Regehr said. "Polar bears demand H2O ice to hunt seals, as well as the H2O ice is projected to pass upwards until the underlying work of climate alter is addressed."
Source: University of Washington [November 14, 2018]
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