Hexbyte Glen Cove Melting sea ice forces polar bears to travel farther for food

Hexbyte Glen Cove

Anthony Pagano. Credit: WSU

In recent years, polar bears in the Beaufort Sea have had to travel far outside of their traditional arctic hunting grounds which has contributed to an almost 30% decrease in their population.

The bears’ home range, or the amount of space they need for food and other resources, was around 64% larger from 1999-2016 than it was in 1986-1998, according to a recent study in the journal Ecosphere.

“Having to travel farther means these bears are expending more energy which can threaten their survival,” said Anthony Pagano, a postdoctoral researcher in Washington State University’s School of the Environment and lead author of the study. “If we want to preserve the of these amazing mammals, then we need to focus on the root of the problem, which is slowing .”

For the study, Pagano and colleagues from the U.S. Geological Survey used satellite tracking data to analyze the movement patterns of female polar bears from 1986-2016 in the Beaufort Sea area north of Alaska.

Their work showed over the last two decades polar bears are having to travel farther north of their traditional hunting grounds on the continental shelf to remain on their receding sea ice habitat.

Extending around 100 miles north of Alaska and Canada, the continental shelf is a shallow water habitat that contains plenty of fish for the bears’ favorite prey, seals.

During the when seals are weaning their pups and most vulnerable to attack, polar bears will often double their body weight from eating the fatty meat.

The researchers’ data shows that as the sea ice over the continues to recede earlier and further; the bears are being displaced from this primary foraging habitat and traveling further north into deeper waters where there are fewer seals to prey on.

“The combined impact of having to move farther and farther north with the ice in the summer and then having to move back in the fall and winter as the ice freezes is taking a major toll,” Pagano said. “Our work highlights the worrying impact of sea ice decline on polar bear movement patterns.”

Another interesting finding of the study is that around 20% of the polar bear population in the Beaufort Sea is foregoing their traditional sea ice hunting grounds altogether in the summer and fall. These bears are moving inland along the Alaskan and Canadian coast looking for food such as carrion, berries and sometimes even bowhead whale carcasses that are left on the shore by indigenous residents that hunt the large aquatic mammals.

“Sometimes you’ll have 50 to 100 polar bears that congregate around these whale carcasses and compete with each other for food,” Pagano said. “As more and more bears move on land, I suspect there’ll be a lot more competition for these food resources and we’ll probably start seeing further decreases in abundance and survival.”

Moving forward, Pagano and his colleagues with the U.S Geological Survey plan to conduct further studies of the polar bears moving inland to get a better idea of how they are coping with their new terrestrial habitat.

He said the best thing humans can do to help preserve the southern Beaufort Sea’s 800 or so remaining is to focus on curbing global carbon emissions which are the main cause behind receding arctic sea ice.

Recent modeling work has shown that if regulations are enacted to reduce these emissions to avoid global warming greater than 2°C or 3.6°F then it could drastically slow the decline of polar bear habitat in the arctic which would in turn help these animals to survive.

“Coming across a polar bear while flying over the arctic in a helicopter is a surreal experience,” Pagano said. “They are incredibly massive and impressive. It is amazing to observe this animal that is so uniquely adapted to exist in this harsh arctic environment. They are worth the effort it will take to preserve them.”



More information:
Anthony M. Pagano et al, Effects of sea ice decline and summer land use on polar bear home range size in the Beaufort Sea, Ecosphere (2021). DOI: 10.1002/ecs2.3768

Citation:
Melting sea ice forces polar bears to travel farther for food (2021, December 14)
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Hexbyte Glen Cove Melting ice patch in Norway reveals large collection of ancient arrows thumbnail

Hexbyte Glen Cove Melting ice patch in Norway reveals large collection of ancient arrows

Hexbyte Glen Cove

An arrow from c. AD 700 as it was found lying on the stones in the scree, close to the melting ice. Credit: Innlandet Fylkeskommune

A team of researchers affiliated with a host of institutions in Norway and one in the U.K., has unveiled their findings after collecting and studying a very large number of ancient arrows they found near a melting ice patch in Norway’s Jotunheimen Mountains. In their paper published in the journal The Holocene, the group describes how they kept their research secret to avoid the possibility of others contaminating the site and what they have learned about the arrows thus far.

Back in 2006, archeologist Reidar Marstein found an ancient shoe lying near a melting ice patch (which subsequent recent has shown to have formed approximately around 5600BC) in the Jotunheimen Mountains. The shoe was initially believed to have been from the Viking era, but subsequent study showed it to be approximately 3,300 years old. That led the researchers to further investigate the site. They discovered that the area was littered with arrows used by hunters thousands of years ago. That set off a research project that involved detailing the location of each found and then the study of it that followed. To date, the team has found 68 arrows at the site, dating from the Stone Age up to the Middle Ages—the oldest has been dated to 6,000 years ago, which they note is approximately 800 years before Ötzi.

The researchers note that the ice patch is very nearly a glacier and thus is quite large—but not nearly as large as it once was. Global warming has been melting the patch and as that has occurred material once frozen inside the patch has been exposed. The researchers have found most of the arrows on the ground next to the ice patch, which has led to degradation due to exposure to the elements. But they have also found several arrows laying on top of the ice, an indication that they have only recently been exposed. They note that while some of the arrows found on top of the ice were in good condition, many were not, suggesting they had been degraded due to ice movement inside the patch—and perhaps exposure due to prior melting of the .

The researchers have also found reindeer antlers and bones and other biological matter but have been surprised by how few of them have been revealed as the ice melts.



More information:
Lars Holger Pilø et al. Interpreting archaeological site-formation processes at a mountain ice patch: A case study from Langfonne, Norway, The Holocene (2020). DOI: 10.1177/0959683620972775

Prehistoric Arrow Bonanza at Langfonne: secretsoftheice.com/news/2020/ … toric-arrow-bonanza/

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Citation:
Melting ice patch in Norway reveals large collection of ancient arrows (2020, November 27)
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