Ancient polar bears survived low ice periods on dead whales: study

Same study suggests bears aren’t likely to be able to rely on the same solution again

New research suggests an answer to the mystery of how polar bears survived previous eras of low sea ice.

But the same paper, published Tuesday in Frontiers of Ecology and the Environment, says the bears aren’t likely to be able to rely on the same solution again.

“I don’t think we can assume what worked in the past is going to work in the future,” said Kristin Laidre of the University of Washington.

Genetic research says polar bears diverged from other bears at least 150,000 years ago and probably as long as 500,000 years ago. That means the species lived through several low-ice periods, including a major warm period about 130,000 years ago.

At that time, while some year-round sea ice is thought to have remained, total coverage was greatly reduced and mostly found in the very highest reaches of the Arctic. Despite the bears needing sea ice to hunt fat-rich seals, somehow they survived.

RELATED: No change to Canada’s climate plans as UN report warns of losing battle

Laidre and her co-author Ian Stirling from the University of Alberta theorize those long-ago bears made it through an extended period of low ice by scavenging whale carcasses washed up on Arctic beaches.

“Polar bears likely survived those periods by accessing stranded marine mammal carcasses, and most likely large whale carcasses,” Laidre said. “They’re such large carcasses that they can be packages of food for, in some cases, years.”

The researchers calculated that a population of about 1,000 bears would need about 20 bowhead whale carcasses to remain healthy through the spring foraging season and about eight carcasses during the summer, when the bears eat less.

They then looked at mortality rates of large whales and what percentage of them might float long enough to wash up on a beach. Those numbers matched well with observed numbers of whale carcasses found in various parts of the Arctic.

A stretch of Russian coastline along the Chukchi Sea, for example, averages about 10 carcasses a year between July and November. A small number of polar bears have learned to rely on that resource.

The numbers suggest that washed-up whales could have been at least a major supplement during poor seal hunting conditions — especially since polar bears are very good at feasting on and storing fat.

“I think they were very likely the main source of nutrition,” said Stirling.

The future of modern polar bears in the face of rapidly shrinking sea ice is much debated, with some arguing their survival through previous low-ice periods bodes well today.

Laidre and Stirling aren’t so sure.

RELATED: Sick orca J50 declared dead by 1 group while scientists remain hopeful

The pace of change is much faster today than in the past. Bears don’t have much time to learn new behaviours on a wide scale.

As well, there aren’t as many whales as there used to be.

“Most of the whale populations have been overharvested,” Stirling said.

At best, he said whale carcasses could buy bears a little more time.

“We may have a little bit longer timeline. Hopefully, we’ll get climate warming under control.

“For the various different species that depend on a polar ice ecosystem, we may be able to keep some of that in its natural condition.”

Bob Weber, The Canadian Press

Like us on Facebook and follow us on Twitter.

Just Posted

Senior Bandits go 3-1 in weekend action

The Cranbrook Bandits saw their senior team go 3-1 at home and the junior team go 1-3 on the road

Cranbrook RCMP seek help finding missing man

Jeffrey Edward Burns was last seen on the evening of Sunday, June 16.

Cranbrook Boys and Girls Club gets new fully-functioning kitchen

Tim Matwey launches new kitchen at the Youthwise Eco Centre

Eight U.S. senators write to John Horgan over pollution from Elk Valley mines

The dispute stems from Teck Resources’ coal mines

VIDEO: ‘Avengers: Endgame’ to be re-released with new footage

‘Avatar’ holds global box office record at $2.788 billion, while ‘Endgame’ stands at $2.743 billion…

News and Notes from the Cranbrook Public Library

Mike Selby Barry Strauss looks at the four centuries of the Roman… Continue reading

B.C. teen killed by falling tree near Victoria

Second youth also injured in freak incident during field trip at Camp Barnard near Sooke

Elias Pettersson wins Calder Trophy as NHL’s top rookie

Vancouver forward first Canuck to win award since Pavel Bure in 1992

FVRD chair calls B.C. incineration plan for Philippines waste ‘disturbing’

Metro Vancouver ‘uniquely capable’ of safely disposing of waste coming back to Canada, say officials

VIDEO: Acknowledging skeptics, finance minister vows to build Trans Mountain project

Bill Morneau said he recognizes ‘huge amount of anxiety’ in Calgary over future of oil and gas sector

Shovels could be in the ground on Trans Mountain by September, CEO says

Ian Anderson points to weeks likely required for NEB to reinstate 2016 regulatory record

Scorpion gives birth after hitching ride in B.C. woman’s luggage

A Vancouver woman inadvertently brought the animal home from a trip to Cuba

RCMP allows officers to grow beards

Members can now wear beards and goatees, as long as they’re neatly groomed

Most Read