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

Rock slide forces rural Keremeos residents to leave their homes

Witness describes boulders bigger than her car

UPDATE: Destructive blaze in West Kelowna

A unit of a condo complex is on fire in West Kelowna

Okanagan College to develop wellness strategy for drug use

The Kelowna campus has 28 employees trained in the use of naloxone.

BREAKING: Highway 3 near Keremeos closed due to rockslide

Highway 3 just west of Keremeos is closed as of 8:44 p.m.… Continue reading

Black Mountain Cub Crawl returns to Kelowna

Its the 3rd year of the obstacle course fundraiser

Protective human chain forms around Victoria mosque for Friday prayer

Islanders stand arm-in-arm to show support in aftermath of New Zealand shootings

Wildlife activists slam B.C. business, clubs for ‘wolf-whacking’ contests

Chilcotin Guns, Creston Valley Rod and Gun Club and West Kootenay Outdoorsmen Club under fire

‘Families torn apart:’ Truck driver in fatal Broncos crash gets 8-year sentence

Judge Inez Cardinal told court in Melfort, Sask., that Sidhu’s remorse and guilty plea were mitigating factors

Pet Planet picks up Okanagan’s cannabis for pets

True Leaf Medicine International expands retail distribution to 3,500 stores worldwide

AquaVan comes to Okanagan Science Centre

200-litre mobile touch tank allows you to get up-close with marine invertebrates

Army of support behind Black Press saleswoman battling cancer

GoFundMe helps empower Sue Folliott’s fight

Boy who went missing from park remains largest probe in Victoria police history

The four-year old Victoria boy went missing without a trace on March 24, 1991

WestJet sticking with Boeing 737 Max once planes certified to fly

WestJet had expected to add two more of the planes this year to increase its fleet to 13

Motorcyclist dies after three-vehicle crash on old Island Highway

Accident happened at 12:15 p.m. Friday near Country Club Centre in Nanaimo

Most Read