Polar bears losing weight as Arctic sea ice melts, Canadian study finds

Between 1984 and 2009 the weight of female bears in Ontario fell by over 10% while climate change meant they had 30 fewer days a year to hunt seal on ice

Ashifa Kassam in Toronto

Tuesday 5 April 2016 14.05 BST

Three decades of melting sea ice has led to significant weight loss among the world’s southernmost population of polar bears, new data from Canadian researchers suggests.

“It’s a red flag,” said Martyn Obbard, a scientist with the Ontario provincial government and co-author of a recently published study in the journal Arctic Science.

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Researchers looked at a population of about 950 polar bears who live along the northern coast of Ontario, stretching from James Bay to the provincial border with Manitoba. As they live further south than any other population of polar bears, the group is particularly vulnerable to the effects of climate change. 

Using data from 900 bear captures carried out at varying points between 1984 and 2009, researchers found the average weight of males had dropped by 45 kilograms (99lb) and females by 31kg. 

It’s a significant change, Obbard said, given that male polar bears typically weigh about 500kg and females around 250kg. 

The drop in weight was strongly correlated with melting sea ice. Since 1980, the ice season in Hudson Bay has fallen at a rate of about one day a year, forcing polar bears to spent more time on dry land rather than hunting seals – their main source of food – on sea ice. 

Polar bears now get some 30 days less each year on ice than previous generations. “That’s 30 days less out on the sea ice when they’re actively hunting seals,” Obbard said. 

He highlighted the drop in weight among females as worrisome. “It’s more than a 10% decline for adult females,” he said, and could ultimately affect the survival of the population. “We could see females having cubs less often and with less success.” 

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