WINNIPEG -- New research out of the University of Manitoba shows polar bears are eating fewer ringed seals, but it’s not necessarily all good news for the Arctic animals.
The paper, published in the journal “Environmental Science and Technology,” measured carbon and nitrogen isotopes and mercury in both animals to determine how they are using habitat and what they are eating. It found that sea ice reduction in the western Hudson Bay is changing the food chain.
David Yurkowski, a researcher in biological sciences who led the study, said the results were surprising.
“You’d assume you’d see that strong polar bear-ringed seals relationship continue over time but we didn’t see that. We saw contrasting patterns,” he said in a news release.
During their exploration the researchers found a decline in mercury concentrations in ringed seals, but didn’t see a change with polar bears, which shows the two animals are eating different things. This means that as the sea ice melts, the seals are eating a more phytoplankton-derived diet.
Yurkowski said ringed seals are eating for longer periods in open water, which is arguably better for them. But the researcher noted one caveat: ringed seals need ice to rear pups, and therefore less ice can result in fewer being born. Melting ice can also affect the survival rates of pups not ready to be weaned.
“The seals are responding to the changes in the environment but at this point it’s hard to say if it’s going to work out in their favour,” Yurkowski said.
The paper also said that polar bears might be eating other types of seals, such as bearded and harbour seals, noting that polar bears use sea ice as a hunting platform, so as it degrades it limits the bears’ ability to hunt and fatten up ahead of summer.
“The relationship between polar bears and ringed seals is weakening, and that’s likely going to continue,” Yurkoswki says. “The food web is changing, we’ve seen this change, and the food web structure and function in the Arctic is likely going to be different than it was not long ago.”
