This is scientific American's 60 second science. I'm Christopher in Tagyatta.

As climate change warms the Arctic, sea ice there is disappearing at record rates.

See ice that polar bears prefer to prowl.

As a result, some of the bears are spending more time on solid land

and are thus switching up their diets too. Instead of the ringed seals

they ate out on the ice, the bears are foraging on

bowhead whale carcasses, cast up on the beach. So what does this mean for the bears?

It's sort of good news, bad news.

Melissa McKinney, an eco toxicologist at the University of Connecticut.

The bad news is that bears are losing vital habitat,

but the silver lining is that bears decamping to land have lower levels of toxic mercury due to their changes in diet.

McKinney and her team studied hair samples from one polar bear population in Alaska, from 2004 to 2011.

In that time, they saw a 65% drop in the bear's mercury levels

to concentrations below the known threshold

for negative biological effects.

And it looks like the different diet may be the reason.

Because bowhead whales feed on plankton,

while ringed seals eat fish and other animals

in which mercury has had the chance to accumulate. and so if polar bears are feeding on prey items that are lower in the food chain

then they're likely experiencing a less mercury contaminated food source than they would be otherwise.

Bears that feed on whales are also in better condition.

They have a higher body mass index.

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