This is Scientific Americans 60 Second Science.

I'm Jason Goldman.

When the Arctic Ocean freezes over in the autumn,

Polar bears set off in search of their favorite meals, fatty ringed seals and bearded seals.

By the summer the sea ice begins to melt and break apart.

Deprived of access to the tasty seals, polar bears spend the summer fasting.

At least that's what's supposed to happen.

As the planet warms, the warmer ice-free season

is getting longer and longer.

So what's a hungry bear to do?

Scientists once thought that polar bears might survive by supplementing their pineped diet by turning to terrestrial foods like snowgeese, their eggs, and caribou.

We've had this debate in the literature

about whether terrestrial foods are

nutritionally relevant to polar bears

during the on-land season when the ice is melted.

University of Alberta biologist Nick Pilfold.

And we've known for a long time going back to research in the early 70s,

even going back to early explorer logs that polar bears will consume terrestrial-based foods, but the debate was always

whether those foods actually add up energetically.

In other words, do these substitutes provide enough nutrition to make up for the lost seals?

To find out, Pilfold and his colleagues estimated the weight lost each day by polar bears

in the wilds of Western Hudson Bay during the ice-free season when they could ostensibly be chowing down on

...