The risks to polar bears on our rapidly warming planet is clear: Ursus maritimus treks across Arctic sea ice, which it uses as a platform to hunt fatty seals, typically ringed seals. But climate change is freezing Arctic Ocean sea ice later and melting it sooner.

In all but two of the Arctic's 19 polar bear subpopulations, sea ice cover dropped 7 to 19 days per decade from 1979 to 2014. In the Beaufort Sea region, where sea ice now lasts roughly 36 days a year less than it did in the 1990s, scientists found bears spent 31 more days on land—far from their ice-dependent prey. With less sea ice, some bears are growing smaller, having