But first, science: Turns out most hibernating animals shut off their brains during a long winter’s snooze. No neuro activity means no dreaming—but bears don’t actually hibernate. Rather, they go into an extended, ultraslow metabolic state called “torpor.” That means that while they drop their internal temperatures for the winter, it’s not at the expense of brain waves. And that means they go into REM states. But what are they dreaming about all winter? We have our theories.