Normally when an animal is scared, it either remains very still and slows its heart rate and metabolism in hope that danger will pass—like a possum playing dead, in an extreme case—or the body revs up to power a “fight or flight” response.

But when narwhals get caught in fishing nets, surprisingly, they do both. Even as the narwhals pump their fins and tails as fast as they can to escape, their heart rates plummet to just three to four beats per minute, scientists report Thursday in the journal Science. For reference, that’s about as many beats per minute as a ground squirrel while it’s hibernating.

It’s the first time anyone has measured heart rate and performance at the same time