Sloths are capable of incredible feats: They can honk, produce physics-defying poops, and thrive on an all-leaf diet. As TED-Ed lays out in the video above, the latter is harder than it sounds. As a result of their low-energy food source, three-toed sloths have evolved to have the slowest metabolism of any animal. So don’t call their lethargic lifestyle lazy—it’s actually a clever survival adaptation at work.

[h/t TED-Ed]