Why do sloths move so slowly?

Sloths eat mainly leaves, which are low in calories and hard to digest, so they cannot afford to waste energy on quick movement. Their metabolism is extraordinarily slow, and it can take weeks for a sloth to fully digest a single meal. Moving slowly conserves precious energy and, as a bonus, makes sloths hard for predators like eagles and big cats to spot, since these hunters often key in on movement. Their slow lifestyle is supported by a low body temperature and reduced muscle mass, roughly 30 percent less muscle than similar-sized mammals. Far from being lazy, the sloth pace is a finely tuned adaptation to a nutrient-poor diet.