Why are sloths so slow?

Sloth scientist Becky Cliffe discusses why being slow actually contributes to a sloth's survival.

Three-toed sloth

Sloths (here the three-toed) are hunted by big cats such as pumas and jaguars, and birds of prey © Danita Delimont / Getty


A conventional wisdom has it that sloths are simple, lazy creatures that do little other than sleep all day. It seems astonishing that such an animal survives at all, but the fact that sloths have been around for some 64 million years shows that being slow must be a winning strategy.

Contrary to popular belief, sloths only sleep for 8-10 hours a day. They do move, but very slowly and always at the same, steady pace.

In fact, everything about sloths is slow. They have the slowest metabolism of any non-hibernating mammal, survive on a low-calorie diet and take approximately one month to digest a single leaf. Consequently, sloths physically don't have the ability to move very fast. And with this, they cannot defend themselves or run away from predators.

Instead, their survival is entirely dependent upon camouflage, and moving slowly is a great way to blend in with the rainforest canopy. Sloths' main predators - big cats and birds - all primarily detect their prey visually, and the sloths simply move at a pace that doesn't get them noticed.


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