Which Tree-Dwelling Mammal Can Hold Its Breath for 40 Minutes Underwater?

It’s easy to underestimate sloths. Most people know that sloths are incredibly slow (perhaps you'd even call them lazy) and that they spend most of their time hanging upside-down in the trees. But there’s far more to these creatures than meets the eye.

Native to the tropical rainforests of Central and South America, the sloth’s reputation for being slow is well-deserved. They are the world’s slowest mammals. They move so sedately that algae grows in their fur – which is useful for helping to camouflage them in the forest canopy and keep them safe from predators like anacondas, jaguars, ocelots, and eagles.

But they aren’t always slow, nor do they spend all their time in the trees. Sloths are excellent swimmers. They move far more quickly in the water than they do on land, so they sometimes choose to swim when moving to a new spot. A sloth’s physiology makes it particularly well-suited to spending time in water, as it can hold its breath for an incredible 40 minutes, thanks to a very slow metabolism and the ability to lower its heart rate. This fantastic breath-holding capability is very useful when hiding underwater from predators.

Sloths have many other unusual physical traits to complement their unique lifestyle. For example, since sloths spend so much time in the trees, their excretory system works incredibly slowly, so they only need to come down to the ground to urinate and defecate about once a week. Once on the ground, they are at their most vulnerable to predators, as they typically only cover a few feet per minute.

In praise of sloths: