Between their serene movement and their permanent smiles, it’s hard to not love sloths. Hanging high up in the trees of Central and South America, both two- and three-toed sloths have captured so many human hearts that some cry at the mere sight of them. (Have you ever seen a baby sloth wearing pajamas? Now you have.)
Because sloths often prefer to keep their distance from us, there’s still a lot to learn about them — but what we do know is fascinating. After all, how many animals have miniature ecosystems in their fur and helped avocados survive? These six facts about sloths will have you running toward your nearest sloth rescue.
Sloths Navigate Mostly By Touch
Sloths don’t have great hearing or eyesight, so they navigate the world primarily by touchusing their incredible spatial memory — and they have a keen sense of smell, which helps them find food. Their vision is especially bad; sloths have a condition called monochromacy, meaning they have no cone cells in their eyes at all. This makes them not only colorblind, but mostly blind in dim light and completely blind in bright light. Three-toed sloths can’t even see 5 feet in front of them.
For Tree-Dwelling Animals, They Have a Terrible Sense of Balance
Despite living high up in trees, sloths have little use for balance; they hook themselves onto trees firmly (so firmly, they can sleep suspended), and move very slowly. Since sloths don’t need the same level of motion control as many other mammals, the mechanisms that help a human or a squirrel, for example, find their footing in a tree eroded over generations. When sloths do lower themselves to the ground, usually for their once-per-week trip to the bathroom, they have a lot of troublemoving around gracefully.
Sloths Are Weirdly Good Swimmers
Sloth senses, their musculature, and even their ears have evolved almost perfectly for a narrow set of circumstances: hanging from trees, and moving slowly around trees. On the ground, they’re clumsy and vulnerable. So it might surprise you that they’re actually kind of speedy swimmers. Amazingly, they move three times as quickly in the water as they do in trees. The gas in their stomachs makes them surprisingly buoyant, so all they have to do is paddle those big long arms to cross even wide rivers in the Amazon.
The Three-Toed Pygmy Sloth Is Critically Endangered
Three-toed pygmy sloths are the smallest in both size and population. They’re about 40% lighter than brown-throated sloths, and only became recognized as a distinct species in 2001. Sadly, they are critically endangered, meaning they have an extremely high risk of becoming extinct. Three-toed pygmy sloths started evolving separately from their larger counterparts on Escudo de Veraguas, an island that became isolated from mainland Panama around 9,000 years ago. Researchers still don’t know a lot about their diet, habitat, or even their population — it could be anywherebetween 500 and 1,500.
Most sloths are not endangered. However, the maned three-toed sloth, which lives along a small stretch of rainforest coastline in southeastern Brazil, is considered vulnerable.
Elephant-Sized Sloths Used to Roam All of North America
Today, sloths seem elusive. They live exclusively in lowland forests in Central and South America, and spend most of their time camouflaged high up in the treetops. However, they were far more commonplace for our human ancestors of the late ice age, who could have encountered sloths the size of elephantsas far north as Alaska and the Yukon Territory. One fossil was even found more than 8,000 feet above sea level in the Rocky Mountains.
Large clawed ground sloths (Megalonyx) grew to about 10 feet long and weighed around 2,200 pounds. Shasta ground sloths were a little smaller, and had a much narrower habitat, but were still quite large at 9 feet long and up to 550 pounds. You may have extinct giant sloths to thank for avocados existing, since they were one of a handful of large mammals able to swallow an entire avocado pit and pass it in a new location, allowing more trees to grow. However, humans eventually had to take over cultivation of avocados manually.M