Twelve things that make sloths extraordinary
Sloths look like the rainforest pressed pause on them, but almost everything about their slowness is a finely tuned survival strategy. "Sloth" is not one animal but six living species split between the three-toed sloths (genus Bradypus) and the two-toed sloths (genus Choloepus). Here are twelve facts that show why these gentle tree-dwellers are far stranger than they first appear. For the full overview, see our sloth species guide.
Slowness as a superpower
- They are the slowest mammals on Earth. On the ground a sloth manages only about three metres per minute, a pace that keeps them all but invisible to predators that hunt by spotting movement.
- Their metabolism runs at roughly 40 to 45% of what their body size predicts. Leaves are a low-energy food, so sloths simply burn less.
- A single leaf can take weeks to digest. Food can spend up to around 30 days passing through a sloth's multi-chambered, fermenting stomach.
- They descend to the ground only about once a week, usually just to defecate, which is one of the most dangerous moments in a sloth's life.
A living ecosystem in the fur
- Algae grows in their coat. Sloths move so little that green algae colonise their fur, giving older animals a faint green tinge that improves camouflage.
- Their fur has its own moths. Specialised sloth moths live in that coat, part of a small ecosystem riding on a single animal.
- Their hair grows "backwards." The outer fur runs from belly to back so rain sheds off while they hang upside down.
Surprising bodies
- They are excellent swimmers. Sloths can move about three times faster in water than on land, using their long arms in a slow breaststroke.
- They can hold their breath for a remarkably long time by slowing their heart rate, which helps them cross rivers and flooded forest.
- "Two-toed" and "three-toed" refers to the front claws only. All sloths have three toes on their hind limbs.
- They can rotate their heads a long way around, helped by extra neck vertebrae in three-toed species, so they can scan the canopy without moving their bodies.
- Two are in serious trouble. While four of the six living species are Least Concern, the maned sloth is Endangered and the pygmy three-toed sloth is Critically Endangered.
Those last two facts are a reminder that "slow and safe" only goes so far. Habitat loss, the illegal pet trade, road traffic and power-line electrocution all weigh on wild sloths, especially where forest meets growing towns. Our partner-funded shelters in countries such as Brazil and Colombia take in orphaned and injured sloths, and you can help quietly via our donation page.
Read the full Sloth wildlife guide for the facts, IUCN status and conservation context — or donate to WARN to help fund the local partners protecting this species.
