# 12 Amazing Facts About Sloths You Probably Didn't Know

*Central and South America · JUN 20 2026*

> Sloths are the slowest mammals on Earth: they move about 3 metres per minute, run a metabolism only 40-45% of the rate expected for their size, can take up to 30 days to digest a single leaf, and host algae and moths in their fur as camouflage.

From algae gardens growing in their fur to digesting a single leaf for weeks, here are twelve genuinely surprising, science-backed facts about the world's slowest mammal.

## What are the key takeaways from this briefing?
- "Sloth" covers six living species in two groups: three-toed (Bradypus) and two-toed (Choloepus).
- Sloths are the slowest mammals on Earth, moving about 3 metres per minute on the ground.
- A leaf can take up to roughly 30 days to digest, and their metabolism runs at only 40-45% of the expected rate for their size.
- Their slow lifestyle lets algae and specialised moths live in their fur, aiding camouflage.
- Four of six species are Least Concern, but the maned sloth is Endangered and the pygmy three-toed sloth is Critically Endangered.

## 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](/wildlife-guides/sloth/).

### 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](/donate/).

**[Read the full Sloth wildlife guide](/wildlife-guides/sloth/)** for the facts, IUCN status and conservation context — or **[donate to WARN](/donate/)** to help fund the local partners protecting this species.

## What do people ask about this briefing?
### Why does algae grow in a sloth's fur?
Because sloths move so little and their grooved hairs trap moisture, green algae can colonise the coat. The algae give a faint green tinge that improves camouflage in the canopy and may offer a minor nutritional supplement, while specialised sloth moths live in the same fur.

### Are sloths really the slowest mammals?
Yes. On the ground sloths travel only about three metres per minute, the slowest of any mammal, an adaptation to their low-energy leaf diet. Oddly, they move roughly three times faster when swimming than when crawling on land.

### How many types of sloth are there?
There are six living species, split into four three-toed sloths in the genus Bradypus and two two-toed sloths in the genus Choloepus.

## Which sources does this briefing use?
- [Smithsonian's National Zoo - Why are sloths so slow, and other sloth facts](https://nationalzoo.si.edu/animals/news/why-are-sloths-so-slow-and-other-sloth-facts)
- [Smithsonian Tropical Research Institute - Life in slow motion](https://striresearch.si.edu/rainforest/how_animals_adapt/life-in-slow-motion/)
- [Britannica - Sloth](https://www.britannica.com/animal/sloth)

Human-readable page: https://worldanimalrescuenetwork.org/newsroom/sloth-12-amazing-facts/