Head to head
Koala vs Sloth
The koala of Australia and the sloth of Central and South America are often mentioned together as the world's sleepiest animals. They are not related — one is a marsupial, the other a xenarthran cousin of anteaters and armadillos — but both solved the same problem in the same way: living on a diet so poor it forces you to slow down.
| Koala | Sloth | |
|---|---|---|
| Group | Marsupial (Phascolarctidae) | Xenarthran (two families of tree sloth) |
| Where | Eastern Australia | Central and South American rainforest |
| Diet | Eucalyptus leaves, almost exclusively | Leaves, buds, some fruit |
| Sleep | 18–22 hours a day | 15–20 hours a day (less in the wild than once thought) |
| Metabolism | Very low; slow gut fermentation | The lowest of any non-hibernating mammal |
| Movement | Slow; can move fast in short bursts if threatened | Extremely slow; ~4 m per minute on a good day |
| Toilet habits | Goes in the tree | Climbs all the way down once a week to defecate on the ground |
| Conservation status | Vulnerable (Endangered in NSW, QLD, ACT) | Varies — most Least Concern; the pygmy three-toed sloth is Critically Endangered |
Koala vs Sloth: common questions
Are koalas and sloths related?
Not at all. The koala is a marsupial, most closely related to the wombat. Sloths are placental mammals in the group Xenarthra, alongside anteaters and armadillos. Their shared sleepiness, slowness, and leaf diet are a classic case of convergent evolution — two lineages arriving at the same lifestyle independently.
Which sleeps more, a koala or a sloth?
The koala, on average. Koalas sleep 18 to 22 hours a day to conserve energy while digesting toxic eucalyptus. Wild sloths, tracked with data loggers, sleep closer to 9 to 10 hours — the "20 hours" figure comes from captive animals; but the sloth still moves and burns far less energy overall.
Why does a sloth climb down to poop but a koala does not?
It is a genuine puzzle. About once a week a sloth makes the slow, dangerous descent to the base of its tree to defecate, losing a lot of body weight and exposing itself to predators. Leading ideas involve fertilising its favourite trees, or a relationship with moths that live in its fur and lay eggs in the dung. The koala simply drops its pellets from the canopy.