Why do koalas sleep so much? originally appeared on Quora, the place to gain and share knowledge, empowering people to learn from others and better understand the world.

It used to be thought that koalas sleep a lot because their diet of eucalyptus leaves is low in nutrients and high in toxins. So it was assumed that they either had to save energy by sleeping, or that the toxins made them ‘stoned.’ Neither seems to be the case though.

There is no evidence that eucalyptus leaves make animals ‘high,’ although some of the toxins do make most mammals feel nauseous if they eat too many of them. Koalas are better able to tolerate these toxins than other mammals. And while eucalyptus leaves are not particularly nutritious they have much the same feed value as grass and low quality herbivore food—so koalas eat about the same weight of leaves each day as other similar sized herbivores do grass.

Other herbivores stay awake longer probably because they are vulnerable to predation in open grassland, or have to move around a lot looking for food, or because they digest their food by chewing it twice. Koalas are reasonably safe from predators in a tree (particularly if they stay still—they’re very hard to spot!), they have all the food they need for that meal within easy reach, and they can digest eucalyptus leaves in their sleep.

Instead of regurgitating a cud to chew, they store the finely chopped leaves in a microbial soup in their extremely long caecum (the equivalent of our tiny appendix) until the nutrients are broken down by the bacteria. So the answer to why koalas sleep so much is—because they can! Just like pet cats or dogs do.

This question originally appeared on Quora.

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