Australia’s native koalas are incredible creatures—and they’re also incredibly bizarre. These eucalyptus-loving marsupials have a number of strange quirks, but the most famous might be their habit of sleeping over 20 hours a day. While this is a common practice of predators like lions and tigers, who spend their waking hours hunting, it’s very odd behavior for a peaceful herbivore like the koala. So, why do koalas sleep so much? The answer is kind of ridiculous.

Marsupial Nap Time

To understand why koalas sleep so much, we have to understand their diet. Typically, the creatures live in the eucalyptus forests of Australia, so the eucalyptus leaf makes an easy and abundant meal for the koala. After all, if all you had to do was roll over and dinner was served, wouldn’t you take advantage of it?

Though eucalyptus leaves are infamously toxic to most animals, koalas have a special enzyme called cytochrome P540 that lets them digest the greens without any trouble; the marsupials even have preferred strains of the plant. Eucalyptus leaves are also very high in water content. In fact, smaller females can get their necessary daily water intake just from eating the leaves.

As a result, there are a lot of good things about the koala’s diet—eucalyptus is convenient, common, and often high in protein and water. But there’s one huge problem. Eucalyptus just doesn’t work as hearty food. As any fad dieter can tell you, eating salad all day is a sure way to lose weight. Likewise, eucalyptus leaves are incredibly low in calories and don’t give koalas a whole lot of energy to work with.

Sleeping the Day Away

So how do koalas survive off of a diet made up mostly of leafy greens? Well, they make sure not to exercise much and sleep a lot. On average, koalas are really only active for four hours of the day, usually at night. The next 20 hours of the day, they’re sleeping it off and saving their energy for the next time they have to go foraging.

This is also partly why koalas tend to eat and sleep in the same tree before moving on to another branch the next day. It’s so much simpler that way, and simpler means less energy. All of these behaviors slow down the koala’s metabolism to a stand-still, letting them conserve calories. You can think of a koala’s sleeping habits as a kind of daily, mini-hibernation—much like the longer hibernation of a bear getting ready for the scarce days of winter.

Though koalas’ eucalyptus obsession gives them low energy and a hefty sleeping habit, all in all, it’s not a bad life to live.

Sources: 1, 2

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