Mammal:

Koalas might be mostly cute and fluffy, but there’s plenty about them that’s just plain nasty – chief of which being that the baby, or joey, koalas regularly eat their mothers’ poop. Not just normal poop either, but a special “wet” kind of poop called “pap”.

In order to get its fix of pap, the joey will have to stimulate the mother’s cloaca with its mouth (translations: they pretty much lick her butthole), this usually happens at about 6 months old. The poop-eating, or coprophagy if you want to get technical, is not just for fun, but a vital part of the koala’s development.

The pap contains vital gut bacteria from the mother’s intestines that allow her to digest a tough diet of eucalyptus leaves. If the joey, for whatever reason, doesn’t get a good dose of these bacteria, then it will never be able to eat eucalyptus – a big problem for koalas.