Koalas spend almost their entire lives alone perched in trees. They don’t make nests, but sleep in a tree fork or on a branch for up to twenty hours a day. They live almost exclusively on eucalyptus leaves, but they’ll also eat manna gum, blue gum, and swamp gum leaves. Eucalyptus leaves are actually poisonous, but koalas can eat them because of their specially evolved digestive systems—their livers deactivate the toxic parts of the leaves and the bacteria in their stomachs help them get the most amount of nutrients from the leaves as possible. Females can be very territorial and rarely leave their home ranges. Males aren’t territorial, but don’t really tolerate one another; most adult males have scars from fighting. Koalas’ powerful claws help them climb even the tallest trees. They usually move really slowly but can climb quickly if necessary. Southern koalas from the cooler climates are typically larger than their northern counterparts and have longer, thicker soft gray fur often with chocolate-brown highlights.