Koalas live in forests and eat only eucalyptus leaves. They are sedentary animals that need to sleep a lot to give them time to digest their food. Being on the ground would be a disadvantage, because predators could catch them easily. Instead, they live up in the trees, rear end firmly planted in the fork of branches, so they can chew leaves and nap all they want without feeling threatened.
Koala hands and feet are designed to curl around and hang onto tree branches. Their hands have two opposing thumbs to increase their grip and sharp claws to dig into bark. The feet have a toe that is really two toes fused together, which they use to groom themselves, and a toe that doesn’t have a claw that acts like a thumb for gripping. Rough, ridged pads on the hands give them traction. Strong arm and shoulder muscles help a koala climb 150 feet to the top of a tree and even enable it to leap between branches in the trees.