On the ground they move in an unhurried quadrupedal walk, but can move quickly if the situation demands it. Koalas typically associate only for mating. Males are not territorial, but there is a dominance hierarchy, and dominant males chase and attack subordinates. Most adults carry scars from these encounters. They violently defend occupied trees.
Males become quite aggressive during breeding season as they compete for females.
They use their sternal scent gland as well as a loud barking call to mark their territory. Their low quality diet of leaves provides little usable energy and the koala typically sleeps 18 hours per day. Females become sexually mature at about two years. After a short gestation period the female licks a trail of saliva from the pouch to the cloaca. The joey emerges and follows that trail up to the pouch, where the mammary glands are.