Koala dominant. Older males usually have accumulated scratches, scars, and cuts on the exposed parts of their noses and on their eyelids. The koala's gestation period lasts 33–35 days, and a female gives birth to a single joey (although twins occur on occasion). As with all marsupials, the young are born while at the embryonic stage, weighing only . However, they have relatively well-developed lips, forelimbs, and shoulders, as well as functioning respiratory, digestive, and urinary systems. The joey crawls into its mother's pouch to continue the rest of its development. Unlike most other marsupials, the koala does not clean her
Koala separate) are used for grooming. As in humans and other primates, koalas have friction ridges on their paws. The animal has a sturdy skeleton and a short, muscular upper body with proportionately long upper limbs that contribute to its climbing and grasping abilities. Additional climbing strength is achieved with thigh muscles that attach to the shinbone lower than other animals. The koala has a cartilaginous pad at the end of the spine that may make it more comfortable when it perches in the fork of a tree. The koala has one of the smallest brains in proportion to body weight