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 cooler than the surrounding air. The koala hugs the tree to lose heat without "panting". On warm days, a koala may rest with its back against a branch or lie on its stomach or back with its limbs dangling. During cold, wet periods, it curls itself into a tight ball to conserve energy. On windy days, a koala finds a lower, thicker branch on which to rest. While it spends most of the time in the tree, the animal descends to the ground to move to another tree, walking on all fours. The koala usually grooms itself with its hindpaws,