Koalas are marsupials, females having a pouch in which their young first develop. Their pouch faces the rear and has a drawstrikinglike muscle that the mother can tighten. They are the sole member of the family Phascolarctidae .
Size is larger in the southern regions.
At birth young weighs only 0.5 gm. The fur of the koala in southern region is thick and woolly and is thicker and longer on the back than on the belly. The color and pattern of the coat varies considerably between individuals and with age. Thickest of the marsupials. Rump consists of tougher connective tissue dappled with white patches.