Many kangaroos and wallabies have gestation periods ranging from about three and a half to five weeks, depending on the species. After birth the tiny, blind young climb up the mother's belly to her pouch for nursing. Upon reaching the pouch, a baby marsupial grasps a nipple, which becomes engorged in its mouth. In many species the young remain firmly attached to the nipple for several weeks, consuming a constant supply of milk. In most species the young remain with the mother in some manner for many months.
Marsupials generally have small litters.
Some of the larger species, such as wombats, koalas, wallabies, and kangaroos, normally have one offspring or occasionally twins. Tasmanian devils have two to four young, and Virginia opossums have an average of between six and ten. The females of some marsupial species give birth only once a year, whereas others routinely rear two or more litters annually. After marsupial young are weaned, they begin roaming for short distances and eating food on their own. The young of many species, however, remain with the mother for some time after weaning, sometimes returning to her pouch in search of rest or protection.