Female opossums give birth about two weeks after mating. Babies are naked, blind, almost transparent, and slightly smaller than a honeybee. At this stage only the front legs are developed. These are fixed with claws and are sufficiently powerful enough to allow the embryo-like young opossums to make their way a few inches up their mother’s belly and into her fur-lined pouch. Here they attach themselves to one of thirteen teats arranged in a horseshoe configuration. If there are more than thirteen babies, only those babies able to grasp a teat will survive. Once the nipple is in the baby’s mouth, it swells, making it virtually irremovable. This vital connection remains unbroken for about two months. The average opossum litter contains eight young (range: 5-15), but half or more of these may perish before reaching the mother’s pouch.
At around two months after birth, the eyes of the young open and they begin to spend time out of the pouch. Eventually they begin to find food on their own and often travel on the female’s back rather than in her pouch. They become fully independent when about three months old. It’s possible that a mother possum that has been hit by a car and killed could still have live babies in her pouch. It’s always good to stop and make sure if you see one on the side of the road.