Newborn opossums need sustenance, transportation and protection, usually provided by their mother. If separated from its mother, a newborn opossum needs special care as directed by a wildlife rehabilitator to keep it warm and hydrated.
When opossums are born, they are the size of a honeybee. The newborns must crawl into their mother's pouch so they can nurse. Some of the newborns do not make it to the pouch, and ultimately fewer than half of the babies survive to adulthood. Depending on the species of opossum, mothers can nurse as many as 13 babies. The young opossums nurse for 70 to 125 days.
During this time, the babies cannot walk and depend on their mother to move around. Neither can they defend themselves, so they must hide in their mother's pouch. As the young mature, they may crawl out the mother's pouch and ride on her back. After about 4 months, baby opossums can walk and gain independence.
A newborn opossum separated from its mother needs to be kept warm, but not hot. It also needs hydration, preferably from diluted electrolyte solution, and stimulation to eliminate. A wildlife rehabilitator must give specific instructions for providing care to a young opossum.