Blind, nearly helpless, hardly larger than honey bees, and embryonic in appearance they crawl unaided into the abdominal pouch of the mother, each attaching itself to a nipple. Shortly after a young one begins to nurse, the nipple swells and completely fills its mouth, thereby firmly attaching it to its mother. It remains attached until it is about 7 weeks of age, at which time it has grown large enough to detach itself. This peculiar adaptation compensates in part for the brief period of uterine development and assumes part of the function performed by the placenta in higher mammals. Since the number of teats is seldom more than 13, young born in excess of that number are doomed to die.
Mortality is high during the first year of life, and population turnover is relatively rapid.
Known predators include foxes, coyotes, horned owls, and barred owls. Opossums are commonly seen killed on highways. The normal lifespan may be as low as 2 years. The opossum is the second most commonly harvested furbearing animal in Texas, but the value of its pelt is low. Their fur is used primarily for trim on less expensive coats and hats.