The opossum, North America’s sole marsupial, is unique among mammals on the continent. Unlike placental mammals, opossums carry their young in an external pouch, a characteristic feature shared with their distant relatives like kangaroos and koalas. This distinctive reproductive strategy allows for a rapid developmental cycle.
Opossum Breeding Habits
Opossums have a flexible breeding season, extending from late winter through fall. In northern climates, breeding occurs from February to September, while in southern regions, it can begin as early as January and continue until August. A female opossum can produce between one and three litters annually, depending on climate and available resources.
A female opossum has an estrous cycle lasting about 28 days, with a short 36-hour mating window. If pregnancy does not result, she will continue to cycle until breeding is successful. The gestation period for opossums is brief, lasting only 11 to 14 days.
Following this, a female can give birth to a large litter (4 to 25 young). However, the average litter size is typically 6 to 9. Despite this, a female opossum usually has only 13 teats, so any offspring exceeding this number will not survive.
Life in the Pouch and Beyond
Newborn opossums are underdeveloped at birth, resembling tiny, hairless “pinkies” no larger than a bee or a dime, weighing about 0.13 grams. Immediately after birth, they instinctively crawl from the birth canal into their mother’s marsupium (pouch). Once inside, they must locate and firmly attach to one of the mother’s nipples, which then swells in their mouth to secure their hold and provide continuous nourishment.
Young opossums remain in the safety of the pouch for about 2.5 months (50 to 70 days), where they continue their development. During this period, their eyes open, and they begin to grow fur. As they grow too large for the pouch (around 2 months), they venture out for short periods.
They transition to riding on their mother’s back, clinging to her fur, learning survival skills like foraging and predator avoidance. This stage can last for about a month. Opossums are typically weaned around 3 months of age and become fully independent when they are about 4 to 5 months old, measuring about 7-9 inches long from nose to rump, excluding the tail.