The Virginia opossum, often simply called a possum, is North America’s only native marsupial. This pouched mammal has a highly unusual reproductive cycle that contributes to its successful survival across diverse environments. This article details the timing of the opossum’s breeding season, the unique birth process, and the developmental journey of its young.
Seasonal Timing and Frequency
The opossum breeding season is extensive, generally beginning in late winter and continuing through summer. Most births occur between February and October in warmer regions. Mating activity typically starts as early as January in the south, with peak breeding times noted in February and June. The female’s estrous cycle lasts about 28 days, and she is receptive for only a brief period.
A female can produce multiple litters per year, though the exact number depends heavily on climate and food availability. In the southern United States, females commonly give birth to two litters annually, and sometimes even a third. However, in the far northern limits of their expanding range, the season is shorter, and one litter per year is more typical due to the colder conditions.
The reproductive cycle is characterized by rapid turnaround, which helps maximize the number of offspring produced during the favorable months. The male attracts the female with clicking sounds during mating season, after which the short gestation period quickly follows. If the first litter is successful, the female can quickly re-enter her reproductive cycle to begin developing a second set of young.
The Unique Marsupial Birthing Process
The opossum’s reproductive strategy is defined by an extremely short gestation period, lasting only 12 to 14 days—the shortest of any North American mammal. This brief internal development means the young are born in an intensely undeveloped, almost embryonic state. At birth, the young are blind, hairless, and remarkably small, often described as being the size of a jellybean or a honeybee.
The newborns possess surprisingly strong forelimbs and claws, which are necessary for their first and most challenging journey. Immediately after birth, these tiny infants must crawl unaided from the birth canal, across the mother’s abdomen, and into her pouch, known as the marsupium. This upward climb is completely instinctive, as they are not assisted by the mother.
Once inside the pouch, the surviving young must locate and securely latch onto one of the mother’s nipples. A female opossum typically has 13 nipples, which limits the maximum size of a successful litter, even though she may give birth to 20 or more young. Any newborn that fails to find an available nipple will not survive.
Development Stages and Independence
The young, called joeys, remain firmly attached to a nipple inside the marsupium to complete their development. This phase of rapid growth within the pouch lasts approximately 50 to 70 days. During this time, the nipple swells inside the joey’s mouth, ensuring a constant and secure attachment to the milk source.
Around two months of age, the young have grown significantly, and their eyes begin to open. They start to occasionally release their hold on the nipple and explore the inside of the pouch. When they become too large to fit entirely within the pouch, the next developmental stage begins.
The young then emerge and transition to clinging tightly to their mother’s back, a behavior commonly referred to as “riding.” The mother carries her growing litter as she forages, exposing the joeys to the outside world and teaching them survival skills. They continue to ride on her back for several weeks, occasionally returning to the mother’s underside to nurse.
Full weaning and dispersal from the mother typically occurs when the young are about 90 to 100 days old, or three to four months after their birth. Once the young reach a sufficient size, they leave the mother permanently to seek out their own territories. At this age, they are fully independent and must immediately begin to fend for themselves.