Common opossums are opportunistic omnivores. Their diet includes plants, nectar and fruits, as well as both invertebrates and vertebrates, such as birds, amphibians, small mammals and even some venomous snakes. They also eat carrion and occasionally root through human garbage to find food. The opossum's diet fluctuates seasonally, but some items, such as earthworms and grasshoppers, are consumed year-round. Common opossums play a significant role in seed dispersal throughout their range.
At the Smithsonian's National Zoo, the common opossum eats biscuits, greens, vegetables, fruits and meat, including fish, eggs and mice.
Common opossum breeding seasons vary by location. Some have a single, long breeding season that spans from January through September. Others have multiple, shorter breeding windows throughout the course of a year. Females build leafy nests, and males breed with multiple mates, competing for breeding rights.
These marsupials have a short gestation of just 14 to 15 days. Babies are 0.4 inches (1 centimeter) long when they emerge and weigh less than 0.005 ounces (0.13 grams). Although extremely small and underdeveloped, a newborn opossum has the strength to crawl to its mother's pouch. Once there, it attaches to one of the mother's nine nipples and continues to develop for another 50 days. A female can give birth to a litter of 20 opossums, but those unable to attach to a nipple do not survive. After emerging from the pouch, young remain with their mother, sometimes riding on her back for up to a month and a half until they are fully weaned and independent.
Common opossums in regions with access to ample resources tend to give birth to litters of mostly male offspring, while those in regions with scarce resources tend to have more females in their litters. Additionally, litter size tends to decrease closer to the equator. Litters with as few as two young have been observed.
Common opossums are considered a species of least concern, according to a 2008 evaluation by the International Union for Conservation of Nature. They are considered a widespread and adaptable species. Human-caused mortality is most often due to hunting or collisions with vehicles; opossums are hunted for their fur, meat, as sport or by farmers looking to protect their animals. Opossums are most often hunted when other game becomes difficult to find. In Suriname, common opossum meat is harvested and illegally traded to French Guiana.
As opportunistic feeders tolerant of many different habitats, including suburban areas with significant human development, common opossums do not face significant threats from human development and expansion. No formal protection measures for the species are in place, but common opossums do occur in several protected areas within their natural habitat.
In some areas, opossums are considered pests, because they feed on garbage and are known to carry parasites. Some communities view them more favorably, hunting them for medicinal use. Their natural predators include ocelots, jaguarundis and harpy eagles.