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small mammals, fruits, grains, plants, and the flesh of dead animals it happens to find. It forages intensively in a small area on whatever is available. When food resources become depleted in one place, the animal simply moves to a new area.
Although the foods an opossum eats are varied, they must be abundant and closely spaced. Extreme weather conditions, such as a severe drought or extended cold, can reduce food availability and have devastating effects on opossum populations.
Reproduction
A female opossum usually has two litters per year. Mating occurs in mid-January through February and continues into August. Young partially-developed opossums are born 13 days after mating. They migrate to the female's pouch where they continue to develop for several weeks. The young emerge from the pouch when they are 1 l/2 to 2 months old and ride on their mother's back. They are weaned at three months. The adult female mates again soon after the first litter is weaned, and the first litter disperses within one month of weaning. Young from the second litter are weaned and on their own by September or October.
There are 8 to 10 young in an average litter, but litters of 17 have been reported. The young are capable of reproducing at six months of age, but usually don't until the year after they are born.
Mortality
An opossum is short-lived and has high mortality rates at all stages. Mortality of young still in the pouch ranges from 10 to 25 percent. Of those that survive through weaning, fewer than 10 percent live longer than one year. The oldest known wild opossums were 2 l/2 to 3 years old.
The most important mortality factors are caused by humans, predation, parasites and disease, exposure and starvation. Human-caused mortalities include hunting, trapping and highway collisions. Important predators include great horned owls, dogs and coyotes. An opossum is a host to a multitude of internal and external parasites including intestinal worms, fleas and ticks. These generally are debilitating and increase susceptibility to diseases and malnutrition. An opossum is highly resistant to rabies.
Importance
Opossums seldom cause problems for homeowners, ranchers or farmers. They sometimes raid trash cans or dog food containers, but these situations are easily remedied by denying access to the containers.
The opossum is classified as a furbearer in Nebraska but is not taken in large numbers by hunters or trappers, and its pelt has little value. Opossum furs are primarily used to trim inexpensive cloth garments.
From 1941 to 1989, over 350,000 opossums were taken by fur hunters and trappers. Harvest totals from 1980 to 1989 indicate an average annual harvest of 11,900 opossums valued at $7,200. From 1984 to 1989, only 42 percent of the harvested opossum pelts were sold.
The uniqueness of the opossum intrigues scientists and nature enthusiasts. It is the only marsupial in the United States. In Australia and elsewhere, marsupials have been out-competed and even driven to extinction by more modern mammals. Yet, the opossum has adapted to the changing environment in the U.S. with its simple manner, and continues to thrive.
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