The most common species of the opossum in the United States is the Virginia opossum (Didelphia virginiana) or common opossum. This animal is usually referred to as simply an opossum. The opossum is the only marsupial native to North America. Although they are best suited for warmer climates, the opossum is found throughout most of the United States.
Opossums are a medium sized mammal. They usually range in weight from four to six pounds with the females weighing slightly less than males, but in some cases opossums weighing over twelve pounds have been observed. They range from thirteen to twenty one inches in length; their tail can be 93% as long as the length of their head and body.
Opossums typically have a dense undercoat of gray fur, but in some instances the fur may have a red, brown, or even black tint. Besides the under coat, opossums also have longer hairs that extend beyond the dense undercoat called guard hair. The opossum’s guard hairs are tipped with white. Opossum’s coats vary due to where they are found. Those found in cooler climates tend to have lighter colored guard hairs, thicker under fur, and a more grizzled appearance. Opossums found in warmer areas tend to have darker colored fur which is often thinner than that of those found in the north. The fur on the face of the opossum is lighter than the rest of their body. Most often, the facial hair is a light grayish-white.
An opossum’s tail is long, hairless, and prehensile. A prehensile tail (a tail that is able to grasp) allows the opossum to grab items and also can be used for stabilization while they are in a tree. Opossums also have opposable, clawless thumbs on their rear limbs. Their thumb is called opposable because it can be moved around to touch the other digits, which gives the opossum the ability to grasp things easily like a human can grasp with their hand.
The opossum’s relatively large furless ears, a furless tail, and a pointy face make many people assume that they are related to the rat. This however is not the case; in fact, opossums are much more closely related to kangaroos and koalas than rats and mice.
Opossums are omnivores. Their diet varies depending on the season and where they live. Opossums are known to eat vertebrates (mice and rats especially), invertebrates, carrion (dead animals), plants, fruits, grains, and human garbage. As can be expected, when the weather is colder their diet consists more of small vertebrates; in warmer weather they eat more invertebrates, plant material, fruits and seeds. Opossums are drawn to places that have both food and water. Leaving food and water out for an outdoor pet will often attract opossums at any time of the year.
Most opossums are born between February and June. A female opossum may have one to three litters per year. Opossums are marsupials. Like other mammals, marsupials give live birth, but instead of a fully formed young, the opossum gives birth to an embryo which climbs from the birth canal to a pouch. Once in the pouch, the embryo attaches to a nipple and then is unable to dislodge itself. The nipple increases in size so that the embryo is only able to dislodge itself from the nipple when it has grown and become more developed.
Opossums are born and move to the pouch after an eleven to thirteen day gestation period. Up to twenty opossums may be born at one time, however, the average size of a litter is six to nine young. In most cases it is not possible to have a litter of more than thirteen opossums because the mother opossum only has thirteen nipples from which to feed her young.
When the opossum first enters the pouch it is small, pink, deaf, and blind. In fact, the new born opossum is about the size of a honey bee (0.006 ounces). The small opossum continues to develop inside the pouch. By the end of the tenth week in the pouch, the young opossum will open its eyes and begin to venture out of the pouch and onto its mother’s back.
As they grow and the pouch becomes full, young opossums ride on their mother’s back until they are old enough to go out on their own. Opossums are not weaned until approximately one hundred days after birth. They become sexually mature at about eight months
The average wild opossum lives for one to two years. Due to the access to consistent food and the lack of predators, opossums in captivity generally live longer (about three to four years). In rare cases, captive opossums have lived to be ten years old.
Opossums can be found in a variety of habitats. They prefer areas near a water source, such as a stream or swamp, but may also be found in the woods and are often found in areas where humans have made water and food available. Their range has expanded and they can now be found throughout Central and North America from Costa Rica to southern Canada. In the U.S. opossums are found on the East coast as far west as the Rocky Mountains and also on the West coast.
Although they are very adaptable, opossums have issues with extreme cold and deep snow. When opossums were first discovered by European settlers, they were not found north of Kentucky, Indiana, or Ohio. By the 1970’s they were found in Vermont and New Hampshire; and now they are found in southern Canada. Opossums that live in colder climates often try to find shelter in man-made structures during the coldest parts of the year. Even when they use human shelters, opossums that live in colder climates are often found to have frost bite, especially on their tails.
Opossums are solitary animals. They come together to mate, but otherwise live alone. In fact, during mating time is one of the only times opossums are social. After mating, female opossums become aggressive when any other opossums comes into their area.
Opossums are nocturnal; they sleep through the day and wake at dusk to begin to gather and hunt for food. Although opossums do not actually hibernate, they reduce their activity in the colder months of the year. Opossums have learned to adapt to colder climates by using their fat stores during the winter when food is scarce.
Opossums are terrestrial. Although they live on the ground, they have been known to create their dens in trees or other sites not on the land including buildings and hollow trees. When they find a suitable space, opossums fill their dens with dry leaves or shredded paper. Opossums move to new dens frequently. Only females with young remain in the same den for long periods.
The behavior that is most associated with opossums is “playing possum”. “Playing possum” is when an animal goes into a catatonic state when they are threatened. The opossum will stay motionless for as little as a minute, or up to 6 hours. Although this behavior is well known it is actually quite rare for an opossum to do this. It is most frequently seen in young opossums. In actuality, when most adult opossums are threatened they will bare their teeth and stand their ground, or flee.