The opossum is a medium-sized mammal, about the size of a house cat, with gray to black fur, a pink nose, naked ears, and an almost hairless prehensile tail (able to grasp, hold, or wrap around). They are North America’s only marsupial. They are solitary, slow-moving animals who are most active at night, when they wander randomly in search for food.
Although they are excellent climbers and have been known to live in tree cavities, they prefer to den on the ground in old woodchuck burrows, brush/wood piles, and even in spaces under decks or patios. Opossums are omnivorous and are beneficial to humans because they cause very little damage and they consume insects, snails, and slugs.
The many beneficial qualities of opossums include:
- Keeping neighborhoods clear of pests like cockroaches, rats, and mice.
- Reducing the Lyme-disease carrying tick population, by eating nearly 95% of ticks that cross their path.
- Controlling venomous species of snakes, which is possible because of their resistance to venom.
- Having an extremely low risk of contracting rabies!
- Keeping gardens blooming by eating snails, slugs, and fallen, overripe fruit.
Opossums are usually shy and harmless animals, with two main defense mechanisms. First, if an opossum is frightened and unable to flee, she may display her teeth and hiss. Although this behavior might appear fierce, it is usually just a warning. Second, if they feel they are in real danger, they might “play possum” and have the appearance of being dead. When the opossum feels that he is no longer in danger, he will revive himself and move on.
The life span of opossums is very short. A four-year old wild opossum is a rarity. The average female probably lives through one breeding season in which time she may raise two litters of approximately a dozen young. Once born, the young instinctively crawl upward into the mother’s pouch where they will nurse for approximately fifty days. When they grow to be approximately 3 to 4 inches long, they crawl out of their mother’s pouch and ride around on their mother’s back. If they fall off, their mother may not notice because they are so small. If very young opossums are found, a wildlife rehabilitator should be contacted because they may be orphaned and too young to survive on their own. They are independent of their mother at about three months old. These large litters help accommodate for the high mortality rate opossums face.
POSSIBLE CONFLICTS & SOLUTIONS
Around Horses – Equine Protozoal Myeloencephalitis (EPM)
Equine protozoal myeloencephalitis (EPM) is caused by the protozoal parasites Sarcocystis neurona and Neospora hughesi, although most cases are due to S. neurona. The definitive host for S. neurona is the opossum, and horses become infected when they ingest feed or water contaminated with opossum feces. In areas where the opossum is common, approximately 50% of horses are seropositive (have antibodies to the parasite in the blood), indicating exposure to the organism. Opossums shed the infective sporocysts (egg-like stages of development) in their feces. An estimated 50-90% of horses in the U.S. have been exposed to the organism, but only a small percentage (typically <1%) develop EPM. A thorough neurologic examination and diagnostic testing are required to distinguish between EPM and other neurologic diseases that can have similar clinical signs. Learn more about this parasite from UC Davis Center for Equine Health.
Around Your Home
If an opossum has taken up residence under your home or shed, the first step is to encourage the opossum to move on with mild harassment techniques. Place loose leaves or loose straw in the entranceway of the den, place items with a human scent (e.g., old shoes or dirty socks) at least two feet away from and not blocking the entrance to the den, or turn a radio on a few feet from the entrance to the den. The opossum should move on in a day or so, but this depends on how quickly she can find a safe replacement den nearby.
Exclusion using a one-way door is easy and effective. You simply wait until approximately two hours after dark when the opossum should be out foraging, and loosely close the opening with netting, straw, a one-way door, or other material. This way an animal inside can easily push his way out but an animal on the outside will not be able to regain entry.
If an opossum has entered your house or a building, these slow-moving animals can be guided out with a broom to gently nudge them along to an open door.
If an opossum is seen in a yard or neighborhood, the best thing to do is to be patient since she will most likely move on within a short time without the need for human intervention.
While it is not common for opossums to raid garbage cans or gardens, you should discourage visits by opossums and other urban wildlife by purchasing trash containers with secure lids or using bungee cords to secure trash container lids, and picking up food bowls if your pets have been fed outdoors.
PUBLIC HEALTH CONCERNS
Opossums are susceptible to a variety of diseases but their role in transmitting these to humans is uncertain. Similar to all warm-blooded animals, rabies occurs in opossums but it is very rare.
MSPCA OPOSSUM FACT SHEET pdf