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Common opossums are marsupials native to the Western Hemisphere, all belonging to the family Didelphidae in the order Didelphimorphia. Shrew opossums belong to the order Paucituberculata; a sister order to Didelphimorphia. Common opossums and shrew opossums are sometimes called possums in everyday speech, but the true possums are an entirely different order of animals, Phalangeriformes, living in Australia. This article is about the common opossums only; not about shrew opossums or possums, and all information within it pertains to common opossums unless otherwise specified.
Opossums are small to medium-sized marsupials; the smallest species do not grower larger than mice while the biggest ones can become as large as big pet cats. Most species have a long snout, a narrow braincase and prominent sagittal crest. A sagitall crest is a ridge of bone running lengthwise along the middle of the top of the skull and the presence of such a ridge indicates that the animal has very strong jaw muscles. The opossum jaw is filled with a myriad of teeth; considering the size of the jaw opossums have more teeth than most other land mammals. The hind feet have a clawless opposable digit and opossums walk with their feet flat on the ground. They are excellent climbers and most species are at least semi-arboreal. Opossums have prehensile tails but it is usually only the juveniles that can be seen hanging from their tails since adult specimens tend to be too heavy. Instead, the long tail is used for support when climbing and can also grip bunches of leaves or bedding material gathered for the burrow.
In the wild
Opossums are normally solitary animals, but families can be seen living together in burrows. They don’t dig their own burrows; they use burrows excavated by other animals, including man-made burrows (e.g. the crawl space under your house). They are nocturnal and do not like to be out in the open during the day. Opossums are nomadic and will only stay in one area as long as they can find food and water.
The expression “to play possum” comes from the opossums’ habit of playing dead when threatened. By mimicking the appearance and smell of a dead animal, the opossum deters predators that won’t eat carrion, and it may also convince animals that it is no threat against them or their young. When “playing possum” the opossum will draw back its lips to bare its teeth, saliva will foam around the mouth, and a smelly fluid that makes the opossum stink like old carrion is secreted from the anal glands. This behaviour is involuntary rather than a conscious act and it can take minutes or even hours before the opossum regains consciousness. A threatened opossum doesn’t always become unconscious; especially the males are known to growl to dissuade attackers, gradually raising their pitch as the threat becomes more imminent.
Opossums are not commonly kept as pets and as far as I know, there is no such thing as domesticated opossums, i.e. opossums that have been selectively bred over several generations to become more tolerant towards humans than their wild counterparts. Some degree of so called self-domestication might be going on, but more research is necessary before we can know anything for sure. There is one notable exception here: the pouch-less Gray short-tailed opossum (Monodelphis domestica) is a popular pet and has been bred in the USA since 1994.
People who keep other species of opossum than the GTO are usually wild-life rehabilitators who take care of orphaned opossums and raise them until they can be released back into the wild. In some cases, individual opossums can not be safely released and will remain with humans throughout their entire lives.
Opossums cared for by humans can bond strongly with them and learn to rely on them for food and protection, just like they would rely on their biological mother in the wild. As the opossum matures, it is however common for it to develop an interest in life outside the nest – just like it would in the wild.
Before you decide to take care of an opossum, it is very important to check up on laws and regulations pertaining to your part of the world. Since the opossum is a wild animal, you may need a special permit. Separate permits may also be required for transporting or breeding opossums.
Always obtain detailed care guidelines before your take on an opossum and do not hesitate to seek the advice of more experienced opossum keepers. There are many pitfalls; did you for instance known that really young opossums can’t empty their bowels without assistance? They rely on their mother (or a human care giver) to help them with this. When searching for advice regarding opossum care, make sure the advice you get pertain to your specific species of opossum. Sometimes people tend to forget that there are many difference species of opossum out there and give seemingly general advice that in fact isn’t general at all.
Opossums are opportunistic omnivores with a very broad diet and this flexibility is one of the reasons why these creatures have been comparatively good at handling habitat destruction and human encroachment. Many opossums even take advantage of human activities and can for instance be seen rummaging through garbage cans, nicking pet food and scavenging highways in search of road kill.
The exact feeding habits naturally vary depending on species, size and geographical location but most species will feed on carrion and eggs and hunt animals large enough for them to overcome, from insects and worms to snakes, birds, amphibians and small mammals. Opossums also eat a lot of vegetable food and are especially fond of fruits, such as apples and cashews.
Young opossums live on milk produced by their mother.
Males are usually a bit bigger than females and will make a clicking smack-noise when searching for a mate. Females will sometimes repeat the sound in return.
The male is equipped with a bifurcated (forked) penis that fits into the bifurcated vagina of the female opossum. Opossums are born after a very short gestation period (usually less than two weeks) and the offspring will instinctively find their way to their mothers’ pouch and try to grab on to a teat. It is common for female opossums to give birth to large batches, but quite a high percentage of the young die soon after birth after failing to hold on to a teat.
Young opossums typically nurse for 70-125 days before being weaned. Female opossums can sometimes be seen carrying older offspring on their backs. Opossum youngsters are remarkably good at holding on to their mother even as she’s climbing, but if they fall off they will make a sneezing, wheezing sound to alert their mother of their position.
General signs of poor health in opossums
- Runny nose
- Watery or cloudy eyes
- Excessive scratching
- Tail biting
- Dirty, unkempt fur
- Appetite loss (not the same thing as being a bit finicky and only excepting certain types of food)
- Weight loss
- Changed faeces
- Trembling, shaking or stumbling
- Decreased mobility
Common health problems in opossums
Trembling, shaking or stumbling are all signs of dehydration. Check that the opossum have enough water and feed it some high-moisture food, e.g. melon and berries.
If your opossums get into a fight with another opossum, you can expect it to receive injuries on ears, eyes and tail. Opossums usually heal well as long as they’re otherwise healthy and have access to food and water.
Diarrhoea is usually brought on by a dietary change. Also keep in mind that diary products aren’t really natural for opossums; it would be quite difficult for a wild opossum to milk a cow or goat so their digestive system isn’t really used to lactose. (But babies will of course drink the milk produced by their mother.) The safest course of action is to let any dietary change be slow and gradual and to avoid diary products. Make sure the opossum gets a lot of fluids until the diarrhoea clears up.
Apathy, trembling and laboured breathing are all signs of pneumonia in opossums and should prompt veterinary care.
Opossums can become infested with internal and external parasites. Before trying any remedy, ideally check with a vet or wild-life rehabilitator to make sure its safe for opossum use.
Important information regarding parrots and horses
- Opossums can spread a parasite to horses that causes equine protozoal myeloencephalitis (EPM).
- Opossums can spread a parasite to parrots that causes sarcocystosis. Old world parrots are more susceptible to the disease than new world parrots.
Opossum fact # 1
The word opossum was first used for the Virginia opossum (Didelphis virginiana) only.
Opossum facts # 2
The first opossums are believed to have developed in South America during the late Cretaceous or early Paleocene. They didn’t spread to North America until the Central American land bridge was formed. The Virginia opossum is the only North American marsupial.
Read more Opossum facts
For a mammal of its size, the opossum has a comparatively short life span. Most opossums die before the end of their second year and finding opossums older than four years is extremely uncommon. There are however reports of Gray Short-tailed Opossums (Monodelphis domestica) reaching an age of 6 years in captivity.