The Virginia Opossum (Didelphis Virginiana)
Image credit: Uris at English Wikipedia. Public domain.
If you live in the Americas, you've likely seen a slow-moving critter in the backyard, or lurking in a tree. If the critter falls over in an apparent faint, you have definitely spotted an opossum.
It is often said that an opossum is 'playing dead' when it falls over. Actually, the opossum is not playing at anything. Fear causes an involuntary response which throws the opossum into a comatose state. An opossum in such a state cannot get up for quite a while, perhaps forty minutes, perhaps four hours.
An Opossum's Faint
Image credit: Johnruble. Public domain
Not only is the opossum immobile at these times, but it emits a foul, death-like odor and exudes ooze from its mouth. In the wild, this might be a good defense mechanism. Predators that do not feed on carrion will move on.
However, not all predators reject dead animals as food. Scavengers, for example, readily eat carcasses, as do some other animals when food is scarce. So, "playing possum" actually becomes a death sentence, in that case. Also, on modern highways, freezing in place will likely turn an opossum into roadkill.
The Opossum as a Casual Parent
And if you see one of these critters and it has a passel of little ones hanging on its back, you've spotted a female opossum with her offspring. If that situation looks precarious for the young, it is. Sometimes a baby opossum will fall off and the mother will keep going.
Virginia Opossum With Young
Image credit: Specialjake. Used under CC 3.0 license.
And, if you did spot an opossum, it was probably at night. The opossum is a nocturnal creature and also, is rather shy.
Virginia Opossum at Night
Image credit: Melissa McMasters from Memphis, TN, United States. Used under a CC. 2.0 license.
While many people regard the opossum as a pest, it is not. Opossums are not rodents. They are marsupials. As a matter of fact, opossums eat rodents. And they also eat cockroaches, crickets, beetles, snakes, and even dead animals. Opossums seem to have partial immunity to snake venom. This immunity is of interest to researchers who think they might discover an effective anti-venom in the opossum's immunity.
Opossums also eat ticks with relish. They are tick vacuums. It is estimated that a single opossum eats 5,000 ticks in a single season. This omnivorous marsupial also has partial immunity to Lyme disease.
These strange looking, slow-moving shy creatures are a beneficial addition to your backyard fauna.
Intelligence of the Opossum
There are some who believe the opossum is not "the brightest of animals". Research has proven this to be a mistaken view. Studies reveal opossum intelligence rates high on the animal scale. When it comes to remembering, they outperform dogs, cats, rats and rabbits. However, humans score higher. When it comes to tackling a maze, opossums score higher than cats and rats. And, when it comes to identifying toxic substances, once exposed to the substance, a (mature) opossum will not repeat the mistake.
The Opossum Is a Mammal
Chart credit: AG Moore
Opossums are marsupials, which means offspring are born live and develop in the mother's pouch (called the marsupium). Marsupials are distinguished in this type of gestation from placentals, in which the young are carried and nourished inside the mother until fully developed. The developing offspring in a marsupial is called a joey.
Image credit: Geoff Shaw. Used under CC 3.0 license. Here the underdeveloped kangaroo joey is attaching itself to the mother's teat in order to get nutrition. In a placental animal, nutrition at this stage of development would be provided by the placenta inside the mother.
Opossums have the shortest gestation period of any mammal. The young gestate for only 12 days. After that they migrate up to the mother's pouch. This perilous journey is often too much for the fragile young. Some don't make it. Others make it, but find there is no room for them. An opossum has 13 teats. Usually, however, the opossum will give birth to 20 offspring. Late comers to the pouch perish.
After the extinction of the dinosaurs about 65 million years ago, the three types of mammals evolved (marsupials, placentals and monotremes). While mammals existed before the dinosaur extinction, they were few in number and species.
It is believed that marsupials arose around the same time that Pangaea, the earth's early supercontinent, started to break up.
Image credit: Fama Clamosa. Used under CC 4.0 license.
According to the The British Journal of Ophthalmology, this division of the continents isolated marsupials on what would one day be Australia, Antarctica and South America. The South American marsupial eventually made its way up across the isthmus of Panama and the modern-day Virginia opossum is a result of that long journey.
White-Eared Opossum in Brazil
Image credit: Rhalah. Used under CC 3.0 license. According to the caption under this picture, the opossum was foraging in a kitchen when the photo was taken.
About 120 marsupial species evolved in Latin America, and about 250 in Australia. In the U. S., there is but one species, the Virginia opossum. The oldest marsupial fossil (or antecedent of marsupials) was discovered in North America, and is 110 million years old.
Image credit: Ghedoghedo. Used under CC 3.0 license.
This fossil is said to be 125 million years old. It is so well preserved that it even has fur on it. It was once believed to be the oldest marsupial fossil ("The Mother of all Marsupials"), but recent research indicates that it is actually an ancestor of placentals. This evolving notion of placental/marsupial development reveals that a definitive evolutionary record has yet to be established.
Virginia Opossum Opposable Thumb
Image credit: Tony Alter. CC 4.0.
The opossums hind feet are constructed very much like a human hand. The 'thumb' on these hind legs is called a hallux and is the only one of the opossum's digits that does not have a nail. Just as is true with primates, this 'thumb' gives the opossum great flexibility in grasping.
Opossum's Prehensile Tail
Image credit: Banta, Nathaniel Moore, 1867- Schneider, Albert, 1863- Higley, William Kerr, 1860-1908 Abbott, Gerard Alan in the book, "Nature Neighbors" 1914. Public domain.
Opossums have a prehensile tail, which is hairless. They use the tail as a fifth limb. It gives them greater flexibility in getting around, especially in climbing trees.
Random Opossum Facts
***Opossums have more teeth than any other mammal in North America. When intimidated, an opossum will open its mouth, hiss, and show its teeth. Just like playing dead, this is just a ruse. Opossums are not aggressive toward humans.
Image credit: User PiccoloNamek on en.wikipedia. CC 3.0 license.
***Opossums are nomadic. They are not territorial. They tend to wander around in the night and find a place to rest in the daytime. Check out this Youtube video and watch an opossum strut its stuff:
***Opossums get frostbite. They may lose ears or a tail. The Virginia opossum evolved in a warm climate and is not well suited to winter. Many opossum deaths are attributed to cold weather.
***Opossums in the wild have a short lifespan. It turns out that walking slowly and playing dead are not conducive to long life. In the wild, an opossum may live from 1.2 to 2 years. In captivity, it may live to 4 years, although there are reports of captive opossums living 10 years.
Opossum on a Fence
Image credit: Sergey Yarmolyuk. Used under CC 4.0 license.
***The opossum has a low susceptibility to rabies because of a low body temperature.
I was interested in learning about opossums because we have seen them around our property over the years. They seem to get along well with the feral cats we care for. Recently we found an opossum in one of the cat houses.
We provide heating pads, so the house might have been irresistible for a cold opossum. Plus, of course, there's food :)
Some Sources Used in Writing This Blog
Platypus: Pearson Scott Foresman
Dedicated to the public domain
Kangaroo: From the book Dot and the Kangaroo (1899), By Ethel Pedley
I drew them, using as a model a public domain image from Wikimedia Commons.