By Fran Stoddard © 1984
Issue: September, 1984
Q: The Possum looks very much like a rat. Is it a Rodent?
A: The Possum or Opossum does look like a giant rat with its hairless tail and long pointed nose, but it does not belong to the Order of Rodents. To classify it, we know it is an animal of the Class Mammalia. A mammal is a warm-blooded animal that feeds its young milk from the mammary glands of the females.
The possum has the distinction of being one-of-a-kind. It belongs to the order of Marsupial of which there is only one species in the United States, namely the didelphis virginiana or Virginia Opossum. The south is fortunate to have an abundance of this unique creature.
A marsupial is a mammal whose young are carried inside a pouch on the abdomen, for several weeks after they are born. A well known marsupial is the Kangaroo of Australia.
Opossums differ from rodents in many ways. There are more species of rodents in the world than any other order of Mammal. They range is size from a mouse weighing a fraction of an ounce to Beaver weighing over 100 pounds. Most are relatively small.
Rodents are distinguished by having two pairs of incisors (front teeth); uppers and lowers. they do not have canines, so there is a gap between the front teeth and molars (grinding teeth), near the back of the mouth. If you were to examine the teeth of a rodent they would appear orange or yellow in front but soft in back. They wear away by the workings of the upper and lower incisors against each other. This produces a very sharp hard edge that rodents need for gnawing. Throughout its life, the rodent's incisors continue to grow. If they didn't they would be worn away. If they weren't worn down, however, they would continue to grow too long and incapacitate the creature.
Possums do not have teeth like a rodent. Instead they have more teeth than any other mammal. They have 50 very sharp teeth.
Rodents have bulging eyes on the side of their heads which help them to detect danger in front, on the side and behind. Look at the eyes of the possum. They are closer together, small and not bulging
Some rodents hibernate in winter. The possum may den up for a few days in severe weather, but it does not hibernate.
Compared to possums, rodents are geniuses. Opossums have very small brains and a very hard skull. The skull bones of many rodents are much thinner.
Though the tail of an opossum may resemble a rat, it is known as a prehensile tail. Monkeys have prehensile tails. For the opossum, it can use its tail like a fifth foot, or hand. If it isn't too heavy, it can hang from a branch to obtain food, as in getting eggs from nests. It is a good climber. When the young crawl out of the pouch and begin riding on their mother's back, she will often hang her tail over her back so they can hang on to it.
When in danger, a possum will sometimes "play possum." That is, it will roll over, shut its eyes, its tongue may hang out and it will look dead. Most other predators will leave it alone, as it has an offensive odor. In fact, about the only things that will eat a possum are some owls and humans. A vulture will eat dead ones.
It was once believed that a possum feigns this death act consciously. But, scientists now believe that it merely gets "scared to death" and faints!
Opossums are not fussy. They will eat about anything, vegetation or meat, dead or alive or decayed.
The most amazing thing about the opossum is the way the young are cared for. They are born after a gestation period of about 12 days. At that time, the young are not much more than embryos about the size of a small bean. The hind legs and eyes are not yet developed, its internal organs can be seen through transparent skin, but the forelegs are developed enough so they can find their way, by crawling or dragging themselves through the mother's fur into the pouch which contains about 12 nipples. It's first come-first served. As each one reaches a teat, it literally swallows it and stays attached while it finishes its growth, or development. If more babies are born than there are faucets, they don't survive. They that are more fortunate will stay attached about two months. Then they will be about mouse size and venture out. In case of danger, they will hurry back inside for safety. At three months they are usually on their own. Opossums may have 2 or 3 litters a year unlike a rat for example that may have 12 litters a year and up to 22 in a litter.
So you see, although an opossum may look like a rodent, it is quite different.