The Opossum: Possibly the most underestimated mammal in North America
The opossum is a marsupial of the order Didelphimorphia, which is endemic to the Americas. This is the largest order of marsupials in the Western Hemisphere consisting of approximately 110 species. Nonetheless, the only marsupial in North America is the Virginia opossum (Didelphis virginiana), or simply the “opossum” or “possum.” Despite its unique taxonomy, we are all very familiar with this species and its characteristics. Opossums are most famous for the females’ pouch where they protect and nurse their young, their prehensile tail, and their response to danger by “playing possum.” An attribute of the opossum, which most people know and some use to disparage our poor opossum friend, is its apparent lack of what we call intelligence. Indeed, the opossum has a very small brain case, and lacks what we would call problem-solving intelligence, such as is exemplified by the highly intelligent raccoon.
There are many reasons to the astounded by the lowly opossum. First, the opossum is an ancient species and is considered a living fossil. The oldest opossum fossils are from the early Miocene (roughly 20 million years old). Very few species have existed virtually unchanged for that long. The opossum is clearly successful. Despite the range of difference in intelligence between the opossum and raccoon, they both are among the most common and successful meso (medium-sized) mammals. Opossums are generalists in both habitat and food habits. These characteristics allow them to exploit numerous and diverse resources, including those created by humans in suburban and urban habitats.
Regarding other unique characteristics, the birth and rearing of young are among the most fascinating and least known. Of course, most of us know that the opossum nurses her young in her pouch, but there are some other amazing details. The gestation period is similar to that of many other small marsupials, at only 12 to 14 days. They give birth to litters of up to 20 young and once born, the tiny, blind, and hairless offspring, which are approximately the size of a navy bean, crawl through their mother’s fur until they reach the pouch and attach to a teat. They remain attached 70 and 125 days, when they finally leave the pouch. However, they do not leave their mother but will often travel on her back.
Opossums are usually solitary and nomadic, which means that they do not have a strict home range area, but rather wander from place to place staying only as long as food and water available. When threatened, they will "play possum," when they essentially play dead and mimic the appearance and smell of a dead animal. They lie stiff, with saliva dripping from their mouths, while they emit a vile and noxious-smelling green substance from their anal glands. It is enough to discourage all but the most desperate predator. What is commonly unknown is that this response to fear and/or danger is physiological and involuntary (similar to fainting), and not a conscious behavior. You can rarely rouse a possum from its “death-like” state. Usually only time allows opossums to return to a conscious state and then they retreat to safety.
However, opossums do not always play “possum,” especially females with young in their pouches and older males. These individuals fight with all their might if handled and it is quite hard to hold on to them and I would never even attempt it without thick gloves. Opossums have very sharp teeth and more of them (50 teeth) than any other North American mammal. Finally, opossums are not long lived. In the field, a 2-year-old opossum is considered old and even in captivity, they seldom live longer than 4 years. Nonetheless, opossums are immune to many wildlife diseases, as well as having some immunity to the venom of poisonous snakes, which they may prey upon. One of the biggest services that they do for us is based on their fastidiousness. When they clean themselves they remove ticks, which they then eat. Some estimates suggest they can eliminate up to 5,000 ticks in a season!
Most of us know that opossums have prehensile tails, and although they can hang upside down by their tail, this is not a common occurrence nor do they sleep in this position. Rather, the opossum uses its tail as a climbing aide. Furthermore, opossums often use their tail to scoup up and carry leaves and other bedding material to their nest. Believe me, I would not have believed this, if I had not seen it for myself! It is one of the most amazing opossum traits that I have observed. Unfortunately, in the northern latitudes, the winters are too cold for the opossum, and they often lose part of their tails and their ears to frostbite.
I hope that I have impressed upon you the unique and wonderous characteristics of our awesome opossum, which is deserving of our respect and admiration.