Many marsupials commonly referred to as “possums” have long tails, but the animal most associated with this feature is the North American Opossum. The long tail is a defining characteristic, often appearing hairless and robustly built for grasping objects. This feature is a significant adaptation that allows these animals to navigate their arboreal environments. The structure and function of the tail vary greatly across the different species, requiring a distinction between the two groups of marsupials.
Defining the Difference: Opossum vs. Possum
The confusion surrounding the name stems from a taxonomic mix-up centuries ago, but the two groups are distinct. The animal native to the Americas is correctly termed the Opossum, belonging to the order Didelphimorphia, and is the only marsupial found north of Mexico. The word “opossum” derives from the Algonquian word wapathemwa, meaning “white animal.”
The term “possum” refers to the approximately 70 species of marsupials found in Australia, New Guinea, and surrounding islands. These Australian species belong to the order Diprotodontia, which also includes kangaroos and koalas, making them only distantly related to their American namesakes. The Australian animals were given the similar name by Sir Joseph Banks because he thought they resembled the American Opossum. In North America, people frequently drop the initial “O,” using “possum” as a colloquial shorthand for the Virginia Opossum.
Anatomy and Function of the North American Opossum’s Tail
The North American Opossum (Didelphis virginiana) possesses a long, thick, and highly muscular tail that can be nearly as long as its body, adding up to 21 inches to the animal’s total length. This appendage is mostly hairless and features scutes, which are scale-like plates, on its surface. This structure makes the tail flexible and durable.
The tail is prehensile, meaning it is capable of grasping and wrapping around objects, effectively serving as a fifth limb. This capability is used for maintaining balance while climbing, stabilizing the animal on branches, and assisting in locomotion. Opossums also use the tail to carry nesting materials, such as leaves and sticks, back to their den.
While the tail is strong, the common image of an adult opossum hanging by its tail for long periods is largely a myth. Juvenile opossums frequently exhibit this behavior, but the tail of a mature adult is primarily used for stability and grasping rather than supporting the full weight of the animal for extended time. The strength is concentrated in the muscles at the base, allowing for precise control and grip.
The Diverse Tails of Australian Possums
Australian possums display a greater variety of tail types, demonstrating that the long, naked tail is not a universal trait for all “possums.” The Common Brushtail Possum (Trichosurus vulpecula) has a long, bushy, and heavily furred tail, which is partially prehensile. This tail is often used as a counterbalance and a prop, aiding stability when the possum is navigating branches.
In contrast, the Common Ringtail Possum (Pseudocheirus peregrinus) has a long, slender tail that is fully prehensile and often ends with a distinctive white tip. This species is highly arboreal and uses its tail constantly, employing a friction pad on the underside to help cling to branches. Some specialized species, like the Yellow-bellied Glider, have long, sparsely furred tails that function as rudders, helping to steer the animal while gliding through the air.