The confusion between the terms “opossum” and “possum” is a linguistic accident that obscures a major biological separation. Both are marsupials—mammals that raise their underdeveloped young in a pouch—but they represent two entirely distinct evolutionary branches. American opossums and Australian possums have been evolving independently on separate continents for millions of years. Understanding the difference requires looking at their geographic origins, physical traits, and ecological roles.
The Linguistic and Geographic Split
The term “opossum,” spelled with the initial ‘O,’ refers exclusively to marsupials of the order Didelphimorphia, which are native to the Americas, spanning from South America up into North America. This name is derived from apassum, a word from the Algonquian language of the Virginia Indians, which roughly translates to “white animal.” The American opossum was the first marsupial encountered and named by European colonists in the New World.
The term “possum,” without the initial ‘O,’ refers to the marsupials of the suborder Phalangeriformes, which are found only in Australia, New Guinea, and surrounding islands. These Australian animals were named “possums” by early English settlers, who noted a superficial resemblance to the American opossum. Australian possums belong to the order Diprotodontia, which includes kangaroos and wombats, making them only distantly related to their American namesakes.
Key Physical Distinctions
The physical differences between the American opossum and the Australian possum are immediately noticeable. The American opossum typically has a long, hairless, and scaly tail, which is fully prehensile and used for gripping branches. In contrast, most Australian possums possess a tail that is fully or partially covered in dense fur, often having a distinctly bushy appearance.
American opossums have large, thin, naked ears and their body is covered in coarse, shaggy fur that is usually a grayish-white color. Australian possums generally have softer, denser fur, ranging from golden-brown to silver-gray, with smaller, often furred ears. The American species has an elongated, pointed snout, while Australian possums often have a rounder face with larger, more prominent eyes. Opossums possess a full set of 50 teeth, while Australian possums, being diprotodonts, have a characteristic pair of large, forward-jutting incisors.
Ecological and Behavioral Divergence
The American opossum is a highly adaptable, generalist omnivore and scavenger, consuming a wide range of foods including fruits, insects, eggs, and carrion. This scavenging lifestyle means they spend a significant amount of time foraging on the ground. They are semi-arboreal and utilize their prehensile tail for climbing.
Australian possums are primarily specialized arboreal species, highly adapted to life in trees, and rarely descend to the ground. Their diet consists mainly of leaves, flowers, nectar, and fruits, classifying them as herbivores or specialized omnivores. The American opossum’s famous defense mechanism is “playing dead,” or tonic immobility, which is not characteristic of Australian possums. American opossums have large litters, with young often riding on the mother’s back, while Australian possums typically give birth to only one or two young.