Didelphis — genus of large American opossums

Characteristics

Animals in this genus are notable for a set of shared physical and behavioral traits: a prehensile tail able to grasp branches, an opposable hallux on the hind feet, coarse fur, and an omnivorous dentition. Females possess a pouch (marsupium) in which the undeveloped young complete early development; the offspring are commonly called joeys. Didelphis species are largely nocturnal and solitary, feeding on fruit, invertebrates, small vertebrates and carrion.

Evolution and distribution

Didelphimorphia is one of the most ancient marsupial lineages, with fossil records that place their origin deep in the Cenozoic. The genus Didelphis diversified in South America, and at least one species expanded its range northward after land connections formed between continents. Today members of the genus occupy varied ecosystems, demonstrating adaptability to both wild and modified environments.

Ecological role and human interactions

Didelphis opossums play useful ecological roles as scavengers and seed dispersers and help reduce populations of pest insects and rodents. They are sometimes tolerated in urban settings because they consume refuse and pests, though they can create conflict when nesting in buildings. Opossums are subjects of ecological and medical research because of traits such as a relatively high number of teeth (often cited as up to fifty) and varying tolerance to some snake venoms.

Notable facts and distinctions

• Common confusion: North American "opossums" are distinct from Australasian "possums," which are unrelated marsupials with different biology.
• Behavior: some Didelphis species exhibit thanatosis, commonly called "playing dead," as a defensive response.
• Diversity: the genus contains multiple species; for an authoritative list see Species.

Overall, Didelphis species are recognizable, adaptable marsupials that illustrate both the antiquity of marsupial lineages in the Americas and the ecological roles medium-sized omnivores play in continental ecosystems.