Didelphis marsupialis
southern opossum

The range of the southern opossum extends from eastern Mexico to northeastern Argentina (Redford and Eisenberg, 1992).

Didelphis marsupialis tolerates a variety of habitat types including primary and secondary forests, coffee plantations, urban and suburban area (Elizondo C, 1999), but are not found at elevations above 2,232 m or in arid regions. Didelphis marsupialis is replaced by its close relative, Didelphis albiventris (white-eared Opossum), in montane regions of northern South America (Eisenberg, 1989).

There is considerable color variation in southern opossums. Generally there are varying degrees of black in the dorsal pelage, while the ventral side is white. This species is similar to D. albiventris, but has a darker dorsal pelage and black ears. Females are generally smaller than males (Cerqueira, 2000). The length of the head and body ranges from 263mm to 430 mm, with a tail length ranging from 295mm to 450 mm (Elizondo, 1999). Males are larger than females.

See Reproduction.

Males mark territories more heavily with saliva prior to the breeding season. Females construct leafy nests for their new families. (Eisenberg, 1989; Eisenberg and Redford, 1992) Mating is most likely polygynous, with males mating those females present in their territories.

Mating season begins in January, with males marking their home range more heavily with saliva and females building leaf nests in tree cavities or burrows. In captivity it has been reported that females can have an average litter size of ten, and up to three litters have been reported in one year. Also, the smallest litter sizes are found near the equator.

The young are born naked and blind and on average weigh about 0.005 oz and measure 10 mm in length. This amazingly small body size means that twenty four newborns can fit into a teaspoon! The newborns must find their way to their mother's marsupium or pouch. They can only move with their forelegs, which are more developed than their hind legs. There are two theories as to how the newborns find their way to the marsupium. The first, and best supported, theory is that newborns find their way to the marsupium by smell. Before birth the mother will lick a path to the opening of the pouch so that the young can follow the trail. The second theory is that the young find their way to the pouch through gravity. Once the newborns have found the marsupium, they attach to the teats, which then swell at the tip preventing the newborns from falling off. The young grow rapidly and are ready to leave the marsupium after about sixty days. (Parker, 1990)

The young are weaned around 100 days. The young reach sexual maturity between 8 and 12 months of age. (Eisenberg, 1989; Eisenberg and Redford, 1992)

The female cares for the young in her marsupium, or pouch, for 60 days. The young are not weaned until they are about 100 days old. (Eisenberg, 1989; Eisenberg and Redford, 1992)

These animals probably do not live that long in the wild. It has been reported that they usually live about two years in their natural habitat, but they can live up to seven years in captivity.

Didelphis marsupialis is solitary except during the breeding season. These opossums navigate mainly by olfaction and touch. They climb well but frequently forage on the ground, and seek refuge in hollow trees, a den under roots, or holes in the ground. They do not actively defend a specific area or territory. When home ranges overlap, each animal (usually males) will mark the area with urine, droppings and saliva. Southern opossums typically avoid one another, and if males come into contact, they become aggressive. Threatening behavior begins with the mouth opening, and is followed by hissing, growling, and finally snapping. Females are more sedentary than males. Southern opossums can't maintain body warmth below an environmental temperature of minus seven degrees celsius. During cold spells, these opossums will sleep in dens, but they do not hibernate. (Eisenberg, 1989)

Southern opossums are omnivorous and will eat a large variety of food. In captivity they especially like bananas. They are opportunistic feeders and will readily shift home ranges in search of food. Feeding habits of males and females do not differ significantly, but there are differences in food preferences between young and old. Younger individuals primarily consume invertebrates, fruits, and plant remains, whereas older individuals consume all of these, as well as mammals and birds.

Foods eaten include: insects, frogs, birds, small mammals, earthworms, fruits and plant remains.

(Cordero and Nicolas, 1987)

The most well-known adaptation for evading predators is known as "playing dead" or "playing opossum." An opossums will lie on its side as if dead with its tails rolled up, eyes and mouth open, and its paws partially closed. (Parker, 1990) Common predators of southern opossums include owls, snakes, and mammalian carnivores.

Didelphis marsupialis plays an important role in food webs. Because of its feeding habits, this species is likely to be important in controlling populations of small mammals and invertebrates. Because it is a prey species, it also plays an important role in regulating populations of owls and small, mammalian carnivores.

No reported positive effects on humans exist.

In Venezuela, D. marsupialis is an important host for the parasite Trypanosoma cruzi, which is the source for the human illness known as Chagas Disease (Eisenberg, 1989).

This species has no special conservation status.