Museo Nacional de Costa Rica
Common Opossums - American Opossums

Didelphimorphia (Common Opossums, American Opossums)

ImageFrancisco Durán Biologist, Mastozoology Collection from the National Museum

Didelphimorphia is a group of animals similar to marsupials. Genera Didelphis (common opossum), Philander (gray four-eyed opossum), and Chironectes (water opossum) have a well developed pouch while it is reduced or even absent in other genera, where they keep their offspring even during hatching. Mostly, their tails are long, bare, and prehensile. They are nocturne and lonely animals. They build their burrows with leaves, weeds, and other materials. In Costa Rica, there are about 8 species.

The most popular species is the common opossum ( Didelphys marsupialis ). It can be usually seen in forests, agricultural areas, coffee plantations, villages or wherever it can find edible matter. It can give birth to up to 20 children at once, but only 9 of them survive in the end because that is as many mammalian glands mothers have. It lives from Mexico to Peru. It is hunted as food in some places.

The common opossum or Virginia opossum ( Didelphis virginianus )is very similar to the previous one. It is from the Dry Pacific area. It eats almost everything, like the previous one, too. It can have 7 or more children. It lives from the south of Canada to Costa Rica. Curiously, it fakes dead when it is in danger.

Another species is the gray four-eyed opossum ( Philander opossum ), with its dark gray back and outstanding white spots on its eyes –which give its common name. It lives on trees as well as on the ground and from sea level up to about 1600 m. It is fond of fruits, invertebrates and small vertebrates, such as frogs. It can be found from south Mexico down to Paraguay and some regions in Argentina.

Even another less known species is the brown four-eyed opossum ( Metachirus nudicaudatus ). In Costa Rica, it seems to be more common in the South Pacific, but it can be found in other areas of the country as well, from 0 to 1,200 m (3,937.01 ft) above sea level. It is very shy, goes by on the ground of primary forests looking for insects, eggs or small vertebrates, and also fruits. It can also live in other habitats such as secondary or gallery forests. It can have from 1 to 9 offspring and can be located from Nicaragua to Peru and Argentina, and in some regions in Mexico.

The gorgeous derby's pale-eared woolly opossum ( Caluromys derbianus ) can be found in almost all Costa Rica and from the 0 up to 2,500 m (8,202 ft) above sea level, but especially, in middle lands. Its smooth and thick, red-brownish fur gives its name. It is an athletic climber that looks for fruits, invertebrates, eggs, small vertebrates, and nectar, which make it important as a potential pollinator. It can be found from Mexico to Colombia and Ecuador.

The very interesting water opossum ( Chironectes minimus ) is adapted to a semi-aquatic life and shows adaptations to fit this purpose: rear legs with membrane-joined toes. It used to live in streams nearby San Jose, buy today it is restricted to areas with non-polluted rivers. It is a great fish-catcher. It dives and gets mollusks, fish and maybe aquatic insects. It lives from South Mexico to some of Argentina, and from low lands, up to 2,000 m (6,561 ft) above sea level.

Small opossums ( Marmosa Mexicana and Micoureus alstoni ) are much smaller and hard to see. The former species can be found from Mexico to Costa Rica and from 0 m. to 2,000 m. (6,561 ft). The latter lives from Belize down to Panama and between 0 m and 1,500 m. (4,921 ft) above sea level or more. They search for food in high forest levels or down on the ground. They eat particularly fruits and invertebrates.

Image Gallery