The Water opossum is a semiaquatic marsupial found in the Americas. Its fur is in a marbled grey and black pattern, while the muzzle, eyestripe, and crown are all black. A light band runs across the forehead anterior to the ears, which are rounded and naked. There are sensory facial bristles in tufts above each eye, as well as whiskers. The Water opossum's tail furred and black at the base is yellow or white at its end. Its hind feet are webbed, while the forefeet ("hands") are not. The forefeet can be used to feel for and grab prey as the animal swims, propelled by its tail and webbed back feet.
Water opossums are found from Mexico through Central and South America to Argentina. They live in and near freshwater streams, lakes, rivers, and other bodies of water in tropical moist forests.
Water opossums are solitary creatures. They live in bankside burrows, emerging after dusk to swim and search for prey, which they eat on the bank. These are excellent swimmers and divers; their broad webbed hind feet are used for propulsion through water, moving with alternate strokes. The hindfeet are symmetrical as well, which distributes force equally along both borders of the webbing; this increases the efficiency of the Water opossum's movement through the water. The long tail of these animals also helps them in swimming. When threatened, Water opossums usually jump into the water and often this way escape predation.
Water opossums are polygynandrous (promiscuous) which means that both the males and the females have multiple partners. They usually breed in December. After the gestation period of 12-14 days, the female gives birth to a litter of 1-5 young in the nest. The newly born offspring climb to the mother's pouch, where they begin nursing. By 22 days the young are beginning to show some fur, and by 40 days or so their eyes are open. At 48 days of age, the young opossums detach from the nipples, but they still nurse and sleep with the mother.
The main threats to Water opossums include the loss of suitable habitat due to deforestation and pollution of freshwater ecosystems.
According to IUCN, the Water opossum is locally common throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.