This animal is marsupial carnivore, the descendant of the southern opossum (Didelphis albiventris), ecological analogue of clambering weasels. It lives in woods of a temperate zone of South America. Length of a body is up to 30 cm, length of a tenacious tail - 25 - 30 cm. The animal is adapted to clambering habit of life, can make long jumps from tree to tree and easily runs on trunks upwards and downwards. Paws are short, tenacious, mobile in joints (so, foot can be easily turned back as at the squirrel), the thumb is opposed the others. On all fingers there are long bent claws. The claw on the big toe has a comb-shaped structure, it is intended for a care of fur. Skull low, the muzzle part is extended in length. Ears are short, jut out wool only a little. The wool is rich, it covers the top part of hands and feet and also almost all tail (excepting the strip on its bottom side); colouring of a body is brown with cross light grey strips on shoulders and sides, above eyes there are rounded light spots, throat and chest are white. It is the solitary predator eating small mammals and birds. In summer animal includes in a ration vegetative food: fruits and berries, oily seeds. Pairing usually occurs in middle of winter though in cold years it can proceed closer to spring. Pregnancy can be delayed because of pausing of development of embryos. Usually underdeveloped cubs (8 - 10) are born in the beginning of spring. About 9 weeks they spend in female’s marsupium, later getting to her back (usually to this time no more than 3 - 5 cubs survives). From 11-week age the female accustoms them to meat food. Youngsters keep with mother up to the end of summer, training to hunt. Later mother expels them from the territory.