The “monkey of the mountains”, the Monito del monte, is not a monkey. It is a South American marsupial, and is often referred to as a “living fossil” because it is the only living member of Microbiotheria, an otherwise extinct order. It looks like a large mouse, and has short, silky dense fur, fawn-gray on the top and dirty yellowish-white on the undersides. Females are usually much heavier and longer than males, and are also distinguished, like most other marsupials by their abdominal pouch and the four mammae, where the tiny baby will develop.
Monitos del monte live in south-central Chile, from Concepción southwards to Chiloé Island, and in the east to the mountains a little way beyond the Argentine border. They inhabit dense, cool, humid forests, and prefer thickets of Chilean bamboo.
Monitos del monte seem to live in pairs, at least for the duration of the breeding season. These animals are nocturnal. They are arboreal or adapted to climbing, using their prehensile tails, large paws, and opposable thumbs to climb trees. Monitos del monte sleep in nests made under shelter of overhanging rocks, tree trunks that have fallen or amongst tree roots. The nests are made from water repellent leaves, often covered with warm and protective moss. In the winter when food is scarce and temperatures drop, these animals enter hibernation. Prior to hibernation, the tail’s base swells with a deposit of fat, and the animal’s heart rate slows from 230 beats a minute to fewer than 30 a minute. Monitos del monte communicate using sound. At night they make trilling calls that end with a coughing noise, as well as buzzing noises.
Monitos del monte are mostly insectivorous, and eat insects, larvae and pupae from tree branches and in bark crevices, as well as moths and butterflies. During the austral summer, these animals eat lots of fleshy fruits, such as mistletoe fruits. In captivity, these animals eat a wide range of food, including fruits, meat, fish, vegetables, potatoes, oats, vertebrates, invertebrates, eggs and cheese.
Monitos del monte are monogamous, with one male mating with one female exclusively. The breeding season is August to September. Females will construct a small, rounded nest from water-repellent bamboo and sticks. The nest will be located at a height of 1 to 2 meters. Young are born about 3 or 4 weeks after mating, climb up to the pouch, staying there for about 2 months. Up to 5 in a litter have been observed, but the mothers are unable to feed any more than 4 offspring. At about 5 months, when the young are old enough to leave their pouch, they go to a distinctive nest to be nursed. Then they are carried on their mother’s back. They stay associated with their mother after weaning. Both genders are sexually mature at 1-2 years.
The numbers of Monito del monte have declined over recent years, due to loss of habitat, which was already limited. The species continues to be under threat from urbanization, in terms of the building of highways, hydroelectric complexes and tourism developments.
The global population size of Monito del monte has not been quantified. According to the IUCN Red List, it has been catalogued as a rare species in Chile, due to its reduced population size. This species’ numbers are decreasing and currently it is classified as Near Threatened (NT) on the IUCN Red List.
Within Patagonia’s temperate forests, Monitos del monte are the only animal that disperses the seeds of mistletoe, which pass undamaged through the animal’s digestive tract and are then deposited directly onto host trees. This is very important for the area’s biodiversity. Nearly 100 species of mammals and birds rely on mistletoe for nectar, fruit, and nesting material. Other small mammals may destroy the seeds that they consume, but, Monitos del monte act to disperse seeds from most of the of the fleshy fruit-producing species in their region.