Marsupials originated in the Americas and reached Australia through Antarctica when the three continents were joined. Dromiciops is the last living member of Microbiotheria, a lineage that separated early and whose closest relatives are the Australian orders. Fossil microbiotheres are known from South America and from Antarctic deposits on Seymour Island, which fits the dispersal route.
Its ecology is South American, and central to its forest. The monito del monte is the principal, and for the mistletoe Tristerix corymbosus effectively the only, disperser of several plant seeds; the mistletoe germinates poorly unless the seeds have passed through this animal, so the plant's reproduction depends on a single marsupial species.
It also hibernates. Individuals fatten the base of the tail, then enter torpor for extended periods through winter, with body temperature tracking ambient. The Spanish name means little mountain monkey, a reference to its climbing rather than to any relationship with primates.