Dromiciops gliroides is an arboreal marsupial found in the temperate forests of South America (36- 43 °S). This species is the sole extant representative of the order Microbiotheria, and is a key seed disperser of many native plant species, including the keystone mistletoe Tristerix corymbosus. Here, we synthesized the current knowledge on the ecological aspects of this species, and compared the available information from Argentina and Chile. Population density (23±2 (mean ± SE) individual/ha) and home range (1.6±0.6 ha) appear to be relatively similar across a marked ecological gradient in the mainland, but lower densities (7±2 individual/ha) and smaller home ranges (0.26±0.04 ha) were detected at island sites.We detected regional variation in body condition in Chile, but there were no significant differences across a wider E-W gradient. Movement patterns fit a random walk model; such behavior might have important consequences in shaping plant's spatial patterns. Although our data sug