Brazilian gracile opossum habitats than more purely arboreal animals. It has also been found in artificial plantations. There are no recognised subspecies. Brazilian gracile opossums are arboreal and nocturnal, spending the day nesting in tree hollows. They are solitary animals, with each individual inhabiting a home range of anything from , depending on habitat. Males tend to have larger home ranges than females, presumably because, being larger, they require more food. The species is insectivorous, and is an opportunistic forager, not specialising in any particular kind of insect. Individuals have also been reported to eat some spiders, snails, and even fruit (including passionfruit).
Sexual dimorphism in non-human primates to the likelihood of higher vulnerability to predators. Another hypothesis suggests that arboreal primates have limitations on their upper body size, given that larger body size could disrupt their usage of terminal branches for locomotion. However, among some species of guenons ("Cercopithecus"), arboreal blue monkeys ("C. mitis") appear to be more sexually dimorphic than terrestrial vervet monkeys ("C. aethiops"). It has been hypothesized that niche divergence between the sexes attributes to the evolution of size dimorphism in primates. Males and females are known to have different preferences for ecological habitat due to different reproductive activities, which could possibly lead to