Equally at home high amongst the branches of a tree as on the forest floor (4), the southern giant slender-tailed cloud rat is a slow-moving animal (5), that is only active at night, spending the day in hollow trees or logs (10). It usually lives singly, or in pairs consisting of an adult male and female, or a female and her young, but larger groups have also been seen (6). Their diet consists primarily of tender, young leaves (6), but fruit is also reportedly eaten (2).
The southern giant slender-tailed cloud rat typically gives birth to a single young each year, with data indicating that most births take place during the late rainy season (6). The young is born in the hollow of a standing or fallen tree, or in a hole in the ground (8). The mother carries her young firmly attached to a nipple. In captivity, one cloud rat lived for over 13 years (5).