These lemurs are an arboreal forest dweller. Progression is by walking or running on larger branches, and leaping from tree to tree. Locomotion is more labored and cautious than with other Lemur species. They are crepuscular, being most active from 5:00 pm to 7:00 pm, when their peculiar calls are commonly heard. Vocalizations include an intense roar of alarm, and a powerful, plaintive call for territorial expression. Group sizes can range from 2 to 16. All group members use a common home range, and aggression has been noted between groups. Females form the core of the group, and defend the territory. The weakest social bonds are between males. Grouping patterns change seasonally. Females group in larger numbers during the wet summer, and are more dispersed during the drier winter.