Ruffed lemurs appear to have a variable social system which changes depending on the season and the quality of their habitat. In some areas of Madagascar, the animals are found in small groups of two to five individuals, with a home range of 25 ha. In other areas, loose affiliations of between 18 and 32 animals occupy home ranges around 60 ha in size. All group members use a common core home range, and groups are occasionally aggressive towards other groups at the borders of these territories. There is a strong correlation between the location of home ranges and the location of the largest fruiting trees in the area. Females are the driving force in group dynamics and are always dominant to males. Ruffed lemurs will form larger groups during the wet season when food is plentiful, and disperse during the dry season in search of scarcer fruit. When foraging for fruit, large groups might fragment completely as individuals go their separate ways, which is in striking contrast to other diurnal lemurs which always forage and move through the forest together as cohesive groups.
Ruffed lemurs are among the most vocal of the non-human primates. Their raucous, barking vocalizations might serve several purposes: they allow distant members of the same group to maintain contact with each other even when they are foraging separately, they warn would-be competitors of territory already occupied, and they might also serve to alert other group members of the presence of an aerial or ground predator. Natural predators that can trigger alarms in Madagascar include boa constrictors, eagles and hawks, and the fossa (a weasel-like animal found only on Madagascar). One individual ruffed lemur can set off an alarm call that will alert even the farthest ranging group members.
As many as twelve different ruffed lemur calls have been recorded at the Duke Lemur Center, and each call has a different meaning to the lemurs. Scent marking is another means of communication strongly utilized by the ruffed lemurs.