Group sizes of up to 29 individuals have been observed for common brown lemurs and collared lemurs. Sanford's lemurs live in groups of up to 15 animals although the average seems to be 3 - 9 individuals. Grooming is a way for E. fulvus to establish and maintain social bonds. Their unique method of grooming is a result of their 6 lower procumbent teeth that form a dental comb. This instrument is used to groom their own fur and that of the other members in the group.
Communication is achieved by both olfactory and vocal means.
Olfactory communication is extremely important and is made possible by the scent glands located at the wrist throat. This type of communication is used for transmitting physical state, location, and individual recognition. The sounds brown lemurs use for vocal communication have been described and partly deciphered. A nasal sound used in maintaining group cohesion has been described as 'ohn'. A 'cree' or high pitched sound is used as a territorial call, and 'Crou' is the alarm call of this lemur.