Harem groups of the Jamaican fruit-eating bat (Artibeus jamaicensis) are well-defined units that occupy different crevices in caves. For two consecutive years, we analyzed the non-random associations among female bats and their interactions with other members of the harem. Female members occupying the edges of the harems came from different parts of the cave and were more frequently expelled from the roosting site. Females from the central core of the harem were attacked less often and received more affiliative interactions. Females occupying areas between the central core and the edges were the most active in repelling arriving females and were responsible for grooming the central core females. During the breeding season, aggressive activities decreased and females became more tolerant, which suggests that a potential benefit of roosting together is that it provides for a more suitable place to nurse newborns, because all females produce a better environment, in thermoregulatory ways.