Female-biased immigration and male peace-keeping in groups of the shell-dwelling cichlid fish Neolamprologus multifasciatus

The small cichlid fish Neolamprologus multifasciatus is endemic to Lake Tan ganyika and is unique among fish because it lives in complex social groups with several reproductive males and females, all of which participate in de fending their territory against neighbors and intruders. Individuals use em pty snail shells for breeding and shelter. Previous parentage analysis usin g microsatellites suggested occasional exchange of individuals between grou ps. In field experiments, we found that females showed a higher tendency th an males to migrate into territories already occupied by a resident pair. T he phenomenon and causes of female-biased immigration were further investig ated in aquarium experiments: Nine of 15 females, but only 2 of 15 equally sized males, settled in territories of established pairs. Territorial males exhibited more aggression toward strange males (potential reproductive com petitors) than toward strange females (potential additional mates); their f emales were more aggressive toward strange females (probably competitors fo r shells) than toward strange males. Apparently, a conflict exists between the sexes regarding the immigration of additional females. This conflict se ems to be the selective basis for observed active male interference in aggr essive disputes between females in the territory. Interfemale tolerance in a group was greater in the male's presence than in his absence.