C. Schradin et J. Lamprecht, Female-biased immigration and male peace-keeping in groups of the shell-dwelling cichlid fish Neolamprologus multifasciatus, BEHAV ECO S, 48(3), 2000, pp. 236-242
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.