Sex differences in the effect of social status on the growth of subordinates in a co-operatively breeding cichlid

Social influences on the growth of the co-operatively breeding cichlid Neolamprologus pulcher were studied by examining the size structure of existing laboratory groups and the responses of males and females to removals of higher-ranked fish, which created larger size differences with more dominant fish. The size differences between adjacently ranked group members were predicted to differ from expected based on random size distributions of group members. Both males and females were predicted to respond to removals by increasing growth rate. In previously established groups, the size difference between dominant and highest-ranked subordinate males was greater than expected based on random group-assembly rules. The size difference between dominant and subordinate females did not differ from the null expectation. Third-ranked subordinate males increased their growth rate upon moving up one place in the dominance hierarchy (after the removal of higher-ranking fish) relative to fish that did not change rank. Contrary to predictions, however, females did not increase growth upon increasing rank. # 2008 The Authors