The functional role of sibling aggression and “best of a bad job” strategies in cichlid juveniles

Siblings often compete for limited resources such as food provided by their parents. However, although several functions of non-lethal sibling (non-siblicidal) aggression have been proposed, there is currently little empirical evidence for these, apart from food monopolization. Here, we investigated the functions of non-lethal sibling aggression in the biparental-caring territorial herbivorous cichlid Varibilichromis moorii. We found that the juveniles of this species are highly aggressive and that larger juveniles are more aggressive toward their smaller siblings. Larger juveniles feed on algae more frequently than smaller siblings, thereby indicating a dominance hierarchy. Sibling aggression decreased when algae in the nest was experimentally removed. Furthermore, removal of smaller juveniles decreased sibling aggression among the remaining larger juveniles, whereas removal of larger juveniles increased aggression among smaller juveniles. The algal feeding rate of juveniles only incre...