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...同胞幼体间常会争夺亲代提供的有限资源（如食物）。尽管已有多项研究提出非致命性同胞攻击（non-siblicidal，即不引发死亡的同胞争斗）的潜在功能，但目前除食物垄断假说外，相关实证证据仍极为匮乏。本研究以双亲抚育、具有领地性的植食性慈鲷（Varibilichromis moorii）为研究对象，探究其非致命性同胞攻击的功能。研究发现，该物种的幼体极具攻击性，且体型更大的幼体对体型较小的同胞表现出更强的攻击性；体型更大的幼体取食藻类的频率高于体型较小的同胞，这表明群体中存在优势等级。实验移除巢内藻类后，同胞攻击行为有所减少。此外，移除体型较小的幼体会降低剩余体型较大幼体间的同胞攻击行为，而移除体型较大的幼体则会提升体型较小幼体间的攻击性。幼体的藻类取食率仅会...