Data from: A test of male infanticide as a reproductive tactic in a cichlid fish

Infanticide and offspring cannibalism are taxonomically widespread phenomena. In some group-living species, a new dominant individual taking over a group can benefit from infanticide if doing so induces potential mates to become reproductively available sooner. Despite widespread observations of infanticide (i.e. egg cannibalism) among fishes, no study has investigated whether egg cannibalism occurs in fishes as a result of group take-overs, or how this type of cannibalism might be adaptive. Using the cooperatively-breeding cichlid, Neolamprologus pulcher, we tested whether new unrelated males entering the dominant position in a social group were more likely to cannibalize eggs, and whether such cannibalism would shorten the interval until the female’s next spawning. Females spawned again sooner if their broods were removed than if they were cared for. Egg cannibalism occurred frequently after a group take-over event, and was rarer if the original male remained with the group. While dominant breeder females were initially highly aggressive towards newcomer take-over males, the degree of resistance depended on relative body size differences between the new pair, and ultimately, female aggression did not prevent egg cannibalism. Egg cannibalism, however, did not shorten the duration until subsequent spawning, or increase fecundity during subsequent breeding in our laboratory setting. Our results show that infanticide as mediated through group take-overs is a taxonomically widespread behaviour.杀婴行为与后代同类相食是分类学上广泛存在的现象。在部分群居物种中，新的优势个体接管种群后可通过杀婴行为获益——若此举能促使潜在配偶更快进入可繁殖状态。尽管学界已在鱼类中广泛观察到杀婴行为（即卵同类相食），但尚无研究探讨鱼类是否会因种群接管而出现卵同类相食，亦未阐明此类同类相食的适应性机制。本研究以合作繁殖的慈鲷（Neolamprologus pulcher）为实验对象，检验了进入社会群体优势地位的陌生雄性是否更易发生卵同类相食，以及此类相食行为是否会缩短雌鱼下次产卵的间隔时长。相较于卵群得到照料的情况，若卵群被移除，雌鱼会更快再次产卵。种群接管事件后卵同类相食行为频发，而若原雄性仍留在种群中，则此类行为较为少见。尽管作为优势繁殖者的雌鱼最初会对接管种群的陌生雄性表现出极强的攻击性，但抵抗程度取决于新配对个体间的体型相对差异，且最终雌鱼的攻击性并未阻止卵同类相食行为的发生。但在本实验室的实验条件下，卵同类相食并未缩短雌鱼后续产卵的间隔时长，亦未提升后续繁殖的繁殖力。本研究结果表明，由种群接管介导的杀婴行为是一类在分类学上广泛分布的行为。