From cannibal to caregiver: tracking the transition in a cichlid fish

Although the consumption of one's own offspring is often viewed as maladaptive, under some circumstances this behaviour can be a beneficial way to terminate parental care. When the costs of providing care are extremely high or the benefits of performing care are especially low, parents will sometimes cannibalize their own young, which is called filial cannibalism. This behaviour enables them to cease to care while recouping lost energy. Most studies examining the link between the cost/benefit ratio of care and filial cannibalism have focused on species with male-only care. In contrast, filial cannibalism in biparental caring species has been studied only rarely. To increase our understanding of filial cannibalism in biparental species and examine the transition from cannibal to caring parent, we conducted four experiments with Neolamprologus caudopunctatus, a biparental cichlid fish from Lake Tanganyika, Africa. First, in experiment 1 we show that the establishment of a pair bond and nest construction did not inhibit cannibalism of foreign eggs. Second, in experiment 2 we removed eggs from parents for various durations and showed that the act of spawning and the presence of the parents' own brood nearly always maintained care and inhibited cannibalism. Third, parents did not discriminate between their own and foreign broods of eggs or hatched young when supplied with complete or with half-cross-fostered young (experiments 3 and 4). Atypically, across all experiments cannibalism was mostly performed by the female. Taken together, our results trace the behavioural transition from egg consumer to egg carer in this biparental species and expand our understanding of cannibalism to biparental species.