Do maternal food deprivation and offspring predator cues interactively affect maternal effort in fish?

The state of the environment parents are exposed to during reproduction can either facilitate or impair their ability to take care of their young. Thus, the environmental conditions experienced by parents can have a transgenerational impact on offspring phenotype and survival. Parental energetic needs and the variance in offspring predation risk have both been recognized as important factors influencing the quality and amount of parental care, but surprisingly, they are rarely manipulated simultaneously to investigate how parents adjust care to these potentially conflicting demands. In the maternally mouthbrooding cichlid Simochromis pleurospilus , we manipulated female body condition before spawning and exposure to offspring predator cues during brood care in a two‐by‐two factorial experiment. Subsequently, we measured the duration of brood care and the number and size of the released young. Furthermore, we stimulated females to take up their young by staged predator attacks and recorded the time before the young were released again. We found that food‐deprived females produced smaller young and engaged less in brood care behaviour than well‐nourished females. Final brood size and, related to this, female protective behaviour were interactively determined by nutritional state and predator exposure: well‐nourished females without a predator encounter had smaller broods than all other females and at the same time were least likely to take up their young after a simulated predator attack. We discuss several mechanisms by which predator exposure and maternal nutrition might have influenced brood and offspring size. Our results highlight the importance to investigate the selective forces on parents and offspring in combination, if we aim to understand reproductive strategies.