Male activity under risk predicts paternal care and reproductive success in a bi-parental cichlid

Here, we explored a hypothesis from a framework proposing that sexual selection plays a role in shaping and maintaining consistent among-individual behavioral variation, commonly referred to as personality differences. This framework suggests that parental care may be a mechanism linking personality differences with reproductive fitness. To test this hypothesis, we repeatedly measured boldness as activity under simulated predation risk in male and female rainbow kribs, Pelvicachromis pulcher, a bi-parental West African cichlid. We then formed breeding pairs with varying degrees of behavioral contrast in boldness, recorded parental care (parental activity under risk and brood guarding) for both parents, and assessed key reproductive outcomes: the likelihood to reproduce, clutch size, offspring survival, and offspring size at the end of breeding. We observed consistent among-individual variation in all three behaviors. Males with higher pre-breeding activity under risk were less likely to reproduce. However, when these males did breed successfully, they achieved higher offspring survival rates compared to their less active counterparts. This relationship was mediated by parental care: males with higher pre-breeding activity under risk spent more time guarding their brood, and increased brood guarding was associated with higher offspring survival. Female pre-breeding activity under risk was not associated with parental care or reproductive success. These results suggest that male, but not female boldness might be subject to sexual selection. The observed pattern of bold males siring fewer but larger broods than less bold males could maintain among-individual variation in male boldness if it results in equal average fitness (eg due to environmental heterogeneity).