Predator burden and past investment affect brood abandonment decisions in a parental care-providing teleost

Reproductive success of parental care-providing species is contingent upon the level of parental investment into a brood. When the expected fitness contribution of a brood is outweighed by the costs of parental care (e.g. decreasing parent somatic condition), an individual may reduce its level of care, or may altogether abandon a brood in trade-off for potential future reproductive success. Leading parental care hypotheses have established parental stress, oxidative stress, nutrition and androgen condition, as well as reproductive value and the threat of brood depredation, as drivers of investment into parental care. The concomitant effects of parent physiological condition and the threat of brood depredation have yet to be considered in their direct effect on the reproductive success of a parental care-providing individual. Using largemouth bass (Micropterus salmoides) as a model parental care-providing species, we investigated the relative influence of these factors, together, on a direct fitness measure: the decision by a parent to abandon its brood. By employing a novel combination of multivariate and information-theoretic modelling, our findings indicate that reproductive success of parental largemouth bass is contingent primarily on the threat of depredation to a brood (i.e. the density of brood predators adjacent to nest locations), past investment into a brood and reproductive value of the brood. Parent physiological condition had limited influence on the decision by largemouth bass to abandon parental care. Modelling indicated that parental circulating androgen concentration and antioxidant capacity may play a minimal role in driving brood abandonment; nutrition and stress condition of the parent did not differ between reproductive outcomes. Findings here suggest that a holistic approach should be implemented when studying parental care and that a definite experimental endpoint, e.g., brood abandonment or reproductive success, be utilized as a direct metric of the cost to fitness of parental care decisions.