The costs of being a good dad: egg-carrying and clutch size impair locomotor performance in male midwife toads (Alytes obstetricans)

Abstract

Abstract Parental care is widespread across the animal kingdom. Parental behaviours are beneficial by increasing offspring survival but induce significant costs to the parents. Because parental care is far more common in females, the associated reproductive costs have been largely studied in this sex. Although male parental care is likely to involve significant costs, it has been markedly less well investigated. We studied the costs of egg-carrying on locomotor performance in an amphibian species (Alytes obstetricans) with male parental care. We examined complementary parameters including hopping performance, righting response, hindleg muscle response to egg burden, and homing time in males carrying or not carrying eggs. We found that carrying males showed altered locomotor performance for most traits. In addition, alteration of performance was closely related to relative clutch size. Clutch desertion occurred in smaller individuals carrying larger relative clutch mass, and performance after desertion was similar to that of non-reproductive individuals. Overall, our study demonstrates that carrying eggs significantly alters male mobility and that performance–clutch size trade-offs are relevant in understanding the evolution of paternal care.