Sexual selection in the tortoise Chelonoidis denticulata: Dominant partner or healthy partner?

Abstract

Sexual selection consists of differential reproductive success due to individuals choosing mates who provide more direct or indirect benefits. When partners present conflicting advantages, it is unclear how animals decide with whom to reproduce. Chelonoidis denticulata have a hierarchical society defined by ritualized fighting whose winners have access to limiting resources, however, they also harbor large amounts of ticks, which cause diseases and can affect partners’ choice. In this study we tested which is more important in mate choice: dominance hierarchy or parasite biomass. We observed 57 individuals kept in semi-captivity; compared mating success in different hierarchical levels and ectoparasite load. Successful males were not more dominant, but had fewer parasites. We conclude that, when parasitism and hierarchy are in conflict, female tortoises choose a healthy partner over a dominant male.