Mate-guarding behaviour in anurans: intrasexual selection and the evolution of prolonged amplexus in the harlequin toad Atelopus laetissimus

The term 'mate guarding' refers to the monopolization of the reproductive potential of a conspecific. Mate guarding has been recorded in invertebrates and vertebrates, but is poorly known in anuran amphibians (frogs and toads), the terrestrial vertebrates with the highest diversity of reproductive modes. Mate guarding in anurans may consist of a prolonged amplexus or copulatory clasping by the male starting well before egg laying. In this study we combined field observations and experimental studies of the Santa Marta harlequin toad, Atelopus laetissimus, to elucidate whether prolonged amplexus (more than 1 month) in A. laetissimus evolved as a mate-guarding strategy promoted by intense intrasexual selection in males engaging in amplexus displacement attempts. First, we asked how the ability of a male to successfully defend its amplexus status against interlopers is related to body condition and 13 other morphological traits. Second, we tested whether the following characteristics were associated with mating success and mate guarding in A. laetissimus: clasp force, amplexus duration and male reproductive effort. Under natural conditions, amplectant males had significantly higher body condition, were larger and had wider forearms relative to unmated males. In trials, successful mate guarding in A. laetissimus was associated positively with body condition and clasp force, yet the overall probability of successful displacement of amplectant males was low (< 0.20). Our results support the hypothesis that intrasexual selection in A. laetissimus favours mating success of males that clasp females sooner, even before females are ready for breeding. (c) 2021 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the origin and mate-guarding strategy of prolonged amplexus behavior in the Santa Marta harlequin toad. The results suggest that body condition and clasp force are positively associated with successful mate guarding, but the overall probability of successfully displacing amplectant males is low.