Adaptive Choice of Reproductive Microhabitat and Its Potential for Sexual Conflict in Túngara Frogs

Reproductive habitat selection—deciding where to mate and where to raise offspring—is a critical component of successful reproduction. Parents selecting sites to signal to or search for mates may, e.g., experience strong predation pressure, whereas their offspring may have to compete for food. Here we assessed how the presence of vegetation cover affects site selection for signaling and oviposition by Túngara Frogs (Engystomops pustulosus) and how this choice influences reproductive output in terms of tadpole survival and growth. We found males to call more often from artificial puddles covered with vegetation compared to open puddles in a large-scale field experiment. A follow-up mesocosm experiment revealed the pattern observed in the field to be the result of an active choice and not caused by selective predation. We found that the presence of foam nests was not related to vegetation cover, suggesting that some females actively move away from male call sites. Finally, we found tadpoles to grow heavier in vegetated compared to open puddles in a small-scale experiment. Our data show that male frogs prefer to display from vegetated sites, most likely to reduce risk of predation by eavesdropping predators, such as frog-eating bats. Alternatively, males prefer to call from vegetated sites to improve their offspring development and survival, although choice of breeding site appears to be largely under control of females. Call site choice thus appears to provide some adaptive benefits to males in terms of survival, whereas oviposition choice does not provide females with better developmental conditions for their offspring. Active avoidance of sites with calling males may, however, reduce tadpole competition, but future studies should reveal to what extend puddle quality is weighted against competition in female breeding choices. Our findings reveal that breeding site choice differs across the important life-history stages of mating and oviposition, and we argue that this can have important consequences for any conflict between the sexes.