Parental Care and Acoustic Communication of the Smooth Guardian Frog Limnonectes palavanensis, a Bornean Frog With Possible Sex-Role Reversal

Sexual selection theory predicts that the sex contributing most toward the viability of the offspring will become the choosy sex. In most animal species, females have higher parental investment; thus, sexual selection typically acts more strongly on males, making the females choosy. On rare occasions, male parental investment is so high that it limits the potential for additional mating opportunities. In these cases, females compete for males and males become the choosy sex, leading to a sex-role reversed system. The sex-role reversal hypothesis states that males invest more in the offspring that females do, females display sexually selected traits more intensely than males, and females outnumber males in the mating pool, leading to more intense intrasexual competition among females. I characterized the vocal repertoire and parental care behaviors in the smooth guardian frog Limnonectes palavanensis in Brunei Darussalam (Borneo Island) in order to test predictions of the sex-role reversal hypothesis. I found that males perform all parental duties, attending the eggs for 9–11 days, and then transporting the tadpoles on their backs to a suitable deposition site. These deposition sites are scarce, which may increase the number of days it takes a male to return to the mating pool. Choice experiments testing deposition site preferences demonstrated that males do not avoid predators or conspecific tadpoles. In addition, males may split their tadpoles among nearby pools. Moreover, I described the vocal repertoire of male and female L. palavanensis. Males exhibit an advertisement call and a courtship call not previously described for this species. Remarkably, I found that females gather around a calling male and start calling spontaneously at higher rates than those of the males, a behavior not previously reported in anurans. Using playback stimuli, I found that males do not defend territories and lack an aggressive call, however, they exhibit male-male acoustic interference. Females increase their calling rate when a simulated male is present but there was no evidence that they respond differently to female calls. The prolonged male parental care behavior and the calling behavior of L. palavanensis constitute evidence for sex-role reversal in this species