FEATURED STUDENT RESEARCH PAPER Calling behavior of males and females of a Bornean frog with male parental care and possible sex-role reversal Johana Goyes Vallejos 1 & T. Ulmar Grafe 2 & Hanyrol H. Ahmad Sah 2 & Kentwood D. Wells 1 Received: 2 January 2017 /Revised: 2 May 2017 /Accepted: 8 May 2017 # Springer-Verlag Berlin Heidelberg 2017 Abstract In many species that use acoustic signals for mate attraction, males are usually the most vocal sex. In frogs, females typi- cally remain silent, while males produce advertisement calls to attract mates. In some species, females vocalize, but usually as a response to an initial male advertisement call. The smooth guardian frog (Limnonectes palavanensis), found on Borneo, has exclusive paternal care while the females mate and desert after laying the clutch. Males provide care to the eggs until hatching and then they transport the tadpoles to small bodies of water. The vocal repertoire of this species has never been described. Males have a distinctive advertisement call to at- tract females, but produce the call very infrequently. We found that females of L. palavanensis not only respond to male ad- vertisement calls but also vocalize spontaneously, forming lek-like aggregations around a single male. Males may or may not respond to a particular female with a short courtship call, which is elicited only by the female call and not the male advertisement call. The calling rate of females is consistently higher throughout the night compared with the calling rate of males. These observations suggest that this species exhibits a reversal in calling behavior and possibly a sex-role-reversed mating system. Significance statement Exceptional cases of species with a sex-role reversed mating system have been observed in fishes and birds, but not in frogs. For sex-role reversal to occur, there must be intense parental care by the males and a surplus of females. Additionally, females should exhibit characteristics that are usually observed in males in species with conventional sex roles. We found that in L. palavanensis, females are highly vocal, exhibiting higher calling rates compared with the call- ing rates of the males. This behavior, where females out-signal males has not been observed in anurans. This female calling behavior coupled with observations of several females ap- proaching a male provides evidence of a female-biased oper- ational sex ratio, a characteristic of a sex-role-reversed mating system. Thus, this study provides quantitative evidence that L. palavanensis exhibits various aspects consistent with a sex- role reversed mating system. Keywords Female calling . Frogs . Sex-role reversal . Vocal behavior . Calling rate . Limnonectes palavanensis Introduction In most birds, acoustic insects, and frogs, acoustic signals are used to attract or court prospective mates (Andersson 1995; Wagner and Reiser 2000; Gerhardt and Huber 2002; Searcy and Nowicki 2005; Rebar et al. 2009). In most cases, males devote more time and effort to acoustic displays than do fe- males. Nevertheless, there is considerable variation in signal- ing sex roles within and among clades. For example, in pas- serine birds, species with male-only song are common in the Communicated by K. Summers Electronic supplementary material The online version of this article (doi:10.1007/s00265-017-2323-3) contains supplementary material, which is available to authorized users. * Johana Goyes Vallejos johana.goyes@uconn.edu 1 Department of Ecology and Evolutionary Biology, University of Connecticut, 75 N Eagleville Rd. Unit 3043, Storrs, CT 06269, USA 2 Department of Biology, Faculty of Science, Universiti Brunei Darussalam, Gadong 1410, Brunei Darussalam Behav Ecol Sociobiol (2017) 71:95 DOI 10.1007/s00265-017-2323-3