Terrestrial toadlets use chemosignals to recognise conspecifics, locate mates and strategically adjust calling behaviour

Among anuran amphibians evidence for chemical communication is scarce. We carried out three experiments to evaluate whether chemosignals influence the sexual behaviour of an Australian terrestrial toadlet, Pseudophryne bibronii. Substrate choice trials (experiment 1) revealed that females preferred to associate with substrate marked by either sex rather than an unmarked substrate and that males preferred substrate marked by females, but avoided substrate marked by other males. These results suggest that the odour of both sexes functions as a sexual attractant and that male odour may also function to repel potential male competitors. In experiment 2 we assessed whether females use male chemosignals during mate location by making gravid females navigate a two-choice Y-maze to reach calling males. Almost invariably, females followed a path outlined with male gland secretions. This result indicates that male chemosignals combined with acoustic signals improve the ability of females to find nest sites. In experiment 3 we tested whether conspecific odour influences the callingbehaviour of nesting males. Female odour stimulated a twofold increase in advertisement calling and male odour stimulated a switch to territorial calling. These findings indicate that nesting males use conspecific odour as a cue for regulating investment in acoustic courtship and territory defence. Our results advance a small body of evidence to suggest that anurans use chemosignals to identify and locate potential mates and provide the first demonstration that odour can influence anuran callingbehaviour.