Chemical Communication in Archaic New Zealand Frogs

Abstract

The most archaic lineages of frogs, represented by the New Zealand family Leiopelmatidae, communicate by chemical rather than bioacoustic signals. We analyzed how chemical signatures mediate social recognition in Hamilton’s frog, Leiopelma hamiltoni. In the wild, Hamilton’s frogs live 40 years or more, rarely moving outside small (<25 m2), well-defined home ranges. At night, individuals travel slowly above ground around their home ranges and return to diurnal refuges as morning approaches. We collected frogs, held them in captivity for 72 h, and then tested their preferences for substrates that they had marked themselves to those marked by conspecifics. Individuals showed evidence of self-recognition as they spent more time on their own substrates than on those marked by frogs collected from other home ranges. This social discrimination was strongest when subjects were presented chemical cues of conspecifics from home ranges that did not overlap with their own. Next, we collected samples of skin secretions, urine, and feces from subjects, and we examined their saliency as signals of individual identity. Skin secretions were most effective in eliciting self-recognition, as subjects readily discriminated between their own odors and those of conspecifics when exposed only to secretions swabbed from the skin. Subjects also discriminated between substrates marked by self and nonself urine. However, subjects did not consistently discriminate between their own feces and those of conspecifics. Our findings raise the possibility that chemical communication may complement bioacoustic signaling abilities to serve a variety of social functions in anuran amphibians.