Female Túngara Frogs Discriminate against the Call of Males Infected by Chytridiomycosis

Abstract

Species worldwide are disappearing in the most devastating mass extinction in human history and one of the six most profound extinctions in the history of life. Amphibians are greatly affected, approximately one third of living species are threatened, and many others are extinct. One of the main causes of amphibian species extinctions and population declines is the emerging infectious disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd). Although some species are somewhat tolerant of the disease, the non-lethal effects of the infection with Bd and their short or long term consequences are poorly understood. In these species there is the potential for behavioral responses to mitigate the spread of the fungus. Here we show that in túngara frogs, infection status influences the males’ mating calls. These infection-induced changes in the quality of males’ mating calls ultimately reduce the calls’ attractiveness to females making females less likely to respond to and thus mate with infected males. More broadly, our results imply that females might avoid mating with disease-infected males by assessing the acoustic signal only, and that such recruitment of behavioral responses might potentially ameliorate some of the effects of this sixth mass extinction. Lay summary Chytridiomycosis is an amphibian disease well known for its lethal effects. Túngara frogs are infected in nature, but seem to be resistant to the disease. Here we show that chytridiomycosis has non-lethal behavioral effects on túngara frogs. Females discriminate against infected males by assessing only their acoustic signal. The mating call of a male that is not infected with the disease is more attractive to females than the call of that same male when he is infected.