Because so many amphibians are vocal, they have been important study organisms to understand why females prefer exaggerated male mating displays, and a recent study combined mating displays with questions of disease ecology and evolutionary biology. Specifically Messersmith et al (2024) tested the Hamilton-Zuk hypothesis that the expression of mating displays is limited by parasitism and females prefer parasite-resistant males. Their study used Pacific treefrogs (Pseudacris regilla) and natural infections by the fungal pathogen Batrachochytrium dendrobatidis (Bd), to test whether (1) call properties, correlate with Bd infection, and (2) whether females discriminate against highly infected males based on the properties of their mating call. The study found that energetically costly call properties were not influenced by Bd infection; however, males with high levels of Bd infection produced calls with faster pulse rates than males with lower levels of infection. In two-choice tests, females did not show a preference between calls that resemble males with either high or low levels of Bd infection. The results provide little support for the Hamilton-Zuk hypothesis in this system and suggest that Bd infection may have little effect on female choice for this species. Interestingly, this species has been shown to be able to tolerate high levels of infection and may serve as a reservoir host to the pathogen. Similar studies should be conducted in more Bd-susceptible species and in species that occur in areas with different amphibian host/Bd pathogen histories (e.g., newly invaded areas vs endemic areas).

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