Impacts of Batrachochytrium dendrobatidis infection on tadpole foraging performance.

Pathogen-induced modifications in host behavior, including alterations in foraging behavior or foraging efficiency, can compromise host fitness by reducing growth and development. Chytridiomycosis is an infectious disease of amphibians caused by the fungus Batrachochytrium dendrobatidis (Bd), and it has played an important role in the worldwide decline of amphibians. In larval anurans, Bd infections commonly result in reduced developmental rates, however, the mechanism(s) responsible are untested. We conducted laboratory experiments to test whether Bd infections reduced foraging performance of Grey Treefrog (Hyla chrysoscelis) and Fowler's Toad (Anaxyrus [= Bufo] fowleri) tadpoles. In the first experiment, we observed foraging behavior of Bd-infected and uninfected tadpoles to test for differences in foraging activity. In a second experiment, we tested for differences in the ingestion rates of tadpoles by examining the amount of food in their alimentary track after a 3-hour foraging period. We hypothesized that Bd-infected tadpoles would forage less often and less efficiently than uninfected tadpoles. As predicted, Bd-infected larvae forage less often and were less efficient at obtaining food than uninfected larvae. Our results show that Bd infections reduce foraging efficiency in Anaxyrus and Hyla tadpoles, and that Bd differentially affects foraging behavior in these species. Thus, our results provide a potential mechanism of decreased developmental rates of Bd-infected tadpoles.