Do Frogs Infected with Batrachochytrium dendrobatidis Avoid Water While Sloughing?

Abstract

Chytridiomycosis is a skin infection caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), that has been responsible for amphibian declines and extinctions worldwide. Chytridiomycosis increases the permeability of amphibian skin leading to low plasma ion levels and loss of physiological homeostasis. Because temporary increases in cutaneous salt loss and water uptake occur during sloughing, potentially exacerbating the effects of Bd infection, avoiding water while sloughing might help to alleviate these effects, and could contribute to intra- and interspecific differences in pathophysiology. Furthermore, because the amount of time an infected individual spends in contact with water could affect the severity of ion loss, we questioned whether amphibian behavior is altered in response to infection with Bd. This project utilized continuous infrared video footage of captive Australian Green Tree Frogs (Litoria caerulea) as a method of behavioral analysis, to determine whether infection with Bd altered the duration of water contact, activity levels, and the location of sloughing events. We found that although frogs became less active once infected, there was no change in the duration of time spent in contact with water. Infected frogs showed a decrease in the proportion of sloughing events occurring in contact with water as the experiment progressed. Our study is novel in that it provides insight into the behavioral effects of chytridiomycosis, demonstrating that Bd infection can induce behaviors that might alter disease progression.