Evidence of Effects of Endemic Chytridiomycosis on Host Survival, Behavior, and Emigration: Reply to Schmidt

Abstract

[Extract] In our recent publication (Murray et al. 2009), we documented a marked disease-associated reduction in apparent survival of threatened frogs infected with pathogen Batrachochytrium dendrobatidis (Bd), despite a long period since its invasion. This result raises concern for hundreds of species of amphibians globally because it demonstrates that endemic chytridiomycosis can remain virulent for long periods, potentially placing ongoing pressure on amphibian populations that may elevate extinction risk. In response, Schmidt claims the apparent monthly survival estimates of Murray et al. are likely confounded with permanent emigration from study site… . If infected and uninfected frogs have different emigration probabilities, then one would obtain different apparent survival estimates from mark-recapture analysis for Bd-positive and Bd-negative frogs. Schmidt concludes, I believe that most of difference [in survival rate between infected and uninfected animals] is caused by permanent emigration from study site.