Is Batrachochytrium dendrobaidiss really the proximate cause of frog decline?

Frog decline has been of major concern in many parts of the world over the last two decades and Australia appears to be a ‘hot spot’ of decline. Arguably the current, most popular hypothesis for decline of frogs is Chytridiomycosis infection caused by Batachochytrium dendrobatidis. As part of a much larger study that involved pitfall trapping frogs in three different habitat types associated with a large ephemeral wetland in natural bushland adjacent to agricultural and urban development, we observed an epidemic of Chytridiomycosis and confirmed the rate of infection by this fungal organism. Individuals from only one species in the frog assemblage died of the symptoms of the disease in any one year and the only evidence of an epidemic occurred in a single year in a single species (Limnodynastes tasmaniensis Spotted Grass Frog) despite several closely related species being a part of the same assemblage. Of those animals that died exhibiting the typical symptoms of Chytridiomycosis, only 22% carried fungal infection on their epidermis. Although Chytridiomycosis was present in the population, we concluded that it was not the proximate cause of mortality in this population. Based on this observation we question the validity of the hypothesis that B. dendrobatidis is necessarily the primary cause of frog mortality.