Reservoir frogs: seasonality of infection in robber frogs in Dominica and Montserrat.

Emerging infectious diseases are an increasingly important threat to wildlife conservation, with amphibian chytridiomycosis, caused by , the disease most commonly associated with species declines and extinctions. However, some amphibians can be infected with in the absence of disease and can act as reservoirs of the pathogen. We surveyed robber frogs ( spp.), potential reservoir species, at three sites on Montserrat, 2011-2013, and on Dominica in 2014, to identify seasonal patterns in infection prevalence and load ( genomic equivalents). On Montserrat there was significant seasonality in prevalence and load, both of which were correlated with temperature but not rainfall. prevalence reached 35% in the cooler, drier months but was repeatedly undetectable during the warmer, wetter months. Also, prevalence significantly decreased from 53.2% when the pathogen emerged on Montserrat in 2009 to a maximum 34.8% by 2011, after which it remained stable. On Dominica, where emerged seven years prior to Montserrat, the same seasonal pattern was recorded but at lower prevalence, possibly indicating long-term decline. Understanding the dynamics of disease threats such as chytridiomycosis is key to planning conservation measures. For example, reintroductions of chytridiomycosis-threatened species could be timed to coincide with periods of low infection risk, increasing potential for reintroduction success.