Chytrid infection and post-release fitness in the reintroduction of an endangered alpine tree frog

Abstract

Global amphibian decline and extinction has been associated with the spread of the pathogenic chytrid fungus (Batrachochytrium dendrobatidis, Bd). Despite extensive research, there have been no examples of effective management abating the ongoing impact of this pathogen in the wild. The endangered alpine tree frog (Litoria verreauxii alpina) has been extirpated from 80% of its former range because of Bd. We directly tested whether source population or host site influenced the efficacy of a reintroduction of L. v. alpina. We captive reared and released 1241 individuals from three different populations, two with a history of Bd exposure and one that was Bd-naive, into two sites where they had historically occurred, and two sites where the species currently persists. Between 6 and 9 months post-release, we recaptured 4.83% of the released animals, and observed breeding at all sites. Both released and extant animals had similar susceptibility to infection; both groups increased in Bd infection prevalence and infection intensity throughout the breeding season. We did not detect any effect on survival by site of release; however, population of origin had a relatively large impact (ω = 0.454), and animals from one Bd-exposed population were recaptured significantly more than the animals from the other Bd-exposed population and the Bd-naive population. Population exposure history to the disease of reintroduced amphibians may be used to increase post-release fitness and conservation success. Selection for mechanisms of resistance should be further explored to help mitigate the impact of chytridiomycosis during reintroduction programmes.