Data from: To treat or Not to Treat? Experimental Pathogen Exposure, Treatment, and Release of a Threatened Amphibian

Species reintroductions may mitigate the effects of severe amphibian
declines, but chytridiomycosis—the often-deadly amphibian disease caused
by the fungal pathogen Batrachochytrium
dendrobatidis (Bd)—can hinder these efforts. Exposing amphibians
to the pathogen ex-situ may improve disease outcomes
post-release. We experimentally inoculated the federally threatened
California red-legged frog (Rana draytonii) ex situ, cleared Bd
infections, then released them to the wild for monitoring in an area where
Bd is present. Ex situ, previously-exposed frogs had lower Bd
loads than previously uninfected frogs, and all exposure groups, including
previously uninfected frogs, naturally reduced their Bd loads in two
independent experiments. After release to the wild, we observed no
differences in field-contracted Bd infection among exposure groups.
Treating post-metamorphic R. draytonii ex situ may not
confer additional post-release benefits to this species in terms of
chytridiomycosis burden. Our results, however, do not necessarily mirror
Bd susceptibility throughout the amphibian life cycle, with other source
populations that may have different Bd infection histories or responses to
different Bd strains. These results provide a clearer understanding of
post-release disease responses of a threatened, Bd-susceptible species
with prior pathogen exposure. Following ex situ experiments
with in situ applications can provide a more
comprehensive understanding of threat outcomes for declining species in
reintroduction programs, and strengthen critical links between ex
situ and in situ conservation partners.