Changes in Population Size and Survival in Atelopus spumarius (Anura: Bufonidae) Are Not Correlated with Chytrid Prevalence
2014
Tarvin, Rebecca D. | Peña, Paula | Ron, Santiago R.
Approximately one-third of amphibian species are experiencing population declines. Among the most affected groups are the Harlequin frogs (Bufonidae: Atelopus), nearly all of which are threatened with extinction. We monitored one of the last known Ecuadorian populations of Atelopus spumarius (Pebas Stubfoot Toad) with a mark–recapture survey between February 2009 and December 2010. We aimed to determine the effect of the fungal pathogen Batrachochytrium dendrobatidis (Bd), previously recorded at the site, on population size and survival. We also analyzed the effect of selective logging which occurred along the transect in April 2010. We tested every individual captured or recaptured for Bd presence using end-point PCR. All 679 Bd swabs (from 356 individuals) were negative, suggesting that Bd did not influence population size and survival. Population size increased during the first 9 months of the study (August 2009–April 2010), from an estimated 47 to 92 individuals, but then decreased by November 2010 to an estimated 48 individuals. Probability of survival was 0.13 lower in months following selective logging compared to previous months; emigration decreased by 0.37 after the logging event. Pairs in amplexus were found between April and December, suggesting a long, if not year-round, reproductive period. Although most Atelopus spp. declines have been attributed to Bd, we present a case in which Bd has been detected in the area yet changes in population size cannot be attributed to chytridiomycosis. Analyses of survival and male body condition index suggest that the decline at the end of the study was the result of habitat destruction.
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