Rediscovery of frogs of conservation concern in Panama using passive acoustic monitoring and pattern-matching analysis

Passive acoustic monitoring offers promising solutions for monitoring elusive amphibian species, but the method’s effectiveness for detecting rare or potentially extinct amphibian species remains poorly evaluated. We conducted observer surveys along transects and deployed autonomous recording units (ARUs) at 19 stations across three localities in Panama during two rainy seasons (2022, 2024) to detect species of conservation concern that were thought to have been extirpated following disease related declines in 2005-2008, including the potentially extinct Rabb’s treefrog Ecnomiohyla rabborum. Using template-based pattern matching and expert validation of acoustic data, we documented four conservation-priority species: Silverstoneia nubicola, Oophaga vicentei, Triprion sp inosus , and Ecnomiohyla veraguensis . Three of these species were previously presumed extirpated from the study localities following chytridiomycosis-related declines; one ( E. veraguensis ) was a new distribution record for the species. ARUs detected common species at twice as many stations compared to observers on transects, though pattern-matching efficiency varied substantially (35-97%) depending on call characteristics with repetitive patterns performing better than single notes. Bd prevalence in the amphibian community was 21% with continuing evidence of Bd-related frog deaths. The current amphibian abundance (mean 5.82 amphibians/100m transect) may indicate partial recovery of amphibian communities approximately 20 years post-epizootic decline. While we found no evidence of Ecnomiohyla rabborum , our results validate ARUs as an effective tool for detecting rare arboreal Ecnomiohyla species and for monitoring amphibian recovery. The persistence of presumed extirpated populations highlights the value of continued acoustic monitoring and suggests the potential evolution of disease resistance in some species.