Frogs in sight and sound: passive acoustics and visual surveys reveal complementary species detection in tropical rainforest anurans

Amphibian surveys in remote tropical rainforests are often constrained by rugged terrain, dense vegetation, high logistical demands, and the invasive nature of observer-based methods. Passive acoustic monitoring (PAM) using autonomous recording units (ARUs) has emerged as a promising, non-invasive tool for biodiversity assess ments; however, its effectiveness can vary across taxa and landscapes. This study conducted a comparative evaluation of PAM with conventional visual encounter surveys (VES) to document the anuran community in a tropical wet evergreen forest within the Indo-Burma biodiversity hotspot. The results indicated that PAM effectively detected most visually observed species, as well as many vocally active cryptic, arboreal, and fossorial species that were missed by VES. Its ability to function effectively in dense tropical rainforests underscores its potential for broad-scale assessments, particularly in the Indo-Burma biodiversity hotspot. However, VES detected non-calling and conspicuous species, highlighting the limitations of a single-method approach. A mixed-method approach integrating PAM with VES yielded a more comprehensive inventory. These findings provide crucial insights into optimizing amphibian monitoring protocols and support the adoption of integrated survey methodologies for long-term assessments, particularly in landscapes where conventional methods are constrained by terrain and effort.