Optimising acoustic listening efforts as a tool to efficiently capture anuran diversity: first assessment in a southern temperate wetland

Passive Acoustic Monitoring (PAM) using autonomous recording units offers a promising approach for monitoring anuran communities. Here, we evaluate how to select the optimal listening protocol to efficiently capture anuran diversity. We used a set of 3,456 one-minute audio files obtained via PAM from the Paraná River Delta, a temperate South American wetland. First, we investigated the acoustic activity patterns and how species detectability fluctuates over a 24-h cycle; then, we assessed periods of similar vocal activity and their species composition; subsequently, we analysed the effect of different inspection rates on anuran diversity estimates; and finally, we used the generated information to optimise the audio inspection programme. As a result, we focused on the crepuscular-nocturnal window and reduced the inspection rate to 2 min/h and 1 min/h. In the first case, the estimated completeness profile for the 2 min/h rate was statistically indistinguishable from that of the standard programme (6 min/h for 24 h), highlighting its efficiency. With the 1 min/h rate, completeness remained above 98% for all Hill numbers assessed, while reducing inspection effort by more than 90%. Our findings can guide PAM research of amphibians in southern temperate wetlands towards optimised inspection protocols.