Digital recorders increase detection of Eleutherodactylus frogs

Improved methods for large-scale and long-term amphibian monitoring projects would aid species status assessments and identification of potentially declining species (e.g., Stuart et al. 2004). Acoustical surveys allow researchers to quickly determine species presence and calling activity level (Lips et al. 2001; Zimmerman 1994). The North American Amphibian Monitoring Program, a large-scale monitoring effort, uses acoustical surveys to monitor species in ponds and wetlands (United States Geological Survey 2004). A challenge of this approach is accurate species identification, which is particularly problematic in a tropical area with high anuran species diversity (e.g., anuran species richness in the Neotropics was greater than in the Neartic, Duellman 1999). Furthermore, abundant or loud species may lower the detection probability of other species. An assumption that needs to be tested in acoustical surveys is that detection is highly correlated with the species presence or activity. W...