Comparison of Anuran Call Survey Durations in Tennessee Wetlands

Anuran breeding call surveys are widely used to document species richness and relative abundance. Call survey protocols used by the North American Amphibian Monitoring Program are five minutes in duration. However, recent studies have suggested that 5-minute call surveys may not be long enough to accurately estimate species richness or relative abundance. Therefore, we tested whether anuran species richness and relative abundance differed between 5and 10-minute breeding call surveys. We conducted 344 call surveys from March–August 2005 and 2006 at eight wetlands on the Cumberland Plateau in Tennessee. On average, 95% of species recorded in 10 minutes were heard within the first five minutes. Mean species richness did not differ (P = 0.17) between 5and 10-minute surveys. For species we detected, mean relative abundance was not different (P > 0.07) between 5and 10-minute surveys. However, mean species richness and relative abundance of northern cricket frog (Acris crepitans) and American toad (Bufo americanus) was different (P < 0.03) between two observers. Our results suggest that 5-minute breeding call surveys are adequate to document common anurans in Tennessee wetlands. Also, coordinators should consider assigning only one individual per monitoring route because of the possibility of multiple-observer bias.