Improving calling surveys for detecting Fowler's toad, Bufo fowleri, in southern New England, USA

Abstract

Effectively monitoring population trends in Bufo fowleri is a priority in certain regions of this species' range. To determine the most appropriate sampling regime for B. fowleri at Cape Cod National Seashore, we sampled 67 sites with weekly calling surveys from 12 April to 24 July 2003, 2004 and 2005. Surveys were conducted from sunset to approximately midnight. B. fowleri calls were documented on 327/1350 sampling events and at 40 sites, 26 of which supported breeding aggregations. In 96% of sampling events resulting in a calling index value of 1, time to first detection was within three minutes. For all sampling events resulting in index values of 2 or 3, event maxima were recorded within the first survey minute. Most detections occurred within two hours of sunset on calm nights in June when surface water and air temperatures were >17.85°C and 20.75°C, respectively. Surface water temperature and Julian date were important predictors of calling, and June was identified as the optimal time to survey for this species.