Effects of temperature and temporal factors on anuran detection probabilities at Cape Cod National Seashore, Massachusetts, USA: Implications for long-term monitoring

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To evaluate the efficacy of calling surveys, we studied effects of temperature and temporal factors (diel, seasonal, annual) on detection probabilities for anurans of southeastern Massachusetts, USA. We used automated recording systems (ARS) to quantify diel chronology during one field season, and conducted calling surveys to investigate seasonal and annual variation in calling at 103 wetlands over six years at Cape Cod National Seashore. Five species detected with ARS called primarily between sunset and midnight, with mean calling time of Anaxyrus fowleri and Lithobates sylvaticus nearer to sunset than Pseudacris crucifer, Lithobates catesbeianus, or Lithobates clamitans. Of eight species recorded during calling surveys (the preceding five plus Scaphiopus holbrookii, Hyla versicolor, and Lithobates palustris), detection probabilities of all but Scaphiopus holbrookii and Lithobates sylvaticus varied seasonally. Peak detection periods ranged from 11 to 33 days and peak period detection probabilities ranged from 0.06 for Scaphiopus holbrookii to 0.84 for Pseudacris crucifer. There was strong to moderate support for models with annual variation for all species except Hyla versicolor. Detectability was affected more by surface water temperature than by air temperature, but models with both received greater support in five species. For six species, models with temperature and seasonal effect received the greatest support, indicating that detectability is a function of both temperature and day of year. Durations of peak calling periods were long enough and detection probabilities high enough to effectively monitor six of the eight species with calling surveys. © 2011. Robert Cook. All rights reserved.

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Herpetological Conservation and Biology