|Abstract of article submitted
to Journal of Herpetology
Assessing the Use of Call Surveys
to Monitor Breeding Anurans in Rhode Island
William B. Crouch III
Stroud Water Research Center, Avondale, Pennsylvania 19311,
Peter W. C. Paton
Department of Natural Resources Science, University of Rhode Island,
Kingston, Rhode Island, 02881, USA.
ABSTRACT.-Our objective was to develop a long-term monitoring
program that quantified anuran population trends in Rhode Island.
Since road-based, manual call surveys are widely used in North
America to monitor anurans, we assessed the efficacy of using this
method to monitor the impact of anthropogenic change of anuran populations
in the state. We quantified interspecific variation in calling
chronology, calling frequency, and calling intensity at 31 breeding
ponds in southern Rhode Island in 1998. Four distinct sampling
periods were needed to monitor the seven species we detected. During
a species' peak sampling period, males of some species called only
sporadically within our 16-min surveys, such as pickerel frogs (Rana
palustris), while other species called continually (spring peepers
[Pseudacris crucifer] and green frogs [Rana clamitans]).
Based on accumulation curves, we suggest that call surveys in Rhode
Island be conducted for 10-min at breeding ponds to have a high
probability of detecting all species. Assuming we conducted
one call survey annually during the four sampling periods, a power
analysis estimated that we need to conduct 283 or 690 10-min surveys
annually to detect 10% or 5% annual declines, respectively, to monitor
most anurans in Rhode Island. Common species that are widespread
and call frequently could be monitored with road-based call surveys.
However, rarer species or those that call infrequently would be
difficult to monitor with call surveys in Rhode Island, therefore
other monitoring methods might be more appropriate.