Surveying a threatened amphibian species through a narrow detection window

Perry J. Williams, Nathan J. Engbrecht, Joseph R. Robb, Vanessa C.K. Terrell, Michael J. Lannoo

Research output: Contribution to journalArticle

13 Scopus citations


Crawfish Frogs (Lithobates areolatus) are a relatively widespread but understudied North American species suspected to be in steep decline. Discussions to petition this species for federal listing have begun and therefore effective techniques to survey and monitor populations must be developed. Crawfish Frogs produce unusually loud breeding calls, making call surveys the most efficient way to assess populations; however, their peak breeding period lasts for only a few nights, sometimes for only one night. We used automated calling survey techniques at two wetlands where the numbers of Crawfish Frog males present were known (±1%) for the entire length of the breeding season to examine detection probabilities in relation to season, time of day, weather variables, survey duration, and the numbers of males present. We then used these data to ask three simple but important questions: 1) When should researchers listen-that is, what times and under what environmental conditions should surveys for Crawfish Frogs take place? 2) How long should surveys last? and 3) What can call surveys tell us about the size of a population? The most supported model for detection included the quadratic relationship of time and date, a positive linear relationship with temperature, and a negative linear relationship with recent rain, while the most supported model for estimating abundance included the quadratic relationship of time and date, and call rate. Five-minute surveys should suffice during peak breeding for known large populations; 15-minute surveys with repeat visits should be used for small populations or when sampling new areas. These findings should improve manually collected (auditory) call survey efficiencies for Crawfish Frogs, surveys that are being organized to provide the first objective data on the status of this species across its range.

Original languageEnglish (US)
Pages (from-to)552-561
Number of pages10
Issue number3
StatePublished - Sep 1 2013

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Animal Science and Zoology

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  • Cite this

    Williams, P. J., Engbrecht, N. J., Robb, J. R., Terrell, V. C. K., & Lannoo, M. J. (2013). Surveying a threatened amphibian species through a narrow detection window. Copeia, (3), 552-561.