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1 September 2004 Using Chorus-Size Ranks from Call Surveys to Estimate Reproductive Activity of the Wood Frog (Rana sylvatica)
Cameron E. Stevens, Cynthia A. Paszkowski
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Call surveys are a relatively new and efficient technique for detecting the presence of breeding male anurans. Using data from multiple surveys of breeding choruses of Wood Frogs (Rana sylvatica) combined with counts of egg masses on ponds in west-central Alberta we determined (1) the relationship between ranks of chorus size and total number of egg masses in ponds, and (2) number of breeding males in standard chorus-size ranks (1, 2 and 3). Estimates for Rank 3 choruses were based on a formula with number of egg masses present per pond and a fixed male to female ratio of 2:1 calculated from the literature. Calling males were recorded from all ponds that had evidence of female reproductive activity (i.e., egg masses). Generalized linear models suggested that ranks were positively and linearly correlated with the number of egg masses in a pond. In addition, call data from only the second of four sampling periods (each 3–6 days) significantly predicted number of egg masses in ponds, suggesting that timing is important when surveying calling wood frogs. The mean number of chorusing males per rank did not correspond to aural ranks of calling intensity: Rank 1 = 1.3 males, Rank 2 = 3.7 males, and Rank 3 = 118 males. We recommend similar assessments for other widely distributed species to improve our ability to detect and interpret habitat-use patterns and population trends of amphibians through monitoring programs.

Cameron E. Stevens and Cynthia A. Paszkowski "Using Chorus-Size Ranks from Call Surveys to Estimate Reproductive Activity of the Wood Frog (Rana sylvatica)," Journal of Herpetology 38(3), 404-410, (1 September 2004).
Accepted: 1 May 2004; Published: 1 September 2004

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