Age structure, mortality, and longevity in syntopic populations of three species of ranid frogs in central Ontario

Abstract

Syntopic populations of bullfrogs (Rana catesbeiana), green frogs (Rana clamitans), and mink frogs (Rana septentrionalis) were monitored between May and October in each of 1985 through 1987 and 1991 through 1993 in Algonquin Provincial Park, Ontario, Canada. We assessed the descriptive and predictive utility of a dichotomous system for classification of anuran life histories by testing the hypothesis that large body size and large clutch size are associated with a survivorship curve in which mortality is highest for very small individuals. Ages of individuals were estimated from size-frequency and recapture data. Survivorship and longevity were estimated from standing age distributions smoothed with the log-polynomial method. Survivorship was also estimated by comparing the number of animals in an age-class in a given year with the number in the next age-class in the next year. Age distributions were unstable in all three species. The strengths and weaknesses of both methods of estimation of survivorship are discussed.