The superpopulation approach for estimating the population size of ‘prolonged’ breeding amphibians: Examples from Europe

Abstract

Individual members of a population of ‘prolonged’ breeding amphibian species are asynchronously present at
their breeding sites. Therefore, population size estimates can be misleading when based on commonly used closed or
open-population capture-mark-recapture approaches. The superpopulation approach, a modified Jolly-Seber model, has
been successfully applied in taxa other than amphibians with distinct migratory behaviour and where individuals are
asynchronously present at the sampling site. In this paper, we suggest that the superpopulation approach is a useful population
size estimator for ‘prolonged’ breeding amphibian species. Two case studies on European anurans show that superpopulation
estimates are much higher than simple population counts. A simulation study showed that superpopulation estimates are
unbiased but that accuracy can be low when either survival or detection probabilities (or both) are low. We recommend
the superpopulation approach because it matches the natural history and phenology of amphibian species with prolonged
breeding seasons.
Keywords: abundance,