Changes in the first spawning dates of common frogs and common toads in western Poland in 1978-2002

Abstract

We analysed longitudinal data of observations of the first spawning dates of two anuran species (Rana temporaria and Bufo bufo) from western Poland (1978-2002). For both species, a trend towards earlier breeding was found, corresponding to an eight to nine day shift over the 25-year period. These shifts appear to be associated with increased temperatures in the winter and early spring in our study area.