Morphological abnormalities in amphibians in agricultural habitats:: A case study of the common frog Rana temporaria

Recent studies suggest that the incidence of morphological abnormalities has increased in many amphibian populations, often exceeding the estimated background deformity frequency of 0-5%. Many chemical contaminants, including agrochemicals, can cause abnormalities in amphibians, but data on the occurrence of morphological abnormalities in wild amphibian populations in Europe is anecdotal at best. In a large-scale study covering 264 ha and 26 farmland breeding populations of the Common frog (Rana temporaria) in southern Finland, we investigated whether the incidence of morphological abnormalities in metamorphs differed from the background level of 0-5% and among populations along an agrochemical gradient. Abnormalities occurred in a low frequency (1% of the studied individuals; 40/4115), the highest population-specific frequency being 4%. We found no evidence for increased abnormality frequencies in the habitats most likely exposed to agrochemicals. Hence, the data suggest that current Finnish agrochemical practices are not causing increased incidences of morphological abnormalities in Common frog populations breeding in farmland areas.