Amphibian situation in urban environment – history of the common toad Bufo bufo in Kraków (Poland)

Abstract

Rapid urbanization processes are not neutral to the environment, especially amphibians. Their double-environment lifestyle makes them particularly vulnerable to negative changes in the environment. Inventory research on batrachofauna carried out in urban areas usually provides data on its current state, but there is little information about changes in its composition over the years. The aim of the study was to investigate the situation of amphibians in urban areas of Kraków (Poland) over the last 90 years. As an example of amphibian species the common toad Bufo bufo (Linnaeus, 1758) was selected, because of its widespread occurrence and high environmental plasticity. Three periods were chosen for the analysis: 1) before the Second World War (1928-1939), when the nature of the city seemed to be the least exposed to treats, 2) after the rapid urban transformation associated with the expansion of the territory of the city (1986 -1992), and 3) the present time. In order to determine the current situation of amphibians, in 2011-2012, 30 water bodies of Kraków were inventoried, with particular emphasis on the common toad. The occurrence of the same species in the city over the last 90 years was shown. The proportion of occupied habitat (POH) by the common toad (POH=0.57) is currently similar to the pre-Second World War proportion (POH=0.58). Between these two periods, there was a significant increase in the number of Bufo bufo in Kraków (POH=0.86). At that time the common toad was the only amphibian which increased, while the others declined. These results may suggest the high resistance of the species to the negative impact of urbanization during this period (loss and fragmentation of habitat and pollution). However, its resistance is limited, as evidenced by the recent decline of the species, just as most other amphibians of Kraków.