Characterization of tree frog (Hyla arborea) calling ponds in western Switzerland

A tree frog (Hyla arborea) metapopulation in western Switzerland was studied during spring 2001. All potential calling ponds in an area of 350 km2 were searched for tree frog calling males. Twenty-nine out of 111 ponds sheltered between 1 and 250 callers. Most ponds were occupied by less than 12 males. Pond parameters were measured at three different levels using field analysis and a Geographical Information System (GIS). The first level was water chemistry and pond-associated measures. The second level was the surrounding land use in a 30 m buffer around the pond. The third level consisted of landscape indices on a broader scale (up to 2 km). Logistic regression was applied to identify parameters that can predict the presence of calling males in a pond. Response variable was the presence or absence of callers. Four significant parameters allowed us to explain about 40 % of the total deviance of the observed occupational pattern. Urbanization around the pond had a highly negative impact on