Distribution and status of the green toad Bufo viridis in Northrhine-Westfalia Verbreitung und Bestandssituation der Wechselkroete Bufo viridis in Nordrhein-Westfalen

Vences, M.; Becker, J.; Sauer, H.; Glaw, F.

In the German state Northrhine-Westfalia, the green toad reaches its northwestern distribution border. The species is restricted to the Northern Rhineland region, although a few dubious records from Westfalia, probably due to introductions, exist. Mapping results from the periods 1986/87, 1992/93 and 1997/98 indicate a rather stable status of about 60-100 populations. with some declines at the distribution borders. A comparison of historical maps of the Erftkreis region from 1845 and 1895 with recent maps from 1990 indicates a shift from a dense network of small open mines (mainly gravel pits) towards few large gravel pit complexes (from 715 in 1895 to 219 in 1990). This change had obviously deep impact on the green toad which in the Northern Rhineland occurs almost exclusively in open mining areas, resulting in increasing isolation of populations, especially along the regional distribution border, where definitive local extinction events mostly took place. In the city of Cologne, in which a complete mapping was carried out in all three mapping periods, seven out of 22 populations apparently got extinct between 1986 and 1997, whereas only two new populations were found.