Environmental change as a cause of natterjack toad (Bufo calamita) declines in Britain

An investigation was made into factors which have influenced the decline of natterjack toads Bufo calamita in Britain over the last 40 years. Natterjacks are limited in Britain to two types of habitats, coastal dunes and inland heaths. By comparing the relative declines of the species on these two habitats with other changes which have occurred on them, it became clear: (1) That Bufo calamita has declined much more extensively on heaths than on dunes: (2) that this selective decline cannot be attributed to climatic changes, public pressure or direct development; (3) that large-scale changes in the flora of heathland areas have occurred concurrently with natterjack declines. These changes, which in general have not been reflected on dunes, have occurred subsequent to altered patterns of land use on the heathlands. Cessation of grazing and increased forestry activity have permitted widespread encroachment by tall vegetation, which creates shade, both changes being directly undesirable for natterjacks, and more importantly, enabling the common toad Bufo bufo to enter as a successful competitor. This latter factor is thought to have been one of the most important causes of natterjack declines on heathland.