The spatial habitat requirements are studied for two amphibian species: the tree frog ( Hyla arborea ) and the moor frog ( Rana arvalis ). Fragmentation, the destruction of suitable habitat, results in small fragments that are separated by unsuitable habitat or barriers. Metapopulation theory implies that a species can survive on a regional level if local extinctions are compensated for by recolonisations. For nature conservation it is relevant whether species can cope with habitat destruction or have crossed the viability threshold. Connectivity for ground-dwelling species with low dispersal capacity, such as amphibians, depends on the distance and the relative resistance of the landscape between suitable habitat patches.In chapter 2 the distribution pattern of the tree frog in Zealand Flanders is analysed. The occurrence of apparently suitable but unoccupied patches and the fact that the occupation probability increases with higher connectivity are indications that the distribution pattern is affected by habitat fragmentation.Chapter 3 focuses on the distribution pattern of the moor frog in south-west Drenthe. The positive effect of pond size and the negative effect of road density on the probability of occupation indicate negative effects of habitat fragmentation.In chapter 4 the genetic distance between populations of the moor frog is studied, as an indirect indicator of dispersal. The genetic distance correlates positively with geographical distance between populations, especially when distance is weighted for (rail)road density. This points to some exchange between local populations and that the connectivity between ponds is reduced by (rail)roads.In chapter 5 it is concluded that the tree frog in Zealand Flanders functions as a metapopulation. Firstly, extinctions take place regularly and extinction probability decreases with patch size. Secondly, empty patches are recolonised and colonisation probability increases for large patches with high connectivity. Finally, the observed dispersal distances and the ...