Habitat Fragmentation and Vertebrate Species Richness in an Urban Environment

Abstract

(1) Species of terrestrial mammals, reptiles and amphibians were surveyed in patches of semi-natural and disturbed vegetation within the City of Oxford. The patches were delimited by roads, walls or other artificial barriers, and ranged from 0 16 ha to 20 ha. (2) A total of twenty species of mammals was recorded, two to seventeen species occurring per patch. Mammalian species richness (the number of species) within patches decreased with increasing percentage of barren ground per patch, with proximity to buildings, and with patchiness in the total vegetation cover, but increased with increasing density of vegetation in the layer 21-50 cm above ground. (3) Five species of amphibians and four species of reptiles were recorded, zero to seven species occurring per patch. The richness of these taxa within patches increased with patch area, but declined away from sources of permanent water. (4) More species of mammals, amphibians and reptiles were retained in two small habitat patches than in one large patch equal to their combined area. (5) For mammals, excluding large species such as deer, species richness in the urban environment can be preserved by maintaining a system of small (>0 65 ha) patches of undisturbed woodland throughout the city area. The richness of reptiles and amphibians can probably be preserved by maintaining patches of )0 55 ha that provide permanent water.