Distribution of generalist and specialist predators along urban gradients

摘要

The distribution of predators in urban areas is overlooked by urban planners. Due to the homogenizing power of urbanization, towns are expected to favour the settlement of generalist predators. We compared the frequency of specialist and generalist predators along an urban gradient (centre, inner periphery, outer periphery, and scarcely built areas) in towns of different size (small, medium, large). We obtained data on specialist (diurnal and nocturnal raptors, Dendrocopos major) and generalist (Larus michahellis, corvids) predators breeding in each square of the grid of 27 urban atlases. The number of species per square of specialist predators decreased in more urbanised sectors, whereas the number of generalist predators either did not change or increased in the same sectors. However, some specialist (nocturnal raptors except Athene noctua) and generalist (Garrulus glandarius, Pica pica) predators did not follow such a pattern of distribution. Town size may affect the distribution of predators. Some species (D. major, G. glandarius, P. pica) were more frequent in the more urbanised sectors in small towns. Data gathered in few towns on a limited number of predator species may not fully represent the complex response by predators to urban gradients. Urban planners should consider the distribution of predators in towns to limit risks for urban wildlife.