The role of spatial scale in understanding responses of medium-sized carnivores to forest fragmentation

Abstract

Increased predation has been suggested as a proximate factor causing the decline of vertebrate diversity in many human-altered landscapes. Previous studies on this topic have provided conflicting results, perhaps as a consequence of the limited spatial scale used in these investigations. We incorporated a multiscaled approach (using site, plot (1.44 km2), and landscape (54 km2)) to investigate the distribution of activity of medium-sized carnivores relative to habitat edges and the numeric responses of these predators to habitat diversity. Among the taxa surveyed, raccoons (Procyon lotor) did not show an affinity for habitat edges at any spatial scale. However, raccoons were more abundant in landscapes characterized by a diversity of cover types. Free-ranging domestic dogs (Canis familiaris) and cats (Felis domesticus) did not respond to the proximity of habitat edges in summer but showed a strong affinity for edge habitats (especially those associated with human dwellings) during winter. Wild canids (Vulpes vulpes and Canis latrans) also selected sites in close proximity to edges in winter and were more abundant in diverse landscapes. Although human-dominated habitats (agricultural areas, grass–brushland, and developed sites) represented only 7–27% of the three landscapes studied, populations of generalist predators (raccoons and wild canids) increased as landscapes became more diverse. As a result, even moderate levels of habitat fragmentation may elevate predation rates and subsequently alter the composition of prey communities.