Effect of Spatial Heterogeneity on Ground-Nest Depredation

Abstract

Field enclosures [in Florida, USA] were used to test the effects of spatial heterogeneity on raccoon (Procyon lotor) depredation of dummy nests. Three levels of spatial heterogeneity were created by varying the density, species composition and interspersion of nesting cover. Trials consisted of releasing a raccoon into an enclosure in which 5 clutches of bobwhite quail (Colinus virginianus) eggs had been placed randomly. High levels of spatial heterogeneity increased (P < 0.01) search time and reduced the number of clutches found. Foraging efficiency (the number of clutches found per unit time) decreased greatly as spatial heterogeneity increased. Handling and consumption time did not differ (P > 0.05) among levels of heterogeneity. All raccoons reduced their search time with experience, irrespective of heterogeneity level. Depredation did not differ (P > 0.05) between partially and totally concealed nests. Spatial heterogeneity may be more important than nest concealment in reducing nest depredation.