Spatial and temporal patterns of predation of simulated sage grouse nests at high and low nest densities: an experimental study

Abstract

We examined patterns of predation on 252 simulated sage grouse (Centrocercus urophasianus) nests placed at two densities around six active leks in southeastern Wyoming, U.S.A. Predation intensity, as measured by the frequency of multiple-nest predation events, was significantly greater at high-density sites, implying enhanced prey capture (functional and (or) numerical response) by predators. Significant spatial aggregation of nest predation further implies enhanced prey capture by predators at high prey densities. Predation varied significantly among sites, but there were no significant first-order differences in predation between densities. Predation was also significantly affected by year–density and site–year–density interactions. Several factors, including nest cover, prey defense mechanisms, study site location, nest location, year, search methods of predators, number of predators, and random encounter may inhibit or confound density-dependent nest predation. Enhanced prey capture provides a mechanism for density-dependent population regulation.