Differential Vulnerability of Wild, Domestic, and Hybrid Norway Rats to Predation by Great-Horned Owls

Abstract

Wild, domestic, and hybrid Norway rats (Rattus norvegicus) reared in the laboratory under identical conditions were simultaneously exposed to predation by great-horned owls (Bubo virginianus) in a large outdoor enclosure. Wild rats were most vulnerable to predation under these conditions whereas hybrids experienced the lowest mortality. Subsequent enclosure and laboratory investigations suggested that the rat populations studied did not actively avoid aerial predation. Differences between stocks in vulnerability to predation were best explained by factors related to the ease with which the presence and location of prey are perceived and associated activity rhythms. The effect of domestication on the fitness of the Norway rat is discussed.