Differential Owl Predation on White and Agouti Mus musculus

Abstract

DICE (1947) demonstrated selection against conspicuous phenotypes of mice (Peromyscus maniculatus) by owls. His experiments were conducted in a laboratory room with either a Barn Owl (Tyto alba) or a Long-eared Owl (Asio wilsonianus) as predators. Vegetation was simulated by a latticework of boards. Subsequently Kaufman (1974) found that Barn Owls and Screech Owls (Otus asio) selected against conspicuous phenotypes of old-field mice (Peromyscus polionotus) in field enclosures with natural vegetation. It then became of interest to examine the effectiveness of selection against conspicuous prey whose conspicuousness was greatly increased; this was done by using white and agouti house mice (Mus musculus). In field experiments white mice (Mus musculus) disappeared faster than agouti mice during 3and 6-day periods in a 1acre enclosure (Kaufman and Wagner 1973). Under similar vegetation conditions, wild Loggerhead Shrikes (Lanius ludovicianus), diurnal predators, captured more white than agouti Mus released in pairs near the birds (Kaufman 1973a). Here, I report the results of a study designed to test the effectiveness of nocturnal predators, Barn Owls and Screech Owls, in capturing the conspicuous phenotype with white and agouti Mus used as prey. Effect of the amount of vegetation and changes in illumination on effectiveness of owls are also discussed.