Cooperative Fish and Wildlife Research Units Program: Wyoming
Education, Research and Technical Assistance for Managing Our Natural Resources

The use of predator removal to increase the reproductive success of a prey species of concern is relatively common in wildlife management. The efficacy of such an approach, however, depends partly on the extent to which predation risk is additive or compensatory, which remains unknown for many systems. We experimentally reduced the local abundance of deer mice (Peromyscus maniculatus), a primary nest predator of three sagebrush-obligate songbirds (Brewer’s Sparrow [Spizella breweri], Sagebrush Sparrow [Artemisiospiza nevadensis], and Sage Thrasher [Oreoscoptus montanus]) in western Wyoming, USA to assess whether nest predation risk was additive or compensatory, and whether nest predator removal could comprise a potentially effective management tool. Deer mouse removal did not affect the daily nest survival of songbirds, despite a reduction of 68 ̶ 85% in the deer mouse population within treatment areas. Nest mortality in this system therefore likely operates in a compensatory way, in which new immigrants or other species of nest predator can maintain similar levels of nest predation risk regardless of the prevalence of a dominant predator. We caution that predator removal may not be an effective management tool in open systems with many potential predator species, even when a single species typically is responsible for the majority of predation events.