Proceedings of the Vertebrate Pest Conference

The California meadow vole, Microtus californicus, is a major vertebrate pest in artichoke fields of Castroville, California. Complaints from growers about the effectiveness of the only available rodenticide, chlorophacinone treated artichoke bracts, led researchers to the test the bait and baiting strategies. When laboratory trials were conducted in 2001, the poor dose-response correlation and apparent low sensitivity to chlorophacinone in some animals suggested the possibility of anticoagulant resistance. The current study was initiated to examine potential resistant of voles from artichoke fields in the Castroville area. Baseline blood coagulation data were obtained from wild, anticoagulant-susceptible voles trapped in Yolo County, California and compared to data from Castroville voles. Results indicate a significant difference in clotting times 24 hours after dosing with anticoagulant between voles from Castroville artichoke fields and voles from the Yolo population. This supports the hypothesis that voles from Castroville artichoke fields are resistant to anticoagulants.