Potential non-target risks from strychnine-containing rodent carcasses

Abstract

Underground strychnine baiting is a common technique used to suppress pocket gopher ( Thomomys sp.) populations until seedlings are established. Non-target risks from underground baiting can still occur if strychnine-baited animals die aboveground. Accordingly, the fate of strychnine-baited carcasses of four small mammal species, Thomomys, Mus, Microtus, and Peromyscus, were documented during four trials on the Rogue River National Forest. We found no difference among species and type of damage, either insect or predator, during the four trials. However, survival differed between species in two trials where fewer Thomomys carcasses survived until completion of the study. We also examined the risk to tertiary non-targets from insects collected at the sites. Strychnine concentration among insect groups from treated carcasses differed with Diptera larvae and ants consistently containing higher concentrations. Even with high strychnine concentrations (0.2756 μg/g), risk assessments showed negligible tertiary risks from consuming strychnine-laced insects.