Wildlife Damage Management, Internet Center for


Date of this Version

April 1991


In February 1985, the Environmental Protection Agency (EPA) established standards for reregistering strychnine for controlling ground squirrels. One standard required efficacy data on strychnine concentrations below those presently registered with the EPA. The 8.0 mg of strychnine per treated egg currently registered in North Dakota (ND820001) for controlling Franklin ground squirrels (Spermophilus franklinii) on waterfowl production areas (WPA's) was included in this standard. The U.S. Fish and Wildlife Service (USFWS) decided to maintain the strychnine egg registration because this is the only method available for controlling this species on WPA's. In 1986, the Denver Wildlife Research Center (DWRC) conducted laboratory tests indicating that no ground squirrel mortality occurred after they fed on 0.5 mg, 1.0 mg, or 2.0 mg strychnine-treated eggs. Ground squirrel mortality was 88%, 89%, and 88% after feeding on 3.0 mg, 4.0 mg, and 5.0 mg strychnine eggs, respectively. All died after feeding on 6.0 mg strychnine eggs (Matschke, unpublished data)