Population Recovery of Black-tailed Prairie Dogs Following Control with Zinc Phosphide

Abstract

This study evaluated the efficacy of 2% zinc phosphide grain bait as a control agent for black-tailed prairie dogs (Cynomys ludovicianus) and the rate at which prairie dogs returned to treated areas. Visual counts of prairie dogs closely corresponded to actual population trends and were chosen as the technique to evaluate changes of prairie dog numbers. Treatment of all of 2, and portions of 5, prairie dog colonies with zinc phosphide grain bait between 30 July and 25 August 1978 resulted in an average of 85% (range 65 to 95%) reduction in prairie dog numbers. Best results were obtained in the 2 colonies treated totally. The 2 colonies treated along the perimeter had the lowest percentage decrease in numbers of prairie dogs and were among the treatment types with the fastest population recovery. Prairie dogs returned to pretreatment levels within 1 year posttreatment at 1 colony. After 2 years posttreatment, 3 other colonies were approaching pretreatment population levels. Three to 5 years posttreatment appeared to be needed to obtain pretreatment numbers in the 2 colonies treated totally.