Efficacy of three formulations of zinc phosphide for managing black-tailed prairie dogs

We evaluated the effectiveness and cost of three zinc phosphide (Zn3P2) baits for managing black-tailed prairie dogs (Cynomys ludovicianus). Sixty-six 0.4-ha treatment and paired control plots were delineated within 13 prairie dog colonies in central Nebraska. Treatment plots were prebaited with untreated stream-rolled oats according to Zn3P2 label directions. After 2–3 days, we applied each of the three formulations of Zn3P2 baits according to label directions to 22 randomly assigned treatment plots. Prairie dog activity was reduced 80% with Zn3P2-treated rolled oats (Pocatello Supply Depot, US Department of Agriculture-Wildlife Services, Pocatello, ID, USA); 78% with Zn3P2-treated crimped oats (Bell Laboratories, Inc., Madison, WI, USA), and 71% with Zn3P2-treated pellets (Bell Laboratories), as measured by a plugged burrow technique. No significant differences (P=0.342) in efficacy were detected among the three treatments. Material costs varied among the Zn3P2 treatments (rolled oats-$1.04 kg−1, crimped oats-$1.32 kg−1, and pellets-$2.21 kg−1). Each treatment, including prebaiting with untreated rolled oats, required 3.6 h ha−1 to apply. The total costs for 70% to 80% control of black-tailed prairie dogs (@ $5.00 h−1 labor) were $18.71 ha−1 for rolled oats, $18.82 ha−1 for crimped oats, and $19.16 ha−1 for pellets.