Zinc Phosphide Residues in Gray-Tailed Voles (Microtus canicaudus) Fed Fixed Particles of a 2% Grain Bait

Authors

• R. T. Sterner, USDA/APHIS/WS
• D. A. Goldade, USDA/APHIS/WS
• R. E. Mauldin, USDA/APHIS/WSFollow

Document Type

Article

Date of this Version

1998

Comments

Published in International Biodeterioration & Biodegradation 42 (1998) 109-113.

Abstract

This study measured depelted-carcass residues of zinc phosphide (Zn₃P₂, CAS # 1314-84-7) in 8 (4 males and 4 females) gray-tailed voles (Microtus canicaudus). Six (3 males and 3 females) voles were confined individually in 1.89 dkl (5 gal) plastic pails that contained 5,2% Zn₃P₂ steamrolled- oat (SRO) groats; 2 voles (1 male and 1 female) served as analytical (unbaited) controls. Four test voles (3 males and 1female) died within 7.5 h after bait exposure; whereas, 2 test voles showed no signs of toxicosis and were euthanized 7.0 h after bait exposure. Whole carcasses were stored frozen and depelted carcasses were analyzed within 31 days for Zn₃P₂ residues using a acid-hydrolyzation, gas-chromatographic (GC) method. Analytical controls were euthanized, with carcasses stored and analyzed the same as test voles. A mean (± SD) 4.7 (±0.8) SRO groats were consumed by the test voles; this converted to a mean (±SD) intake of 2.15 (±0.38) mg Zn₃P₂ and dose of 73.25 mg/kg ( ± 22.95) Zn₃P₂. The mean (± SD) Zn₃P₂ residue in the 6 test vole carcasses was 0.42 mg (± 0.68); control carcasses contained <0.009 mg Zn₃P₂- 3P₂ in voles are variable, but typically < 50% of ingested rodenticide and (2) risks of secondary poisoning posed by Zn₃P₂-baited voles to avian and mammalian predators/scavengers are low due to the relatively high toxic thresholds (> 20 mg/kg) required to affect these species.