REGRESSORS OF WHOLE-CARCASS ZINC PHOSPHIDE PHOSPHINE RESIDUES IN VOLES - INDIRECT EVIDENCE OF LOW HAZARDS TO PREDATORS/SCAVENGERS/

Whole-carcass residues of the rodenticide zinc phosphide (Zn3P2) and h ydrolyzed phosphine (PH3) were determined for voles (Microtus spp.) th at died following ingestion of a 2% Zn3P2 steam rolled oat (SRO) great s bait. Procedures involved: a three-day acceptance test to assess vol e consumption (n = 27) of control SRO greats and several one-day Zn3P2 - (n = 13) or control-bait (n = 4) tests to characterize onset of pha rmacotoxic signs and to obtain fatally-dosed carcasses for residue ana lyses. Carcasses were stored in liquid nitrogen (LN(2)) to maximize re tention of Zn3P2/PH3 residues prior to chemical determinations. Linear regressions were computed between pairs of consumption and residue va riables. Main results were the following: (1) mean (+/-SD) consumption of control bait was 2.5 (+/-0.9), 3.0 (+/-0.9), and 2.8 (+/-0.8) g on days 1, 2, and 3, respectively (greater than or equal to 10.6 +/- 4.6 % of body weight); (2) all test-bait voles (n = 13) died similar to 4- 12 h after bait presentation, with lethargy and respiratory distress k ey signs of toxicosis; (3) whole-carcass Zn3P2 residues averaged 1.73 mg (min-max: 0.31-4.95), and PH3 residues averaged 10.6 mu g (min-max: 0.5-21.0); and (4) significant linear regressions were found between bait consumption/Zn3P2 intake and body weight (r(2) = 0.64, p less tha n or equal to 0.001), carcass Zn3P2 and bait consumption/Zn3P2 intake (r(2) = 0.32, p less than or equal to 0.043), and carcass Zn3P2 and bo dy weight (r(2) = 0.60, p less than or equal to 0.002). Certain analyt ical and hazards issues are discussed.