In the United States, new regulations on second-generation anticoagulant rodenticides will likely be offset by expanded use of first-generation anticoagulant rodenticides. In the present study, eastern screech-owls (Megascops asio) were fed 10 µg diphacinone/g wet weight food for 7 d, and recovery was monitored over a 21-d postexposure period. By day 3 of exposure, diphacinone (DPN) was detected in liver (1.63 µg/g wet wt) and kidney (5.83 µg/g) and coagulopathy was apparent. By day 7, prothrombin time (PT) and Russell's viper venom time (RVVT) were prolonged, and some individuals were anemic. Upon termination of exposure, coagulopathy and anemia were resolved within 4 d, and residues decreased to <0.3 µg/g by day 7. Liver and kidney DPN elimination occurred in 2 phases (initial rapid loss, followed by slower loss rate), with overall half-lives of 11.7 d and 2.1 d, respectively. Prolonged PT and RVVT occurred in 10% of the exposed owls with liver DPN concentrations of 0.122 µg/g and 0.282 µg/g and in 90% of the owls with liver concentrations of 0.638 µg/g and 0.361 µg/g. These liver residue levels associated with coagulopathy fall in the range of values reported in raptor mortality incidents involving DPN. These tissue-based toxicity reference values for coagulopathy in adult screech-owls have application for interpreting nontarget mortality and assessing the hazard of DPN in rodent-control operations. Diphacinone exposure evokes toxicity in raptors within a matter of days; but once exposure is terminated, recovery of hemostasis occurs rapidly.

No abstract

Zinc phosphide (Zn 3 P 2 ) recovery from small mammal tissues is assessed for the first time by an analytical method developed for the determination of Zn 3 P 2 residues in the gastrointestinal (GI) tracts of California ground squirrels (Spermophilus beecheyi) by gas chromatography-flame photometric detection (GC-FPD). GI tracts from field-collected squirrels were removed, and the stomachs and intestines were separated. Emptied stomachs were fortified with varying combinations of Zn 3 P 2 and partially digested range grass; intestines were fortified with Zn 3 P 2 only. Tissues were processed and acid hydrolyzed in a sealed flask to produce phosphine (PH 3 ) gas, and samples of the PH 3 -containing headspace gas were analyzed by GC. Recovery data were used to develop predictive linear equations relating tissue weights and Zn 3 P 2 observed with actual Zn 3 P 2 residues. The validated linear range was 0.1-103.4 µg of Zn 3 P 2 /mL headspace (0.102-100.3 mg of Zn 3 P 2 /sample, r 2) 0.9993). The limits of detection of the method were 0.015 mg (≈250 ppb) and 0.013 mg (≈154 ppb) in stomachs and intestines, respectively. No chromatographic interferences were observed.