Rozol prairie dog bait (0.005% chlorophacinone) was fed to male and female adult/subadult black-tailed prairie dogs (Cynomys ludovicianus) over a 2-day period. The residue levels of chlorophacinone in prairie dogs were determined over a 27 day period. Most prairie dogs (n=36; T1 group) were allowed to eat up to 53 g (EPA label application rate) while a group of 3 prairie dogs (T2 group) were allowed to eat bait ad libitum for a 2-day period. All remaining animals (n = 11) served as the control group. The T1 group consumed an average of 48.5 g (SD = 7.2 g) of bait, while the T2 group consumed an average of 33.0 g (SD = 24.1 g) of bait. Highest residue levels were found on Day 3 after the bait was first offered: an average of 5.499 ìg/g (SD = 2.034 ìg/g) in livers and 1.281 ìg/g (SD = 0.369 ìg/g) in whole bodies. Levels quickly declined after Day 3 and a half-life of about 5-6 days in livers and whole bodies was interpolated from the graphed results. No chlorophacinone was found in the control animals (all values below the Method Limit of Detection). Residue levels were not significantly different in males and females nor in animals that died versus those euthanized in the same time period. No control animals died during the course of the study. The 3 T2 animals were euthanized 3 days after bait was offered and no conclusive signs of anticoagulant poisoning (hemorrhaging) were observed from this limited time of exposure. Of the 36 T1 animals, 3 died of anticoagulant poisoning and 9 were considered to be moribund or had bleeding injuries and were euthanized. The remaining 24 animals in the T1 group appeared healthy when they were euthanized as per the schedule. The first clinical symptoms of anticoagulant poisoning (lethargy) were observed on Day 5, while main symptoms (external bleeding or blood in feces) began to be observed in Day 8 after the bait was first offered. Twenty of the 36 (56%) T1 animals showed evidence of hemorrhaging (external and/or internal) when necropsied.
