U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



Published in Bird Behavior Vol. 16, pp. 1-4.


One component of brown tree snake (Boiga irregularis) management on Guam is the use of a toxic bait that consists of acetaminophen tablets inserted into a dead neonatal mouse (DNM), which in turn is placed within a cylindrical polyvinyl chloride (PVC) bait station suspended above ground. Whereas this technique is effective in killing snakes, possible hazards to nontarget species, especially the Mariana crow (Corvus kubaryi), are of concern. We used the fish crow (C. ossifragus) as a surrogate for the Mariana crow to evaluate (1) oral toxicity of acetaminophen, (2) behavior of crows exposed to DNM containing acetaminophen tablets, and (3) ability of crows to remove DNM from cylindrical bait stations. In the oral toxicity test, all five crows that were each force-fed two 40-mg acetaminophen tablets survived and at least two birds regurgitated the tablets. Five additional crows received a double dose (four 40-mg tablets); each regurgitated all of its tablets, but one bird died. Crows given DNM containing two 40-mg acetaminophen tablets consumed the DNM but avoided eating tablets by picking them from the carcass and either setting them aside or dropping them from the perch. Forty individually caged crows were tested with various size bait station cylinders containing an untreated DNM. Only the longest (45.7 cm), narrowest (5.1 cm) cylinder prevented crows from removing the DNM. In brown tree snake control operations, it appears that the risk of accidental exposure of Mariana crows to toxic acetaminophen bait can be minimized through appropriate bait station design. Even if crows encounter a DNM containing acetaminophen, they are likely to reject the tablets before consumption or regurgitate if tablets are accidentally ingested.