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In 2008, approximately 70 Canada geese were recovered dead in the Moro Cojo Slough area of Monterey County, California. Birds were necropsied and showed signs of abnormal internal bleeding. A total of 37 livers were analyzed for anticoagulants and 36 of these livers contained chlorophacinone. Death was attributable to chlorophacinone poisoning. Two turkey vultures and a barn owl also died, probably as a result of secondary chlorophacinone poisoning. The source of the chlorophacinone was not obvious, as chlorophacinone is used in several different forms on many different crops and also in commensal use. In addition, there often are several days between exposure and death, allowing the movement of the animal from the site of exposure. The ensuing investigations, which lasted several months, suggested that the exposure was due to expanded use of chlorophacinone pellets on artichokes used to control California voles. Subsequently, the label of the rodenticide product was modified to restrict its use when conditions favor goose presence in artichoke fields. No deaths have occurred since the label modification.

Concerned that San Joaquin kit foxes from urban areas may be exposed to commensal anticoagulants, the California Department of Fish and Game, Pesticide Investigations Unit, in conjunction with the Endangered Species Recovery Program’s Urban Kit Fox Project, began monitoring San Joaquin kit foxes from the Bakersfield, CA population. Necropsies were performed and liver tissue samples collected from kit fox carcasses. Livers from archived kit foxes dating back to 1977 were also analyzed. A non-urban population of San Joaquin kit foxes from Lokern was used as a control. Other predators in the area, including coyotes and red foxes, were also analyzed for comparison. Between 1999 and 2007, tissue samples from 45 animals have been analyzed for residues of anticoagulant rodenticides. Anticoagulant compounds identified included brodifacoum, bromadiolone, pival, and chlorophacinone. Twenty-six of the 30 San Joaquin kit foxes from Bakersfield contained at least one anticoagulant, and the most commonly detected anticoagulant was brodifacoum. None of the 12 Lokern San Joaquin kit foxes contained anticoagulants. Other predators followed the same pattern: both red foxes from Bakersfield contained anticoagulant residues, but the coyote taken from Lokern did not.