Anticoagulant Rodenticide Toxicity in BC Owls

Barred Owl. Photo Credit: Shelly Fisher

Over the past few months, a significant number of owls submitted to the BC Ministry of Agriculture, the BC node of the Canadian Wildlife Health Cooperative, have had gross lesions suggestive of anti-coagulant rodenticide toxicity and traces of rodenticide compounds detected in the liver. Most of the affected owls have been barred owls, but other species, such as great horned owls, have also been occasionally affected. The owls have come from widespread locations across Southern British Columbia. While some of the owls have had single anticoagulant compound detected in the liver, multiple compounds have been detected in the liver of a number of owls. The most frequently detected compounds are brodifacoum and bromadiolone; both of these are potent anticoagulants and are lethal at relatively small doses. Anybody using anticoagulant rodenticides is reminded to strictly follow application guidelines and to make every effort to prevent access of owls and other animals to the anticoagulants and to rodents that have ingested anticoagulants.

Submitted by: Tony Redford, Avian Pathologist, CWHC-BC

Great grey owl coming in to pounce on prey. Photo Credit: DM Jefferson