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Owls and other wildlife dying from rodent bait

December 17, 2013

SALEM, Ore.— Oregon Department of Fish and Wildlife veterinarians advise home and land owners that poison baits used to control mice and rats can sicken or kill owls, hawks, foxes, bobcats and other species. To protect wildlife, people should carefully follow product directions and explore other options for rodent control.

According to Julia Burco, ODFW Assistant Wildlife Veterinarian, wildlife deaths are generally the result of secondary poisoning from anticoagulant rodenticides used in the baits. Birds and other wildlife eat dead or dying rodents that have consumed the poison and, as a result, they are poisoned. Some wildlife will also eat the bait directly, as will pets.

Anticoagulant rodenticides are used both indoors and outdoors, in urban and rural settings.  They are usually formulated into pellets, blocks or bars and can be brightly colored.

“In Oregon, we have documented cases of raptors and bobcats that have died from anticoagulant rodenticides,” said Burco. “Most recently, a great horned owl found in the Willamette Valley with significant bruising under the skin was confirmed to have died from anticoagulant rodenticide poisoning.”

Owls are especially vulnerable as their diet consists largely of rodents. Ironically, they are expert natural rodent control agents. It is estimated that a barn owl can consume a third of its body weight per night—that is about six voles or rodents a night. 

While the Environment Protection Agency is working to ensure safer pesticide products to control rodents and reduce risks to children, pets and wildlife, one of the best things people can do is to prevent potential rodent problems in the first place.

  • Block entry by mice, rats and squirrels into your home, basement or building by sealing holes.
  • Reduce potential food sources and nesting areas in and near buildings, including seeds around bird feeders.
  • Use mechanical rat and mouse traps for rodent control—this is the most humane method.
  • Employ a licensed wildlife control operator or licensed pesticide applicator.
  • If you must use rodenticide baits, use them according to manufacturer label directions and current EPA safety standards.

According to Rose Kachadoorian of the Oregon Department of Agriculture, “Everyone who applies pesticides is required to follow the directions on pesticide labels, including the restrictions. For example, if the product is labeled for use to control rats and mice in and around buildings, you cannot legally use it to control voles in your garden. The label is the law.”

About Anticoagulant Rodenticides

Anticoagulant rodenticides work by blocking the body’s ability to conserve vitamin K, which in turn stops the body from producing and activating new factors needed for normal coagulation of blood. The result is widespread bleeding throughout the body and eventual death.

Links to additional information

Anticoagulant Rodenticide Fact Sheet,
Environmental Protection Agency: Safer Rodenticide Products,
National Pesticide Information Center,
Oregon Department of Fish and Wildlife: learn about the state’s owls,




Anne Mary Myers, ODFW Assistant Wildlife Biologist, (541) 757-5227
Julia Burco, ODFW Assistant Wildlife Veterinarian, (541) 757-5233
Meg Kenagy, ODFW Conservation Communications Coordinator, (503) 947-6021
Rose Kachadoorian, ODA Pesticide and Endangered Species Specialist, (503) 986-4651

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