Secondary rodenticide poisoning kills thousands of barn owls annually when they consume rodents contaminated with anticoagulant rodenticides, causing prolonged internal bleeding deaths.
Secondary rodenticide poisoning causes one of the most prolonged and distressing deaths in wildlife. Anticoagulant rodenticides prevent blood clotting; affected owls die over several days from internal hemorrhage and progressive weakness. Finding a barn owl with anticoagulant poisoning means finding an animal that has been slowly dying for days from internal bleeding before collapse. The scale of contamination — the majority of tested barn owls carrying residues — indicates that secondary poisoning is not an exceptional event but a routine outcome of widespread rodenticide use. The owls that die are not collateral damage of targeted pest control but predictable casualties of a pest control method that concentrates toxic compounds in the prey items that barn owls depend on. Switching to lower-risk alternatives addresses this welfare harm directly.