Rodenticide Poisoning in Barn Owls and Raptors: A Preventable Crisis

Second-generation anticoagulant rodenticides (SGARs) cause prolonged, painful internal bleeding in non-target wildlife — particularly barn owls, red kites, and other raptors that consume poisoned rodents. Studies consistently find SGAR contamination in the majority of tested raptors, making this a pervasive wildlife welfare crisis.

Key Facts

SGARs (brodifacoum, bromadiolone, difenacoum, difethialone) prevent blood clotting and cause death through internal haemorrhage over several days
Studies in the UK, US, and Europe consistently find SGAR residues in 70-80% of barn owls and red kites tested post-mortem, demonstrating near-universal exposure
Non-target poisoning occurs through secondary exposure: raptors and other predators consume rodents that have ingested bait but not yet died, accumulating rodenticide in their own tissues
Barn owls and other raptors may not show obvious signs before sudden collapse from internal bleeding; the condition is insidious — birds appear normal until haemorrhage is critical
First-generation rodenticides (warfarin, chlorophacinone) are less persistent in the environment and in prey tissues, reducing secondary poisoning risk while maintaining rodent control efficacy in most situations
Integrated Pest Management (IPM) approaches — physical exclusion, snap traps, habitat management — reduce the need for rodenticides and are welfare-superior for all non-target species
The UK's Campaign for Responsible Rodenticide Use (CRRU) has developed stewardship schemes to reduce SGAR use, but compliance and enforcement are limited

Welfare Considerations

Anticoagulant poisoning causes a prolonged and painful death: internal bleeding develops over days, causing progressive weakness, neurological signs, and eventual death from haemorrhage. The process is not rapid — poisoned raptors may suffer for a week or more before dying. The near-universal exposure rates documented in UK barn owls suggest that essentially the entire breeding raptor population is chronically sub-lethally exposed to these compounds, with effects on reproductive success and immune function beyond direct mortality. The welfare harm is compounded by its invisibility: poisoned raptors often die unseen, and the connection between rodenticide use and raptor mortality is not visible to the person who placed the bait. Consumer pressure and regulatory change are the most effective levers.

What You Can Do

Never use second-generation anticoagulant rodenticides (brodifacoum, bromadiolone, difenacoum, difethialone) in outdoor or roof settings where non-target wildlife can access poisoned rodents
Use first-generation rodenticides only as a last resort, in tamper-resistant bait stations inaccessible to non-target species, and follow label instructions precisely
Prioritise Integrated Pest Management: seal entry points, remove food sources, use snap traps in areas inaccessible to raptors and other wildlife
Support the Barn Owl Trust and Wildlife Incident Investigation Scheme (WIIS), which monitor raptor poisoning and advocate for stronger rodenticide regulation
Report dead raptors to wildlife authorities for post-mortem analysis — surveillance data drives regulatory change