Rodenticides and Wildlife: Secondary Poisoning and Alternatives

Anticoagulant rodenticides used to control rats and mice kill vast numbers of raptors, foxes, badgers and other wildlife through secondary poisoning — a preventable and significant welfare harm.

Key Facts

An estimated 95% of barn owls and red kites in England carry detectable levels of rodenticides in their livers
Second-generation anticoagulant rodenticides (SGARs) accumulate in predator livers over multiple poisoned prey animals
Death from anticoagulant poisoning takes 1-7 days and involves internal haemorrhage — a prolonged and painful process
The UK Campaign for Responsible Rodenticide Use (CRRU) sets stewardship codes for minimising non-target exposure
First-generation rodenticides (warfarin) are now largely ineffective due to resistance; SGARs are increasingly restricted

Welfare Considerations

Secondary poisoning of raptors and carnivores from rodenticide-contaminated prey is a serious and systematic welfare harm. Barn owls that ingest multiple poisoned mice accumulate liver concentrations of brodifacoum or difenacoum sufficient to cause fatal internal bleeding. The death is prolonged and involves haemorrhage into multiple organ systems. The same compounds harm foxes, polecats, stoats, weasels and badgers that consume poisoned rodent prey. The tragedy is that the harm is largely preventable through responsible use protocols — rodent proofing and bait security that prevents non-target access.

What You Can Do

Avoid using second-generation anticoagulant rodenticides, particularly outdoors or in locations accessible to wildlife
Invest in physical rodent exclusion — proofing buildings — rather than chemical control as a primary strategy
Never use rodenticides near wildlife habitats, owl nesting sites or waterways
Report suspected wildlife poisoning incidents to your national wildlife agency and wildlife crime officers
Support the Campaign for Responsible Rodenticide Use and follow their stewardship guidance