Secondary rodenticide poisoning risk arising from winter farmyard use by the European polecat Mustela putorius Original Research Article

The polecat Mustela putorius is a carnivore of unfavourable conservation status in Europe. It is believed to be vulnerable to accidential secondary rodenticide poisoning through the consumption of farmyard rodents. To confirm the mechanism of exposure, radio-tracking was used to examine the speciesʹ use of agricultural premises during winter when rodenticides are mainly applied to control commensal rodents. Ten out of 11 polecats radio-tracked made some use of such premises, and compositional analysis indicated that these were the most preferred of all habitats utilised. Foraging for farmyard rodents (which comprised 65% of the diet of farmyard-using polecats in this study), rather than a response to cold weather, is believed to explain this behaviour. 45.4% of animals made heavy use of farmyards, and were thus vulnerable to secondary poisoning through ingestion of rodents contaminated with rodenticides. Current government monitoring does not reveal the true level of contamination because severely affected animals tend to die out of sight in farm buildings. Since polecats are commonly killed by motor vehicles, screening of liver tissue from winter/spring road casualty polecats is recommended as a means of monitoring background levels of rodenticides.