Exposure to second-generation anticoagulant rodenticides is widespread in the non-target British wild mammals Erinaceus europaeus and Vulpes vulpes.

Anticoagulant rodenticides (ARs), molluscicides, and neonicotinoids are widely used biocides for plant protection and pest control and are considered a potential health risk to non-target wildlife. Here, we investigate these compounds in convenience samples derived from 100 European hedgehogs (Erinaceus europaeus) and 181 red foxes (Vulpes vulpes) from England (2013 to 2020), screening liver tissues using liquid chromatography-tandem mass spectrometry. Whilst no molluscicides or neonicotinoids were detected, except for low level clothianidin in a single fox, ARs were found in 62% of hedgehog and 90% of fox samples at variable concentrations (0.05-3430 ng/g). In 83% of animals with detectable ARs, more than one AR compound was found, consistent with multiple, cumulative exposures. Additionally, 25% of hedgehog and 64% of fox samples contained summed AR concentrations above the commonly used reference value of 100 ng/g for potential poisoning or regulatory concern. There was no significant association with geographical region or sex (for fox or hedgehog), or with age, location, habitat type, or the assigned category of cause of death (for hedgehog). Despite the high AR levels detected, there was no evidence of acute haemorrhage indicative of AR toxicosis in hedgehogs. However, since hedgehogs are of conservation concern in Great Britain, further investigation of potential adverse health impacts of ARs and other pesticides is warranted. Our study findings indicate widespread AR exposure among the sampled animals and support further structured monitoring of these omnivorous non-target mammals. Within our convenience sample, we found no evidence of reduced AR exposure following the introduction of the UK rodenticide stewardship scheme in 2016.