Monitoring agricultural rodenticide use and secondary exposure of raptors in Scotland
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Despite the documented risk of secondary poisoning to non-target species by anticoagulant rodenticides there is no statutory post-approval monitoring of their use in the UK. This paper presents results from two Scottish monitoring schemes for the period 2000–2010; recording rodenticide use on arable farms and the presence of residues in raptor carcasses. More than three quarters of arable farms used anticoagulant rodenticides; predominately the second generation compounds difenacoum and bromadiolone. There was widespread exposure to anticoagulant rodenticides in liver tissues of the raptor species tested and the residues encountered generally reflected agricultural use patterns. As found in other studies, Red Kites (Milvus milvus) appeared to be particularly vulnerable to rodenticide exposure, 70 % of those sampled (n = 114) contained residues and 10 % died as a result of rodenticide ingestion. More unexpectedly, sparrowhawks (Accipiter nisus), which prey almost exclusively on birds, had similar exposure rates to species which prey on rodents. Although, with the exception of kites, confirmed mortality from rodenticides was low, the widespread exposure recorded is concerning. Particularly when coupled with a lack of data about the sub-lethal effects of these compounds. This raises questions regarding whether statutory monitoring of use is needed; both to address whether there are deficiencies in compliance with approval conditions or whether the recommended risk management procedures are themselves adequate to protect non-target wildlife.
KeywordsAnticoagulant rodenticides Secondary exposure Raptors
The authors would like to thank those who have assisted in the coordination and collection of rodenticide use data (Chris Bierley, Chris Griffiths, John Kerr, Gillian Reay, Louis Thomas, Andrew Walker and Jeremy Snowden) and those who conducted residue analyses (Anna Giela and Jennifer Watson). The authors would also like to thank the paper’s anonymous reviewers whose comments greatly improved the manuscript.
Conflict of interest
The post-registration surveillance of wildlife poisoning is funded by the pesticide industry under the Food and and Environmental Protection Act 1985 (FEPA) and the Control of Pesticides Regulations (COPR). The monitoring of rodenticide use is funded by the Scottish Government. The authors declare that they have no conflict of interest.
All experiments comply with the current laws of the country in which they were performed.
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