Abstract
Anticoagulant rodenticides (ARs) are used globally to control rodent pest infestations in both urban and agricultural settings. It is well documented that non-target wildlife, including predatory birds, are at risk for secondary anticoagulant exposure and toxicosis through the prey they consume. However, there have been no large-scale studies of AR exposure in raptors in Ontario, Canada since new Health Canada legislation was implemented in 2013 in an attempt to limit exposure in non-target wildlife. Our objective was to measure levels of ARs in wild raptors in southern Ontario to assess their exposure. We collected liver samples from 133 raptors representing 17 species submitted to the Canadian Wildlife Health Cooperative (CWHC) in Ontario, Canada, between 2017 and 2019. Liquid chromatography-tandem mass spectrometry (LC–MS/MS) was used to quantitatively assess the level of exposure to 14 first- and second-generation ARs. Detectable levels of one or more ARs were found in 82 of 133 (62%) tested raptors, representing 12 species. The most commonly detected ARs were bromadiolone (54/133), difethialone (40/133), and brodifacoum (33/133). Of AR-positive birds, 34/82 (42%) contained residues of multiple (> 1) anticoagulant compounds. Our results indicate that AR exposure is common in raptors living in southern Ontario, Canada. Our finding that brodifacoum, difethialone, and bromadiolone were observed alone or in combination with one another in the majority of our sampled raptors indicates that legislative changes in Canada may not be protecting non-target wildlife as intended.
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Data availability
The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.
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Acknowledgements
We are grateful to the wildlife rehabilitation organizations, wildlife biologists, and members of the public who submitted carcasses to the Canadian Wildlife Health Cooperative (CWHC), especially Fatal Light Awareness Program (FLAP) Canada, the Owl Foundation, Shades of Hope Wildlife Refuge, and the Toronto Wildlife Centre. CWHC colleagues, including Laura Dougherty and Dan Hughes, the staff of the Avian and Exotics service of the Ontario Veterinary College, and Rachel Finer provided technical support. We thank Dr. Doug Campbell for his support in develo** this project.
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Project funding was through the Ontario Animal Health Network, which is supported by the University of Guelph-OMAFRA Partnership Agreement.
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All authors contributed to the study conception and design. Data collection was performed by Grace L. Thornton and Brian Stevens. Laboratory and data analysis were performed by Grace L. Thornton, Shannon K. French, Leonard J. Shirose, Felipe Reggeti, and Nick Schrier. The first draft of the manuscript was written by Grace L. Thornton, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
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Thornton, G.L., Stevens, B., French, S.K. et al. Anticoagulant rodenticide exposure in raptors from Ontario, Canada. Environ Sci Pollut Res 29, 34137–34146 (2022). https://doi.org/10.1007/s11356-022-18529-z
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DOI: https://doi.org/10.1007/s11356-022-18529-z