Anticoagulant rodenticide exposure in raptors from Ontario, Canada

Thornton, Grace; Stevens, Brian; French, Shawn; Shirose, Leonard J.; Reggeti, F.; Schrier, Nick; Parmley, E. Jane; Reid, Alexandra; Jardine, Claire M.

doi:10.1007/s11356-022-18529-z

Cited by 8 publications

(8 citation statements)

References 33 publications

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“…Studies elsewhere have found generally lower exposure rates and concentrations in accipiters and falcons (Hughes et al, 2013; Walker et al, 2015). A recent study from the Canadian province of Ontario reported similar results to those of the present study, with zero or low incidence of SGARs in sharp‐shinned hawks and falcons but higher incidence in Cooper's hawks (Thornton et al, 2022). However, northern goshawks collected from Berlin, Germany, had the greatest SGAR incidence and concentrations among collected species; and the authors of that study speculated that the pathway was likely via passerine birds entering bait stations (Badry et al, 2021), as reported in Walther et al (2020).…”

Section: Discussionsupporting

confidence: 89%

“…However, our previous data suggest that in more urbanized or interface habitats, targeted rats appear to provide an important pathway of exposure in owls. Regardless of whether the pathway is via target or nontarget small mammals, AR deployment in bait stations, often permanent, is contaminating birds of prey throughout the sampled areas of western Canada and in many other parts of the world (López‐Perea & Mateo, 2018; Okoniewski et al, 2021; Rial‐Berriel et al, 2021; Serieys et al, 2019; Thornton et al, 2022). Whether target or nontarget rodents are the primary pathway is perhaps not an important question unless it is possible to design bait stations to allow targeted rats to enter but exclude nontarget small mammals.…”

Section: Discussionmentioning

confidence: 99%

“…Other reports from the United States made the same conclusion (Quinn, 2019) and may be partly the result of online availability of SGARs (e.g., https:// www.amazon.com/bromadiolone/s?k=bromadiolone). Data from Ontario, Canada, 2017-2019 and thus subsequent to risk mitigation measures, reported that SGAR incidence in a broad suite of raptors was similar to studies taken before that period elsewhere in North America (Thornton et al, 2022). They questioned the effectiveness of the measures.…”

Section: Temporal Trendsmentioning

confidence: 97%

“…Evidence of the widespread SGAR exposure and poisoning of nontarget predators and scavengers has continued to increase (López‐Perea & Mateo, 2018; Nakayama et al, 2019; Serieys et al, 2019; Okoniewski et al, 2021; Rial‐Berriel et al, 2021; Thornton et al, 2022). Concern over their spread as contaminants has led to an intensified search for alternatives, as well as for regulatory and voluntary mitigation measures (Elliott et al, 2016; Witmer, 2018).…”

Section: Introductionmentioning

confidence: 99%

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Anticoagulant Rodenticide Contamination of Terrestrial Birds of Prey from Western Canada: Patterns and Trends, 1988–2018

Elliott

Silverthorn

Hindmarch

et al. 2022

Enviro Toxic and Chemistry

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As the dominant means for control of pest rodent populations globally, anticoagulant rodenticides (ARs), particularly the second‐generation compounds (SGARs), have widely contaminated nontarget organisms. We present data on hepatic residues of ARs in 741 raptorial birds found dead or brought into rehabilitation centers in British Columbia, Canada, over a 30‐year period from 1988 to 2018. Exposure varied by species, by proximity to residential areas, and over time, with at least one SGAR residue detected in 74% of individuals and multiple residues in 50% of individuals. By comparison, we detected first‐generation compounds in <5% of the raptors. Highest rates of exposure were in barred owls (Strix varia), 96%, and great horned owls (Bubo virginianus), 81%, species with diverse diets, including rats (Rattus norvegicus and Rattus rattus), and inhabiting suburban and intensive agricultural habitats. Barn owls (Tyto alba), mainly a vole (Microtus) eater, had a lower incidence of exposure of 65%. Putatively, bird‐eating raptors also had a relatively high incidence of exposure, with 75% of Cooper's hawks (Accipiter cooperii) and 60% of sharp‐shinned hawks (Accipiter striatus) exposed. Concentrations of SGARs varied greatly, for example, in barred owls, the geometric mean ∑SGAR = 0.13, ranging from <0.005 to 1.81 μg/g wet weight (n = 208). Barred owls had significantly higher ∑SGAR concentrations than all other species, driven by significantly higher bromadiolone concentrations, which was predicted by the proportion of residential land within their home ranges. Preliminary indications that risk mitigation measures implemented in 2013 are having an influence on exposure include a decrease in mean concentrations of brodifacoum and difethialone in barred and great horned owls and an increase in bromodialone around that inflection point. Environ Toxicol Chem 2022;41:1903–1917. © 2022 Her Majesty the Queen in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Temporal Trendsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Anticoagulant Rodenticide Contamination of Terrestrial Birds of Prey from Western Canada: Patterns and Trends, 1988–2018

Elliott

Silverthorn

Hindmarch

et al. 2022

Enviro Toxic and Chemistry

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“…Although the use of ARs may be necessary for rodent control, the well-known risks of primary and secondary poisoning of non-target species necessitates debate on the need to require measures to mitigate the risks of ARs use (Buckle and Prescott, 2018;Eisemann et al, 2018;Witmer, 2018;Thornton et al, 2022). Indeed, the Convention on the Conservation of Migratory Species of Wild Animals (the CMS, or Bonn Convention) highlighted secondary exposure to ARs as one of the most important toxicological hazards for migratory birds (CMS, 2014).…”

Section: Introductionmentioning

confidence: 99%

Second-generation anticoagulant rodenticides in the blood of obligate and facultative European avian scavengers

Oliva‐Vidal

Martínez

Sánchez-Barbudo

et al. 2022

Environmental Pollution

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Anticoagulant Rodenticide Toxicity in Terrestrial Raptors: Tools to Estimate the Impact on Populations in North America and Globally

Elliott,

Silverthorn,

English

et al. 2024

Enviro Toxic and Chemistry

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Anticoagulant rodenticides (ARs) have caused widespread contamination and poisoning of predators and scavengers. The diagnosis of toxicity proceeds from evidence of hemorrhage, and subsequent detection of residues in liver. Many factors confound the assessment of AR poisoning, particularly exposure dose, timing and frequency of exposure, and individual and taxon‐specific variables. There is a need, therefore, for better AR toxicity criteria. To respond, we compiled a database of second‐generation anticoagulant rodenticide (SGAR) residues in liver and postmortem evaluations of 951 terrestrial raptor carcasses from Canada and the United States, 1989 to 2021. We developed mixed‐effects logistic regression models to produce specific probability curves of the toxicity of ∑SGARs at the taxonomic level of the family, and separately for three SGARs registered in North America, brodifacoum, bromadiolone, and difethialone. The ∑SGAR threshold concentrations for diagnosis of coagulopathy at 0.20 probability of risk were highest for strigid owls (15 ng g−1) lower and relatively similar for accipitrid hawks and eagles (8.2 ng g−1) and falcons (7.9 ng g−1), and much lower for tytonid barn owls (0.32 ng g−1). These values are lower than those we found previously, due to compilation and use of a larger database with a mix of species and source locations, and also to refinements in the statistical methods. Our presentation of results on the family taxonomic level should aid in the global applicability of the numbers. We also collated a subset of 440 single‐compound exposure events and determined the probability of SGAR‐poisoning symptoms as a function of SGAR concentration, which we then used to estimate relative SGAR toxicity and toxic equivalence factors: difethialone, 1, brodifacoum, 0.8, and bromadiolone, 0.5. Environ Toxicol Chem 2024;00:1–11. © 2024 His Majesty the King in Right of Canada and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC Reproduced with the permission of the Minister of Environment and Climate Change Canada.

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Anticoagulant rodenticide exposure in raptors from Ontario, Canada

Cited by 8 publications

References 33 publications

Anticoagulant Rodenticide Contamination of Terrestrial Birds of Prey from Western Canada: Patterns and Trends, 1988–2018

Anticoagulant Rodenticide Contamination of Terrestrial Birds of Prey from Western Canada: Patterns and Trends, 1988–2018

Second-generation anticoagulant rodenticides in the blood of obligate and facultative European avian scavengers

Anticoagulant Rodenticide Toxicity in Terrestrial Raptors: Tools to Estimate the Impact on Populations in North America and Globally

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