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Spadetto L, Gómez-Ramírez P, Zamora-Marín JM, León-Ortega M, Díaz-García S, Tecles F, Fenoll J, Cava J, Calvo JF, García-Fernández AJ. Active monitoring of long-eared owl (Asio otus) nestlings reveals widespread exposure to anticoagulant rodenticides across different agricultural landscapes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 918:170492. [PMID: 38307270 DOI: 10.1016/j.scitotenv.2024.170492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 01/24/2024] [Accepted: 01/25/2024] [Indexed: 02/04/2024]
Abstract
The widespread use of anticoagulant rodenticides (ARs) poses a worldwide threat to farmland wildlife. These compounds accumulate in tissues of both target and non-target species, potentially endangering both direct consumers and their predators. However, investigations on ARs in blood of free-ranging predatory birds are rare. Here, the long-eared owl (Asio otus) has been used as a model predator to assess AR exposure in different agricultural landscapes from a Mediterranean semiarid region. A total of 69 owlets from 38 nests were blood-sampled over 2021 and 2022, aiming to detect AR residues and explore factors that determine their exposure, such as land uses. In addition, prothrombin time (PT) test was conducted to assess potential effects of AR contamination. Overall, nearly all the samples (98.6 %) tested positive for at least one compound and multiple ARs were found in most of the individuals (82.6 %). Among the ARs detected, flocoumafen was the most common compound (88.4 % of the samples). AR total concentration (ΣARs) in blood ranged from 0.06 to 34.18 ng mL-1, detecting the highest levels in the most intensively cultivated area. The analysis of owl pellets from 19 breeding territories showed relevant among-site differences in the contribution of rodents and birds into the diet of long-eared owls, supporting its high dietary plasticity and indicating AR presence at multiple trophic levels. Moreover, a positive and significant correlation was found between ΣARs and PT (Rho = 0.547, p < 0.001), which demonstrates the direct effect of ARs on free-living nestlings. Our results provide a preliminary overview of AR exposure in a little-studied owl species inhabiting agricultural and rural landscapes. Despite the low detected levels, these findings indicate widespread exposure -often to multiple compounds- from early life stages, which raises concern and draws attention to an ongoing and unresolved contamination issue.
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Affiliation(s)
- Livia Spadetto
- Toxicology Research Group, Faculty of Veterinary, Campus de Espinardo, University of Murcia, 30100 Murcia, Spain
| | - Pilar Gómez-Ramírez
- Toxicology Research Group, Faculty of Veterinary, Campus de Espinardo, University of Murcia, 30100 Murcia, Spain.
| | - José Manuel Zamora-Marín
- ULULA Association for Owl Study and Conservation, 30100 Murcia, Spain; Department of Applied Biology, Centro de Investigación e Innovación Agroalimentaria (CIAGRO-UMH), Miguel Hernández University of Elche, Elche, Spain; Department of Zoology and Physical Anthropology, Faculty of Biology, University of Murcia, 30100 Murcia, Spain
| | - Mario León-Ortega
- ULULA Association for Owl Study and Conservation, 30100 Murcia, Spain
| | - Sarah Díaz-García
- ULULA Association for Owl Study and Conservation, 30100 Murcia, Spain
| | - Fernando Tecles
- Interdisciplinary Laboratory of Clinical Analysis (Interlab-UMU), Veterinary School, Regional Campus of International Excellence 'Campus Mare Nostrum', University of Murcia, 30100 Murcia, Spain
| | - José Fenoll
- Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario, IMIDA, 30150 Murcia, Spain
| | - Juana Cava
- Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario, IMIDA, 30150 Murcia, Spain
| | - José Francisco Calvo
- Department of Ecology and Hydrology, Faculty of Biology, University of Murcia, 30100 Murcia, Spain
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Elliott JE, Silverthorn V, English SG, Mineau P, Hindmarch S, Thomas PJ, Lee S, Bowes V, Redford T, Maisonneuve F, Okoniewski J. Anticoagulant Rodenticide Toxicity in Terrestrial Raptors: Tools to Estimate the Impact on Populations in North America and Globally. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2024. [PMID: 38415966 DOI: 10.1002/etc.5829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/05/2023] [Accepted: 01/17/2024] [Indexed: 02/29/2024]
Abstract
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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Affiliation(s)
- John E Elliott
- Ecotoxicology and Wildlife Health Directorate, Environment and Climate Change Canada, Delta, British Columbia, Canada
- Applied Animal Biology, University of British Columbia, Vancouver, British Columbia, Canada
- Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Veronica Silverthorn
- Ecotoxicology and Wildlife Health Directorate, Environment and Climate Change Canada, Delta, British Columbia, Canada
| | - Simon G English
- Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Pierre Mineau
- Pierre Mineau Consulting, Salt Spring Island, Canada
- Biology Department, Carleton University, Ottawa, Ontario, Canada
| | - Sofi Hindmarch
- Ecotoxicology and Wildlife Health Directorate, Environment and Climate Change Canada, Delta, British Columbia, Canada
| | - Philippe J Thomas
- Ecotoxicology and Wildlife Health Directorate, National Wildlife Research Centre, Environment and Climate Change Canada, Ottawa, Ontario, Canada
| | - Sandi Lee
- Ecotoxicology and Wildlife Health Directorate, Environment and Climate Change Canada, Delta, British Columbia, Canada
| | - Victoria Bowes
- Animal Health Centre, British Columbia Ministry of Agriculture, Abbotsford, British Columbia, Canada
| | - Tony Redford
- Animal Health Centre, British Columbia Ministry of Agriculture, Abbotsford, British Columbia, Canada
| | - France Maisonneuve
- Ecotoxicology and Wildlife Health Directorate, National Wildlife Research Centre, Environment and Climate Change Canada, Ottawa, Ontario, Canada
| | - Joseph Okoniewski
- Wildlife Health Unit, New York State Department of Environmental Conservation, Delmar, New York, USA
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Carrillo-Hidalgo J, Martín-Cruz B, Henríquez-Hernández LA, Rial-Berriel C, Acosta-Dacal A, Zumbado-Peña M, Luzardo OP. Intraspecific and geographical variation in rodenticide exposure among common kestrels in Tenerife (Canary Islands). THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 910:168551. [PMID: 37979878 DOI: 10.1016/j.scitotenv.2023.168551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 11/07/2023] [Accepted: 11/11/2023] [Indexed: 11/20/2023]
Abstract
This study assesses the impact of second-generation anticoagulant rodenticides (SGARs) on the common kestrel (Falco tinnunculus canariensis) in Tenerife, Canary Islands. The analysis of 390 liver samples over 19 years using HPLC-MS/MS showed that 93.1 % of kestrels were exposed to SGARs in this island. A notable shift in SGAR profiles was observed, with bromadiolone and flocoumafen decreasing, while brodifacoum levels increased sharply from 2018 onwards. Comparatively, Tenerife kestrels had a higher detection frequency of SGARs (93.1 %) than those in the rest of the islands of the archipelago (68.2 %), with median concentrations nearly double (∑AR = 180.9 vs 102.4 ng/g liver, P < 0.0001). Furthermore, on average, kestrels from Tenerife were found to have a higher number of different rodenticide compounds per individual. A Generalized Linear Model (GLM) analysis revealed that several factors contribute to the likelihood of SGAR exposure: being an adult kestrel, the enactment of legal restrictions on SGAR bait concentrations in 2018, higher livestock density, and greater human population density. These findings suggest that both bioaccumulation over the birds' lifespans and environmental factors related to human and agricultural activity are influencing the levels of SGARs detected. Alarmingly, 44.7 % of kestrels had SGAR levels above the toxicity threshold established for other raptor species (200 ng/g liver), signaling a high poisoning risk. This is despite EU regulations to protect wildlife, with our findings indicating an increase in both exposure rates and SGAR concentrations since these laws were enacted. The data highlight a critical environmental threat to endemic species on islands like Tenerife. The common kestrel, not considered globally endangered, is nonetheless facing regional threats from SGAR contamination. These results emphasize the urgent need for effective regulations to address the persistent and growing impact of SGARs on island biodiversity.
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Affiliation(s)
- José Carrillo-Hidalgo
- Island Ecology and Biogeography Research Group, University Institute of Tropical Diseases and Public Health of the Canary Islands (IUETSPC), University of La Laguna, 38206 San Cristóbal de La Laguna, Tenerife, Canary Islands, Spain
| | - Beatriz Martín-Cruz
- Toxicology Unit, Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera s/n, Las Palmas de Gran Canaria 35016, Spain
| | - Luis Alberto Henríquez-Hernández
- Toxicology Unit, Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera s/n, Las Palmas de Gran Canaria 35016, Spain; Spanish Biomedical Research Centre in Physiopathology of Obesity and Nutrition (CIBERObn), Madrid 28029, Spain
| | - Cristian Rial-Berriel
- Toxicology Unit, Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera s/n, Las Palmas de Gran Canaria 35016, Spain
| | - Andrea Acosta-Dacal
- Toxicology Unit, Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera s/n, Las Palmas de Gran Canaria 35016, Spain
| | - Manuel Zumbado-Peña
- Toxicology Unit, Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera s/n, Las Palmas de Gran Canaria 35016, Spain; Spanish Biomedical Research Centre in Physiopathology of Obesity and Nutrition (CIBERObn), Madrid 28029, Spain
| | - Octavio P Luzardo
- Toxicology Unit, Research Institute of Biomedical and Health Sciences (IUIBS), University of Las Palmas de Gran Canaria, Paseo Blas Cabrera s/n, Las Palmas de Gran Canaria 35016, Spain; Spanish Biomedical Research Centre in Physiopathology of Obesity and Nutrition (CIBERObn), Madrid 28029, Spain.
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Regnery J, Rohner S, Bachtin J, Möhlenkamp C, Zinke O, Jacob S, Wohlsein P, Siebert U, Reifferscheid G, Friesen A. First evidence of widespread anticoagulant rodenticide exposure of the Eurasian otter (Lutra lutra) in Germany. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 907:167938. [PMID: 37866608 DOI: 10.1016/j.scitotenv.2023.167938] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 10/13/2023] [Accepted: 10/17/2023] [Indexed: 10/24/2023]
Abstract
Exposure of wildlife to anticoagulant rodenticides (ARs) has been extensively documented for species directly or indirectly linked to pest rodents via the terrestrial food web. Recently, the scientific focus extended to a former blind spot, namely AR emissions to the aquatic environment, and provided clear evidence of AR residues in freshwater fish. As second-generation ARs are likely to be transferred along the aquatic food chain, a total of 122 Eurasian otter (Lutra lutra) individuals found dead in Germany between 2005 and 2021 were investigated to shed more light on resultant environmental risks. Target analytes comprised one pharmaceutical and eight biocidal anticoagulants, as well as one suspected bait impurity. Notably, all target compounds were detected in the analyzed livers of otters, a primarily piscivorous top predator and indicator species for the aquatic environment, strictly protected by conservation laws. In regions with pronounced rodent control measures, otters were frequently exposed to biocidal ARs. The elevated AR levels measured in multiple otters, compared to freshwater fish, hinted at biomagnification of second-generation ARs within the aquatic food web. The results indicated that risk mitigation measures implemented in Germany within the biocidal product authorization may not be sufficient to protect aquatic non-target wildlife from AR exposure, challenging the effectiveness of current regulatory measures.
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Affiliation(s)
- Julia Regnery
- Federal Institute of Hydrology, Department of Biochemistry and Ecotoxicology, 56068 Koblenz, Germany.
| | - Simon Rohner
- University of Veterinary Medicine Hannover, Foundation, Institute for Terrestrial and Aquatic Wildlife Research, 25761 Büsum, Germany
| | - Julia Bachtin
- Federal Institute of Hydrology, Department of Biochemistry and Ecotoxicology, 56068 Koblenz, Germany
| | - Christel Möhlenkamp
- Federal Institute of Hydrology, Department of Biochemistry and Ecotoxicology, 56068 Koblenz, Germany
| | - Olaf Zinke
- Museum of the Westlausitz Kamenz, Department of Zoology, 01917 Kamenz, Germany
| | - Stefanie Jacob
- German Environment Agency, Section IV 1.2 Biocides, 06844 Dessau-Rosslau, Germany
| | - Peter Wohlsein
- University of Veterinary Medicine Hannover, Foundation, Department of Pathology, 30559 Hannover, Germany
| | - Ursula Siebert
- University of Veterinary Medicine Hannover, Foundation, Institute for Terrestrial and Aquatic Wildlife Research, 25761 Büsum, Germany
| | - Georg Reifferscheid
- Federal Institute of Hydrology, Department of Biochemistry and Ecotoxicology, 56068 Koblenz, Germany
| | - Anton Friesen
- German Environment Agency, Section IV 1.2 Biocides, 06844 Dessau-Rosslau, Germany
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Gomez EA, Prestridge HL, Smith JA. Anthropogenic threats to owls: Insights from rehabilitation admittance data and rodenticide screening in Texas. PLoS One 2023; 18:e0289228. [PMID: 37540671 PMCID: PMC10403058 DOI: 10.1371/journal.pone.0289228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 07/13/2023] [Indexed: 08/06/2023] Open
Abstract
Owls (Strigiformes) provide myriad ecosystem services and are sentinels for ecosystem health. However, they are at continued risk from anthropogenic threats such as vehicle collisions, entanglement with human-made materials, and exposure to anticoagulant rodenticides (ARs), a widespread pesticide known to affect owls. Texas is an important region for numerous migratory and non-migratory owl species in the United States (US), yet assessments of threats owls face here are lacking preventing the development of informed conservation strategies. This study coupled assessment of admittance data from two wildlife rehabilitation centers in Texas with AR liver screening to (1) identify which species of owls are commonly admitted, (2) evaluate seasonality of admittance, and (3) assess causes of admittance for owls in Texas. Between 2010 and 2021, 1,620 owls were admitted into rehabilitation, representing eight species of which the Great-horned Owl (Bubo virginianus) was the most common. For all owls combined admittance rates were highest in the spring, driven by an influx of juveniles (n = 703, 43.40%). The leading cause of admittance amongst species was 'no apparent injury' (n = 567, 34.94%). Where clear diagnoses could be made, the leading causes of admittances were 'entrapment in human infrastructure' (n = 100, 6.11%) and 'collision with vehicles' (n = 74, 4.56%). While the admittance data did not reveal any cases of AR poisoning, liver screening demonstrated high incidences of AR exposure; of 53 owls screened for ARs, 50.94% (n = 27) tested positive with 18 showing exposure to multiple ARs. Brodifacoum was the most frequently detected AR (n = 19, 43.18%) and seven owls (25.93%) tested positive within lethal ranges. Our results suggest that owls in Texas are at risk from myriad anthropogenic threats and face high exposure rates to ARs. In doing so, our results can inform conservation strategies that mitigate anthropogenic threats faced by owls in Texas and beyond.
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Affiliation(s)
- Eres A Gomez
- Department of Integrative Biology, The University of Texas at San Antonio, San Antonio, Texas, United States of America
| | - Heather L Prestridge
- Biodiversity Research and Teaching Collections, Department of Ecology and Conservation Biology, Texas A&M University, College Station, Texas, United States of America
| | - Jennifer A Smith
- Department of Integrative Biology, The University of Texas at San Antonio, San Antonio, Texas, United States of America
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Oliva-Vidal P, Martínez JM, Sánchez-Barbudo IS, Camarero PR, Colomer MÀ, Margalida A, Mateo R. Second-generation anticoagulant rodenticides in the blood of obligate and facultative European avian scavengers. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 315:120385. [PMID: 36257565 DOI: 10.1016/j.envpol.2022.120385] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Revised: 09/30/2022] [Accepted: 10/04/2022] [Indexed: 06/16/2023]
Abstract
The widespread use of second-generation anticoagulant rodenticides (SGARs) and their high persistence in animal tissues has led to these compounds becoming ubiquitous in rodent-predator-scavenger food webs. Exposure to SGARs has usually been investigated in wildlife species found dead, and despite growing evidence of the potential risk of secondary poisoning of predators and scavengers, the current worldwide exposure of free-living scavenging birds to SGARs remains scarcely investigated. We present the first active monitoring of blood SGAR concentrations and prevalence in the four European obligate (i.e., vultures) and facultative (red and black kites) avian scavengers in NE Spain. We analysed 261 free-living birds and detected SGARs in 39.1% (n = 102) of individuals. Both SGAR prevalence and concentrations (ΣSGARs) were related to the age and foraging behaviour of the species studied. Black kites showed the highest prevalence (100%), followed by red kites (66.7%), Egyptian (64.2%), bearded (20.9%), griffon (16.9%) and cinereous (6.3%) vultures. Overall, both the prevalence and average ΣSGARs were higher in non-nestlings than nestlings, and in species such as kites and Egyptian vultures foraging in anthropic landscapes (e.g., landfill sites and livestock farms) and exploiting small/medium-sized carrions. Brodifacoum was most prevalent (28.8%), followed by difenacoum (16.1%), flocoumafen (12.3%) and bromadiolone (7.3%). In SGAR-positive birds, the ΣSGAR (mean ± SE) was 7.52 ± 0.95 ng mL-1; the highest level detected being 53.50 ng mL-1. The most abundant diastereomer forms were trans-bromadiolone and flocoumafen, and cis-brodifacoum and difenacoum, showing that lower impact formulations could reduce secondary exposures of non-target species. Our findings suggest that SGARs can bioaccumulate in scavenging birds, showing the potential risk to avian scavenging guilds in Europe and elsewhere. We highlight the need for further studies on the potential adverse effects associated with concentrations of SGARSs in the blood to better interpret active monitoring studies of free-living birds.
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Affiliation(s)
- Pilar Oliva-Vidal
- Institute for Game and Wildlife Research, IREC (CSIC-UCLM-JCCM), Ronda de Toledo, 12, 13005, Ciudad Real, Spain; Department of Animal Science, Faculty of Life Sciences and Engineering, University of Lleida, Av. Alcalde Rovira Roure, 191, 25198, Spain.
| | - José María Martínez
- Gobierno de Aragón, Subdirección General de Desarrollo Rural y Sostenibilidad, Departamento Medio Ambiente, C/ General Lasheras 8, E-22003 Huesca, Spain
| | - Inés S Sánchez-Barbudo
- Institute for Game and Wildlife Research, IREC (CSIC-UCLM-JCCM), Ronda de Toledo, 12, 13005, Ciudad Real, Spain
| | - Pablo R Camarero
- Institute for Game and Wildlife Research, IREC (CSIC-UCLM-JCCM), Ronda de Toledo, 12, 13005, Ciudad Real, Spain
| | - Mª Àngels Colomer
- Department of Mathematics, Faculty of Life Sciences and Engineering, University of Lleida, Avda. Alcalde Rovira Roure, 191, 25198, Spain
| | - Antoni Margalida
- Institute for Game and Wildlife Research, IREC (CSIC-UCLM-JCCM), Ronda de Toledo, 12, 13005, Ciudad Real, Spain; Pyrenean Institute of Ecology (CSIC), Avda. Nuestra Señora de la Victoria, 12, 22700, Jaca, Spain
| | - Rafael Mateo
- Institute for Game and Wildlife Research, IREC (CSIC-UCLM-JCCM), Ronda de Toledo, 12, 13005, Ciudad Real, Spain
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Elliott JE, Silverthorn V, Hindmarch S, Lee S, Bowes V, Redford T, Maisonneuve F. Anticoagulant Rodenticide Contamination of Terrestrial Birds of Prey from Western Canada: Patterns and Trends, 1988-2018. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2022; 41:1903-1917. [PMID: 35678209 PMCID: PMC9540899 DOI: 10.1002/etc.5361] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 03/06/2022] [Accepted: 05/04/2022] [Indexed: 06/15/2023]
Abstract
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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Affiliation(s)
- John E. Elliott
- Ecotoxicology and Wildlife Health DirectorateEnvironment and Climate Change CanadaDeltaBritish ColumbiaCanada
| | - Veronica Silverthorn
- Ecotoxicology and Wildlife Health DirectorateEnvironment and Climate Change CanadaDeltaBritish ColumbiaCanada
| | - Sofi Hindmarch
- Ecotoxicology and Wildlife Health DirectorateEnvironment and Climate Change CanadaDeltaBritish ColumbiaCanada
| | - Sandi Lee
- Ecotoxicology and Wildlife Health DirectorateEnvironment and Climate Change CanadaDeltaBritish ColumbiaCanada
| | - Victoria Bowes
- Animal Health CentreBC Ministry of AgricultureAbbotsfordBritish ColumbiaCanada
| | - Tony Redford
- Animal Health CentreBC Ministry of AgricultureAbbotsfordBritish ColumbiaCanada
| | - France Maisonneuve
- Science & Technology BranchEnvironment and Climate Change CanadaOttawaOntarioCanada
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