Second generation anticoagulant rodenticide residues in barn owls 2018

Shore, Richard F.; Walker, Lee A.; Potter, Elaine D.; Chaplow, Jacky S.; Pereira, M. Gloria; Sleep, Darren; Hunt, Alexander G.. 2019 Second generation anticoagulant rodenticide residues in barn owls 2018. Lancaster, NERC/Centre for Ecology & Hydrology, 24pp. (CEH Project no. C05766) (Unpublished)

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The current report is the fourth in a series of annual reports that describe the monitoring of second generation anticoagulant rodenticide (SGAR) liver residues in barn owls Tyto alba in Britain. This work is an element of an overarching monitoring programme undertaken to track the outcomes of stewardship activities associated with the use of anticoagulant rodenticides. The barn owl is used for exposure monitoring as it is considered a sentinel for species that are generalist predators of small mammals in rural areas. The specific work reported here is the measurement of liver SGAR residues in 100 barn owls that died in 2018 in locations across Britain. The residue data are compared with those from 395 barn owls that died between 2006 and 2012 (hereafter termed baseline years), prior to changes in anticoagulant rodenticide (AR) authorisations and onset of stewardship. As in the baseline years, the compounds detected most frequently in barn owls that died in 2018 were bromadiolone, difenacoum and brodifacoum. Overall, 87% of the owls had detectable liver residues of one or more SGAR. The metrics to be used for stewardship monitoring are reported below in terms of differences between owls that died in 2018 and in baseline years. Numbers of barn owls containing detectable residues of flocoumafen and difethialone. There was no significant difference in the proportion of barn owls with detectable liver residues of flocoumafen between the baseline years and 2018. There was a significantly higher proportion of barn owls with detectable liver residues of difethialone in 2018 compared to baseline years (8% vs 0.3% ). The ratio of birds with ”low” (<100 ng/g ww) vs “high” (>100 ng/g wet wt.) concentrations for any single SGAR or for ∑SGARs. There was no significant difference between barn owls from baseline years and from 2018 for any individual compound or for summed SGARs (∑SGARs), although a decrease in the proportion of birds with “high” difenacoum residues approached significance. Average concentrations of brodifacoum, difenacoum, bromadiolone and ∑SGARs in the cohort of owls with “low” residues (<100 ng/g ww) and “high” residues (>100 ng/g ww). There was no significant difference between barn owls from baseline years and from 2018 in the concentrations of either “low” or “high” residues for bromadiolone, difenacoum (data tested statistically only for “low residues”), all residues summed (∑SGARs), or “high” brodifacoum residues. The median concentration of “low” brodifacoum residues was higher in birds from 2018 than in baseline years. Overall, there were few differences in liver SGAR accumulation between barn owls that died in baseline years and in 2018. The lack of significant reductions in SGAR residues in barn owls in 2018 suggests that full implementation of stewardship since 2016 has yet to result in a reduction in exposure of barn owls to SGARs.

Item Type: Publication - Report
UKCEH and CEH Sections/Science Areas: Pollution (Science Area 2017-)
Funders/Sponsors: NERC/Centre for Ecology & Hydrology, Campaign for Responsible Rodenticide Use (CRRU)
Additional Information. Not used in RCUK Gateway to Research.: Freely available via Official URL link.
Additional Keywords: rodenticide, barn owl, difenacoum, bromadiolone, brodifacoum, flocoumafen, difethialone, monitoring; United Kingdom (UK), stewardship
NORA Subject Terms: Ecology and Environment
Related URLs:
Date made live: 27 Oct 2020 14:00 +0 (UTC)

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