Second generation anticoagulant rodenticide residues in barn owls 2017

Shore, Richard F.; Walker, Lee A. ORCID: https://orcid.org/0000-0002-1471-7075; Potter, Elaine D.; Pereira, M. Gloria ORCID: https://orcid.org/0000-0003-3740-0019; Sleep, Darren ORCID: https://orcid.org/0009-0002-1128-1883; Thompson, Nicola J.; Hunt, Alexander G.. 2018 Second generation anticoagulant rodenticide residues in barn owls 2017. Lancaster, NERC/centre for Ecology & Hydrology, 22pp. (CEH Project no. C05766)

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Abstract/Summary

CEH contract report to the Campaign for Responsible Rodenticide Use (CRRU) UK. A wide range of avian and mammalian predators and scavengers in rural Britain is known to be exposed to Second Generation Anticoagulant Rodenticides (SGARs). The barn owl Tyto alba is a sentinel for species that are generalist predators of small mammals in rural areas in the UK and monitoring of liver SGAR residues in barn owls has been adopted as an element of the monitoring undertaken as part of anticoagulant rodenticide stewardship. Monitoring of liver SGAR residues in some 100 barn owls per year is conducted in support of stewardship and annually collected data are compared with those from 395 barn owls that died between 2006 and 2012 (hereafter termed baseline years), prior to the 2016 changes in anticoagulant rodenticide (AR) authorisations and onset of stewardship. The rationale for using data on SGAR residues in barn owls that died between 2006 and 2012 as a baseline was that all measurements had been made using the same analytical techniques, there had been little clear change in exposure over that time period, and the data were the most recent available. The aim of the current study was to measure SGAR exposure in barn owls in 2017. As in the baseline years, the compounds detected most frequently in barn owls that died in 2017 were bromadiolone, difenacoum and brodifacoum. Overall, 90% 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 2017 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 either flocoumafen or difethialone between the baseline years and 2017.  The ratio of birds with ”low” (<100 ng/g wet wt.) 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 2017 for any individual compound or for summed SGARs (∑SGARs)  Average concentrations of brodifacoum, difenacoum, bromadiolone and ∑SGARs in the cohort of owls with “low” residues (<100 ng/g wet wt.) and “high” residues (>100 ng/g wet wt.). There was no significant difference between barn owls from baseline years and from 2017 in the concentrations of either “low” or “high” residues for bromadiolone, difenacoum and brodifacoum, or for all residues summed (∑SGARs). Although not statistically significant, the median and 75th percentile values of “low residues” of most compounds and ∑SGARs were lower in 2017 [and 2016] than in the baseline years Overall, the lack of statistically significant differences in SGAR accumulation by barn owls in 2017 compared within baseline years suggests that full implementation of stewardship since 2016 has yet to be reflected by a detectable general reduction in exposure of barn owls.

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:	Project Website
Date made live:	14 Nov 2018 14:08 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/521500

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