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Dowding et al (2010) hedgehog accumulation anticoagulant rodenticides

Title: Accumulation of anticoagulant rodenticides in a non-target insectivore, the European hedgehog (Erinaceus europaeus), Environmental Pollution 158; 161-166.  2010

Authors: C.V. Dowding, R.F. Shore, A. Worgan, P.J. Baker & S. Harris

Country: UK

Background to study

An investigation into the presence and concentration of first-generation anticoagulant rodenticides (FGARs) and the more potent second-generation anticoagulant rodenticides (SGARs) in hedgehogs, detailing regional and sex differences and comparison of two methods for determining contamination prevalence.

Method

  • 120 hedgehog carcasses were collected from wildlife rehabilitation centres from six of the seven geographical regions of England (samples from northern England were not obtained) and dissected, inspected for lesions, injuries or other injuries or illness and the livers removed for analyses.
  • The presence and concentrations of FGARs, coumatetralyl and warfarin (most commonly used) in liver tissue residues were analysed using liquid-chromatography mass spectrometry (LCMS), whilst SGARs, brodifacoum, bromadiolone, difenacoum and flocoumafen were quantified using LCMS and high performance liquid chromatography coupled with fluorescence detection (HPLC).
  • For both measurement techniques, the detection and concentration of FGARs and SGARs were quantified by comparison with rodenticide standards.
  • The average residue concentrations were compared between LCMS and HPLC and the influence of region, the batch in which an individual was processed and the sex of the animal on the presence/absence of contamination was assessed using regression analyses.

Key results

  • No signs of haemorrhage, other than that associated with trauma, were found during post-mortem analyses suggesting that contamination of anticoagulant rodenticides had not caused lethal poisoning.
  • In total SGARs were detected in 23% of animals analysed using HPLC, whilst LCMS detected a significantly higher proportion (57.5% of animals) which resulted from an additional 30 animals being detected to have low levels of difenacoum and bromadiolone residues that were not identified using HPLC. This suggests LCMS is a more sensitive analytical technique for quantifying anticoagulant accumulation in species.
  • Overall, residues of at least one FGAR or SGAR were detected in two thirds of hedgehogs analysed using LCMS with the highest proportion of individuals having residues of one compound (44%) and 18%, 4% and 1% of animals containing residues from two, three or four compounds respectively.
  • Geographical region was not significantly associated with the presence/absence of FGARs or SGARs, despite regional differences in the use of rodenticides.
  • Males were significantly more likely to accumulate rodenticides than females which may be due to their larger range sizes when compared with female hedgehogs.
  • The frequency of occurrence of SGAR residues measured using HPLC were towards the mid or low end of the spectrum documented for predatory birds and mammals in the UK.
  • The magnitude of residues were broadly similar to those measured in predatory birds and mammals in Britain suggesting hedgehogs are at similar risk of exposure.

Key messages to landowners and managers derived from these results

  • LCMS should be used in preference to HPLC for detecting anticoagulant rodenticides in species.
  • Research on the pathways of contamination of anticoagulant rodenticides into the ecosystem is recommended so that preventative measures can be implemented.
  • Increasing public awareness of the adverse effects of anticoagulant rodenticides on hedgehogs and other species is recommended to try and prevent their misuse in rural and urban environments.
  • Research into the use of rodenticide bait stations by hedgehogs is recommended, for instance using tracking tunnels either side of bait stations to detect whether contamination in species is directly attributed to the use of bait stations.
  • Research into the prevalence of anticoagulant rodenticides in hedgehogs occupying different landscape types (urban, rural, agricultural etc) would help to identify main causes of contamination and thus direct measures to reduce the accumulation of rodenticides in hedgehogs and other species.

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