The exposure of primary and secondary non-target species to Second Generation Anticoagulant Rodenticides (SGARs) is widespread and is a cause for concern amongst conservationists. Levels found in wild non-target species range from trace amounts to lethal levels and occur in up to 81% of barn owl carcasses surveyed. The harm caused by low level AR residues carried by many animals in the wild is not well understood, as is the relative toxicity of the different AR compounds to bird species. My experimental work investigated both sub-lethal residues carried by laboratory mice, Mus musculus, and the comparative toxicity of three SGARs (bromadiolone, difenacoum and brodifacoum) to feral pigeon, Columba livia. Laboratory mice were given >LDso doses of three SGAR compounds and were maintained initially with vitamin K supplements. These mice were monitored for 175 days post-dosing, including through pregnancy. No measurable effect of carrying a SGAR-residue was seen on the growth and breeding activity of mice. Using blood-clotting response testing in pigeons, an EDso was determined for SGAR compounds. Bromadiolone was the least toxic compound to pigeons while the toxicity of difenacoum did not differ significantly from brodifacoum. Data from field trials conducted against AR-resistant rat populations was modelled to compare the exposure levels posed by three SGAR compounds used to control the wild rat infestations. The model was in two parts, the uptake and persistence in the rat population, and the secondary exposure posed by the trials. The AR-resistant rat populations were not controlled completely by bromadiolone or difenacoum and this resulted in much higher levels of SGAR entering the food chain through the rats. This in turn led to higher exposure levels in the secondary non-target species. The need for understanding the toxicity level of each compound to the non-target species of concern was highlighted by this work.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:559253 |
| Date | January 2011 |
| Creators | Daniells, Laura J. |
| Publisher | University of Reading |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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