Temporal variation of Water vole exposure to bromadiolone following the recolonization of a treated plot
Résumé
The anticoagulant rodenticide bromadiolone is widely used as plant protection product to control Water vole outbreaks in European grasslands. Following a treatment, vole population declines rapidly and reaches very low density 3 weeks after bait applications. Then, the plot could be recolonized by voles coming from surrounding plots. When buried in artificial galleries, the persistence of bromadiolone in baits has been showed to be short (DT50 ~ 3 to 6 days). However, baits may be stored in cavities by voles, which increases dramatically the persistence of bromadiolone in the environment (DT50 from 25 to 43 days, Sage et al. 2007, Environ. Pollut. 147). In this study, we aim to document the exposure to bromadiolone of Water voles recolonizing a plot several months after a treatment. To simulate the recolonization, some water voles were trapped alive in non-treated grasslands and marked. Then, they were reintroduced in an experimental plot 1.5, 3 and 6 months after bait application, trapped during the 7 to 10 days following their re-introduction and bromadiolone residues were measured in their tissues. Measured residues were compared to those measured by Sage et al. (2008 STOTEN 407) in voles trapped during the days following bait application. Most of the time, concentrations were lower, but our results show that bromadiolone may persist in vole populations during several months after a treatment and thus, may lead to chronic exposure of wildlife to low doses of rodenticides.