The Hertfordshire Mammal Group have contributed information to the water vole survey and are continuing to research into Hertfordshire s mammals. New members are always welcome. There are several reasons. The factors listed below do not act in isolation but in combination. Many water courses have been damaged by expansion of urban areas, intensification of agriculture and dredging works.
Water voles live in localised groups.
The removal of bankside vegetation with increased predation results in isolated communities which are unable to colonise other areas leading to local extinction. The introduced American mink is now widespread and occurs along many of the rivers in Hertfordshire. Mink were recorded from 5 sites where water voles were no longer present. Climatic factors together with increased abstraction reduces water flow. Six of the survey sites were completely dry.