MR Vole of Wind in the Willows fame is in great danger.
To my complete horror I once killed a water Vole. It was on a canal bank, I had never seen one before, I was 14 and I thought it was a Rat. I aimed a mighty kick which propelled it into the water where a stream of bubbles were the only evidence it had ever been. I have felt guilty about that for years especially when I realised my prey was not a Rattus but a Vole.
Animal liberationists have over the years released thousands of Mink from fur farms. I cannot find it in my heart to totally berate them as they did not consider the consequences. The problem is that the Mink have bred successfully in the wild and are voracious predators. Indigenous Frogs, Birds and Mammals feature in their dietary plan. They follow Atkins and consume all protein. Ergo the Water Vole is now in a high risk situation.
A similar situation has arisen in the South East. The very large American Bullfrog was imported to stock domestic ponds. These reptiles have either escaped or been released and now create a threat to domestic wildlife. A voracious Carnivore American Bullfrogs feed on indigenous creatures from waterfowl, to frogs and newts. These Frogs can, under the right condistions easily sever a child finger.