The decline in water vole numbers has been halted in Cambs

Cliff Carson, Fenland project officer, has suggested an easy to build device to show where they thrive in Cambs.

It is a flat wooden board like a raft on which water voles like to rest and where they leave tell-tale droppings.

He wants people with water voles living near to them to leave the rafts at the water's edge then contact him with their findings.

'Very wary'

The little mammals prefer ditches with clean water that do not dry out in summer and offer a good cover of varied vegetation.

Mr Carson said: "Water voles cannot resist sitting on any flat object floating at the water's edge and when they do, they leave calling cards, their droppings.

"These are very distinctive - less than half an inch long and rounded at both ends. They quickly become black as they dry.

"Simply moor a short length of plank to the ditch side. The plank needs to be reasonably thick, about 30mm, so that it does not get swamped when the water vole gets aboard.

"If water voles are present, droppings can appear quite quickly, sometimes overnight, usually within a few days.

"You will be exceptionally lucky if you see a water vole actually on the raft as they are very wary and will probably visit it mainly at night."

Mr Carson can be contacted on 01354 602902.