Left: Surveying for water voles along the River Chess
The water vole (Arvicola terrestris) is Britain's most endangered mammal, its UK population having declined by 95% in the last 100 years. Water voles live on vegetated river banks and their diet includes watercress and rushes. They can be confused with the brown rat, although water voles have a furry tail and their round ears are largely hidden by their fur. Notoriously shy, water voles are most easily detected by discovering their latrines and by spotting signs of feeding. Find out more about the water vole on the People's Trust for Endangered Species web site.
Nationally, water vole populations are threatened by predators, habitat destruction and poor riparian management. On the Chess, the water vole population crashed by 97% between 2001 and 2003 and the major factor identified as responsible was the movement of predatory American mink into the catchment. A recovery scheme was introduced by BBOWT in 2004, involving mink trapping and habitat improvement. A biennial survey programme conducted by BBOWT and the Chiltern Chalk Streams Project has found that the recovery scheme is working; in 2009 the population had recovered to 87% of its size in 2001. This equates to approximately 300 voles on the river. In 2013, RCA volunteers joined forces with BBOWT and the Chilterns Chalk Streams Project to provide additional manpower to survey the river's water vole population. The results showed a worrying 32% decline in water vole numbers, suggesting that mink predation may still be a problem.
Photo above right: spotting droppings is one of the ways in which surveyors assess the size of the river's water vole population
If you live by, work by or own stretches of the riverbank, the way in which you manage this habitat is vitally important for the survival of this charismatic mammal. There is good advice from the Environment Agency on how to look after riverbanks: