The water vole (also known as the water rat) was made famous in Kenneth Grahame's 'The Wind in The Willows' and is the lovable character of 'ratty'. There are three native voles in Britain - the field vole, bank vole and water vole. The water vole however is Britain's only aquatic vole and its largest measuring about 20 cm in length (head and body) with a tail up to two thirds its body length. They are relatively easy to observe and are active during the day. If disturbed they will enter the water with a characteristic 'plop'. The water vole has a wide distribution from Britain throughout Europe to East Siberia.
Water voles prefer slow flowing or still water courses with lush bankside vegetation such as tall herbs, grasses, sedges and rushes which all provide cover and food. They prefer areas that are not too heavily tree lined as this reduces the lushness of bankside vegetation.. They prefer to construct their burrows in steep sided or stepped banks. The burrows, which are fronted by small holes in the bank, can be below or above the waterline. They will line their chambers with vegetation and can store food over winter here.
Rats can often be confused with water voles as they can also swim and live in the same areas. Water voles however are more 'rounded' with a blunt muzzle, small eyes and less prominent ears and a shorter tail. Whereas the rat is a grey-brown colour the water vole is chestnut brown with its tail being covered in silky hairs. Because of this confusion between the two species water voles can be accidentally poisoned.
The water vole is predominantly a herbivore and has to consume approximately 80% of its body weight each day!
Breeding occurs between March to October; April is therefore a good month to begin looking for water voles in your area as they will be more gregarious at this time of year. Females mate with only one male and hold exclusive territories but males have larger territories and will often mate with more than one female. Latrines will often mark the end of one territory and the start of another. Latrines are maintained from April to November and are another good indicator of water voles populations. Water voles can have up to five litters a year with between three and seven young. The young become independent after 14 days.
To evade predators water voles will either escape into burrows or dive into water kicking mud from the bottom behind them to hide their escape route. The new young are at most risk and most water voles will not last more than three winters.
National water vole surveys conducted by the Vincent Wildlife Trust have recorded a massive decline in water voles since 1989. A survey in 1989 and 1990 found that water vole shad disappeared from 67% of historical sites, and in 1996-1998 this had increased to 89%.
Several reasons have been suggested for this decline including:
The American mink was released into this country and the water vole has no defence against these voracious predators. The female mink can even follow water voles into their burrows. They have been partly responsible for wiping out water voles sites across the country.
The Cambridge Green Belt Project began surveying for water voles in 1996 and has found populations to be diminishing. Monitoring known water vole sites is essential to allow effective conservation work to take place. It means existing populations and their habitats can be protected and adjacent areas can be targeted to increase suitable areas for colonisation. It also means that any further decline from new threats will be noted early on, so action can be taken.
The free Adobe Reader is needed to view and print files in pdf format. If you need this you can get it here.
Water vole monitoring is co-ordinated by the Cambridge Green Belt Project, the Wildlife Trust for Cambridgeshire and the Environment Agency. However, this work could not go ahead without the help of volunteers. We are appealing for volunteers to help us monitor the remaining populations in the Cambridge Green Belt Project area and in the City to help us to create a clearer picture of water vole activity. It will also help to pinpoint areas which are used regularly or occasionally.
Each volunteer surveyor will be allocated a stretch of river bank or ditch and are asked to survey the site three times, once in May, July and September. If you would like to help with water vole surveying please contact the Project Officers on 01954 713530.
All of these records whether negative or positive are recorded and help to determine the status of water vole in the county. They will be used to plan conservation work at important sites such as Cherry Hinton Brook, where regular conservation work is helping to maintain suitable habitat for the water vole.
Find out about what's been seen on our sightings page, or take a look at details of some of the projects and sites that we work on.