Laura Drake is the Membership and Surveys Co-ordinator for The Mammal Society which is dedicated to the study and conservation of all British mammals. One of the most endangered species is the water vole which is often confused for a rat. Laura outlines the reasons why we should all know the difference between a water vole and a rat.
Why is the water vole protected in Britain?
Recent evidence indicates that water voles, a native British mammal, have undergone a long term decline in Britain. They have disappeared from 94% of their former sites, a decline exceeding even that for the otter. Predation by the introduced American mink has had a severe impact on the native water vole populations, even causing local extinctions. This may be because their usual way of evading predators, by diving and using burrows with underwater entrances, does not protect them from the mink.
Habitat degradation and pollution are also thought to have contributed to the decline. Dredging and clearance of bankside vegetation removes the plants water voles depend on for food and causes disturbance. Water voles are also probably affected by poor water quality, through contamination of water bodies with pollutants and through build up of nitrogen levels in water which causes algal blooms and loss of their food plants.
Does the American Mink attack rats too?
Definitely, the American mink will attack either a rat or water vole indiscriminately.
Will the water vole scavenge from bins?
While the brown rat is omnivorous and will eat almost anything, the water vole is vegetarian and tends to stick to reeds and grasses, but might scavenge from bins if they contain vegetable waste like cabbage.
What are the chances of finding a water vole in your house?
While the brown rat population is estimated at up to 10 million, the population of the water vole is only around 800,000, occurring mainly along well vegetated banks of slow flowing rivers, ditches, dykes and lakes, making their homes in riverbank burrows with entrances below the water level for protection.
This makes it a lot less likely that one will be found in a house, except perhaps in rural areas or in homes by rivers.
When/ where is the best time to spot a water vole?
Water voles tend to be active more during the day than at night. It is usually found near open water and dives and swims with great ease. “Lawns” of closely cropped grass, occasionally with piles of chopped food, may surround burrow entrances. They also leave characteristic tracks in mud flats close to the water. The forefoot has four toes which leave a distinctive star shaped pattern, while the hind foot has five toes with the first and fifth toes leaving prints almost at right angles to the three central toes. The latrines are very distinctive, as are the “lawns” around burrow entrances.
Why isn’t the water vole a pest?
Because the water vole is an aquatic species, they remain within a waterside habitat, and do not encroach into urban areas and housing estates like rats do. Also, their populations are so low that they tend not to be nearly as invasive as the brown rat, if one could consider them to be invasive at all. If you had millions of water voles with no predator to keep the population managed then the main problem one would face is the undermining of river banks. A healthy population in the presence of natural predators, including birds of prey, stoats, weasels and other carnivorous mammals, will still not cause significant damage.
They are a treasured native species (see “Ratty” the water vole in Wind in the Willows) and much rarer than rats and mice. They are endearing little creatures inhabiting our rivers and should be protected from an over zealous predator that should not be in this country.
7 Comments
Very informative. I have no idea the American mink was such a threat. I shall do my best not to confuse a water vole with a rat from now on. Difficult though, as from seeing any rodent for only a split second, your first thought is always that its either a rat or a mice.
Great, informative post Laura. The common brown rat which is spotted along river banks is often the Norwegian Rat. This invasive species costs the British economy £62 million a year. The water vole causes no damage at all and does not spread disease so we all must take care to observe the difference between the two.
Thanks Alicia. The Common or Brown rat is called Rattus norvegicus. This and the ‘Norwegian rat’ are one and the same =)
Mink are a huge threat to Water voles, but we hope to learn more about their distribution so that we can protect voles.
There’s an article on the BBC News site today about a river conservation scheme in Scotland which is removing American mink from the River Don to conserve water voles and moorhens. Even the RSPCA supports the culling of mink; I never knew the problem was that bad!
Apparently there are even several acts of Parliament in place to limit the spread of mink. It’s an offence to release mink or allow them to escape into the wild under the Wildlife and Countryside Act 1981 and the Mink Keeping Order 2003 prohibits the keeping of mink in Scotland. I’m pleased to see the problem has been at least partially addressed by the law.
You’ll be delighted to know that as a result water voles are making a comeback in that area and they expect moorhens to do the same. The long term goal is to make the entire UK a mink-free zone.
I watched a mink for about 10 minutes on open bit of River Don at Halfpenny Bridge,
Rotherham side of Meadowhall. Fascinating.
Thursday 29th March 2012
My husband saw something that he thought was a rat the other night. We were in our somewhat unenclosed woodshed outside our kitchen. We did endure Irene here in Southern Vermont last year and thought we had rat carcasses in our cellar, but now we question and hope that they were voles. Any insight on this would be appreciated!
I’m no expert on North American mammals (I much prefer European insects), but this might help:
http://www.planet-mammiferes.org/drupal/en/node/38?indice=Rattus+norvegicus
http://www.planet-mammiferes.org/drupal/en/node/38?indice=Microtus+richardsoni
Which is a great website: type in the common name of any mammal on the planet and it will tell you a bit about it. More generally:
Rat have a longer pointier faces, Vole have a shorter, rounder faces.
Rats has very prominent ears, whilst vole’s ears are hidden under fur.
Rats have bare tails, whereas voles have shorter fur-covered tails.