The Water Vole is generally distributed in Britain, but does not occur in Ireland, or the Scottish islands; nor is it known outside Britain.
The surface of the molar teeth in all the Voles presents a pattern of alternating triangular prisms. In the Water Vole and the Field Vole these teeth are not rooted in the jaw; in the Bank Vole they are in the adult.
In addition to the definitely black sub-species (reta) referred to above, the southern brown sub-species occasionally throws up black, pied, or albino variations.
Field Vole (Microtus agrestis, Linn.).
To country folk the Field Vole is known generally as the Short-tailed Field Mouse, to distinguish it from the Wood Mouse which is also the Long-tailed Field Mouse. Being different in organisation from the true Mice the attempt was made in natural history works many years ago to substitute the name Vole for these blunt-muzzled Rodents. Recently, after about a hundred years' use of the word Vole in all the works on mammals, Mr. Barrett-Hamilton has objected to it, at least in connection with the present species, on the ground that Field Vole is a duplication, the word Vole meaning "field." This would be almost as bad as Mr. Barrett-Hamilton's own use of such scientific names as Pipistrellus pipistrellus, Barbastella barbastella, Martes martes, and Capreolus capraea, which are duplications in the same language! In East Anglia this species is the Marsh Mouse, and in Surrey Dog Mouse.
The general appearance of the Field Vole is so different from that of a Mouse that it should be obvious at a glance that they are not very closely related. The general stumpy form with the blunt oval outline of the head, the short, round ears just protruding from the reddish-brown fur, and the short, rather stiff tail, are points sufficient to distinguish it from either of our Mice. The colour mentioned refers to the upper parts; on the underside the fur is greyish-white. The hind feet have six pads on the under surface as compared with the five of the Water Vole. The length of head and body is about four inches, and of the tail only an inch and a quarter, that is, about a third of the body length.
The chief resorts of the Field Vole are meadows and damp pastures, but it will also be found in gardens, orchards, and plantations, doing enormous damage in every place, for its food is mainly of a vegetable character. It must, however, be placed to its credit that it catches and consumes large numbers of insects, among them the destructive Larch Sawfly (Nematus erichsonii). It has extensive underground stores where it lays up food for the winter; but it is a mistake to say, as it has been said repeatedly, that the underground burrows include its summer nest. These burrows connect with a network of above-ground runs through the grass and herbage, with occasional holes that enable the Vole to bolt underground. These runs are made without disturbing the grass blades, which cross above them and so enable the Vole to run or creep along them without being seen by the hawk that circles high overhead. He is not so successful in eluding the Owl, who hunts much nearer to the ground and with the Weasel keeps a salutary check upon its increase. Beside a rank tuft of grass along one of these runs the female makes her nest, roofed with a circular dome of grass blades divided longitudinally and plaited and felted. It very much resembles the ground-nest of the Humble-bee, but on a much larger scale. There is nothing to distinguish it from its surroundings, so that only an eye trained to find it would see it. It may be detected by the finer character (due to shredding) of the grass. The parent enters or emerges from any point under the edge of the dome, and in the case of our uncovering the nest will at once bolt, leaving her five youngsters at our mercy. This we have found to be a characteristic callousness on her part. We have frequently torn off the roof of such nests suddenly, but have only been able to catch sight of the rapidly moving mother and trace her for a short distance along a run, so unhesitating and rapid was her flight. Like all our Rodents with the exception of the Hares, the young are naked and blind at birth, and there may be five, six, or seven in a litter. Those shown in the photograph, though their eyes were not open, had beautiful coats of short fur. There are several litters in a season.
[Pl. 68.]][H 106.
Nest of Field Vole.
The dark run at left connects with the nest at right.