Arvicola

Water voles Temporal range: Early Pleistocene - Recent
Arvicola amphibius
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Cricetidae
Subfamily:	Arvicolinae
Tribe:	Arvicolini
Genus:	Arvicola Lacépède, 1799
Species
Arvicola amphibius Arvicola sapidus Arvicola scherman

The water voles are large voles in the genus Arvicola. They are found in both aquatic and dry habitat through Europe and much of northern Asia. A water vole found in Western North America was historically considered a member of this genus, but has been shown to be more closely related to members of the genus Microtus (Conroy and Cook, 2000; Musser and Carleton, 2005).

Head and body length are 12–22 cm, tail length is 6.5–12.5 cm, and the weight is 70–250 g. The animals may exhibit indeterminate growth. They are thick-furred and have hairy fringe on feet that improves their swimming ability.

Species

• European (or Northern) Water Vole (Arvicola amphibius or Arvicola terrestris)
• Southwestern (or Southern) Water Vole (Arvicola sapidus)
• Montane Water Vole (Arvicola scherman)

Distribution and Habitat

The water vole is found in much of Great Britain, northern and central Europe, and in parts of Russia.

There is another water vole found in north-western USA and south-western Canada. However, some sources classify the North American water vole as a separate species.

In Britain, water voles live in burrows excavated within the banks of rivers, ditches, ponds and streams. These burrows are normally located adjacent to slow moving, calm water which they seem to prefer. Also, they live in reed beds in which they weave ball shaped nests above ground if no suitable banks exist.

Water voles prefer lush vegetation that provides important cover to conceal animals when they are above ground and next to the water body. They generally avoid heavily grazed and tramped areas. Water voles may be displaced by the introduction of woodland and scrubland near the water as they prefer more open wetland habitats away from tree cover. They are also just as at home in areas such as upland 'peat land' vegetation, where they utilise suitable.

In Europe and Russia, they may venture into woods, fields and gardens. In the winter they will live underneath the snow.

Normally, they do not live in large groups. Adult water voles each have their own territories, which they mark with faecal latrines located either near the nest, burrow, or favoured water's edge platforms. Latrines are known to be a good survey indicator of this species, and can be used to gauge abundance of animals. Furthermore, they scent-mark by using a secretion from their bodies (a flank gland). However, this is not normally detectable during a field survey. They may attack if their territory is invaded by another water vole.[1]

Diet

Water voles mainly eat grass and plants near the water. Sometimes they will also eat fruits, bulbs, twigs, buds and roots. In Europe, when there is enough food to last the water voles a long time, water vole "plagues" can take place. During this, they eat ravenously, destroying entire fields of grass and leaving the fields full of burrows.[2]

Reproduction

Water vole mating periods last from March into late autumn, in which they will give birth to up to five litters, each containing an average of six young. The female water vole's pregnancy lasts for approximately 20-23 days. Up to 8 Voles can be born, each weighing around 10 grams. The young Voles open their eyes three days after their birth. By the time they are weaned, they are half the size of a fully grown adult water vole.[3]

Conservation

Water vole numbers have plummeted by more than 90 percent in the UK in recent years. The American mink that have escaped from fur farms are a devastating predator of water voles. Also, changes in farming and flood control over the last 60 years have resulted in the loss of habitats.[4]

References

• Conroy, C. J. and J. A. Cook. 2000. Molecular systematics of a Holarctic rodent (Microtus: Muridae). Journal of Mammalogy, 81:344-359.
• Musser, G. G. and M. D. Carleton. 2005. Superfamily Muroidea. pp. 894–1531 in Mammal Species of the World a Taxonomic and Geographic Reference. D. E. Wilson and D. M. Reeder eds. Johns Hopkins University Press, Baltimore.
• Nowak, R. M. 1999. Walker's Mammals of the World, Vol. 2. Johns Hopkins University Press, London.
• Townsend, C., Begon, M. and Harper, J.L. 2003. Essentials of Ecology: second edition. Blackwell Publishing, Oxford.
• Wildlife World