Water voles seek safety in their burrows and restrict their movements mainly to areas of dense vegetative cover to avoid predation. Their prodigious reproductive rates generally help to maintain viable populations under predation stress by natural predators. However, non-native American mink (Neovison vison) are decimating water vole populations in the British Isles.
Known Predators:
Anti-predator Adaptations: cryptic
Average male body length is 210 mm, with females averaging 187 mm. Tail length averages 124 mm in males and 116.5 in females. Males average 263 g, while females average 232 g (Thompson, 1964).
With a dense coat of fur, small, rounded ears, and short tail, A. amphibius resembles other voles of similar size. Water voles are relatively large voles. Their pelage is thick and extends from the head to the end of the tail. Coloration ranges from light to dark brown on top (sometimes black); and from white to slate gray on their underside. This coloration makes them difficult to see in the dense vegetation they prefer. Claws on each of the feet are well developed, and flank glands on the sides of the body used to mark territory are visible most of the time as well. Water voles possess the typical rodent dental formula and posses continuously growing cheek teeth (Niethammer, 1990; Nowak, 1991).
Range mass: 70 to 250 g.
Range length: 120 to 220 mm.
Other Physical Features: endothermic ; bilateral symmetry
Water voles are short-lived, probably suffering the highest mortality rates in their first year. They can live up to 5 years in captivity but average lifespan is less than a year in the wild.
Average lifespan
Status: wild: 5.4 months.
Range lifespan
Status: captivity: 5 (high) years.
Water voles live in the banks of rivers, streams, ponds, and other bodies of water that maintain a fairly constant water level. They prefer areas with good vegetation cover. They are mainly found in lowland areas near waterways but also sometimes occur in gardens and fields. Water voles dig lengthy burrows, ranging from 34 m in the winter up to 74 m in the summer. Burrows contain one or two nests and in the winter contain storage chambers for food (Niethammer, 1989; Nowak, 1991).
Habitat Regions: temperate ; terrestrial
Aquatic Biomes: rivers and streams
Wetlands: marsh ; swamp
Other Habitat Features: agricultural ; riparian
Water voles (Arvicola amphibius) inhabit the Paleartic region, spanning most of central and western Europe, Siberia, Mongolia and some parts of southwest Asia (Nowak, 1991).
Biogeographic Regions: palearctic (Native )
The diet of Arvicola amphibius is comprised mainly of various forms of vegetation. This includes different types of grasses, herbs, and sometimes fruits and seeds. Water voles also feed on the roots of some plants, causing extensive root damage and sometimes destruction of crops. In addition to vegetation, water voles will sometimes supplement their diet with water snails, freshwater mussels, and mollusks (Cobet, 1966; Thompson, 1964).
In the winter, water voles usually maintain at least one chamber in the burrow as a place to store grasses and other food to feed on during lean winter months. They do not live entirely off this store, and will still forage for food during the winter (Nowak, 1991).
Common foods eaten include: reed grass, reeds, flote-grass, water snails, freshwater mussels, grasses, sedges, rushes, mollusks, dandelions, cattail, soft grass, moor grass, water milfoil, water crowfoot, herbs, twigs, buds, bulbs, fallen fruit (Thompson, 1964; Niethammer, 1990; Nowak, 1991).
Animal Foods: insects; mollusks
Plant Foods: leaves; seeds, grains, and nuts; fruit
Foraging Behavior: stores or caches food
Primary Diet: herbivore (Folivore , Granivore )
One interesting piece of information is that water voles (sometimes also known as "water rats") are thought to be the inspiration for the character of "Ratty" in the British novel "The Wind in the Willows" by Kenneth Grahame (Mammal Society, 2001).
Perception Channels: tactile ; chemical
Some humans have attempted to take actions against water voles in efforts to minimize damage to crops (Neithammer, 1990). However, water voles are on the decline in some regions. For example, in England changes due to habitat and introduction of American mink, Neovison vison, is thought to be playing a large role in the decline of water vole populations (Storey, 2001). Conservation efforts are underway in various parts of the British Isles to protect water vole populations.
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
Negative economic impacts from A. amphibius on humans stems mainly from the destruction of human crops such as beans, peas, and some forms of apple trees (Niethammer, 1990). In rare circumstances they have also been known to weaken river banks due to their extensive burrowing (Thompson, 1964)
In addition to crop damage and bank damage, A. amphibius is also known to sometimes carry and transmit tularemia. The disease affects mostly wild rodents and rabbits, but can be transmitted to humans by contact with animal flesh or tick bites (Nowak, 1991; WebMD, 1999).
Negative Impacts: crop pest
Although their economic benefit is somewhat limited, in some regions (such as that once occupied by the former Soviet Union), water voles are hunted for fur.
Positive Impacts: body parts are source of valuable material
Water voles are an important prey base for many small to medium-sized predators. They are also important in nutrient cycling through their burrowing and grazing activities in the ecosystems in which they live.
Male home ranges overlap those of several females and males continually compete for access to receptive females. Research using microsatellite analysis of genetic patterns confirmed that the mating system was promiscuous (Stewart et. al., 1999).
Arvicola amphibius undergoes one mating season per year, usually ranging from early spring (April/March) to late summer/early autumn (August/October). During this time water voles can have up to four litters with an average number of four to six young each. The gestation period is short, 21 days, and postpartum estrus and mating usually occurs shortly after birth. Newborn weight is usually 5g, with young opening eyes around 5 days, and becoming weaned 14 to 21 days after birth. Sexual maturity is reached during their first summer, if born early in the season, or in the following mating season (Bazhan et al., 1996; Nowak, 1991). Females may mature as early as 5 weeks of age.
Breeding interval: Water voles can have up to 4 litters in each breeding season.
Breeding season: Breeding occurs from April to October.
Range number of offspring: 2 to 8.
Average number of offspring: 4-6.
Range gestation period: 20 to 22 days.
Average weaning age: 21 days.
Range age at sexual or reproductive maturity (female): 5 (low) weeks.
Range age at sexual or reproductive maturity (male): 5 (low) weeks.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
While males sometimes participate in the raising of the young, the females are the main care givers (Niethammer, 1990). The young are born helpless but rapidly develop and become independent.
Parental Investment: precocial ; male parental care ; female parental care
The European water vole or northern water vole (Arvicola amphibius), is a semi-aquatic rodent. It is often informally called the water rat, though it only superficially resembles a true rat.[3] Water voles have rounder noses than rats, deep brown fur, chubby faces and short fuzzy ears; unlike rats their tails, paws and ears are covered with hair.
In the wild, on average, water voles only live about five months. Maximum longevity in captivity is two and a half years.[4]
Water voles reach 14–22 centimetres (5.5–8.7 in) in length, plus a tail which is about half the length of the body. Weights reported for adults are variable. It is possible for large, optimal adults to weigh as much as 225 to 386 g (7.9 to 13.6 oz)[5] However, these are peak weights. Elsewhere, the mean body mass has been reported as 60 to 140 g (2.1 to 4.9 oz), although this figure includes immature water voles.[6] The minimum weight to successfully breed as well as to survive winter is reportedly 112 g (4.0 oz) in females and 115 g (4.1 oz) in males.[7] As a species the mean body mass is claimed as 140 g (4.9 oz).[8]
Overall, European water voles are a uniform dark brown colour, with slightly paler coloration on the underside. Their pelage is quite thick and they are furred over their entire body, including their tail, unlike rats. Their dark colour allows them to blend in well in the densely vegetated areas they inhabit.[9]
The binomial applied to the European water vole is Arvicola amphibius; it was formerly known by the junior synonym A. terrestris. The confusion stems from the fact that Linnaeus described two species of water vole on the same page of the same work. Those two forms are now universally considered the same species. It has been recognized as A. amphibius (Linnaeus, 1758) because the first source to unite the two forms, which Linnaeus had treated separately, into a single species chose A. amphibius as the valid name.[2] The species is widely known by the synonym A. terrestris, which for many decades was treated as the valid name.
Some authorities consider the southwestern water vole (Arvicola sapidus) to be the same species, but it is now generally considered distinct.[1][10]
The European water vole (Arvicola amphibius) is found in most of Europe, Russia, West Asia and Kazakhstan.[1]
In Britain, water voles live in burrows excavated within the banks of rivers, ditches, ponds, and streams. Burrows are normally located adjacent to slow moving, calm water which they seem to prefer. They also live in reed beds where they will weave ball-shaped nests above ground if no suitable banks exist in which to burrow.
Water voles prefer lush riparian vegetation which provides important cover to conceal animals when they are above ground adjacent to the water body. Areas of heavily grazed and trampled riparian habitats are generally avoided.[11] Water voles may be displaced by the introduction of riparian woodland and scrub as they prefer more open wetland habitats away from tree cover.
As well as frequenting typical lowland wetland habitats dominated by rank marginal aquatic vegetation, water voles are also just as at home in areas upland 'peatland' vegetation where they utilize suitable small ditches, rivers, and lochs surrounded by moorland up to 1,000 m asl (e.g., northern Scotland).[12]
In Europe and Russia, they may venture into woods, fields, and gardens. They live under the snow during the winter.
Water voles are currently being reintroduced as a threatened species in Yorkshire, England. In the Massif Central area of France, however, farmers are campaigning for action to be taken against water voles, where plagues of these rodents are causing major damage to crops.
Water voles mainly eat grass and other vegetation near the water, but will also consume fruits, bulbs, twigs, buds, and roots when given the opportunity. In Europe, rich harvest periods can cause water vole "plagues" to take place, during which the voles eat ravenously, destroying entire fields of grass and leaving the fields full of burrows. Water voles in some parts of England have been shown to occasionally prey on frogs and tadpoles; it has been speculated that this is to make up for a protein deficiency in the voles' diet.[13]
Food remains alone are not a reliable indicator of the presence of this species, as other smaller voles can also leave remains of large grasses and rushes.[14]
The mating period lasts from March into late autumn. The female vole's pregnancy lasts for approximately 21 days. Up to 8 baby voles can be born, each weighing around 10 grams (0.4 oz). The young voles open their eyes three days after their birth. They are half the size of a full grown water vole by the time they are weaned.
Water voles are expert swimmers and divers. They do not usually live in large groups. Adult water voles each have their own territories, which they mark with fecal latrines located either near the nest, burrow and favoured water's edge platforms where voles leave or enter the water.[12] Latrines are known to be a good survey indicator of this species, and can be used to gauge abundance of animals.[15] They also scent-mark by using a secretion from their bodies (a flank gland), although this is not normally detectable during a field survey. They may attack if their territory is invaded by another water vole.
As a large and common microtine rodent, the range of predators faced by the European water vole is extensive. However, many species of predator prefer other rodents, such as Microtus voles and wood mice, due to their greater numerical abundance.[7] Wildcats, red foxes, most species of hawk (especially common buzzards), owl (especially the barn owl, genus Strix, and Eurasian eagle-owl) and falcon (in large numbers by the common kestrel) in their range are among their reported predators. A very large number are also taken by mustelids. Reportedly small Mustela weasels as well as European and introduced American mink may take the largest number of water voles of any predator due in part to aligning habitat preferences.[7][16] The rarely checked invasive population of American mink has reportedly caused a decline of water voles in Britain.[17]
The water vole population in the U.K. has fallen from its estimated pre-1960 level of around 8 million to 2.3 million in 1990 and to 354,000 (other source: 750,000) in 1998. This represents a 90–95% loss. It is still declining dramatically: the most recent estimate for 2004 is around 220,000. This decline is partly attributed to the American mink, an aggressive predator of the vole, together with unsympathetic farming and watercourse management which destroyed parts of the water vole's habitat.
On 26 February 2008, the U.K. Government announced full legal protection for water voles would be introduced from 6 April 2008.[18] This makes it an offence to disturb, damage or obstruct their breeding places.
The water vole is the U.K.'s fastest declining mammal and efforts are under way to protect it and its habitat from further destruction. One aspect of water vole conservation in the U.K. is focused on non-linear habitats such as reed beds which support extensive networks or metapopulations. Other areas supporting healthy populations of water voles are large conurbations such as Birmingham and London and some upland areas where American mink are scarce. Across the U.K., the Wildlife Trusts and other organisations are undertaking many practical projects to conserve and restore water vole populations.
Water voles have recently returned to Lindow Common nature reserve in Cheshire, after many years of absence.[19] The reserve rangers credit this to conservation management, which included thinning of woodland.
In September 2019, the Box Moor Trust re-introduced 177 Water Voles in to the River Bulbourne in Hemel Hempstead as part of a three-year plan.[20] There is an existing population in nearby Sarratt, and it is hoped that in time the two groups will breed.
Wetlands West (formerly the Severn and Avon Vales Wetlands Partnership) reports on work done as part of the Water Vole Recovery Project in the Berkeley Vale.[21] In Gloucestershire a new nature reserve for water voles was created in 2009/2010 at Nind (a former trout farm).
Glasgow has recently been identified as a stronghold for water voles, including a distinct population of 'fossorial' water voles, which have been reported as inhabiting brownfield sites, road verges and urban parks.
The European otter has been known to attack mink preying upon water voles. There are also indications that the water vole is increasing in numbers in U.K. areas where the European otter has made a return.[22]
In 2015, People's Trust for Endangered Species launched a new project to try to coordinate conservation efforts for the water-vole in the U.K. The National Water-Vole Monitoring Programme (NWVMP) is the first ongoing monitoring scheme for this species in the U.K. and aims to bring together data from several hundred sites to allow the status of this animal to be assessed year-on-year.[23]
A water vole named "Ratty" is a leading character in the 1908 children's book The Wind in the Willows by Kenneth Grahame: the locality used in the book is believed to be Moor Copse in Berkshire, England, and the character's name "Ratty" has become widely associated with the species and their riverbank habitat, as well as the misconception that they are a species of rat.[24][25]
In the comic novel and film Cold Comfort Farm by Stella Gibbons, one of the characters, Urk, refers to the subject of his unrequited love, Elfine Starkadder, as his little water-vole. Throughout the story, Urk spends a lot of time talking to the water-voles on the farm.
C. S. Calverley a 19th-century writer of (among other things) light verse, in his poem "Shelter", beginning:
By the wide lake's margin I mark'd her lie—
The wide, weird lake where the alders sigh—
Tells of an apparently shy, easily frightened young female by a lakeside, who in the last line of the poem, it is revealed that:
For she was a water-rat.
The Rolling Stones song "Live With Me" includes the line "My best friend he shoots water rats and feeds them to his geese", referring to Keith Richards's habit of shooting water voles in the moat of his Redlands, West Wittering home.[26]
{{cite journal}}: CS1 maint: multiple names: authors list (link) The European water vole or northern water vole (Arvicola amphibius), is a semi-aquatic rodent. It is often informally called the water rat, though it only superficially resembles a true rat. Water voles have rounder noses than rats, deep brown fur, chubby faces and short fuzzy ears; unlike rats their tails, paws and ears are covered with hair.
In the wild, on average, water voles only live about five months. Maximum longevity in captivity is two and a half years.
