Water vole | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Rodentia |
Family: | Cricetidae |
Subfamily: | Arvicolinae |
Genus: | Microtus |
Subgenus: | Pitymys |
Species: | M. richardsoni |
Binomial name | |
Microtus richardsoni | |
The North American water vole or just water vole (Microtus richardsoni) is the largest North American vole. It is found in the northwestern United States and southern parts of western Canada. This animal has been historically considered a member of genus Arvicola , but molecular evidence demonstrates that it is more closely related to North American Microtus species. [2] [3] Water voles are on the USDA Forest Service Region 2 sensitive species list because they maintain very small populations and there is high concern that their required habitat may be declining. [4]
These animals have gray-brown or red-brown fur with gray under parts. Their large hind feet help make them excellent swimmers, and they are found in alpine or semi-alpine meadows near water. They feed on grasses, leaves, roots and seeds, also eating small invertebrates. Water voles dig burrows that are connected to water sources, and are considered a semi-aquatic species. [5]
They are active year-round, tunneling through snow during the winter. Their burrows often have entrances at the water's edge or under water, [5] and they usually live in colonies of 8-40 individuals along the waterway. [6]
The word vole originated in approximately 1805, and is short for vole-mouse, which means field mouse. Vole originated from the Norwegian word vollmus; voll, meaning field, and mus, meaning mouse. It is also possible that there were influences from Swedish vall, which translates to mean field. [7]
Microtus richardsoni is also known as Richardson's water vole, Richardson vole, Richardson's meadow vole, Richardson meadow mouse, water rat, big-footed mouse, giant water vole, and water vole. [8] The specific name is after Scottish naturalist Sir John Richardson. [9]
Although this animal has been historically considered a member of genus Arvicola, molecular evidence demonstrates that it is more closely related to North American Microtus species. Genetic tests have been done that suggest that the closest relative to Microtus richardsoni is Microtus pennsylvanicus (the meadow vole). Paleontological evidence suggests that M. richardsoni diverged from a Mimomys ancestral form in Siberia approximately 1.5 million years before Arvicola evolved in Europe. This could indicate that it is the primitive form of the genus Microtus, and that the morphological similarities between M. richardsoni and Arvicola are likely convergent traits. [5] [ clarification needed ] Approximately 60 species are now considered to be in the genus Microtus.
Water voles have unusually large hind feet, ranging between 25 and 34 mm in length, which can help distinguish the water vole from other similar rodents, and contribute to its speed in the water. Males tend to be larger than females. On average these animals are about 20–27 cm in total length (including the tail), with tails 6–10 cm long, and weigh 125-178 grams. The water vole is the second largest arvicoline in its range (after the muskrat). [5] Their fur is grey-brown, dark brown, or reddish-brown on the upperparts, and is grayish-white on their underside. The water vole's large incisors, combined with its very large skull and well developed zygomatic arch (which strong chewing muscles attach to), [5] contribute to its ability to efficiently dig tunnels and chew through tough roots.
Water voles live in two distinct bands through the western United States and Canada, extending from British Columbia and Alberta through parts of Oregon, Washington, Montana, Idaho, Wyoming, and Utah. They are found in alpine or semi-alpine meadows near water, usually between 914-3,201 m in elevation. The distribution of habitats is found to be extremely variable, due to the geographical barriers of large coniferous forests, mountains, and expansive valleys without readily available waterways. [5] Although, genetic data has been collected that suggests water voles do have the ability to disperse over land to reproduce with other populations, this overland dispersal between colonies tends to be higher with adjacent populations, and less so with increased distance. [4] Because water voles live in such small isolated patches it is necessary for them to form such a metapopulation structure, in which dispersal can balance out local extinction. [10]
Their main source of food is vegetation, including leaves, stems, grasses, sedges, willows, and sometimes seeds or insects. Their food source varies significantly depending on geographic location. Studies have shown that water voles have a very high metabolic rate, and therefore have to consume more food than other rodents their size. Most often, water voles feed on the subterranean portion of plants, which are available to them year round. There is no evidence that they store food for the winter. During the winter they are seen to dig tunnels through the snow, and usually do not surface above the snow once 6 cm have accumulated (approx. 7 to 8 months of the year). [4] Water voles are most active at night, and they travel between tunnels, nests and waterways by means of surface runways 5–7 cm wide through the vegetation. Often tunnel or burrow entrances are found either at water level or submerged along the river banks. They construct these tunnels and nests just below the roots of the vegetation (about 4–6 cm below ground) during the breeding season (June through late September). Females give birth and care for her young in these underground nests, lined with leaves and grass. [4]
Water voles are usually found within 5 to 10 m from waterways. They form a polygynous social group, [10] in which females tend to stay within their territory, which does not overlap other females, and males travel between burrows to reproduce with several females. Because of this system, males travel over a much larger home range than females, and they tend to be more aggressive than females, with aggressiveness coinciding with breeding patterns. [5] Estrus is induced by contact with reproductively active males, [10] and tends to first coincide with the appearance of vegetation in the spring. [5] Both males and females have rather large flank glands, which serve to mark territories so that nests are not invaded by others, as well as signaling to mates during the breeding season. Water voles breed for 3 months during the summer, and young are born from June until late September. Females generally have litters of approx. 5-6 young, with a minimum gestation period of 22 days. Litter size tends to increase with age of the mother, [5] and ranges from 2-10 young. [10] Although water voles appear to have the ability to reproduce in large numbers, as do many other rodents, their population densities are actually kept very low and live in colonies of 8-40 individuals. [11] This may be due to the very short breeding season compared to other rodents who breed for 6 months or more. [6]
Newborn voles are naked and blind, and weigh about 5 g. They are able to vocalize immediately, and within 3 days start to show fur. By day 10 they are running and climbing, and by day 17 they are swimming on their own. Mother feeds them by lactation until they are 21 days old, and they nest together for approximately 32 days, during which time the pups are growing about 1.24 grams per day. [5] Evidence shows that although they may still be nesting with their mother, she provides very minimal parental care after weaning. [6] Around the time they reach 40 days of age, they move to their own nests and about 3 weeks later reach sexual maturity. [5] Approximately 26% of young males and females begin to reproduce during the breeding season of their birth, [6] but overwintered adults are responsible for most of the reproduction. Some adult females may have up to two litters during one breeding season. [5] Among overwintered adults, 90% of females and 100% of males are reproductively active. [6]
The age distribution studied among populations show a 1:1 replacement of adults by young. Most water voles only live through one winter, and die at the end of the second breeding season. Very few adults survive two winters. [5] [6]
There have been several studies done on the habitat of the vole, given its very specific requirements, to find out if grazing or precipitation levels affect the vole populations so that we can protect them. It has been found that higher precipitation levels create increased availability of usable habitat for water voles. In years of that are wetter than usual it has been observed that young water voles become reproductively active sooner, and therefore can have more offspring. The mean number of pups in each litter increased as well. [11] It has also been found that grazing affects the water vole populations as well. In areas of light or moderate grazing not as many young survived, and the population sizes tended to be much smaller than other colonies. Where there was severe grazing it affected the stream bank to an extent that it was no longer a suitable habitat. [11] The presence of livestock presents numerous detrimental changes to the water vole's habitat: altered abiotic characteristics, compacted soil, increased runoff, fractured stream banks, erosion, as well as loss of vegetation as protective cover and a food source. [12] The abundance of ferns, mosses and shrubs are imperative as ground cover to protect water voles from predation, and in areas of grazing these plants were scarce or non-existent, and therefore water voles weren't often found in these areas. [12]
Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars. They are sometimes known as meadow mice or field mice in North America.
The European water vole or northern water vole, 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.
The Arvicolinae are a subfamily of rodents that includes the voles, lemmings, and muskrats. They are most closely related to the other subfamilies in the Cricetidae. Some authorities place the subfamily Arvicolinae in the family Muridae along with all other members of the superfamily Muroidea. Some refer to the subfamily as the Microtinae or rank the taxon as a full family, the Arvicolidae.
The eastern meadow vole, sometimes called the field mouse or meadow mouse, is a North American vole found in eastern Canada and the United States. Its range extends farther south along the Atlantic coast.
The southern bog lemming is a small North American lemming. Its range overlaps with the other species in genus Synaptomys, the northern bog lemming, in southeastern Canada, but extends farther south.
The northern red-backed vole is a small slender vole found in Alaska, northern Canada, Scandinavia and northern Russia.
The long-tailed vole, in some areas known as the San Bernardino long-tailed vole, is a small vole found in western North America. They have short ears and a long tail. Their fur is gray brown with light gray underparts. They are around 18 cm (7.1 in) long with an 8 cm (3.1 in) tail and weigh about 50 g (1.8 oz).
The genus Phenacomys is a group of North American voles. The genus name comes from the Greek for "imposter mouse."
The prairie vole is a small vole found in central North America.
The short-tailed field vole, short-tailed vole, or simply field vole is a grey-brown vole, around 10 cm in length, with a short tail. It is one of the most common mammals in Europe, with a range extending from the Atlantic coast to Lake Baikal. These voles are found in moist grassy habitats, such as woodland, marsh or on river banks. Although they make shallow burrows, they usually build nests above ground. They are an important food source for owls and some other predators and their population size tends to peak and trough cyclically. Field voles breed prolifically, mainly in summer, but often all year round, even under snow. Females produce up to seven litters a year, each averaging from four to six young which are weaned after about fourteen days. The short-tailed field vole is both widespread and common and is listed as being of "Least Concern" by the IUCN.
The bank vole is a small vole with red-brown fur and some grey patches, with a tail about half as long as its body. A rodent, it lives in woodland areas and is around 100 millimetres (3.9 in) in length. The bank vole is found in much of Europe and in northwestern Asia. It is native to Great Britain but not to Ireland, where it has been accidentally introduced, and has now colonised much of the south and southwest.
The gray-tailed vole also known as the gray-tailed meadow vole or gray-tailed meadow mouse, is a rodent in the genus Microtus of the family Cricetidae. Voles are small mammals, and this species lies roughly in the middle of their size range. First collected in 1895, it is endemic to the Willamette Valley, Oregon, and Clark County, Washington, in the Pacific Northwest region of North America. Historically, they were found in the prairie areas of the Valley and, though many of these areas have been converted for agricultural purposes, these animals remain common. For reasons that remain unclear, vole population densities in any area may fluctuate widely from season to season and year to year. They are preyed upon by owls, hawks, and carnivorous mammals, and their parasites include fleas and ticks. These voles build burrows and complex tunnel networks, which they sometimes share with other burrowing animals. Relatively little is known about their behavior in the wild, because they are elusive and unlikely to enter traps.
The California vole is a type of vole which lives throughout much of California and part of southwestern Oregon. It is also known as the "California meadow mouse", a misnomer as this species is a vole, not a mouse. It averages 172 mm (6.8 in) in length although this length varies greatly between subspecies.
The European snow vole or snow vole is a species of rodent in the family Cricetidae. It has dense, pale grey fur and a pale-coloured tail and can reach about 14 cm (5.5 in) long, with a tail which is 7 cm (2.8 in) long.
The beach vole or Muskeget vole is a rodent in the family Cricetidae. This close relative of the eastern meadow vole is endemic to the 0.87 km2 Muskeget Island, Massachusetts. Due to its relatively short period of reproductive isolation, there is debate over the beach vole's designation as a subspecies of M. pennsylvanicus.
The Mediterranean pine vole is a species of rodent in the family Cricetidae. It is found in France, Andorra, Portugal, and Spain where it lives in a network of shallow tunnels.
The montane vole is a species of vole native to the western United States and Canada.
The creeping vole, sometimes known as the Oregon meadow mouse, is a small rodent in the family Cricetidae. Ranging across the Pacific Northwest of North America, it is found in forests, grasslands, woodlands, and chaparral environments. The small-tailed, furry, brownish-gray mammal was first described in the scientific literature in 1839, from a specimen collected near the mouth of the Columbia River. The smallest vole in its range, it weighs around 19 g. At birth, they weigh 1.6 g, are naked, pink, unable to open their eyes, and the ear flaps completely cover the ear openings. Although not always common throughout their range, there are no major concerns for their survival as a species.
Townsend's vole is a species of rodent in the family Cricetidae, the sister species of M. canicaudus. It is found in temperate grasslands of British Columbia in Canada and in the states of Washington and Oregon in the United States.
The Amargosa vole is one of 17 subspecies of the California vole. The most closely related subspecies is M. californicus vallicola.
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