Gray-tailed voles look similar to their relatives, montane voles, except their back is more yellowish, their tail is grayer and their fur is overall less grizzled. They are also similar to creeping voles; however, gray-tailed voles can be twice their size, at over 50 grams and 145 millimeters in length. Their underbelly is grayish-white, their feet are gray and their tail is gray beneath and brownish above. In the summer, their fur is light yellow-brown or yellow-gray, whereas in the winter, their fur has black tipped hairs. Juveniles are gray to grayish-brown, their feet are gray and their tail is gray with a black stripe. (Hsu and Johnson, 1970; Verts and Carraway, 1987)
Gray-tailed voles (Microtus canicaudus) are found in the northeastern United States. They prefer low elevations throughout Willamette Valley in Oregon and areas north of the Columbia River in Clark County, Washington. (Gordon, et al., 1998; Hsu and Johnson, 1970; Verts and Carraway, 1987)
Gray-tailed voles are found in farm lands at low elevations. During the winter, their populations become smaller and smaller populations are often found in fragmented habitats. Gray-tailed voles dig tunnels and burrows 15 to 30 cm below the ground, although they sometimes use burrows made by other species. They use agricultural fields to find food and to hide from predators. (Edge, et al., 1995; Gordon, et al., 1998; Robbins, 1983; Verts and Carraway, 1987)
The mating system used by gray-tailed voles is not known. Males have relatively small testes, which may mean that they are monogamous. However, males keep a larger home range and they are sexually dimorphic, as males are larger than females, both of which may mean they are polygynous. In this species, both females and males are territorial. Relatives of the opposite sex do not keep overlapping home ranges, which helps them avoid inbreeding. Voles also have hip glands that excrete oils used for communication in dominance, recognizing others and marking territory. These glands become much more functional during the breeding season. (Gordon, et al., 1998; Wolff, et al., 1994)
In captivity, females as young as 18 days, who weigh as little as 12.5 grams, are capable of mating and producing offspring. However, although litter sizes were larger, offspring were smaller and less likely to survive than offspring born to a 28-day-old mother. Litter sizes decrease based on the age at which females first mated. Offspring born into large litters usually have a lower birth weight. In the wild, the average litter size is 4.4 young. They breed from March through December, with a 21 to 23 day gestation period. Gray-tailed voles are able to interbreed with montane voles, however, their litters are often small and their offspring generally have a lower survival rate. (Verts and Carraway, 1987; Wolff, et al., 1994)
There is currently very little information available about the parental investment of gray-tailed voles. However, the parental behavior of closely related prairie voles (Microtus ochrogaster) has been studied. In that species, both males and females participate in parental care, although females may limit male participation. It is not known whether gray-tailed voles show similar behavior patterns. (McGuire, et al., 2003)
The lifespan of gray-tailed voles has not been reported. However, the captive lifespan of other members of genus Microtus has been reported. For instance, woodland voles (Microtus pinetorum) have a captive lifespan of 3.8 years. Likewise, field voles (Microtus agrestis) and common voles (Microtus arvalis) have a known captive lifespan of up to 4.8 years. Prairie voles (Microtus ochrogaster) have the longest known captive lifespan within the genus at 5.3 years. (Tacutu, et al., 2013)
Gray-tailed voles make extensive underground runways and burrows and sometimes use the burrows of other species. These burrows are constructed 15 to 30 cm below the ground surface and range in size from 8 to 15 cm long by 3 to 5 cm wide. Nests are built underground or above ground under boards, bales and debris scattered in fields. Heavy rains often flood fields for several days at a time in the winter, so even though air trapped in nest cavities allows them to continue to live inside the burrows; they may need to swim through flooded tunnels to reach their nest. Gray-tailed voles can interbreed with other vole species, although hybrid litters are smaller and have fewer surviving offspring, so interbreeding is avoided among these species. (Boyd and Blaustein, 1985; Gordon, et al., 1998; Robbins, 1983; Verts and Carraway, 1987; Wolff, et al., 1994)
Both males and females hold territories, but male territories are larger and overlap with many female territories. Gray-tailed voles are able to recognize other members of their species based on how familiar they are with others. How they develop this recognition is unknown, but it may have to do with oils secreted from their hip glands. How familiar gray-tailed voles are with each other changes their use of space and mating behavior. Gray-tailed voles possess many behavioral traits to avoid inbreeding, the home ranges of opposite sex relatives do not overlap. Also, individuals that are familiar with each other produce fewer litters than unfamiliar individuals. (Wolff, et al., 1994)
Not much is known about communication among gray-tailed voles. These animals likely communicate using oils secreted from their hip glands, which are thought to help them establish dominance, recognize others and mark their territory. These glands are most functional during the breeding season. The ability to recognize kin also helps them avoid inbreeding, however, their method of recognizing relatives is not known. (Boyd and Blaustein, 1985; Wolff, et al., 1994)
Gray-tailed voles are primarily herbivorous. They are found almost exclusively in agricultural lands, especially grasses grown for seed, small grains and pastures of legumes and grasses. They commonly inhabit forage crops with abundant food and cover. While their specific diet is not well known, it includes grasses, clovers, wild onions and false dandelions. In captivity, they are generally fed white clovers, apples, bluegrasses and ryegrasses. They may also eat some invertebrates, although studies of this are inconclusive. (Edge, et al., 1995; Schauber, et al., 1997; Verts and Carraway, 1987)
Gray-tailed voles have countershaded fur, making them more difficult to hunt. They also avoid predators by building underground tunnels and by hiding in the dense cover provided by agricultural fields. Some common predators of this species include owls (Tytonidae, Strigidae), hawks (Falconidae), foxes (Vulpes vulpes, Urocyon cinereoargenteus), skunks (Mephitis mephitis) and domestic and feral cats (Felis catus). These are common predators to many other vole species as well. (Robbins, 1983; Verts and Carraway, 1987)
Gray-tailed shrews are often associated with many other small mammal species including vagrant shrews (Sorex vagrans), townsend moles (Scapanus townsendii), brush rabbits (Sylvilagus bachmani), eastern cottontails (Sylvilagus floridanus), California ground squirrels (Spermophilus beecheyi), camas pocket gophers (Thomomys bulbivorus), deer mice (Peromyscus maniculatus), dusky-footed woodrats (Neotoma fuscipes), townsend voles (Microtus townsendii), creeping voles (Microtus oregoni), Pacific jumping mice (Zapus trinotatus), long-tailed weasels (Mustela frenata) and striped skunks (Mephitis mephitis). They also host several species of fleas. Gray-tailed voles use the burrows of other species, or dig their own burrows, which can be used by other species. (Robbins, 1983; Verts and Carraway, 1987)
The only known negative economic effect of gray-tailed voles is the minor damage they cause to some agricultural crops. (Edge, et al., 1995)
Gray-tailed voles provide little positive economic impacts, outside of research. Livestock found in their range often have nutrient and vitamin deficiencies, so they have been used as test subjects studying nutrient restrictions. (Verts and Carraway, 1987)
Gray-tailed voles have a stable population, although human activities such as mowing and the use of pesticides have reduced their population and survival. Overall, though, they are thought to have benefited due to human farming practices. (Edge, et al., 1995; Gordon, et al., 1998; Schauber, et al., 1997; Wang, et al., 2001)
Courtney Dibble (author), Northern Michigan University, John Bruggink (editor), Northern Michigan University, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
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