Gray-tailed voles are associated almost exclusively with agricultural lands at low elevations within their limited range. They have invaded formerly forested lands converted to agriculture in coastal range valleys, adjoining the Willamette Valley. Their population typically declines in the winter; small populations are often isolated in fragmented habitats. Within their habitat, they construct intricate and extensive tunnels and subterranean burrows 15 to 30 cm below the surface. They sometimes use the burrows of other species. They use agricultural fields as a form of protection from predators and as a food source. (Edge, et al., 1995; Gordon, et al., 1998; Robbins, 1983; Verts and Carraway, 1987)
This species is similar in appearance and size to their relatives, montane voles, except their dorsum is more yellowish, their tail is grayer and their overall pelage is less grizzled. Their body dimensions are also close to creeping voles, however, their body mass may exceed 50 g, which is double that of creeping voles. Gray-tailed voles average 145 mm in length. In the summer, they have a light yellow-brown or yellow-gray dorsal pelage. Their venter is grayish-white and their feet are gray. Their tail is gray beneath and brownish above. In the winter, black tipped hairs darken their dorsum. Juveniles are gray to grayish-brown, both ventrally and dorsally, their feet are gray and their tail is gray with a black dorsal stripe. Their skull is high, smooth and well arched. Their incisors protrude only slightly beyond the nasals in dorsal view and the incisive foramina are usually less than 5 mm long. Their dental formula is I 1/1, c 0/0, p 0/0, m 3/3, total 16. (Hsu and Johnson, 1970; Verts and Carraway, 1987)
Their mating system is not definitively known. Males have some features, such as relatively small testes, that indicate monogamy within the species. Other traits, such as their sexual dimorphism and the larger home ranges maintained by males, indicate a polygynous mating system. In this species, both females and males are territorial. Relatives of the opposite sex do not keep overlapping home ranges once juveniles became sexually active. This is thought to be an adaptation for inbreeding avoidance. Voles also have hip glands that excrete oils used for a variety of communication functions. They possibly function in dominance displays, individual recognition and territorial marking. While the actual functions of these glands are not known for a certainty, they are more functional during the breeding season. (Gordon, et al., 1998; Wolff, et al., 1994)
In the laboratory setting, females as young as 18 days, weighing only 12.5 g, are capable of mating and producing viable offspring. However, it was found that although litter sizes were larger, the mean mass of offspring was significantly lower and offspring survival to 18 days was significantly lower than among females that first mated at 28 days. This study also showed that up to 70 days of age, litter sizes decrease inversely with the age at which females first mated, but a lower mass at birth is attributed to larger litter sizes. The mean litter size found in the wild is 4.4 young. Their breeding season is from March through December and their gestation period is 21 to 23 days. When gray-tailed voles interbreed with montane voles their resulting hybrid offspring generally have a significantly lower survival rate and are generally born into smaller litters. (Verts and Carraway, 1987; Wolff, et al., 1994)
There is currently very little information available about the parental investment of gray-tailed voles. However, parental behavior has been studied in another member of genus Microtus. Among prairie voles (Microtus ochrogaster), both genders participate in parental care, although male participation may be limited by female interference. 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 construct intricate and extensive systems of runways and subterranean 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 commonly flood fields for several days at a time in the winter, so even though air trapped in subterranean nest cavities permits continued occupancy, they must swim through flooded tunnels to reach their nest. Hybrid litters of gray-tailed voles and other vole species result in smaller litters and 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. The degree of familiarity with other individuals may influence the animal's social behavior, including their use of space and mating behavior. It is unknown how this recognition is developed or achieved, but one proposed way is through the oils secreted from their hip glands. Gray-tailed voles possess many behavioral traits to avoid inbreeding. The home ranges of opposite sex relatives do not overlap when juveniles become sexually active. 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 due to lack of experimentation. One type of communication that is used within related vole species is oils secreted from their hip glands. These glands are thought to function in dominance displays, individual recognition and territorial marking. These glands have been studied minimally within gray-tailed voles and were found to be more functional during the breeding season. Familiarity within this species is important because it influences the animal’s behavior, including their use of space and social behavior. Being able to recognize kin is also a way to avoid inbreeding in this species. It is not completely known how kin recognition is achieved or developed. (Boyd and Blaustein, 1985; Wolff, et al., 1994)
Gray-tailed voles are primarily herbivorous. They are associated almost exclusively with agricultural lands, especially grasses grown for seed, small grains and permanent pastures of legumes and grasses. They commonly inhabit forage crops that provide abundant food and cover. Hence, this species has benefited from agricultural practices. While the specific diet of gray-tailed voles has not been studied extensively, some components of their diet include grasses, clovers, wild onions and false dandelions. They also thrive on white clovers, apples, bluegrasses and ryegrasses in the laboratory. Studies looking at the predation of insects by gray-tailed voles have been inconclusive. (Edge, et al., 1995; Schauber, et al., 1997; Verts and Carraway, 1987)
Gray-tailed voles are countershaded, which is an anti-predator adaptation common to many species of voles. They also avoid predators behaviorally by building underground tunnels. Voles are also associated with agricultural fields, which provide dense cover from predators. 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)
Mammalian associates of gray-tailed voles include 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. In interspecific encounters with other voles, dominant-subordinate or mutual avoidance responses generally occurred. 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)
Gray-tailed voles have little known positive economic importance, outside of research. They have been used in investigations of the impact of dietary selenium and vitamin E on species in Oregon. They were also used as test animals to determine feasibility of enhancing the nutritional quality of residues of annual ryegrass (Lolium multiform) for animal feed by fermentation with torula yeast (Candida utilis). (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)
While the population levels of this species are stable, agricultural practices such as mowing and the use of pesticides reduce population density and growth, survival, recruitment and body growth of these animals. Overall, though, they are thought to have benefited due to human agricultural 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.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in landscapes dominated by human agriculture.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
an animal that mainly eats leaves.
Referring to a burrowing life-style or behavior, specialized for digging or burrowing.
an animal that mainly eats seeds
An animal that eats mainly plants or parts of plants.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
chemicals released into air or water that are detected by and responded to by other animals of the same species
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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Wang, G., D. Edge, J. Wolff. 2001. Rainfall and Guthion 2S Interactions Affect Gray-Tailed Vole Demography. Ecological Applications, 11/3: 928-933.
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