The most common habitat for these voles is grasslands. They can also be found in saltwater marshes, freshwater marshes, and wet meadows. These voles are found in both alpine and subalpine conditions, from sea level to elevations of 1800m . These voles tend to make their homes in riparian areas.
Townsend’s voles are burrowers, commonly building their nests with the entrances near water-ways. Burrows are used by these voles for breeding, as well as female living quarters. The dense grassland areas provide cover for Townsend’s voles. Townsend’s voles are located near oak woodlands, or mixed conifer forests near wetland marshes. Townsend’s voles habitat includes trees such as: Douglass fir (Psuedotsuga menziesii), white fir (Abies concolor), ponderosa pine (Pinus ponderosa,) and incense cedar (Calocedrus decurieris). These voles also occupy second-growth communities while foraging. The diversity of tree species and vegetation is important as habitat, protection, and diet. (Beacham and Krebs, 1980; Lambin, 1994; McGuire and Dumont, 2011; "Natural history of Oregon coast mammals", 1981; "North American rodents", 1998)
Townsend’s voles are rodents with short fur, stout bodies, round visible ears, and dark black eyes. The pelage is grey on the ventral side. They have a long brown or black tail. Adolescent vole pelages are predominantly darker than adults and presumable provide camouflage than the adult pelage.
Average weight of adults is 65g (range 47-83g) and total lengths averages 197mm (range 165-225mm). Juvenile voles, in comparison, average 48 grams in weight and 169 millimeters in length. Females are marginally larger than the males in a study by Lambin (1994).
Due to possible flooding of burrows, one physical key advantage Townsend’s voles have limbs is that allow these voles to be natatorial. Townsend’s voles can cross small streams and are exceptional at diving. The claws of these voles are sharp and curved to accommodate fossorial behavior.
Within the genus Microtus, Townsend's voles are among the largest. Similar but smaller species include creeping voles Microtus oregoni (130-153 millimeters as adults) and grey-tailed voles Microtus canicaudus (140–168 millimeters as adults). (Lambin, 1994; "Natural history of Oregon coast mammals", 1981; "North American rodents", 1998)
Townsend’s voles reproduce sexually. Townsend’s voles can be monogamous or polygynous. Greenwood et al. (1990) suggested if females in a population are polygynous or monogamous, they compete primarily for resources; male voles are primarily competing with other males for breeding access to females. Beacham and Krebs (1980) found that males typically emigrate from their natal grounds, while females stay local. These emigrating males reduce the chance of inbreeding. Female voles are twice as likely as males stay in their natal grounds. When comparing males that are monogamous vs. polygynous, polygynous males traveled further when emigrating. Emigration of males in a population can reduce or limit the probability of inbreeding. Based on male emigration tendencies, territoriality has been suggested. Female Townsend’s voles use pheromones, fecal marking, and additional secretions to attract nearby males. The females are usually aggressive at first encounter. However, after the male retreats the pair of voles share a nest within 24 hours of the occurrence of said event. Copulation occurs approximately 2 days after initial contact. Pregnancy can occur during the estrus period between day 3-6 of diestrus period. (Beacham and Krebs, 1980; Greenwood, et al., 1990; Lambin, 1997)
Townsend’s voles are monogamous or polygynous. According to Beachman and Krebs (1980), both sexes of Townsend’s voles reach maturity at weights of 40-49 g. Most male voles at maturity will disperse from natal sites while mature female voles inherit breeding grounds from their mothers around their natal site. Townsend’s voles are considered iteroparous, having up to 5 litters per year. Their breeding season is typically April through July, but can continue as late as September.
Mcguire et al. (2011) reported instances where voles breeding and caring for a litter can overlap. There is variability between litter size in Townsend’s voles born in the laboratory vs. in the field. Townsend's voles can have as many as seven pups per litter, and as little as two. Townsend’s voles are 2.3g-3.0g at birth. Townsend’s voles lactate until the day 13 to 14 after birth. Beacham and Krebs (1980) found that females born in field have a 12% higher conception rate than laboratory-bred voles. Although the mother may still be lactating, Townsend’s voles are independent as soon as 10 days after birth (maximum time = 15 days). Females experiences postpartum estrus, which usually lasts no longer than 48 hours.
Because age of sexual maturity is measured in weight for Townsend’s voles, Beacham and Krebs (1980) suggested that higher male densities equate to a greater proportion of mature males in the population. Maturity is physically defined as the presence of scrotal testes in males. (Beacham and Krebs, 1980; Cornely and Verts, 1988; McGuire and Dumont, 2011; Mihok, et al., 1985; "North American rodents", 1998)
Townsend's vole males are likely territorial as a way to protect the altricial young. Beyond this, male investment is minimal, and sometimes negative. The fall and summer Townsend’s voles mature faster, and the faster juvenile male voles mature, the more agitated the adult males become. The agitation of adult males can result in premature dispersal as well as infanticide. Both contribute significantly to the decrease in male survival rates. McGuire and Dumont (2011) studied the impact of suckling behaviors on voles. Females involvement is critical development and survival of young. Newborn Townsend’s voles cannot digest solid food until 15 days old. Therefore, females must spend more time in the nest in the first 10 days of postpartum estrus, feeding pups milk. While the females feed the young, they may seek to breed again. Typically, the females spend 60% of their time nursing and parenting their young during the first 10 days of postpartum estrous. The other 40% can compose of finding another partner to breed with or foraging. Cornely and Verts (1988) suggest that identifying pregnant Townsend's voles females is difficult until the last 15 days of pregnancy. Townsend’s voles’ gestation period approximately lasts 21-23 days. Postpartum estrus in female Townsend's voles lasts up to 48 hours. Female voles start weaning the young at 13-14 days and nipple-switching rarely occurs. Burrowing land is usually passed down from the mother to her daughter(s). (Cornely and Verts, 1988; McGuire and Dumont, 2011; "North American rodents", 1998)
Although there is little research done on Townsend's vole lifespan, trends from members of their genus reflects on average a lifespan of approximately 477 days in the wild, and maximum lifespans of 3 to more than 5 years. It's likely that Townsend's voles have a similar lifespan. (Boonstra and Krebs, 1976)
Townsend’s voles are rodents that are classified as cursorial, natatorial, and fossorial. They primarily feed on tubers and vegetation near marsh and waterways. Townsend’s voles have a social order: females compete for land for burrowing, while males compete for their breeding rights. Populations are described as gregarious and social. However, when breeding pressures increase within dense populations, hostility increases and and males avoid interactions.
Townsend’s voles mature within their birth year. The rate of maturation has variability across seasons. Another factor that impacts behavior of the voles are the birth sex ratios. Lambin (1994) found that females in a male-biased litters had elevated levels of testosterone, due to prolonged exposure. Further, male voles in female-dominated litters were less aggressive and possessed lower testosterone levels.
Based on male vole emigration patterns, territoriality has been suggested. Young summer males are faced with excessive aggression from spring males, and the former would be killed if they do not emigrate. Lambin (1994) found that males disperse as far as 16.6m away from their natal site. Females are sedentary, as they often mature and breed close to their birth site. Burrowing land is usually passed down from the mother to her daughter(s). They primarily live in these burrows, but once water levels rise, they build nests located above ground. These nests are in vegetated marsh areas.
Townsend’s voles are not strictly nocturnal. These voles have a daily torpor period and can be active during both morning and night. This characteristic increases the fitness of Townsend's voles by allowing the voles to be active when the risk of predation is lowest.
These voles are herbivore and granivorous, primarily consuming seeds and grass. (Beacham and Krebs, 1980; Boonstra and Krebs, 1976; Cornely and Verts, 1988; Lambin, 1994; McGuire and Dumont, 2011; "North American rodents", 1998)
It is suggested males are territorial, but their territory has not been quantified. (Beacham and Krebs, 1980; Boonstra and Krebs, 1976; Lambin, 1994; "Natural history of Oregon coast mammals", 1981; "North American rodents", 1998)
Townsend’s voles communicate through high-pitched chirping that resembles mice sounds. The frequency is considerably higher than the range humans can perceive. Beachman and Krebs (1980) suggest Townsend's voles weighing less than 50g were less aggressive and matured faster. Dispersion as maturity is reached is more common in the smaller Townsend’s voles. Lambin (1994) suggested late-litter voles disperse, while the early litter offspring (now larger individuals) usually stay and breed where they mature.
These voles use pheromones found in excrement and urine to position and monitor fertile females. The sense of smell is important for recognizing scent marking. Boonstra and Krebs (1976) compared trap efficiency of clean and excrement-and-urine-covered cages. The "stinky" traps captured more, and the authors suggested the scent attracted breeding females.
Enlarged hip glands are another method of dispersion of pheromones into these vole environments. MacIssac (1977) also found that the size of the hip gland was positively related to the state of reproductive maturity. (Beacham and Krebs, 1980; Boonstra and Krebs, 1976; Lambin, 1994; Lambin, 1997; MacIssac, 1977; "Natural history of Oregon coast mammals", 1981; "North American rodents", 1998; Taitt and Krebs, 1982)
Townsend’s vole are herbivores and granivores. They primarily eat grass throughout the year as adults, while during the late summer to fall they eat tuber roots, seeds, and bulbs. Their diet consists of herbaceous plants near grasslands and minor waterways. A few examples of plants in their diet include western blue-eyed grass Sisyrinchium bellum, blue-eyed grass Sisyrinchium sormentosum, velvet grass Holcus lanatus, yellow alfalfa Medicago sativa, and wild mint bulbs Mentha arvensis. During winter months, these voles survive on cached foods. (Beacham and Krebs, 1980; Lambin, 1994; Lambin, 1997; "Natural history of Oregon coast mammals", 1981; Taitt and Krebs, 1982)
Predators of Townsend’s voles include raccoons (Procyon lotor), striped skunks (Mephitis mephitis), weasels (Mustela species), American mink (Neovison vison), coyotes (Canis latrans), red foxes (Vulpes vulpes), gray foxes (Urocyon cinereoargenteus), owls, hawks, and snakes. These voles evade predators by inhabiting burrowing structures with an entrance/exit underwater in summer and densely vegetated areas in winter months. Townsend’s voles are capable swimmers, as well. When Townsend’s voles are young, they have a dark brown and black pelage. As these voles mature their color lightens. Both provide camouflage from predators. Their relatively large ears presumably improving hearing to avoid predation, as well. Mihok et al. (1985) determined that voles that live in forested areas have higher population densities than voles that inhabit fields. As populations increase above 800 individuals per hectare, higher levels of predation are recorded. (Beacham and Krebs, 1980; Boonstra and Krebs, 1976; Cornely and Verts, 1988; Lambin, 1994; Lambin, 1997; Mihok, et al., 1985; "Natural history of Oregon coast mammals", 1981; "North American rodents", 1998)
Townsend's voles maintain a competitive relationship with a few members of their subfamily like meadow voles Microtus pennsylvanicus, northern red-backed voles Myodes rutilus, as well as other rodents like deer mice Peromyscus maniculatus. The relationship between creeping voles Microtus oregoni and Townsend's voles is commensal; as the population of Townsend's voles increases, the population of creeping voles is out-competed. Beacham and Krebs (1980) suggested Townsend's voles are inherently larger and have higher fitness than other species in their genus. Townsend's voles dominate areas by utilizing more resources (e.g., food, breeding territory, and/or burrowing areas).
Townsend's voles also contribute to dispersal of seeds within their ecosystem. Townsend's voles consume primarily vegetation, grains, and alfalfa seeds. These voles contribute to the ecosystem by dispersing seeds once the fruit is digested.
Townsend's voles contribute to the ecosystem by aerating the soil via burrowing. Along with aeration, the burrowing leaves a channel for small critters and insects to travel beneath the soil. During late fall and summer these voles retract to their burrows and eat seed and tubers. The seeds that are not consumed by them may be eaten by a smaller species.
Townsend's voles also play the role of being prey within their ecosystem. Gray foxes Urocyon cinereoargenteus, red foxes Vulpes vulpes, weasels Mustela, owls, and hawks are predators that feed on Townsend's voles.
Townsend's voles are commonly parasitized by northern bot fly Cuterebra grisea larvae. Once voles are infected, they have lower chances of being consumed by a predator. Steen et al. (2002) compiled data to support the notion that parasitism decreases predation on the host; predators will avoid consuming infected prey. However, decreased predation also coincided with a 17% decrease in survival rate of infected Townsend's voles. (Beacham and Krebs, 1980; Boonstra and Krebs, 1978; Lambin, 1997; "Natural history of Oregon coast mammals", 1981; "North American rodents", 1998; Steen, et al., 2002; Sullivan, et al., 2004)
There are no positive economic impacts of Townsend's voles on humans.
There are no known adverse effects ofon humans.
According to the IUCN Red List, Townsend's voles are a species of “Least Concern.” There is no special status for Townsend’s voles on the federal list, CITES, or the State of Michigan lists. Although particular populations fluctuate, the population trends for the species as a whole are stable and positive. There are no major threats to Townsend’s voles, and therefore no conservation measures enacted. These voles do coincide within some protected areas across their range, which affords them some protection from habitat loss. ("Natural history of Oregon coast mammals", 1981)
Nigel Fletcher (author), Radford University, Layne DiBuono (editor), Radford University, Lindsey Lee (editor), Radford University, Kioshi Lettsome (editor), Radford University, Karen Powers (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.
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.
uses sound to communicate
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
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
active at dawn and dusk
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
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.
parental care is carried out by females
an animal that mainly eats leaves.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
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.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
Having one mate at a time.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
chemicals released into air or water that are detected by and responded to by other animals of the same species
having more than one female as a mate at one time
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
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
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
digs and breaks up soil so air and water can get in
places a food item in a special place to be eaten later. Also called "hoarding"
uses touch to communicate
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.
uses sound above the range of human hearing for either navigation or communication or both
uses sight to communicate
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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