Montane voles (Microtus montanus) are a native resident of the northwestern United States. They can be found as far north as southern British Columbia and as far south as Arizona and New Mexico. Their range extends south from British Colmubia, through Washington and Oregon, and into northeastern California, as well as east into Nevada, Utah, Montana, Wyoming, and Colorado. Disjunct populations have been found on the border between central Arizona and New Mexico.
Fifteen subspecies of montane voles have been recognized. Two subspecies, Microtus montanus amosus and M. m. rivularis, are endemic to separate counties in Utah. Two more, M. m. codiensis and M. m. zygomaticus, are endemic to separate counties in Wyoming. Three subspecies, M. m. fucosus, M. m. micropus, and M. m. undosus are endemic to separate counties in Nevada. Microtus m. arizonensis, is endemic to the San Francisco River watershed in Arizona. Seven more subspecies are each endemic to separate counties in Arizona, Washington, Colorado, and Montana. (Cassola, 2016; Hafner, et al., 1998; "Identification of the voles from Aragon, Catron County, New Mexico: Are they endangered Arizona montane vole (Microtus montanus arizonensis)?", 2010; Kays and Wilson, 2010; Naughton, 2012; Sera and Early, 2003)
Montane voles are often found in dry grasslands, sagebrush-grasslands, grassy alpine meadows, and agricultural lands 300 to 1190 m above sea level. Montane voles reach high population densities around agricultural areas, such as crop fields and orchards. Studies suggest areas with abundant canopy cover and soil moisture levels less than 20% are favorable for this species. In the northern part of their range, they inhabit montane and grassy intermontane areas. This differs from southern parts of their range, where they are restricted to grassy montane areas. If population density in one area becomes too high, montane voles will tolerate less favorable habitats.
There is evidence that montane voles inhabit marshy habitats, dense forests, and the banks of streams and rivers. Although this species inhabits mountainous areas, a specific elevation range has not been identified, due to their wide range of potential habitats. In the southern parts of their range, montane voles are found at a higher elevation than that of the northern parts of their range. They are commonly found above the timber line on mountains throughout their range. In Colorado, considered the southern part of their range, they do not live at elevations under 2,074 m, but in northern California, they live as low as 824 m.
Montane voles are considered to be semifossorial. Brood nests are spherical and will always be located below ground, however they also construct cup-shaped nests of grass both above and below ground. Males either dig their own burrow or take advantage of empty holes made by gophers (Thomomys). The average burrow depth for montane voles ranges from 21 cm to 23 cm, and average length ranges from 100 cm to 133 cm. However, burrows located in sandy soil can be deeper. Montane voles construct runways in grassy habitats, which are 30 mm to 60 mm wide and may be worn down 1 cm into the dirt. These paths serve as a highway, connecting different burrows to each other and allowing for easy access to rocks and logs for protection from predators. During the winter, montane voles remain active, burrowing and foraging under the snow. (Hodgson, 1972; Kays and Wilson, 2010; Naughton, 2012; Reynolds and Wakkinen, 1987; Sera and Early, 2003; Verts and Carraway, 1998)
Montane voles range in total length from 140 mm to 220 mm and have masses of 37.3 to 85.0 g. Tail lengths range from 24 mm to 69 mm and hind foot lengths range from 14 mm to 27 mm. They have an average ear length of 13.9 mm. Because they continue to grow throughout their life, mass and size depends on age, as well as subspecies, location, and sex. Generally, males are slightly larger than females, and larger individuals are more commonly found in the southwestern part of their geographical range. They have 16 teeth that grow continuously and a dental formula of 1003/1003. Average metabolic rate is 2.65 cm^3 oxygen/hour.
On their dorsal side, montane voles are brown with black-tipped hair mixed in. Their fur is lighter on their sides and fades to a white/gray ventral side. Their feet are silver gray, and their tail is bi-colored – changing from brown to black on the dorsal side and white to gray on the ventral side. There are variations in coloration depending on geographic location. In the southwestern part of their range, montane voles typically have darker fur, while voles farther north have lighter brown fur, as well as more reddish or gray fur. In general, and throughout their range, fur color tends to vary more in females than males.
There are several characteristics that distinguish montane voles from meadow voles (Microtus pennsylvanicus), which have a range similar to montane voles. Montane voles have lighter colored feet and dorsal fur. Montane voles also have four elements on their upper second molar, while meadow voles have five elements. This is the most precise way to distinguish these two species. During mating season, male montane voles, unlike other vole species, have oily skin glands located on their hips.
Newborns are completely hairless. They are born without teeth, their ear and eyes are closed, and their toes are fused. Their ears open first, 3 days after birth, followed by incisors developing between day 3 and day 5. Fur begins to develop and becomes visible on day 4. Finally, about 10 days after birth, their eyes open and their toes separate. ("Identification of the voles from Aragon, Catron County, New Mexico: Are they endangered Arizona montane vole (Microtus montanus arizonensis)?", 2010; Kays and Wilson, 2010; Naughton, 2012; Sera and Early, 2003)
Chemicals found in vegetation consumed by montane voles influence their breeding season. A chemical found in spring grass, 6-methoxybenzoxazolinone, stimulates reproduction, while cinnamic acids and vinyl phenols found in late-summer grasses suppress reproduction. These chemical cues help montane voles to produce offspring when young have the greatest chance of survival. Chemicals in spring grass indicate an upcoming abundance of food, while chemicals in late summer indicate the opposite.
Pheromones are important to the mating process because they aid in finding a mate. Male pheromones also aid in activating the reproductive systems of females. Montane voles have no regular estrus cycles. Ovulation is induced by copulation. As copulation frequency increases, the probability of female ovulation increases.
Montane voles are typically polygynandrous, meaning both males and females mate with multiple partners. However, when population density is low, facultative monogamy occurs. Males do not share nests with females. Neither sex distinguishes between a mate they have previously mated with or not. They also do not distinguish between mates that have or have not mated with other individuals. Females do not distinguish between dominant males and subordinate males when choosing a mate. Females generally stand still while males approach to mate, although aggressive boxing and chasing sometimes occurs. (Berger, et al., 1981; Dewsbury, 1973; Frederick, 1982; Gray, et al., 1974; Naughton, 2012; Sera and Early, 2003; Shapiro and Dewsbury, 1986; Shapiro and Dewsbury, 1990; Verts and Carraway, 1998)
The breeding season for montane voles begins in spring after the snow melts, typically between April and May, and extends through the fall. While less frequent, midwinter breeding does occur. Chemicals found in their diet have an impact on their breeding system. A chemical in spring grasses, 6-methoxybenzoxazolinone, stimulates reproduction, while cinnamic acids and vinyl phenols, found in mature grasses in late summer, suppress breeding. Females have a gestation period of 21 days and typically have 3-4 litters per year in the wild, averaging 6 pups per litter (range 3 to 9 pups). Typically, litter size increases until the fifth litter and then decreases. The breeding interval can be as little as 21 days. In captivity, females can produce up to 13 consecutive litters. Birth mass averages 2.76 g (range: 2.11 to 3.32 g). On average, pups are weaned at 14 days (range: 13 to 16 days), and become independent on the 15th day, when mothers leave to construct a brood nest for their next litter.
Age of sexual maturity varies greatly depending on the time of year pups are born. The first litter, typically born in May, reaches sexual maturity at 4 to 5 weeks of age. The second litter, born mid-to-late summer, reach sexual maturity by 7 to 8 weeks of age. The third litter, born in the fall, will not reach sexual maturity until the next spring, at around 28 to 30 weeks of age. Litters born during winter typically do not survive. Sexual maturity in females may be accelerated when exposed to unfamiliar males. (Berger, et al., 1981; Dewsbury, 1973; Naughton, 2012; Rabon, et al., 2002; Sera and Early, 2003; Verts and Carraway, 1998)
Males provide no paternal care and do not share nests with pregnant females. Females alone manage nursing, brooding, grooming, and pup retrieval. Newborns have an average birth mass of 2.76 g (range: 2.11 to 3.32 g). They are born hairless and without teeth, their ears and eyes are closed, and their toes are fused. Their ears open first, 3 days after birth, followed by incisors, which develop between day 3 and day 5. Pups are able to right themselves and develop fur by day 4. Finally, about 10 days after birth, their eyes open and their toes separate. Pups leave the nest and first eat solid food between 10 to 13 days after birth.
Pups are given less care the older they get, as their mothers spend more time away from nests, searching for a location to raise their next litter. On average, pups are weaned by 14 days of age. Females abandon brood nests at day 15 to construct a new nest for their next litter. If population density is high, females will not abandon their brood nest and extended maternal families form. When this occurs, the age of sexual maturity for pups is delayed. (Frederick, 1978; McGuire and Novak, 1986; Naughton, 2012; Rabon, et al., 2002; Sera and Early, 2003; Shapiro and Dewsbury, 1990; Verts and Carraway, 1998)
Although lifespan greatly depends on the time of year at which they are born, maximum lifespan of montane voles in the wild is 18 months. The first litter, typically born in May, live approximately 6 months. Litters born mid-to-late summer, live approximately 7 months. Litters born in the fall, have the longest lifespan, living approximately 12 months. Litters born during the winter typically do not survive. Montane voles are kept in captivity for research purposes, but are euthanized before lifespan in captivity can be determined. (Naughton, 2012)
Montane voles are active day and night, but are predominantly nocturnal during the summer. Due to summer heat, diurnal activity is limited to a few hours after sunrise and before sunset. Males and females do not share nests and typically live in burrows or nests alone. In general, females are more active than males when it comes to foraging, drinking, traveling, and nest building. Research has indicated that montane voles are not known to jump or climb, but are able to swim.
Montane voles construct elaborate runway systems and seldom venture off their runways. Runways range from 3.8 cm to 6.4 cm in width. Wider runways mean they are more frequently used. Montane voles and similar species share these runways. For example, other vole species (genus Microtus) and vagrant shrews (Sorex vagrans) have been documented in runway systems of montane voles. Runways serve several purposes. Firtly, as a way to evade predators. Runways provide a path cleared of debris, allowing for quick and silent movement through the habitat and an easy escape from predators. Because home ranges of individual montane voles overlap, runways are shared. This allows montane voles to easily find a mate. Runway systems are maintained under the snow during the winter. Caches of food are also placed alongside runways. (Douglass, 1976; Frederick, 1978; Frederick, 1982; McGuire and Novak, 1986; Sera and Early, 2003; Stoecker, 1972; Toews, 1966; Verts and Carraway, 1998)
Live trapping has indicated an average home range for females is about 291.6 m^2 and, for males, about 317 m^2. Research also indicated that home ranges are smaller in winter. In the same study, radio isotope tracing indicated a home range averaging 145 m^2 for both sexes. Females are both intra- and interspecifically territorial. Territory size has not been expressed in terms of area, but females may defend 10 to 20 m around their brood nest. (Naughton, 2012; Toews, 1966)
Like other species of voles, montane voles communicate vocally. Although specific calls have not been identified, infants use ultrasonic vocalizations to call for their mother when they are unable to thermoregulate. Mothers locate pups using these auditory cues rather than olfactory cues. By day 15, pups are able to thermoregulate and vocalizations cease.
Scent marking is also an important means of communication for montane voles. Males often mark their territories with urine, or by leaving piles of feces in their runaway system. Males also mark their territory using gland secretions. Males have scent glands located on their hips, and scent marking is accomplished by anal dragging and by raising their buttocks in order to rub the gland over their tunnel walls. Little research on montane voles has tested visual, auditory, or olfactory acuity. Research does show that montane voles may lack depth perception. Montane voles use sight to forage both day and night. Pheromones are important in mating season, when species-specific chemical cues help montane voles find mates. (Blake, 2002; Ghett, 1977; Sera and Early, 2003)
Montane voles are primarily herbivores, feeding primarily on leaves of forbs and grasses. Research shows that approximately 85% of their diet consist of forb leaves while 9% consists of grasses. In eary spring, when forbs are just beginning to grow, 10% of their diet is fungus. Montane voles only eat fungi when forbs and grasses are less frequent. Forb leaves make up the vast majority of their diet, because they are high in energy and can support their high metabolism. Montane voles consume arthropods when abundant in the summer. However, during the winter, when forbs are not available, grass becomes a more important component of their diet. In winter they will also chew on bark and tree roots. Research shows that small evening primrose (Camissonia minor) and American vetch (Vicia americana) were the two most commonly consumed plants, making up 20% and 16% of their diet, respectively. Out of the grass species available to them, montane voles were only ever observed eating great basin brome (Bromus polyanthus) and slender wheatgrass (Argopyron trachycaulum).
Overhead cover is essential and is provided by grasses and perennial plants. Montane voles forage year-round and concentrate their foraging around edges of covered areas. This allows them to reach a greater variety of food while also being close to covered areas for protection. Montane voles forage day and night. While most active at night, day activities are concentrated to the early-morning and late-evening hours. (Naughton, 2012; Sera and Early, 2003; Vaughan, 1974)
Montane voles are prey for many predators. Mammalian species that feed on montane voles include raccoons (Procyon lotor), American black bears (Ursus americanus), coyotes (Canis latrans), bobcats (Lynx rufus), American badgers (Taxidea taxus), and striped skunks (Mephitis mephitis). Avian predators include marsh hawks (Circus cyaneus), rough-legged hawks (Buteo lagopus), red-tailed hawks (Buteo jamaicensis), American kestrels (Falco sparverius), great horned owls (Bubo virginianus), long-eared owls (Asio otus), short-eared owls (Asio flammeus), burrowing owls (Athene cunicularia), magpies (Pica), gulls (Larus), and shrikes (Lanius). Reptilian species include western terrestrial garter snakes (Thamnophis elegans) and northern Pacific rattlesnakes (Crotalus oreganus). Montane voles are a substantial part of the diet for ermines (Mustela erminea) and long-tailed weasels (Mustela frenata) during the winter months.
Montane voles have several techniques in order to avoid predation. Similar to other species of voles, montane voles are counter-shaded, meaning they have darker fur on their dorsal side than their ventral side. This allows them to better blend into their surroundings, making it harder for predators to spot them. They also construct tunnels and runaways that serve as highways, connecting different burrows to each other and allowing for easy access to cover under rocks and logs when predators are near. (Fitzgerald, 1977; Lyman, et al., 2001; Naughton, 2012; Sera and Early, 2003; Verts and Carraway, 1998)
Montane voles have several economic roles. First, they are a prey species for a wide variety of predators. Second, common behaviors such as tunneling and burrowing aerates soil.
Many parasites affect montane voles, including mites, ticks, lice, fleas, cestodes, nematodes, trematodes, and protozoans. Species of mites include Glycyphagus hypudaei, Androlaelaps fahrenholzi, Brevisterna utahensis, Echinonyssus isabellinus, Echinonyssus occidentalis, Eubrachylaelaps croweri, Eubrachylaelaps debilis, Eulaelaps stabularis, Haemogamasus ambulans, Haemogamasus liponyssoides, Haemogamasus occidentalis, Haemogamasus reidi, Ischyropoda armatus, Laelaps alaskensis, Laelaps incilis, Laelaps kochi, Listrophorus mexicanus, Psorergates townsendi, Comatacarus americanus, Neotrombicula californica, Neotrombicula cavicola, Neotrombicula harperi, and Neotrombicula microti.
Species of ticks include Dermacentor andersoni, unidentified Dermacentor, Ixodes angustus, Ixodes kingi, Ixodes muris, Ixodes muris, Ixodes sculptus, and unidentified Ixodes. Species of lice include Hoplopleura acanthopus, Polyplax alaskensis, Polyplax serrata, and Polyplax spinulosa.
Species of fleas include Amphipsylla sibirica, Callistopsyllus deuterus, Catallagia decipiens, Catallagia mathesoni, Catallagia sculleni, Corrodopsylla curvata, Dactylopsylla rara, Delotelis hollandi, Epitedia stanfordi, Epitedia wenmanni, Hoplopsyllus anomalus, Hystrichopsylla dippiei, Malaraeus bitterroolensis, Malaraeus euphorbi, Malaraeus telchinus, Megabothris abantis, Megabothris asio, Megabothris clantoni, Megabothris lucifer, Meringis hubbardi, Meringis parkeri, Meringis shannoni, Monopsyllus eumolpi, Monopsyllus wagneri, Nonopsyllus fasciatus, Opisodasys keeni, Oropsylla idahoensis, Peromyscopsylla hamifer, Peromyscopsylla selenis, and Thrassis bacchi.
Species of cestodes include Andrya communis, Andrya macrocephala, Andrya primordialis, Hymenolepis horrida, and Paranoplocephala infrequens. Species of nematodes include Nematospiroides microti and Syphacia obvelata. Trematodes include Quinqueserialis hassalli.
There are no known positive economic impacts of montane voles on humans.
Population densities of montane voles are highest in agricultural areas and cause extensive damage to a wide variety of crops. Montane voles commonly eat the roots or grain heads of crops, causing plants to die. Orchards are also affected my montane voles due to extensive damage caused by chewing on bark and roots of trees. This may weaken or kill trees if girdling occurs. (Clark, 1984; Naughton, 2012; Sera and Early, 2003)
Montane voles are listed as a species of least concern on the IUCN Red List and have no special status on the US Federal List, CITES, or the State of Michigan List. While montane voles as a whole are not listed as an endangered species, montane voles (Microtus montanus arizonensis) are a state endangered species in New Mexico and are listed as near threatened on the IUCN Red List. Virgin River montane voles (M. m. rivularis) of special concern in Utah, and are listed as near threatened on the IUCN Red List. This subspecies are under consideration for federal listing under the Endangered Species Act. Pahranagat Valley montane voles (M. m. fucosus) and Ash Meadows montane voles (M. m. nevadensis) are listed as vulnerable on the IUCN Red List and are also under consideration for federal listing under the Endangered Species Act. Cody montane voles (M. m. codiensis) and Big Horn montane voles (M. m. zygomaticus) are listed on the IUCN Red List as data deficient, as more information is needed to determine their current status.
Due to agricultural damage, humans use weed control, lethal snap-traps, and poison baits to reduce montane vole populations. Major treats to montane voles across the subspecies are their restricted distribution, restricted habitat, small population sizes, and habitat degradation due to grazing.
Despite several subspecies of montane voles being state listed as endangered species or considered near threatened by the IUCN Red List, no conservation efforts are in place for this species. Close surveillance of subspecies is recommended to determine current population levels, genetic diversity, and quantify habitat loss. Montane voles are found within Yellowstone National Park and are therefore protected within park boundaries. (Anich and Hadly, 2013; Cassola, 2016; Clark, 1984; Hafner, et al., 1998; "Identification of the voles from Aragon, Catron County, New Mexico: Are they endangered Arizona montane vole (Microtus montanus arizonensis)?", 2010; Sera and Early, 2003; "Status assessment of the Arizona montane vole (Microtus montanus arizonensis) in New Mexico", 2014; United States Fish and Wildlife Service, 1994)
Carley Stidham (author), Radford University, Lauren Burroughs (editor), Radford University, Layne DiBuono (editor), Radford University, Lindsey Lee (editor), Radford University, Karen Powers (editor), Radford University, Galen Burrell (editor), Special Projects.
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
living in landscapes dominated by human agriculture.
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 eats mainly plants or parts of plants.
ovulation is stimulated by the act of copulation (does not occur spontaneously)
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.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
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
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
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
digs and breaks up soil so air and water can get in
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.
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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