Myodes rutilus
northern red-backed vole

Myodes rutilus is a Holarctic species first described from Siberia. It occurs in northern Europe, Asia, Alaska, and Canada. (Banfield, 1974; Dietrich and Preston, 1977; Nadler, et al., 1978; Rausch, 1953; Runck, 2001; "Clethrionomys rutilus", 1993; West, 1974; West, 1977)

Northern red-backed voles are found in a wide range of terrestrial habitats. They are commonly found in tundra, taiga, and shrub forests. Greatest population densities were recorded in overgrown talus slopes and in stands of dwarf willow, alder, and dwarf birch. (West, 1974; West, 1977; Youngman, 1975; Zuercher, et al., 1999)

Northern red-backed voles are medium mouse-sized, reaching an average total length of 130 to 158 mm and usually weighing about 30 g. The tail is 30 to 40 mm long, hind foot is 18.5 to 21.0 mm long and ears are 10 to 14 mm long. Pelage is light gray with the dorsal surface exhibiting rusty-to-reddish color. Color intensity varies with season (darkest in winter), geographic distribution, and subspecies. The tail is dark gray dorsally, yellow ventrally, and densely covered with hair. Terminal hairs on the tail are often long and dark.

At least 10 subspecies have been described, but researchers differ on the species composition and subspecies validity. Juvenile pelage is similar to adults. There are 8 mammae. The dental formula is I1/1 C0/0 P0/0 M3/3 = 16. Basal metabolic rate is not reported, but average respiratory frequency in normoxic atmosphere is 120 breaths per minute. (Banfield, 1974; Dietrich and Preston, 1977; Gromov and Polyakov, 1992)

Myodes rutilus may sometimes be confused with Myodes gapperi along the southern boundary of the species range. The two species can be distinguished, however, because M. rutilus has brighter reddish coloration than does M. gapperi. Also, the tail of M. rutilus is shorter and thicker than that of M. gapperi. (Batzli, 1999)

Species-specific information on the mating system is not available for wild populations. However, captive colonies in laboratory settings were reported to be promiscuous. (Dietrich and Preston, 1977)

Northern red-backed voles breed from May until September, usually beginning breeding when the snow melts. They can be prolific, producing as many as 5 litters during this time. Postpartum estrus in females helps to increase the rate of reproduction. Winter breeding has been reported to be infrequent.

Pregnancy lasts from 17 to 19 days. Litters of M. rutilus range from 1 to 9, although litters are commonly of 6 to 8 young. The young develop rapidly, and are weaned by about 18 days of age. The young voles become independent at the time of weaning. Reproductive maturity is reached at a minimum age of 2 months. The percentage of sexually mature juveniles varies inversely with population density. (Batzli, 1999; Batzli, 1999; Dietrich and Preston, 1977; Gilbert and Krebs, 1991; Martell and Fuller, 1979)

Males participate in copulation only and do not take any part in parental care. Captive females are reported to enlarge and improve nests prior to giving birth by collecting and modifying soft materials. Both males and females occasionally cannibalize young. It is difficult to estimate average litter sizes and numbers of weaned offspring in the wild, because weaning periods are short and weaned offspring tend to migrate as soon as they leave the nest. As a result, population recruitment rates include immigration, which makes it difficult to estimate reproduction. Captive females that produced average litters of 4.9 offspring weaned only 3.6 young per litter. (Dietrich and Preston, 1977; Martell and Fuller, 1979)

Northern red-backed voles normally survive less than 2 years in the wild; however, average lifespan information varies among publications and is probably affected by locally and temporally varying factors, such as food availability, predation, population density, seasonal weather patterns, etc. Adult mortality is highest in winter and is directly proportional to weather severity. Based on published information, it is unclear whether mortality results mostly from predation, starvation, aging, or other causes. (Dietrich and Preston, 1977; Martell and Fuller, 1979; West, 1974; Zuercher, et al., 1999)

Northern red-backed voles are generally solitary, but may congregate into family groups, especially during winter. They are mostly crepuscular, but may be active during any hour of the day. These voles are avctive year-round. In arctic/subarctic regions, where daylight cycles vary extremely, they rapidly adapt to changing circadian cycles. Pronounced annual cycle in body mass was well documented in interior Alaska. Body mass peaked in early summer for females and in spring for males. (Batzli, 1999; Tavernier, et al., 2004; West, 1977; Zuercher, et al., 1999)

Home range tends to decrease (and overlap with others) during winter and increase during warmer months. A female's home range can be from 0.5 to 0.1 hectares in size. (Batzli, 1999)

Communication and perception are underrepresented in literature. High-pitch vocalization may be produced in high stress situations, such as hostile contacts with potential predators. As in most mammals, it is likely that these voles use some forms of tactile communication during reproduction. Visual cues may also be used. (Morrison, et al., 1976; West, 1974; West, 1977)

Diet varies and includes berries, leaves, shoots, buds, and seeds of various plants, epigeous and hypogeous fungi, and lichens. Their diet includes a large variety of plant materials in the summer when plants are abundant. Voles gather and store food in their nests and the stored food comprises most of their diet during the winter months. Small invertebrates may occasionally be included in the diet and animal foods (e.g. eggs, cat/dog food) are sometimes fed in captivity. (Bangs, 1984; Jones, 1990; West, 1974; West, 1977; Zuercher, et al., 1999)

Northern red-backed voles are common prey to many carnivores and raptors. Cryptic coloration and crepuscular behavior are both antipredatory adaptations. (Kalela, 1957; Lensink, et al., 1955; Thurber, et al., 1992; West, 1974)

Northern red-backed voles act as plant and fungi dispersers (by caching seeds, breaking and relocating parts of vegetation, and ingestion and excretion of spores). They also play an important role as prey to many carnivorous predators, because they are active all winter long when other prey becomes less abundant. (Bangs, 1984; Jones, 1990; Lensink, et al., 1955; Thurber, et al., 1992)

Northern red-backed voles have been used as laboratory animals, but require more care and skill in handling than mice. (Dietrich and Preston, 1977; Morrison, et al., 1976)

Northern red-backed voles readily invade human structures and dwellings. In high densities they can cause damage to farm crops. Interstitial pneumonia and interstitial nephritis were documented in northern red-backed voles, but involvement of viral agents was only suggested. No published information is available on viral or bacterial health threats. (Dietrich and Preston, 1977)

Northern red-backed voles are usually common and not protected throughout their range.