Myodes glareolus
bank vole

Palearctic: Clethrionomys glareolus is found from Europe through Central Asia (Macdonald 2001; Jonsson et al. 2000). Populations have frequently been recorded in Finland (Oksanen et al. 2001; Yoccoz et al. 2001; Oksanen et al. 1999; Prevot-Julliard et al. 1999; Horne and Ylonen 1996, 1998; Koskela et al. 1998; Koskela et al. 1997) and the United Kingdom (Bellamy et al. 2000; Flowerdew and Gardner 1978). (Bellamy, et al., 2000; Flowerdew and Gardner, 1978; Horne and Ylonen, 1996; Horne and Ylonen, 1998; Jonsson, et al., 2000; Koskela, et al., 1998; Koskela, et al., 1997; Macdonald, 2001; Oksanen, et al., 1999; Oksanen, et al., 2001; Prevot-Julliard, et al., 1999; Yoccoz, et al., 2001)

Bank voles are found in a wide variety of habitats, including forests, scrub forests, hedges, banks, and swamps (Macdonald 2001; Bellamy et al. 2000). They appear to prefer deciduous, coniferous, and taiga forests (Yoccoz et al. 2001; Prevot-Julliard et al. 1999; Koskela et al. 1998; Koskela et al. 1997; Ostfeld 1985).

Adult bank voles reach a head-body length of 10-11cm and a weight of 17-20g, with males and females being approximately the same size. The tail is less than body length and reaches a length of 3-4cm. Bank voles are small with small eyes and ears. Their body is covered by thick fur in shades of brown or gray. Their muzzle is blunt and rounded. Relative to body size, M. glareolus has a small brain. Teeth are prismatic and are characterized by flat crowns, which are adapted for their herbivorous diet (Macdonald 2001).

The mating system of M. glareolus can be described as polygamous (Macdonald 2001), and possibly promiscuous (Horne and Ylonen 1998). While females defend territories that may overlap with other females, males defend larger territories that overlap with the territories of several females. Females appear to prefer dominant males and may affect which males get the chance to mate by running away from subordinate males (Horne and Ylonen 1998). As parturition nears, females become more aggressive and each female's territory decreases in size. The home range becomes smaller and the central ranges of different territories become farther from each other (Koskela et al. 1997).

The estrous cycle of M. glareolus lasts four days (Oksanen et al. 1999). The breeding season is from late April to September (Oksanen et al. 2001). Copulation is characterized by a series of intromissions followed by ejaculation (Horne and Ylonen 1996). Gestation lasts from 17 days with optimal nutrition, to 24 days if the female becomes pregnant while lactating during postpartum estrus (Macdonald 2001; Koskela et al. 1998). The average gestation length is 21 days (Macdonald 2001). From 1 to 10 pups are born per litter with approximately 4 litters born per breeding season (Macdonald 2001; Oksanen et al. 2001). The average number of pups per litter is 4-8 (Oksanen et al. 2001). Pups weigh 1-10g at birth, which makes up a total of 22-28% of the female’s weight. During pregnancy and lactation, females require 30-130% more energy (Ostfeld 1985). Infanticide occurs in males and females. Females will kill the pups of their female neighbors and males will kill pups as a mating tactic (Koskela et al. 1998; Koskela et al. 1997; Horne and Ylonen 1996).

Pups are born blind and helpless in an underground nest lined with grass and other vegetation. The female is the sole provider of parental care (Macdonald 2001). The pups are weaned at the age of 20-25 days (Macdonald 2001; Oksanen et al. 2001; Oksanen et al. 1999; Horne and Ylonen 1998).

The lifespan of M. glareolus is very short. Average lifespan is 0.5-2 years, with most individuals not lasting more than one breeding season (Macdonald 2001; Ostfeld 1985). Bank voles mature quickly with females maturing at 2-3 weeks and males maturing at 6-8 weeks (Macdonald 2001).

Clethrionomys glareolus may be diurnal or nocturnal though they are primarily crepuscular (Macdonald 2001). Their social system is characterized by a dominance hierarchy with females dominant over males, especially during the breeding season (Horne and Ylonen 1998). Upon reaching maturity, males disperse, while females stay in their natal area (Macdonald 2001). Female territories average 0.7ha, while male territories are larger, averaging 0.8ha (Macdonald 2001; Koivula et al. 1999).

Clethrionomys glareolus have been characterized as omnivorous (Ostfeld 1985) and herbivorous (Macdonald 2001). When eating grass, C. glareolus clip the stalks and lays the clippings in piles. Food is obtained in the winter by burrowing underground. In the summer and fall food is cached. Diet changes with season and location but includes green parts of plants (Macdonald 2001), fruits and seeds from available trees, such as the European ash tree (Fraxinus excelsior) (Flowerdew and Gardner 1978) and grass (Macdonald 2001).

Many small predators rely on bank voles as prey. Bank voles partially escape predation by remaining under cover in underground tunnels or runways in grass and vegetation. I is thought that avian predators use the ultraviolet reflections of scent marks to locate their prey (Koivula et al. 1999).

Bank voles are important as a prey base for many small avian and mammalian predators and snakes. They are often abundant and can form the main component of the diet of these predators. They may also help in recycling and redistributing nutrients in the ecosystems in which they live through herbivory.

Humans benefit from bank voles through their beneficial ecosystem roles.

Clethrionomys glareolus have been found to spread hantavirus. In temperate climates, they are also crop pests (Macdonald 2001).

Bank voles are widely distributed and often abundant, they are not threatened.

There is a rich fossil record in the Pleistocene (Macdonald 2001).