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Voles

voles.jpgTiny feet blurred, rusty coat touched by the evening sun, a red-backed vole scurries through the moss and into shelter beneath a spruce log. Wee and wary, it's our most common 'short-tailed' mouse. The Yukon has seven species of voles. They can be distinguished from other small mammals by their beady little eyes, small ears, chunky bodies and short tails.

Because of their small size and secretive ways, voles may be unknown to many people. Yet, as the main source of food for valuable furbearers like ermine, foxes and coyotes, voles play an important role in the Yukon's economy. On the non-economic side, Southern Tutchone, Tagish and Inland Tlingit regard these "mice" with affection and amusement, and often credit them with wisdom and power.

RED-BACKED VOLE ( Clethrionomys rutilus )

Distribution

Red-backed voles live round the world in northern countries and occur throughout the Yukon from arctic coast to southern border. They typically inhabit spruce forests but can also be found in many other habitats, including aspen stands, shrub lands, and arctic and alpine tundra.

Characteristics

Bright, rusty-red backs that contrast with tawny sides and brownish underparts give these voles their name. Even their short tails are reddish on top. Red-backed voles are small and slender, weighing about 20 grams as adults.

Life history

As the last snow melts in late May, tiny red-backed voles lie naked, blind and deaf in a nest beneath a spruce log. Within a week the youngsters crawl feebly, and in two weeks they scamper about and groom their soft, reddish brown fur. Less than a week later, when they weigh about the same as a nickel, they're weaned and leave the nest. The youngsters scatter through the forest, sticking to the cover of logs and deadfalls, or scurrying through tunnels in moss and leaf litter. Yukon red-backed voles are active day and night, nibbling at lichens and fungi as well as buds, leaves and twigs of shrubs or forbs. They build nests of grass, moss, or lichen and tuck them beneath rocks and stumps, or into shallow burrows abandoned by other rodents.

Many young voles die in their first month and less than half survive to see the next spring. Some fall prey to the talons of owls and hawks; others to the teeth of roving adult voles, weasels, foxes and coyotes. When our long mid-summer days begin to ripen fruits and seeds, survivors of May litters are red-coated adults.

In the social world of red-backed voles, breeding females are dominant over all other individuals. They set up territories around their nests and have exclusive use of these areas. They're very aggressive and fight off other voles, accepting a male only when they're ready to mate. And mate they do.

Red-backed voles are reproductive wizards, with females breeding continuously from May through August. Pregnant and nursing at the same time, they produce an average litter of six young every three weeks or so, leaving even the prolific rabbit in the dust. However, along with a high reproductive rate, they also have one of the shortest life spans known among mammals, with few living beyond a year.

Even though females born in spring are sexually mature by mid-summer, they don't breed unless they can set up and defend a territory. That's no problem if vole numbers are low. However, Yukon populations fluctuate from year to year and can be ten times higher in one year than another. When numbers are high, space gets tight in good habitats and female young of the year don't breed until the next spring. This may be a way in which Yukon red-backed voles regulate their population size. Yukon Red-backed voles don't breed during the winter, and their numbers drop from the autumn peak to an early spring low.

With the first frosts of late August and early September, the whirlwind breeding season of the red-backed vole comes to an end. Vole numbers reach their annual peak; breeding territories break down, and young voles disperse in search of good places to spend the winter. As the days get shorter and shorter, red-backed voles search for ripe seeds and occasionally raid a root cellar or storage shed. Unlike many small mammals, these voles don't stockpile food for the long winter months ahead.

When winter casts its white cloak over the North, red-backed voles have the freedom of the boreal forest. Beneath the snow, they build long tunnels and place grass nests on the ground. They don't hibernate and are active all winter, feeding on seeds, twigs and winter buds of heaths and shrubs. Snow not only protects red-backed voles from predatory eyes, it also keeps them warm. Temperatures in the subnivean layer may be 200 Celsius warmer than air temperature above the snow.

However, carbon dioxide does build up from ongoing plant decomposition. As CO2 accumulates, voles punch air holes t-hrough to the surface here and there. In the process, they often become meals for hunting owls.

VIEWING OPPORTUNITIES

The best way to see any of the Yukon voles in a natural setting is to first find some sign of their presence, and then to wait patiently for the voles themselves to appear. Think about where these voles like to live, when they're active, and hope that numbers are high in your area. Remember that red-backed voles are active 24 hours a day and stay under cover, so watch for them running along beneath logs.

Before a thick snow layer develops, look for tiny paired paw prints on the snow. They are slightly offset and two or three centimeters apart. Later, when voles are busy beneath the snow, you may be able to spot small round air holes in the surface. They may also have a few droppings at their edges.

OTHER VOLES

MEADOW VOLE ( Microtus pennsylvanicus )

The meadow vole or "field mouse" tunnels its way through wet meadows and grasslands throughout the Yukon. Its chunky body is dark brown above, silvery gray below, and weighs about 35 grams. This is a feisty rodent that lives in large but not very cooperative colonies. Females are dominant to males and defend small territories around their nests. Males are also aggressive and fight viciously during the breeding season. Since neither sex is very sociable, a tussle usually ensues whenever strangers meet. Lik-e their red-backed cousins, these voles are reproductive wonders and rarely live longer than a year.

Hidden in a grassy world, meadow voles are active day and night throughout the year. In spring they feed on new grass shoots; in summer, on grass leaves and seed heads. They build ball-like nests of woven grass and tuck them into shallow burrows or grassy tussocks. Engineers too, these voles build highways or runways by first chewing through grass stems to clear a space, and then trampling down trails.

Come autumn, meadow voles stockpile ripe grass seeds for the long winter ahead. Later they build winter nests of dried grass located on the ground beneath the snow. Their runways get plenty of use in winter too, when snow covering the grass adds insulation and gives an extra measure of protection from avian hunters.

You can often spook a meadow vole into view just by walking through the grass in an area with lots of sign. An especially good time to look for sign is after snowmelt. Then you can spot the runways, droppings, and flattened winter nests. Meadow voles sometimes chew the bark from shrub stems beneath the snow, so look also for bare stems with tiny, parallel tooth marks. In high population years, these voles may girdle ornamental trees and shrubs, and often raid haystacks.

HEATHER VOLE ( Phenacomys intermedius )

Heather voles resemble meadow voles so closely that the two are virtually impossible to tell apart unless you have one of them in hand. If the one you have has very loose skin, a somewhat orange nose, and sits calmly in your hand, it's a heather vole. If neither of the first two characteristics apply, get out the Band-Aids because meadow voles rarely leave your fingers intact. Tooth pattern, by the way, is the most certain method of identification.

The range, preferred habitat, and habits of the heather vole may also help you to separate it from the meadow vole. Heather voles occur only in southern Yukon in broadleaf and coniferous forests, shrublands and meadows. A key element of these different habitats is the presence of heaths and shrubs, such as blueberry, dwarf birch, willow or soapberry.

This vole is solitary in summer and is active during twilight and dark hours. It feeds on the green parts and berries of heaths and shrubs in summer, and on -their bark and buds in winter. It also caches twigs for winter food supplies, and makes its winter nest of heather twigs, lichens, and grasses.

TUNDRA VOLE or ROOT VOLE ( Microtus oeconomus )

The tundra vole may also be confused with the meadow vole since they not only look alike, but have very similar habits too. As well, their ranges overlap throughout the Yukon except for the southeastern corner, where the tundra vole is absent. However, there are some clues as to the tundra vole's identity. Its brown coat has a yellowish wash and it is on average slightly larger and heavier than the meadow vole. The tundra vole also occupies a greater variety of habitats than the meadow vole. Northern populations prefer to live in damp tundra vegetation near lakes and streams, or in sedge and cotton grass meadows. Southern populations can be found in alpine tundra, marshes, and poplar and spruce woods.

In autumn, the tundra vole stores grass seeds and stems of knotweed and licorice root (Hedysarum sp.). This thrifty habit led scientists to give it a specific name meaning the "economic vole". In the past, Southern Tutchone women appreciated the tundra vole's industrious nature, since it saved them the trouble of finding licorice root. They would dig up the small piles of dirt that mark a vole's underground storehouse, then add the licorice root they found to their own winter food supplies.

LONG-TAILED VOLE ( Microtus longicaudus )

Weighing up to 60 grams, the greyish, long-tailed vole is one of the Yukon's larger voles. However, its outstanding feature is a tail of six or seven centimeters, far longer than the tails of our other voles.

The long-tailed vole is found throughout the Yukon except for the arctic coastal plain and lives in a wide variety of habitats, including marshes, closed spruce forests and alpine tundra. Few studies have been done on this vole, but its habits are thought -to be similar to those of the meadow vole.

SINGING VOLE ( Microtus miurus )

The singing vole is another medium-sized Yukon vole, weighing 25 to 40 grams. Its coat is buffy brown all over and it has a very short, bristly tail. It occurs in arctic and alpine tundra, willow thickets, and spruce forests throughout the Yukon except the southeastern corner.

Singing voles are active day or night throughout the year. They live in colonies that dig shallow burrows and make inconspicuous runways. From their burrow entrances they chirp and trill loudly, earning their name. These voles are also called 'hay mice' because they store grasses, lupine and willow leaves in stacks up to 25 centimeters high in preparation for winter.

Not especially wary, the singing vole often comes out into the open to clip off a lupine stem and drag it back to its hay pile. So, if you can find a freshly excavated burrow or a pile of vole hay curing around the stems of a willow or under a log, you may be able to spot a singing vole. Sit quietly, watch the burrow, and listen for single-note, bird-like chirps.

CHESTNUT-CHEEKED VOLE ( Microtus xanthognathus )

Chestnut-cheeked voles are the giants of Yukon voles, weighing up to 170 grams. They too are brown in color, but have obvious rusty-yellow cheek patches. They occur throughout the northern half of the Yukon in colonies that dig deep burrows in forests, logged-over woodlands, or on grassy slopes. Piles of dirt one to three meters in diameter show where burrow entrances are, and wide runways radiate outward from a central burrow.

Like the singing voles, chestnut-cheeked voles are active both day and night and mak-e chirping noises when intruders approach their burrows. Colonies of this rat-sized, orange-cheeked vole appear and disappear with no apparent rhyme or reason, making it a difficult species to observe and study. Look for fresh dirt piles and runways; if you're lucky enough to see one of these voles, you can't mistake it for any other.

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