Voles I have known

Our neighborhood was built in a grassy area next to a coastal sage scrub preserve. One happy result is that small wild creatures appear often in the garden. It helps that we have no pets, and a wall guards the perimeter.

Two years ago, we reseeded a bare spot in the lawn, and when tender grass shoots poked up, we were careful not to run over them with the lawn mower. But the new grass stayed short anyway. Something was delicately trimming the new shoots. It turned out to be a meadow mouse, or vole.

Voles are widespread but unknown to most people. Most people know other kinds of mice, the ones with big ears, long tails and pointed noses. These are enshrined in the popular culture, from Beatrix Potter to Walt Disney. By contrast, voles are short-eared, short-tailed and have a broad, flattened face, like their larger cousin, the lemming.

There are many species of meadow mice across the continent; most live in grassy areas because their favorite foods are grasses and other green vegetation.

Unlike other mice, which are secretive and nocturnal, voles are active night and day, scurrying around the clock.

On a daylight hike, that glimpse of a small brown furry creature alongside a trail in the wilderness is most likely a vole. They cut runways in tall grass and weedy vegetation and live above ground most of the time.

Voles are mature after just a few weeks, and a female can produce five litters a year. In favorable years, voles, like lemmings, have huge population explosions. After they’ve chomped everything green in sight, large numbers of them starve and the population crashes. In the meantime, they’ve fed every predator for miles around. Despite the legend, they don’t really commit mass suicide by leaping off cliffs.

Millions of school children learn about voles from the skulls and other bones found in owl pellets (regurgitated hairballs). Voles are food for a lot of predators, including coyotes, foxes, snakes and owls, caught during their long hours in the field harvesting grass.

Many grass eaters share a common problem. Blades of grass contain silica -- sand -- in their cell walls, perhaps to allow them to stand upright. Silica is harder than tooth enamel, and when grazers’ teeth get ground down by the constant abrasion, the animals can no longer eat, and they die.

To cope with this, grazing animals as different as voles and horses have evolved similar teeth. The chewing surface of their molars has many ridges of enamel, to increase cutting power and resist wear. Under a hand lens, vole teeth are instantly recognizable by the many angular, intersecting ridges of enamel.

Recently I’ve noticed a small, grayish brown ball of fur poking out from bushes around the lawn. It’s a new vole, definitely not the same one as a couple of years ago. Voles live fast and die young; few survive past a few months.

As with other small animals, individuals come and go quickly, but the population is always out there. I look forward to this continuing trickle of voles in the garden.

* ELISABETH M. BROWN is a biologist and the president of Laguna Greenbelt Inc.

20060127h9vgwqkf(LA)