University City

March 15, 2013

Gardening: How to foil any voles in your garden

The voles caught John Neilson by surprise last week.

The voles caught John Neilson by surprise last week.

Neilson, who lives in Autumnwood, is justly proud of his attractive, woodsy front yard. So when three healthy, long-established heavenly bamboo shrubs in his front landscape suddenly collapsed, he didn’t know what to think.

The plants had all been sliced neatly off at the roots. Then, he noticed the tooth marks, like tiny beavers had been chiseling the wood.

Larry Mellinchamp at UNC Charlotte confirmed Neilson’s suspicions. This was the work of voles, the tiny, short-tailed “field mice” that thrive in University City and all across our state, from the mountains to the coast.

Vole problems may be worse this year, since our unusually mild winter may have left vole populations high.

Hard to get rid of them

Eliminating voles is a challenge. The best strategy for gardeners is to learn to live with voles, minimizing their damage while practicing just a bit of non-attachment, knowing that one day your favorite rose or tulip may end up like the Neilson’s nandinas.

The most vital tool for controlling voles is good information. The better you know your enemy, the better you can fight them.

Voles, it turns out, are pretty interesting little critters. They’re closely related to house mice and about the same size, but with shorter tails and different habits. Voles live outdoors, moving around through a system of tunnels that keeps them out of sight most of the time.

They’ve been residing in the Carolinas a lot longer than people have and are very well adapted to local conditions. They live only about a year, on average, but in that time they stay busy having lots of babies, sometimes several litters per year. They don’t hibernate in the winter; they keep right on eating their vegetarian diet of leaves and seeds throughout the year.

In the days before tract-homes landscaping, voles were an indispensable prey buffet for all kinds of predators, from red tailed hawks and great horned owls to red foxes and raccoons. They still are, though the drop in the number of natural enemies contributes to a growing population of voles. The fact that domestic cats also find voles irresistible isn’t enough to keep things in balance.

Two species here

Two types of voles hang out in University City. The pine vole (or, a better name, the woodland vole) is furry all over, with tiny eyes nearly covered up by fuzz. They burrow in the soil and chew on plant roots and bulbs. Pine voles are the prime suspects in the Neilson caper.

The second vole species, the meadow vole, spends more time above ground. They construct tunnels from tall grass and weeds. They damage the tops of plants and can “girdle” mature trees by cutting bark around the entire trunk, eventually stunting or even killing them.

The two vole cousins lead surprisingly different lives. Pine voles practice monogamy and stick close to home in small territories. Meadow vole males wander wantonly from mate to mate in a maze of trails over much larger territories.

That behavior has attracted the attention of scientists, who found that meadow males have a larger hippocampus than females do. That stands to reason, since that’s the brain structure involved in spatial reasoning, including negotiating mazes.

Pine voles of both sexes do not show a difference, suggesting that evolutionary selection might work on the sexual level, not simply the species level.

Practically, those differences between pine and meadow voles give gardeners some tools to work with. For starters, try to determine which species is causing your problems. Pine voles, since they have a restricted range, may be a bit easier to control, though their underground sneak-attack tactics are tough to counter.

Control options

One promising vole control option comes from close to home. The Carolina Stalite Co. in Gold Hill, near Salisbury, is well known for PermaTill, a lightweight soil amendment created from natural volcanic ash slate mined at the company’s site. The company offers VoleBloc, used to establish a barrier within the soil that voles reportedly avoid.

Another well-established alternative is to bury the roots of your plants into underground cages of wire, similar to gopher cages used to protect prized plants on the West Coast. These cages should be installed when new plants are planted, making sure they won’t interfere with root growth. Gardeners should also simply dig up and disrupt any vole tunnels they find.

For meadow voles, with their above-ground habits and wandering ways, a very helpful strategy is to mow short any tall grass or weeds where they might find cover.

(Note to food gardeners: Straw mulch can be wonderful for soil, but be careful not to create vole corridors. They will happily munch on all kinds of crops, including sweet potato roots.)

Another garden basic for our area is to mulch trees correctly. Don’t pile bark mulch right up around a tree’s trunk; always pull it back to create a bare space. With mulch, think “bagel,” not “volcano,” Mulch piled volcano-style invites voles to girdle your tree.

Encouraging predators

For naturally minded types, encouraging natural vole predators by providing habitat makes good sense.

Birds of prey top the list. Vole urinary tracts “leak” as they move around, creating a trail that reflects ultraviolet light, something that some raptors, such as kestrels, can see.

House cats also like voles on their snack menu, though this may set you up for quite a few “gifts” dropped on the kitchen floor, something that’s happening now to friends of mine in Radborne, just off W.T. Harris Boulevard.

Traps can be effective, especially against pine voles, if they are put where voles are active. A standard mouse trap baited with peanut butter may work reasonably well. You need to keep trapping until you are no longer catching anything.

There is broad agreement that poison is not the best approach for homeowners. If you do opt for poison, in the form of a bait, use a “baiting station” that keeps the poison away from pets, children, and other wildlife. Any poison that can kill a rodent can probably kill you, too.

Rather than reaching for the toxins, consider a more environmentally friendly approach. As Hilton Pond Nature Center in South Carolina says on its website:

“Personally, we happen to like pine voles. They seldom bite when handled, and we appreciate the way they fit into the natural scheme: sometimes as prey items, sometimes as consumers of beetle grubs and old persimmons. We welcome pine voles here at Hilton Pond Center and relish the opportunity to watch as they rustle up leaves while foraging for leftover seeds beneath our mid-winter feeders.”

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