Vole invasion? Snowy winter helped rodents thrive | SteamboatToday.com

Vole invasion? Snowy winter helped rodents thrive

A long, snowy winter helped rodents such as voles, pictured here, and pocket gophers escape predators under the snow in the Yampa Valley, so residents are seeing more evidence of the rodents this spring.
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The long, snowy winter helped human recreationalists to thrive and also rodents.

Many Routt County residents have noticed an increase in signs of both voles and pocket gophers in yards, open spaces and fields.

On the networking site Nextdoor, one homeowner in the Elk River neighborhood questioned, “Anyone else in Routt County having a vole invasion?” Answers came back about signs of vole or pocket gopher damage in neighborhoods ranging from Fairview to Whitewood and Steamboat II to Tree Haus.

According to the Colorado State University Extension Office, voles can cause extensive damage to forests, orchards and ornamental plants by girdling trees and shrubs, preferring the bark of young trees.

“Most damage occurs in the winter when voles move through their grass runways under the protection of snow. The greatest damage seems to coincide with years of heavy snowfall,” according to the CSU Extension Office’s “Managing Voles in Colorado” publication.

Routt County CSU Extension Director and Agriculture Agent Todd Hagenbuch said voles, commonly montane voles in Routt County, increase in population on a three- to five-year cycle.

This spring’s ample population was protected from common predators such as fox, coyote and raptors by the extended snow cover.

“Because of last fall’s good moisture and lots of grass growth, there was a ton of feed under our copious amounts of snow,” Hagenbuch said. “This created a perfect situation where they were snug under the snow with lots to eat, creating a perfect situation for increased numbers and damage.”

Voles generally cause thin, surface runways or trails through grasses.
Karen Vail/Courtesy photo

Though voles measure 4 to 8 inches long and weigh only 0.8 to 3 ounces, they do not hibernate and are prolific in reproduction. Voles can have three to six young per litter and three to 12 litters per year. Voles breed year-round and can become pregnant as young as three weeks old with a gestation period of three weeks, according to the CSU Extension.

Senior Naturalist Karen Vail at Yampatika said if homeowners want to try to control or repel rodents, the first step is to identify the rodent correctly, because rabbits, mice or marmots may cause similar plant damage.

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“They need to positively identify what it is and try to use repellants first that are fairly non-toxic,” Vail said.

Voles generally cause thin surface runways or trails through grasses, while pocket gophers tunnel underground leaving dirt trails of eskers above ground. The eskers, or long snake-like mounds, are made from soil from burrow building and look like above-ground soil-filled tubes, according to the CSU Extension publication “Managing Pocket Gophers.”

Along a neighborhood trail west of Steamboat Springs, walkers can notice pocket gopher signs including holes to below-ground tunnels and above-ground eskers of soil from burrow digging through the snowy winter.
Suzie Romig/Steamboat Pilot & Today

In general, gophers eat on roots, so plants may die. Voles eat above ground and leave signs of gnawing marks near the dirt that may eventually girdle and kill trees, Vail and Hagenbuch explained.

“That activity all winter long for these animals that is now visible, they’ve had a long, long winter to feed under the protection of snow,” Vail said. “So, they have done a lot of trail work and a lot of damage.”

Vail suggests rotating herbal and less-toxic repellant products weekly, and the smellier the better. She suggests dispersing castor oil granules around the edges of gardens or yards. Planting strong smelling plants such as garlic, onions and chives may also help repel rodents.

“We live in a world of animals that are going to live with us. I know we have investments in our landscape, but we also have to understand that we can’t protect everything. We can’t have it perfect all the time,” said Vail, who also works as a landscaper.

For pocket gophers, Vail suggests finding the tunnel entrances and putting repellent in those holes. Pocket gophers usually breed in the spring and produce one litter of typically three to four young after a gestation of 20 days. Young pocket gophers usually begin dispersing from the burrows in June when about one-third grown, according to CSU Extension.

Experts and locals agree that management and repellants, even if it comes in the form of a barn cat or a rat terrier, are preferred to poisons that could then harm natural predators or possibly pets.

“When selecting a damage-control program (for pocket gophers), consider nonlethal measures such as habitat modification, resistant crop varieties, crop rotation, flood irrigation or cultivated buffer strips, which may be as cost effective as lethal measures and should minimize adverse environmental impacts,” according to CSU Extension.

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