Rats, Mice And Voles… Oh My!
 | Author:
Allison Kosto, MSU Broadwater County Extension Agent
MSU Broadwater County Extension Agent |
Rats, Mice and Voles… Oh My!
Allison Kosto
MSU Broadwater County Extension Agent
What’s your best story about rats, mice and voles? I know you have one! Let me tell you about mine. I once rented a building for a class with known mice issues. I had everything set up so ran to the restroom before everyone arrived. I was about to sit and do my business when I glanced back at the toilet. Much to my surprise (followed by a loud shriek) I saw two eyes staring back at me from the bowl! Upon investigation I discovered a mouse, very much still alive, clinging to his dead friend in the toilet bowl. My class setup just took a slight deviation…
Rodents are a very common problem. And whether your story is about a new discovery or an unfortunate encounter, I have no doubt it was unpleasant. Controlling rodents can be tricky and often takes multiple strategies to successfully accomplish.
Control of rodents starts by correctly identifying the species. There are two species of rats in Montana. The Bushy-tailed Woodrat, also known as the pack rat, is a native species. The Brown Rat, also known as the Norway Rat, is an invasive species which spread with human expansion of North America. The Woodrat is more common. Its native habitat is timber and rocky areas, but it will inhabit cabins or abandoned buildings. It’s known for stockpiling large amounts of sticks, leaves and other debris to build nests. The Brown Rat has not gained a major foothold in Montana except in isolated cases, primarily in major cities. The Brown Rat is known for spreading disease and inhabiting areas occupied by humans.
Fortunately, in Montana, we don’t have a large problem with rats. However, if you discover one in a garage or old building, there are a few techniques you can use. Trapping can be successful and there are a large variety of traps on the market. However, rats are neophobic, meaning they tend to avoid anything new in their environment. This means it may take a couple of weeks to catch a rat in a trap. Rodenticides (baits) and fumigants are also commercially available for rats.
Mice and voles are easily confused. Mice are typically larger than voles, but not always. Mice have long tails and slim bodies while voles have short tails and stockier bodies. Mice have a pointy nose and big ears while voles a blunt nose and small ears. Mice can be found indoors and outdoors while voles primarily live outdoors. There are five known species of mice in Montana and eight species of voles.
Mice and voles are more of a problem in Montana. Mice can be highly destructive in a home and can harbor diseases including salmonella and Hantavirus. The most effective strategy for mice in a home is to determine how they are getting in and exclude them through habitat modification. Keep the space close to the home open because mice are less likely to cross an area without cover. Close all gaps that are larger than 3/16 of an inch. Small openings should be sealed with a silicone sealant. Expandable foam products stop air flow, but mice will get through them. Large openings should be closed with wood, aluminum or wire mesh. Mice can chew so products such as latex, plastic, rubber or even wood less than ½ thick is not enough.
For mice that are already in the home, there are a variety of solutions. Trapping is often the preferred method. Mice are not as smart as rats so are easy to catch in traps, and there are many products on the market. Rodenticides are a last resort or used in areas where toxic baits are not accessible to humans or other animals.
As the snow melts, we can see the first evidence of voles and the damage left in their wake. Voles work hard all winter creating a maze of runways underneath the snow and removing revegetation. They are busy in the summer too. They eat a variety of plants, but most frequently grasses and forbs. They typically take the vegetation below ground to store in their vast tunnel system and eat it later. Voles can cause issues in the garden by munching on leaves, stems and pods and are also known for girdling trees and damaging roots.
Because of their high production rate, control of voles is difficult, and eradication is virtually impossible. Using multiple methods is recommended for best control. Remove litter and ground cover to reduce food sources. Leaving a tilled area around your garden may discourage them. Tillage also destroys tunnels. Cut the lawn short prior to snow to reduce winter damage. Trapping can be effective with small populations and traps should be placed in their runways. Cats will kill voles but are usually not effective at controlling the population. Wrapping the base of trees or shrubs with hardware cloth can help prevent girdling. Fumigants do not work on voles, but baits can be effective, especially on larger populations.
If you need assistance with control options for these or other vertebrate pests such as ground squirrels or pocket gophers, contact MSU Extension Office in Broadwater County at 406.266.9242 or allison.kosto@montana.edu.
