Dec 10, 2010

A Mouse in the House



[From my "Wild Ideas" syndicated newspaper column, November 2010] 

Mus Musculus, the house mousePhoto by George Shuklin
It’s that time of year. The days are getting shorter and colder, and in the face of oncoming winter, most of us start thinking about being warm in our abodes with plenty of food at hand.

We’re not alone in our thinking—or in our houses. That pitter patter of little feet and gnawing at night could be a native white-footed mouse, meadow vole or meadow jumping mouse, but more likely it is Mus musculus, the common house mouse.

The house mouse is usually happy on its own outside in warm weather, but it starts looking for better shelter and food as the winter approaches. As its name implies, the species long ago figured out that we humans offer comfy digs.

Being mouse free since I moved into my new house in February, I was dismayed when a family of mice apparently took advantage of my being gone on vacation over Labor Day week to set up winter housekeeping early. I bought a couple of live traps, caught nine of the little critters in one week, and thought I was done—until mouse poop started to show up in the kitchen again. It seems as if mice sit around thinking about the most offensive place they can leave their poop and strategically place it there—on the kitchen counter, in the silverware drawer….


The average house mouse is 6 inches long (the tail making up a little more than half of the total) and weighs up to one ounce. It is superbly designed to get into almost any opening, needing only about one-quarter inch of clearance. Dryer vents and spaces around pipes and wiring can be entry points if not sufficiently blocked.


The house mouse will consume anything organic, although they prefer cereal grains and vegetables. It has a lifespan in the wild of about two years, and the females can give birth to several litters of 3–10 young each year. They tend to colonize, especially in the winter to conserve heat, and are nocturnal when enough food is available. Although we learned as kids that mice go “squeak,” the house mouse actually has a wide range of vocalizations.

Mus musculus is not native to Virginia but came over from Europe in ships with the colonists. Except for humans, it is the most widely distributed mammal on the planet. Highly adaptive, it’s been nominated as “among 100 of the ‘World’s Worst’ invaders” by the International Union for Conservation of Nature (IUCN).

While the house mouse is host to a range of diseases and parasites that can infect humans, including bubonic plague and salmonella, IUCN describes them as “relatively unimportant” as vectors for transmitting these diseases to humans. Unlike deer mice, they do not carry hantavirus. Mice can damage crops and even prey on the young of other animals, sometimes endangering native species, but they also provide some benefit by eating pest insects and are also widely used in laboratory research.

Predators include owls, hawks, fox, coyotes, weasels, raccoons and cats, although I the best mouser I ever came across was a dog named Rhubarb on the ranch where I worked in Wyoming. She could clean out a feed room in a matter of minutes.

I seem to be dealing with just one mouse in my house at this point—one apparently immune to the lure of peanut butter in a live trap. I’ve considered and rejected most other removal strategies, including using snap traps (invented in the nineteenth century) and poisons, and repellents ranging from noise to chemicals. Although some people even risk serious health issues by using mothballs, the chemicals in them can cause all kinds of respiratory and other health issues. I hate to kill anything, find sticky traps to be cruel, and avoid poisons and other chemicals because of health risks to other living things. So I use live traps.

I release my prisoners far from any house. Despite what some may say, mice are quick and brave. I’ve had them try to use me as cover when other options were not available, so I make sure I let them loose somewhere they can easily get under cover. Predators may get them, they may freeze or starve, but at least they’re back in the food chain and out of my kitchen.

Like most house pests, the best way to handle an infestation of mice is to keep them from getting into your house in the first place. Use caulking around outside entry points and caulking, steel wool or insulation for inside points. If you can’t keep them out, store food in containers or pantries that are mouse proof.

Although I raised mice as pets when I was a kid, using them for a science-fair project on genetics, their propensity for chewing up anything they can and spreading their excretions around make them unwelcome guests in my house these days. I haven’t figured out that entry point yet, but I will.

In the meantime, I’m wondering if I should switch peanut butter brands. Nine out of ten mice seemed to like what I’m using, so what’s with this guy?

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