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Tales from a Plant Addict

Fun (& a few serious) facts, tips and tricks for every gardener, new and old.


Although the topic of mice is really not a horticultural topic, or exists at the far fringes of horticulture at best, every fall our office gets calls about mice. Fall is the time of year mice are looking for a warm place to spend the winter. This is especially true if you live anywhere remotely rural. Even a park can be a source of mice.

My husband and I live near both woods and farm fields. I expect to see the occasional mouse in the garden and even the garage. And we do. Very occasionally we see a mouse in the garage, put out a trap and catch it. We are certain that what we have caught in the garage are mice, as opposed to voles, which are a problem in our garden each winter. Mice have relatively large ears and tails about the length of the body. Voles have relatively small ears, and stubby tails.

We have traps and poison baits strategically placed around the garage in places that might be attractive to a mouse. We have all our food sources, like bird seed and grass seed, in sealed heavy plastic containers. I figured this was all I would have to do to keep mice out of our house. As it turns out, mice are determined little creatures.

A few summers ago, I opened the closet in our garage to change the furnace filters, and saw mouse droppings and shredded pipe insulation all around the furnace. Mice had apparently gotten in from our crawl space by gnawing through the insulation on the air conditioner pipe which gave them enough space to slip into the closet that holds our furnace. The larger problem we later discovered was a crawl space vent that had a hole in it. It was an open invitation to the local mice to come into our crawl space and make their way into the house from any of dozens of locations. Once we fixed the vent, no more mice showed up in our house. However, it took me a little longer to recover!

Our most recent mouse encounter was thanks to an electric line recently installed to run power out into our yard. The line passes through a hole in our foundation on its way from our house to the yard. It has been there for 2 years, and the hole itself was buried several inches underground. I noticed earlier this summer that the soil had been dug away from the hole. The hole is only slightly bigger than the wiring. I wasn't sure it was big enough for a mouse to get through, and I got sidetracked and forgot about it. Big mistake!

Mice only need a ¼" gap to be able to squeeze through. One method of controlling mice in homes, garages and sheds is to "build them out" by sealing off any gaps that might allow them to enter. It is crucial to use materials that mice cannot gnaw through. They have strong incisors that make most plastic, wood and rubber unsuitable for plugging gaps.

Steel or copper wool mixed with caulking is a good plug for gaps that cannot be sealed with metal or concrete. We have had good luck using copper wool mixed with sanded caulk used to repair concrete. Just stuff it in the hole where mice are entering and they won't chew through it. (At least they haven't so far at our house). Copper wool can be purchased on a roll so you just cut off as much as you need, or copper kitchen scrubbers work just as well.

Preventing mice from entering a building and trapping are the most effective ways to control them. When trapping or setting out poison baits, place them in places where mice travel, usually along the edge of a wall or other structure.

Mice do not travel far from shelter and food. They also tend to travel with one side of their body touching a wall or other structure. This wall-seeking behavior is called thigmotaxis by animal behaviorists. It may be related to staying safe from predators.

We use some traps in our garage, as one of the drawbacks for using traps is you have to check them and dispose of the dead mouse. There are traps available that completely contained, so you don't see the dead mouse. You throw the whole thing away. If you have a substantial mouse problem, this can get expensive.

Another option, though not as effective, are the many different forms of poison baits available for mouse control. Poison baits available to homeowners are usually anticoagulants, which prevents the mouse's blood from clotting after ingestion. These products are typically formulated with a low dose of poison in the bait so that the mouse feeds repeatedly and does not avoid the bait because of odd taste or onset of illness.

A big drawback of poison baits is that when the mouse dies, you have no control of where it dies. I learned about this the hard way too.

There is a closet immediately adjacent to the door leading from our house to the garage. One chilly morning I opened the closet to grab a jacket, and noticed a horrible smell. My husband smelled it too. Further investigation revealed a dead mouse in the bottom of the closet. I was horrified. How in the world did it get there?

There were no holes in the closet or anywhere nearby that could have let a mouse in. It probably came in through the door, but how since there is a big step outside that door? It was surprising to me to read that mice can jump up to 13 inches from the floor to a flat surface, and can climb vertically over a rough surface. That big step was nothing to that little mouse.

As horrified as I was to find a mouse in our house, mice have invaded human dwellings for thousands of years. Mice thrived in early human agrarian settlements, as there was a ready food source from early human farms. Researchers have used mouse populations to document early human migrations. The mice went where the people went.

We will continue to refine our mouse excluding efforts this winter and hope that the word gets out in the mouse world that they are unwelcome at our house.


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