Thursday, October 5, 2023

Mouse Report

Since moving to Vermont in 2011, I've spent a fair amount of time blocking mouse entrances to houses. In Middlebury, mice began to appear just after we moved in. I would find their entrances and block them off, and then, after about two years, they would find new ones. At the sixth year, I seem to have found the last ones, and there were no mice in the house after that. This can be informative about both mouse behavior and house construction. One can use a quasi-scientific method to determine exactly what the mice are doing and what the weak points of a house are as far as mice are concerned. To block the mice, I have used steel wool, caulk, cement and anti-mouse foam, depending on the circumstances.

The Middlebury house was built in 1798 and had a 1974 addition. The mice came in through the old foundation and underneath the foundation of the addition. When those were all blocked, they climbed up wires to the roof and found new openings. The Brandon house has an interesting history. It was originally built in 1976 on a seventeen-acre lot next to another house. A couple bought the entire property in 1983 and lived in the other house. The wife's mother lived in this house as an in-law house, a popular arrangement in Vermont. In about 1999, the couple got divorced. The property was subdivided into three lots, and this one is five acres. They built a new foundation for the in-law house here, cleared a path through the woods, and then moved the house a few hundred yards to the new foundation. The divorcée moved here and the other two lots were sold.

Because this house has a poured concrete foundation with no drains, mice can't get in directly through the basement. They were getting in above-ground and finding their way to the basement and the walls above. There is very little attic space here, and it is filled with solid foam insulation. The outer walls and part of the basement ceiling are insulated with pink fiberglass insulation. The mice have found paths through the attic but don't seem to live there. They seem to prefer the fiberglass and make nests in it. Initially, most of the mice went down to the basement and were caught in humane traps and released. Generally, the mice could not get into the living parts of the house except through a gap under the basement door, which I blocked. One immature mouse did get through a small opening in a wall upstairs and entered the bathtub, where it became trapped. I took it outside.

Since I moved into the house, I have blocked a total of about six mouse entrances. It is difficult to know the exact number, but since those six holes were blocked, no new mice have entered the house. The remaining mice traveled around the house, and at first they went to the basement, where they were trapped. I eventually found and blocked four paths that the mice had been using to get to the basement, and since then there have been no mice in the basement. The closest the mice can get to the outside now is the back porch, which they can reach through an exposed section of attic, which would be difficult to block. So the last few mice were caught on the back porch, and there don't seem to be any more. During this period, some mice occupied a wall in the upstairs bathroom. When the last upstairs mouse had no access to the outside, it also went to the back porch and was caught.

I don't know what the precise conditions were for the previous owner. If she didn't block the basement door, there would have been mice all over the interior of the house, and there is some evidence of that (mouse droppings). The exterminators whom she hired blocked many holes on the exterior and interior of the house, but they appear to have completely missed the main ones actually used by mice. Thus, they eventually placed poison bait throughout the house. I suspect that the previous owner had mice every year that she lived here.  Originally, she kept her garbage in the shed, and that became a mouse habitat. Later, when she added the front porch, she left her garbage in a container out there. Probably as a precaution, she kept no garbage in the house. Deer mice and white-footed mice generally leave houses in the spring and don't return until the fall. Thus, the previous owner strategically put her house on the market in April.

It remains to be seen how successful my de-mousing effort has been here. They will probably continue to try to gain entrance to the house for the next couple of months and try again next fall. They are capable of chewing through screens, so they may attempt to reenter through the back porch. I am keeping an eye out for that. Whatever happens, my future work should be significantly reduced by the work that I've already done.

Mice, as mammals, aren't that different biologically from humans. They seek food and shelter and have babies. Though they don't have nuclear families, some of their behavior mimics it. Although the males have no interest in family life and seek sex with other females, a female with a litter can emit pheromones and make ultrasound calls that induce fathers to help in certain situations.

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