A casually managed compost pile can become a mouse magnet, welcoming rodents in search of seeds, food scraps, and places for nesting. Because mice can squeeze into openings as small as the diameter of a dime, it is very difficult to keep them out of places they find attractive. And while mice serve as prey for everything from snakes and owls to bobcats and wolves, a lack of natural predators in urban and suburban areas lets mouse populations expand to levels that quickly become unacceptable to humans living nearby.
Mice living in a compost pile are just doing what comes naturally. Even so, their role in the spread of serious diseases such as hantavirus, salmonellosis, and Lyme disease makes mice undesirable tenants anyplace where people are at risk of coming in contact with them or their droppings.
To minimize mouse activity in and around a compost project, start by making the pile less attractive as a rodent dwelling. Turn the compost at least once a week and moisten the ingredients thoroughly. Both the increased disturbance and the damp conditions will reduce your compost pile’s mouse appeal. Consider securing compost ingredients in a closed bin lined with quarter-inch wire mesh to exclude mice from the contents.
Finally, take steps to reduce or eradicate populations of mice already living in your compost pile. Deploy traps baited with peanut butter and monitor them regularly until you stop finding mice or evidence of their presence. Avoid using poisons that might wind up harming animals—including neighborhood dogs and cats—that prey on mice. Wear disposable gloves when handling traps containing dead mice and wash your hands with soap and water afterward. Carefully dispose of any mouse nests you find while turning your pile. According to the Centers for Disease Control and Prevention (CDC), hantaviruses excreted by mice remain infectious for 2 to 3 days; exposure to sunlight inactivates the virus. The CDC recommends sanitizing hard surfaces soiled by mouse droppings or urine with a solution of one part bleach in nine parts water.
Photo: Margarethe Brummerman