Nesting mice in the walls or elsewhere in the garage can be a vexing problem. They can make nests in the wall insulation, clumping it and reducing its insulation value, they sometimes chew through electrical wires, and they are unsanitary. While laying traps or poison is one strategy to eliminate them, there are other methods that are more humane and less dangerous for other animals and small children. No single technique for rodent elimination is likely to be 100 per cent effective, and the best strategy involves a combination of them.
Remove any source of mouse food from the garage or seal it well in a plastic or glass container. Take a careful look at the items you store in your garage. Some, like straw, grain or certain kinds of fertiliser, may not look like mouse food but may be in fact very appealing to rodents.
Set live mouse traps at strategic places inside the garage and bait them with small pieces of cheese or dollops of peanut butter. Set each trap near a wall with the open end facing a suspected access point for mice. Check the traps daily, and relocate any mice you catch a mile or more from your house.
Spray mouse repellent around the outside perimeter of the garage to prevent a new infestation while you take care of the existing one. The repellent also encourages mice nesting in the walls to seek food in the garage, where you have set traps, rather than going outside to find it. Commercial repellents are available, or you can make your own by mixing 1 tbsp hot pepper sauce, 1/4 cup washing powder and a gallon of water and spraying it with a garden sprayer.
Seal holes in both the interior and exterior walls with caulk, patching compound or wood when there is no more evidence that mice are present. If you seal the holes while the mice are still nesting in the walls, they will probably make new ones or, worse, die in the walls and create a nasty odour. Mice can squeeze through very small openings, so seal all holes that are larger than 1/4 inch in diameter.
Set conventional mouse traps in the event you don't manage to catch any mice with the live traps. Place each trap near a suspected access and under a shelf, table or other overhead obstruction to keep it out of the path of larger animals and children. Check the traps daily and remove dead mice before they begin to decompose.
Place an ultrasonic mouse repeller inside the garage to prevent further infestations. Although inaudible to humans, the sound it produces is painful to mice and will discourage them from entering or nesting.
Although not as reliable as other methods of mouse control, keeping a cat in or near the garage is another way to reduce the mouse population. Peppermint is a natural mouse repellent. Plant peppermint plants around the perimeter of the garage or spray a solution of peppermint extract and water.
Many types of mouse poison are dangerous for small animals and children. Mice that eat the poison usually go elsewhere to die and if another animal eats a poisoned mouse, it can also become poisoned.