Like the rodents that produce them, rat and mouse droppings are very similar. Knowing which one you're looking at tells you what next steps to take; trap sizes and trapping techniques vary slightly. The most noticeable difference is the size: Mouse droppings are about 1/4 inch in length, or the size of a grain of rice, and have pointed ends. Rat droppings are larger, from about 1/2 to 3/4 inch long, and may have more blunt or rounded ends. Both types of feces are dark brown when fresh and lighten slightly as they dry.
Dangers of Rat and Mouse Droppings
Both rat and mouse droppings can harbor a wide variety of diseases, and the threat is worsened by how these little visitors love to invade food storage and leave lots of droppings everywhere they go. Rats excrete 40 to 50 droppings a day, while mice leave 50 to 75. As the droppings dry out, they disintegrate, meaning that tiny fragments are released into the air. Diseases transmitted by rat and mouse droppings include hantavirus, salmonellosis, leptospirosis and the Rickettsia virus.
Cleaning Up Rat and Mouse Droppings
Wear a high-efficiency particulate air respirator mask, eye protection, a disposable coverall and waterproof gloves. Ventilate your work area as thoroughly as possible. Spray the droppings and surrounding area with disinfectant and let it soak for five minutes. Don't sweep or vacuum. Use damp rags or paper towels to collect the droppings and double-bag them, along with all nesting materials and any porous substance, such as insulation, paper or fabric, that's been soiled. Use a good quality disinfectant to clean the area. Bag and dispose of all rags, gloves and outer clothing that may be contaminated. Wash your hands thoroughly.
Rat and Mouse Proofing
Indoors and out, make sure all garbage, pet food, bird seed and human food are stored in rodent-proof metal or plastic containers, and clean up any spills immediately. Outdoors, keep shrubbery trimmed back. Stack wood, patio furniture and other items at least 100 feet from exterior walls. Check exterior sheathing, especially around doors, pipes, wiring and vents, for any holes larger than the diameter of a pencil, and fill in with steel wool and caulk. Use wire mesh for vents that can't be sealed safely.
Evicting the Stragglers
There are a lot of products that claim to repel rats and mice, including chemicals, sonic devices and strobe lights; none has been proved reliably effective. Sealing all access points and removing all accessible food sources is your only long-term solution. Once you've done that, live traps are a humane method of removing any rodents that have already set up housekeeping. Be sure to check traps frequently and release the animals promptly. If two weeks pass without a capture and you see no more droppings, your campaign has succeeded.