Solved! What Does Mouse Poop Look Like?

Q: This morning, I noticed something along the edges of my kitchen counter: dry-looking pellets that remind me of tiny black rice. I don’t know how long they’ve been there, but I’m worried they might be from a rodent. How can I tell rat poop vs. mouse poop, and what does mouse poop look like?

A: Because rodents like mice and rats are active at night, they’re not usually seen in the home. However, homeowners can find evidence of their presence—specifically mice poop and rat poop. Mouse droppings have a few characteristics that every homeowner should be able to identify, and understanding what mouse poop looks like can confirm an unwanted visitor and if they’re alone or part of a larger nest.

Mouse poop also gives insight into mouse behavior, which can help homeowners and pest control professionals get to the root of an infestation. Here are a few things to know about mouse poop and how it tells the story of mouse activity.

Mouse droppings are usually ⅛ to ¼ of an inch in length.

The average house mouse is less than 5 inches long—including its tail—which means the droppings it leaves behind can be easy to miss. A single piece of mouse poop is between 1/8 and 1/4 of an inch (3 to 6 millimeters) long and smaller than the average grain of rice.

A mouse’s poop becomes noticeable because a mouse doesn’t leave behind a single dropping. Mice defecate as they’re active, and they’re not picky about where they do their business. As they travel from their nests to forage for food and more nesting materials, mice freely release their excrement. A single mouse will leave behind 50 to 75 droppings each day—almost always outside its nest.

Other pests like bats and rats have larger poop, which is about 1/2 inch long. Using the dropping’s size first will narrow down what else to look for when identifying an invasive household pest.

Mouse poop is mostly granular in shape and in black color.

Even though mouse poop is shorter than a traditional piece of rice, it resembles a grain. Each mouse dropping is usually cylindrical with pointed ends. Other common household pests have poop that’s wider, less uniform, and untapered on the ends.

Because mice are omnivores that eat everything from grains and seeds to meat and cheese, the exact color of mouse poop will vary. In general, it’s dark when first defecated. New mouse poop looks slick and shiny, but as it sits in the open air, it loses its sheen and lightens from almost black to brown. Poop that’s been around much longer becomes gray and appears brittle.

When people use mouse baits in their home, they may notice colorful droppings. This is because baits add dye—like red, green, or blue—to track the activation of poisons in the mouse’s system. Colorful poop means a mouse took the bait.

Mouse droppings can often be found in cabinets, pantries, utility closets, vents, attics, and crawl spaces.

Mice are good at getting into the smallest spaces. Because they only need 1/4 inch to fit through a gap, cracks in the home exterior—which may not be noticeable—are opportunities for mice to get in. They can enter through a foundation or crawl to an attic, but once they’re inside the home, mice gravitate toward places with privacy and access to a food source. Very often, their food will come from the kitchen.

A homeowner can track a mouse’s daily journey by following the path of its poop. Mice tend to travel along edges and within enclosed spaces as a protection against predators when they leave their nests to find food. Each time they reach a food source, they’ll usually stay at it to eat—and poop. If there are droppings in food storage spaces—like a pantry, kitchen counters, or cabinets—it’s a sign of mouse activity.

Mouse droppings may harbor harmful bacteria and viruses.

Not every mouse carries disease, but mouse droppings and urine are the top ways they transmit harmful viruses and bacteria to humans.

When droppings are moved, their germs become airborne. This is how humans can contract hantavirus, a disease with symptoms ranging from muscle ache, fatigue, and vomiting to coughing, shortness of breath, and fluid in the lungs. Hantavirus can be fatal. House mice can carry salmonella and pass it to humans through direct contact with their feces, usually as food contamination. Salmonella poisoning causes severe diarrhea and abdominal pain, which is why noticing bite marks in any food or drink containers means they’re no longer safe to consume.

Poop disposal should be done by a pest control professional, but for anyone eager to clear droppings on their own, ventilation, a proper disinfectant spray or cleaner, and protection, like gloves, are key.

The number and size of droppings you see can determine the extent of the infestation.

Because mouse droppings dry out instead of breaking down, they stick around and accumulate with ongoing mouse activity. Gauging the extent of a mouse infestation can be tricky, so consulting a pest control professional will help a homeowner estimate the size of a mouse population. Without a professional opinion, the best guess comes from an extensive search for poop.

After some mouse poop is found, it’s important to look anywhere else mice may spend time in the home for more evidence. Spaces behind appliances, in closets, the back of cabinets, and vents may hide additional poop. If there are too many droppings to attempt to count, it’s probable that the home has an infestation and needs immediate attention from a professional. A large amount of poop will likely come with other observations, too, like scratching noises at night, bite marks in food boxes, and smudges along the edges of counters.

If you’re concerned about a mouse infestation, call a pest control professional.

Using a trap may work to get a single mouse, but house mice are rarely alone. To make sure an infestation is successfully resolved, getting professional help is best.

Pest control professionals know how to find and interpret mouse poop, as well as remove it safely. Once a home is deemed rodent-free, professionals will check the exterior and interior of the home for additional points of entry and attractive food and nesting situations. They’ll offer suggestions on how to keep away future pests.