Rats and Mice
Rats and mice (rodents) can be a nuisance to homeowners, renters, and communities. They can spread disease and cause property damage.
Rodents are looking for food and shelter. Don't attract them to your home or make it easy for them to get inside. Remember these points to prevent infestations, clean up messes, and avoid disease transmission.
- Seal Up - Mice can squeeze through a hole the size of a nickel, and rats can squeeze through a hole the size of a half dollar. Prevent rodents from entering the home by checking inside and outside the house for gaps or holes. Also, eliminate sources of food and hiding places.
- Trap Up - Follow all instructions on traps. Live traps are not recommended.
- Clean Up - Do not stir up dust by sweeping or vacuuming up droppings, urine, or nesting materials. Ventilate the area and disinfect first. Use rubber, latex, or vinyl gloves to clean up the area while it is still wet.
Evidence of a rodent infestation
The most common rat species in Michigan is the Norway rat, also called the brown rat. These rats may be up to 18 inches long (including tail), and may weigh up to about 1 pound. Norway rats live and nest in underground burrow systems. They feed on garbage, pet food, meat scraps, cereal grains, fruits, and vegetables. Norway rats are great climbers, jumpers, and swimmers.
Rats have an excellent sense of smell - and incontinence! Rats will leave a fecal or urine trail to mark a pathway as safe. They need to chew, and will gnaw on surfaces leaving visible marks. Rats have poor eyesight, which means they will follow their trusted trails and stay near walls - they use whiskers like a cat.
Rats walk the same path over and over again, making a path in the grass or dirt. (Photos below courtesy Ferndale Rat Patrol.)
They also leave black smear marks where they rub against surfaces.
Rats burrow into the ground leaving messy holes, usually at an angle.
Rats chew on everything!
Rat droppings are black and slightly larger than grains of rice. Mice droppings are smaller.
What to do if you have a rodent infestation
1. Seal Up
Rodents will eat almost anything! Starve them out by eliminating potential sources of food.
- Use a trash can with a lid. Provide enough garbage cans with tight fitting lids to hold all garbage between pickups.
- Bring garbage to the curb as close to pick-up time as possible. Garbage left on the curb for too long attracts rats.
- Rinse containers before placing in recycling bin.
- Keep outside cooking areas and grills clean.
- Pick up dog poop regularly.
- Don’t leave pet food outside.
- Don’t leave food outside for stray cats, pigeons, or squirrels.
- Keep bird feeders away from the house, and use squirrel guards to limit access to the feeder by squirrels and other rodents. If possible, don’t leave bird feeders out overnight. Use "mess-free" seed, or place bird feeders over concrete so you can sweep up any dropped seed.
Attack their favorite places to seek shelter and reproduce.
- Clean up any clutter or litter in and around your yard.
- Get rid of old trucks, cars, and old tires that rats could use as homes.
- Remove piles of newspapers, paper bags, cardboard, and bottles in your yard.
- Store items away from walls and off the ground.
- Move woodpiles far away from the house.
- Remove dead trees and stumps.
- Rodents are often found in burrows under bushes and plants. Keep tall grass, bushes, shrubs, and mulch away from building foundations.
- Keep grass cut short and shrubbery well trimmed.
- Make space between plants and avoid dense planting.
- Keep gardens free of weeds and trash.
Look for - and fix - gaps or holes outside your home so rodents can’t get inside.
- In the roof among the rafters, gables, and eaves.
- Around windows.
- Around doors.
- Around the foundation
- Attic vents and crawl space vents.
- Under doors.
- Around holes for electrical, plumbing, cable, and gas lines.
Materials can be found at your local hardware store to fix gaps and holes.
- Use caulk to seal small holes and cracks.
- Fill slightly larger holes with steel wool. Put caulk around the steel wool to keep it in place.
- Use lath screen or lath metal, cement, hardware cloth, or metal sheeting to fix larger holes.
- Close gaps under doors with rodent-resistant metal door sweeps.
- Close window gaps with metal flashing.
- Use flashing around the base of the house, and fix any gaps in trailer skirting.
- Use 1/2 inch mesh hardware cloth as a barrier under decks, porches, and crawl space openings.
- Put screens on vents, especially on lower floors.
- Seal pipes leading into walls with escutcheon plates (“pipe collars”). Check pipes regularly for leaks.
- Outbuildings and garages should also be sealed to prevent the entrance of rodents.
An inactive burrow will often have leaves, cobwebs, or other debris around the entrance. These burrows should be closed so rats can’t get back in.
- Close burrows in soil by filling with soil and tamping down with a shovel, or by stepping on them.
- Close burrows in cracked or broken sidewalks with metal filler and cement.
2. Trap Up
If you have extensive issues, contact a licensed pest control company for assistance.
For residents, snap traps are the safest way to get rid of rats.
- For best results, set snap traps at dusk and pick up before daylight.
- Place traps under milk crates or inside boxes in areas where cats, possums, etc. roam so you do not accidentally trap other animals.
- Highly scented bait works best (peanut butter, vanilla, chocolate, stinky meats or cheese, cheap dog treats, suet).
- Place many traps unset for a few days so the rats get used to them, then set the traps.
- When setting traps, place the trap near a wall or fence, with the bait side toward the wall/fence. (Photo courtesy of Ferndale Rat Patrol.)
3. Clean Up
When you begin cleaning, it is important that you do not stir up dust by sweeping or vacuuming up droppings, urine, or nesting materials.
Rats communicate with each other and attract more rats to the area through their urine and droppings. They leave a trail of urine and droppings and black greasy rub marks on surfaces they brush up against. You must clean up the "scent trail" and any droppings, nests, or dead rats or mice.
- Wear rubber, latex, or vinyl gloves when cleaning urine, droppings, nests, or dead rats or mice.
- Spray the urine, droppings, nests, or dead rodent with a disinfectant or a mixture of bleach and water (1 part bleach to 10 parts water) and let soak 5 minutes. When using a commercial disinfectant, follow the manufacturer’s instructions on the label for dilution and disinfection time.
- While the area is still wet, use a paper towel or plastic bag to pick up the urine, droppings, nest, or dead rat. Place the dead rodent or materials in a plastic bag and seal tightly. Place the full bag in a second plastic bag and seal.
- Dispose of the waste in a trash can with a tightly sealed lid.
- After the urine, droppings, nest, or dead rodent has been removed, disinfect items that might have been contaminated by rodents or their urine and droppings. Spray the area with your disinfectant, let sit for 5 minutes, and then wipe up with paper towels.
- Remove gloves, and thoroughly wash hands with soap and water.
Diseases associated with rodents
Diseases from rodents are rare but do occur. Avoid inhaling contaminated particles while cleaning or working in an infested area such as a house, barn or shed. You can prevent exposure to by taking steps to keep mice and rats out of your home and properly cleaning rodent urine, droppings, and nesting materials. The CDC recommends you NOT vacuum (even vaccums with a HEPA filter) or sweep rodent urine, droppings, or nesting materials. These actions can cause tiny droplets containing viruses to get into the air.
Hantavirus is a very rare but severe disease transmitted through infected rodents. Two types of mice found in Michigan may carry hantavirus, the deer mouse and the white-footed mouse. Both are brow in color with white on their bellies.
Hantavirus is most commonly caused by exposure to urine or droppings, but also from rodent bites. Exposure is most likely through inhaling contaminated particles while cleaning or working in an infested area such as a house, barn, or shed. The hantaviruses that cause human illness in the United States cannot be transmitted from one person to another.
You can prevent exposure to hantavirus or other diseases by taking steps to keep mice and rats out of your home and properly cleaning rodent urine, droppings, and nesting materials.
Things such as seeing a rodent while out for a walk or a hike pose no risk to you. Similarly, if your pet finds or kills a rodent, neither dogs nor cats can transmit hantavirus to humans.
If you have more questions, try these resources. You can also call our Environmental Health Division office at 734-222-3800 for more information.
- How to Control Wild Rodent Infestations - Centers for Disease Control & Prevention
- Preventing Rats on Your Property - New York City Department of Health & Mental Hygiene
- Control & Prevention of Rodents - City of Berkeley, California
- Transmission: How People get Hantavirus Infection - Centers for Disease Control and Prevention