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YardSmart Marin

IS THERE A MOUSE IN THE HOUSE?

By: Tracey Liao Van Hooser   |   July 6, 2023

No one wants a rodent infestation! Learn the signs of a mouse problem and what to do. You can manage these rodents without pesticides. This article is a summary of our top suggestions. For more complete advice, visit our Mice page.

 

Prevent Mouse Problems

Prevention is always best. Here are tips for keeping mice away:

• Mice can gain access to your home through a hole as small as a dime or a crevice as thin as a pencil. Inspect your home carefully and secure any possible points of entry. Check out this video and this video for common access points around your home so you can do a preventative review. This video explains how to plug the holes that you may find.
• Garages are a common first entry point. This video shows how to inspect your garage door and replace the weather seal to keep rodents out.
• Don’t leave food and water easily accessible.
  • Bird feeders, chicken coops, and pet bowls attract mice and other rodents.
  • Store food in mouse-proof containers and clean up any spills.
• Mice seek someplace warm and safe to nest. Check your car engine regularly.

Signs of a Mouse Problem

You might never see them because they are most active at night.  Instead, look for signs like:

• Trails of small droppings ⅛” - 1/4” long, urine, and grease marks.
• Gnaw marks on wood, rubber, plastic, cardboard, furniture, or electrical wires in home or car
• Holes in food packaging

Dangers of Mice

Mice can cause serious problems. They can:

• Transmit disease directly, from their waste products, or through the fleas, mites, and ticks they can carry.  Their urine and dander are also associated with an increased risk of asthma. Deer mice are a particular concern as they are an important factor in the spread of Lyme disease and a carrier of the Sin Nombre virus which causes the rare but deadly hantavirus infection.
• Damage your home or car, gnawing through doors, walls, insulation and wires - they can even undermine your foundation

What to do if you have Mice

First, let’s talk about what NOT to do:

• Never use rodenticide (poison)!
  • Some are brightly colored and contain tasty flavorings, which may attract young children, pets, and wildlife.
  • Once the mouse eats the poison, anything that eats it will also ingest the poison. This creates a secondary risk to pets and wildlife. WildCare reports that 76% of raptors and other rodent-consuming wildlife brought into their facility have tested positive forsecondary rodenticide poisoning.
  • There are some eco-friendlier baits but the mice won’t die unless the bait is their only source of food. Since mice eat so many things, these baits are rarely your most effective option.
  • Rodenticides don’t kill immediately. You won’t be happy if the mice die in your walls - the smell is awful. Their decomposing bodies can also attract insects which may later feast on your carpets or clothing.
• Never use glue traps!
  • Children, pets, songbirds, and other wildlife can get stuck to the incredibly sticky surfaces. Learn more about these dangers here.
  • If you find a live mouse caught in the glue trap, you will have to kill it.
  • A trapped mouse  may gravely injure themselves in an attempt to get free and eventually starve to death. Glue traps are cruel so please don’t use them!

To manage mice, we recommend:

• Snap traps are an effective and humane way to kill mice and other rodents. Set multiple traps, experiment to find the right bait, and learn the importance of their placement. Mice are curious creatures so changing the location of your traps and your bait can be a successful strategy. This video provides excellent trapping tips and this video shows how to set a trap while keeping your fingers safe. This video gives an excellent overview of why traps are superior to rodenticides, additional trapping tips (including why you might want to set your traps with non-food materials), and clean-up information.
• It is critical to clean up rodent droppings, urine, and nest materials. Follow this advice from the CDC to do it safely.
• If you already have mice nesting in your car, this video explains how to clean out the engine and then add peppermint oil to prevent reinfestation. (Although there are no studies to prove the efficacy of the essential oil, many people find it works. Reapply if the scent begins to fade.)

Have more questions about mice or other rodents? We have more information on our Mice page and Rodents page. Watch a recording of our webinars on the subject to learn even more:

• “Keeping Rats & Mice Out!” in partnership with Our Water Our World and UC Marin Master Gardeners.
• “The Best Ways to Manage Rats” in partnership with UC ANR and WildCare.

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