Least-Toxic Mice and Rat Control

Whether your house is being visited by mice or rats, the steps you must take to get rid of them are similar:

Remove the attraction (food, habitat)
Cut off access into the house (similar to weatherproofing)
Trapping

Mice generally are easier to deal with than rats and can often be gotten rid of by just removing food sources and plugging up obvious holes. Rats can be more persistent and can require more house proofing and yard clean-up. They are also intelligent and can be difficult to trap. Whichever type of rodent problem you have though, the following suggestions will work to rid your home of rodents without dangerous chemicals.

Removing the Attraction

It is important to remove all food sources from the home, especially the kitchen, including:

Store foods, particularly grains, in tight fitting metal or glass containers
Keep fresh fruits and vegetables in the refrigerator
Clean up all food droppings, including in the oven
Store compost, organic waste and garbage in containers with tight fitting lids
Remove pet food after the pet has eaten
Clean dirty dishes immediately or submerge in soapy water
Give the kitchen a periodic, all-inclusive cleaning

It is also important to remove any nesting materials that may be attracting the rodents:

Stored materials in an attic or basement, typically fabrics or papers, are commonly used for nests. Put materials in rodent-proof containers or discard.
Removing outdoor food and water sources close to the house is especially important when dealing with rats or wild, seasonal mice (which commonly come into the home in Fall.) Removing habitat, such as wood and debris piles, compost heaps and sacks of seeds or pet food is important. Fallen fruit from trees should also be removed and all garbage should be in enclosed garbage bins. Remove cat, dog, and horse feces daily, since rats also feed on this type of organic waste.
Rat proof your compost bin by lining with strong wire-mesh, removing meat and fatty foods from the pile, covering or burying fresh scraps into pile, and turning pile to increase the composting speed.
Rats can nest in dense vegetation, which provides both food and shelter. To discourage them from taking up residence in your yard, prune any low woody shrubs growing next to the house or garage, to expose at least 18 inches of the trunk (rats don’t like exposed ground and can’t reach up above about 11 inches). Prune trees and large shrubs to leave a gap of at least three feet between the branches and the roof of the house or garage, to discourage roof rats.

Cut Off Access

Fill access holes. Even small holes should be searched out and stuffed with steel wool, covered with sheet metal or filled with caulk. Rodents can eat through wood, paper or plastic so use metal or durable caulk.

Start with filling the holes in the areas around where the rodents have been spotted, usually in the kitchen area.

Serious rat problems will require more rat-proofing of home exteriors. You may need to work with a professional pest-control company to ensure that all rat entry points into your house and garage Ð at ground level and at roof level Ð have been identified and secured. Here are the most important:

Check foundations and walls for cracks and holes that develop from normal house settling and rocking; caulk or fill the openings.
Cover all ventilation openings to crawl spaces, basements, and attics with sturdy wire screen; also cover the tops of ventilation pipes for dryers, heaters, stoves, etc.
Ensure that doors to basements and crawl spaces fit tightly into their frames; metal kickplates prevent rats from gnawing entry space in the bottom edges.
Install sheet metal cuff-type barriers on gutter drainpipes and plumbing pipes, to discourage rats from climbing them.
Ensure that rainwater flows properly through your roof gutters and out away from the house: clogged gutters lead to softened, rotted wood that invites pest invasions.
Install screens in the drains in basement and shower room floors.
If you have a bird feeder, make sure that it is inaccessible to rats and is not serving as a late-night rat buffet table.

Trapping

Get a cat, if possible. Females tend to be better mousers.
Live traps or snap traps can be used for mice. Avoid using sticky glue traps, as they are inhumane and the rodent can be in pain for hours or days before they die. Avoid poisons, as the rodents often retreat into the walls to die, causing odors. Using live traps for rats requires special care. Unlike raccoons, skunks, moles, etc., rats live primarily as parasites among human populations, depending on humans for their food supply. Releasing them elsewhere simply means that they will quickly find their way back to your (or someone else’s) house. There is, in addition, the danger of handling them; their bites can cause disease. Be sure to release them in an uninhabited area and to take special safety precautions.
Be sure to use enough traps, 5 to 10 traps per hole, spaced 2 ft to 3 ft apart at right angles to the wall. The bait and trigger end of the trap should be facing the wall. Place traps along walls and along known rodent pathways.
Wear gloves when handling the traps and handle them infrequently because rodents can detect human smells
Use sticky baits, such as peanut butter mixed with mixed oats, raisins, baked breads, gum drops, etc.
Rodents are fairly smart and are suspicious of new objects, so place traps with bait but unset for a few days to get rodents used to them. Once they take the bait, set the trap.
Most trapping fails because too few traps are used.

Further Resources

Olkowski, William, et al, Common-Sense Pest Control; Least-toxic solutions for your home, garden, pets and community, Taunton Press, Newtown, CT, 1991. Incredibly helpful and thorough book, should be consulted for difficult rat problems.

Bio-Integral Resource Center, Berkeley, 510-524-2567, www.birc.org. Great non-profit specializes in least-toxic pest-control advice. Publishes the Common Sense Pest Control Quarterly and the IPM Practitioner with detailed articles on pest and weed control, available in the Ecology Center library.

Ecology Center, 2530 San Pablo Avenue, Berkeley, www.ecologycenter.org. Further reference materials on least-toxic pest control. Live traps for sale and rent.