Keeping mice and rats out of a home takes entry-point repairs, food storage and, when animals are already inside, carefully placed traps. Poison creates another problem: wildlife can eat a rodent after it has consumed toxic bait.
In guidance published October 29, Tufts wildlife veterinarian Maureen Murray recommends prevention and snap traps to reduce those risks.
Find the openings and food sources
A mouse can squeeze through a gap about a quarter-inch wide, according to CDC's exclusion guidance. Check around sink pipes, appliances, doors, vents and utility lines, along with foundations, attics and crawl spaces.
CDC recommends steel wool secured with caulk for small holes. Larger openings need materials such as metal, cement or hardware cloth cut to fit. Garages and outbuildings need attention, too.
Food storage is part of the same job. Keep groceries and animal feed in thick plastic, glass or metal containers with tight lids. Clean spills promptly, put pet food away after feeding and keep garbage covered. EPA also recommends removing possible nesting sites, including leaf piles and deep mulch, and stopping outdoor bird feeding while controlling an infestation, or using huskless feed that leaves less residue.
Choose and position traps
CDC recommends traditional snap traps, with separate sizes for mice and rats. It advises against glue and live-capture traps because frightened rodents may urinate, increasing exposure to germs. Murray also warns that glue traps can injure other animals and leave rodents suffering for hours or days.
Follow the trap's instructions and keep it inaccessible to children and pets. Put a small amount of bait on the bait pan, then place the trap against a wall with the baited end facing the wall, forming a T. Rodents tend to travel beside walls and other objects.
Choose locations with droppings, gnaw marks or other evidence of activity, including behind appliances and in the backs of cabinets. Check traps daily. Rats may avoid unfamiliar objects for several days; CDC suggests baiting their traps without setting them initially, then setting them once bait is being eaten. Keep checking for fresh droppings, gnaw marks and other activity after catches.
Cornell Integrated Pest Management's rodent guide links to videos on trap selection and placement, setting a snap trap and using snap traps.
What a poison station does and does not protect
A bait station holds poison where a rodent can reach it. Its enclosure can reduce direct access by other animals, but a predator may still eat the poisoned rodent after it leaves. Tufts describes this route of exposure for anticoagulants, which interfere with blood clotting. Murray says there is not enough evidence to establish that bromethalin, an alternative rodent poison, poses a lower wildlife risk.
EPA's household bait-station categories differ. Tier 1 products resist tampering by young children and dogs and are weather-resistant; Tier 2 products resist those tampering attempts but are for indoor use. Tier 3 products resist young children's tampering and require locations without pet access. Tier 4 products lack demonstrated tamper resistance and require indoor locations inaccessible to children and pets.
Those categories do not make every station suitable for every room or yard. Read the product label. EPA says consumer bait must remain secured inside its supplied station, and dead rodents should be removed promptly to reduce poisoning risks to pets and wildlife. CDC reserves poison or bait stations for infestations that persist.
Clean up without stirring up waste
Do not sweep or vacuum rodent droppings, urine or nesting material. CDC's cleanup instructions warn that this can put contaminated material into the air. For homes and outbuildings, ventilate by opening doors and windows for 30 minutes and leave during that time before cleaning.
Wear rubber or plastic gloves. Wet urine and droppings thoroughly with an EPA-registered disinfectant and leave it for five minutes, or the time on its label. Wipe up with paper towels, discard them in a covered garbage can and disinfect the surrounding hard surfaces. Spray dead rodents or nests with disinfectant and wait the same contact time before handling. Seal them in a plastic bag, then a second bag, and place them in a covered garbage can. Wash gloved hands with soap and water before removing gloves, then wash bare hands.
Heavy infestations require additional precautions. Rodents in heating or cooling ducts need professional attention. If hiring a pest-control company, ask about integrated pest management: which entry-point repairs it recommends or includes, how it will monitor activity and which traps or poisons it proposes to use.
