How to coexist with mice and rats

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Several species of mice and rats live in Illinois, and people often have negative associations with these rodents because they are known for making their way into buildings, including our homes.

Native mice and rats in Illinois include the deer mouse, the white-footed mouse and the eastern woodrat. Deer mice and white-footed mice live across the state, but the eastern woodrat, which is state endangered, only lives in seven counties in southern Illinois, Wildlife Illinois reports. Norway rats and house mice are the most likely to cause problems around homes and buildings, and neither is native to the United States, Wildlife Illinois reports.

Norway rats, also called subway rats or brown rats, are most common in urban and suburban areas, according to the Illinois Department of Public Health (IDPH). House mice thrive in a variety of conditions and are common around homes and buildings, IDPH reports. Deer mice and white-footed mice are not as common in residential areas, and their populations do not usually overlap because of their preferred habitats, Wildlife Illinois reports. Deer mice are most common in open areas like fields and pastures, while white-footed mice prefer forest edges and areas near trees.

Ecological effects

A white-footed mouse.

Both rats and mice are beneficial to the ecosystem because of their role as a food source for many predators, Wildlife Illinois reports. Among the animals that eat mice and rats are coyotes, foxes, minks, weasels, snakes, owls and hawks.

Mating and reproduction

A deer mouse poking its head of wood.

Mice and rats all produce multiple litters of offspring throughout the year. Norway rats can have six to eight litters a year, and each litter can have six to nine babies, Wildlife Illinois reports. The rats can begin reproducing before they reach 4 months old, while mice can begin reproducing when they are about 2 months old. Deer mice, house mice and white-footed mice produce multiple litters a year of between four and six babies per litter.

While mice and rats can produce a lot of offspring, they have short lifespans. Mice usually live less than a year, according to Wildlife Illinois. Rats can live as long as three years, but they usually live about a year and a half.

Health risks

Close-up of a rat.

Mice and rats can pass diseases to humans. Rats, deer mice and white-footed mice can be carriers of hantavirus, which can be spread to humans by breathing in dust contaminated with feces, saliva or urine from infected rodents, IDPH reports. The deer mouse is the main source of hantavirus in the United States, and the virus is most likely to occur in rural areas where the mouse lives. Hantavirus symptoms include fever, cough, headaches, muscle aches, stomach pain, nausea and/or vomiting.

Mice and rats can also be carriers of leptospirosis, salmonellosis and tularemia, Wildlife Illinois reports. In addition, because white-footed mice are a host in the deer tick life cycle, they can be carriers of Lyme disease.

Rats are also carriers of the bubonic plague, but the disease is not found naturally in Illinois and is not common in the United States, the health department reports. Rodent fleas can also transmit bubonic plague.

Problems and solutions

A white-footed mouse eating a nut.

The main problem associated with mice and rats is that they make their way into homes and buildings and sometimes cause infestations. The species most often associated with infestations are house mice and Norway rats, Wildlife Illinois reports.

Signs of a mice or rat infestation in a building include droppings and fresh gnawing marks, as well as tracks left behind on dusty or dirty surfaces, IDPH reports. When in homes and buildings, mice and rats can contaminate food supplies and also may pose health risks to humans because of the diseases they may carry.

The best way to keep rodents out of your house is by not allowing them a way to get in, the health department reports. Any openings larger than a quarter-inch should be sealed to prevent mice and rats from entering. Mixing caulk with steel wool will make an effective plugging material. It’s also important to seal cracks in the foundation and around any openings where pipes and vents come into the house, In addition, make sure all your doors and windows fit tightly.

Deer mice, house mice, white-footed mice and Norway rats are not protected by the Illinois Wildlife Code and may be removed without a permit from your property. Trapping is an effective means of controlling mice in a home or building, and it is the preferred method when only a few rodents are present, IDPH reports. When placing traps, set them close to walls, behind furniture and other objects, in dark corners or in places where there is evidence of recent rodent activity.

Poison baits should only be used to control rodents in a building when trapping and securing the home to keep them out have not been successful, IDPH advises. Remember that using poison can be equally as deadly for other animals, including pets who may accidentally come into contact with it and those wildlife who may eat the poisoned rodent, whether still alive or dead. Only buy poison baits from reputable stores, and garden centers, and make sure the product is registered with the U.S. Environmental Protection Agency. Ensure products are labeled for indoor use if you are using them inside, and always follow the directions on the label exactly.

Always wear intact plastic or rubber gloves to remove dead rodents or when cleaning items that have been contaminated by rodents, IDPH advises. To disinfect dead rodents, soak or spray them with a commercial disinfectant containing phenol or a disinfecting solution of 3 tablespoons of bleach in 1 gallon of water. Double bag dead rodents in plastic bags and place them in a trashcan with a tight-fitting lid.

All wildlife in Illinois are under the jurisdiction of the Illinois Department of Natural Resources. The Forest Preserve District of Will County does not treat, rescue or remove wildlife from public or private property. Both the Illinois Department of Natural Resources and Wildlife Illinois maintain lists of wildlife rehabilitators you can contact for assistance with injured wildlife.

(Photos via Shutterstock)

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