House Mouse

Identification: Small and slender with gray-brown fur, a pointed nose, large ears, and a long, nearly hairless tail.

Habits: Excellent climbers that can live almost entirely indoors. House mice build nests from shredded paper, fabric, and insulation and may reproduce rapidly when food and shelter are available.

Diet: Seeds and grains are preferred, but house mice sample many stored foods and pet foods.

Deer Mouse

Identification: Brown or gray above with a sharply white belly and feet. The tail is usually distinctly two-colored.

Habits: More closely associated with fields, wooded edges, sheds, cabins, barns, and rural properties than dense urban interiors. They may move into buildings as temperatures fall.

Risk: Deer mice are the North American rodents most often associated with hantaviruses.

White-Footed Mouse

Identification: Similar to a deer mouse, with brown upper fur, white feet and underside, and large ears and eyes.

Habits: Common near wooded areas, brush, and field edges. They may nest in outbuildings, garages, attics, and wall spaces when they find an opening.

Diet: Seeds, nuts, berries, fungi, and insects.

Norway Rat

Identification: A heavy-bodied brown or gray rat with a blunt nose, small ears, and a tail shorter than the head and body combined.

Habits: Strong burrowers found around foundations, alleys, sewers, dumpsters, livestock areas, and places with dependable food and water. They usually stay close to ground level.

Diet: Opportunistic omnivores that consume garbage, grain, pet food, and many other materials.

Roof Rat

Identification: Slimmer than a Norway rat, with a pointed nose, larger ears, and a tail longer than the head and body combined.

Habits: Agile climbers that favor elevated nesting areas. Established roof-rat populations are far less common in northern Illinois than Norway rats, so careful identification is important.

Diet: Fruits, nuts, seeds, stored foods, and other available material.

Contamination and disease

Rodents can contaminate food and surfaces with urine, droppings, saliva, and nesting debris. Diseases associated with rodents include hantavirus infections, leptospirosis, salmonellosis, rat-bite fever, and lymphocytic choriomeningitis. The actual risk depends on the species, exposure, and conditions.

Allergens, parasites, and damage

Rodent urine, dander, and droppings can contribute to indoor allergens. Fleas, ticks, and mites may also be present. Gnawing can damage stored goods, insulation, wood, and electrical wiring, while nesting material can obstruct equipment or ventilation.

Reduce food and shelter

Store food and pet food in durable sealed containers, clean spills and crumbs, manage garbage, remove clutter, trim vegetation away from the structure, and avoid leaving bird seed or other food accessible overnight.

Address entry points

Inspect gaps around foundations, utility penetrations, doors, vents, siding, soffits, roof intersections, and garage-door edges. Rodents can use surprisingly small openings, and durable repairs are more reliable than lightweight filler alone.