Released: January 20, 2004

Could There Actually Be a Mouse in The House?

MANHATTAN, Kan. – It’s a shudder-causing thought that rarely occurs to many people: Rats and mice probably are living right next to your home. They also may be trying to come inside, particularly if winter has reduced their shelter and food supplies.

“We typically don’t think of these rodents as a modern problem. But Norway rats and house mice came to the United States with the first European settlers. They have stayed close to or with the humans living here ever since,” said Charlie Lee, the wildlife damage control specialist for Kansas State University Research and Extension..

The rodents eat and contaminate food. They damage and destroy property. They carry diseases that include plague, hantavirus, salmonella, typhus, trichinosis, infectious jaundice and rat-mite dermatitis

So, why don’t today’s homeowners give them much thought?

Lee thinks part of the reason may be pet myths and modern “rodent-proof” construction methods.

“House cats and dogs will kill rats and mice, just as they do in the cartoons. Unfortunately, though, they usually aren’t a very effective control,” Lee said. “These types of rodents tend to be active at night. They have acute senses of hearing, smell and sight. They bite, they’re fast and they’re very good at hiding.

“Big Norway rats are actually known for living in very close association with dogs and cats – attracted by the food, water and shelter provided for a pet.”

Beyond that, even a well-constructed, modern building can become vulnerable to a rodent invasion as a result of renovations, settling or age. Rats and mice can gnaw through wood, plaster, caulk, latex, plastic, rubber and anything else that’s remotely “chewable.” Plus, an open garage or patio door is the same as an open invitation, the wildlife specialist said.

“In particular, house mice are almost impossible to eliminate through sanitation alone. They can survive in small areas with no water and limited amounts of food and shelter. That’s why most places where food is handled or stored – no matter how clean they are – will have problems unless the buildings are ‘mouse-proofed,’” Lee said.

Mice can gain access to a building through any opening that’s at least one-fourth inch in diameter. Their entry can be a foundation crack, a gnawed hole, or an opening associated with a pipe, utility line, vent, grate, or drain.

Rats need a one-half inch opening, but they can gain entry anywhere on a building so long as they have some traction. Rats are good climbers and can “tightrope walk” utility lines, pipes and tree branches.

“Steel wool is a good temporary plug for access holes. Then you need to tightly seal such entries with concrete or a metal plate,” Lee said. “Vents and drains must have a metal cover with small openings. Doors, windows, screens and garbage can lids must fit tightly. For older homes, you may also need to cover the edges of doors and windows with metal to prevent gnawing.”

Gnaw marks and droppings often are the first clues of a rodent invasion, he said. Rats and mice also emit a characteristic musky smell.

Sometimes greasy “skid” marks will appear low on walls next to where rats and mice are maintaining a “run.” Tracks may show up on muddy or dusty surfaces. Close examination may reveal burrows, nests or runways in any sheltered location – behind cabinets or appliances, in attic or basement, in garage storage areas, in firewood stacks, beside dog houses and other building walls, along fences, under thick garden mulch, under low vegetation and yard debris, near garbage cans.

“If you don’t find any of these signs, that’s great. But you still should check to make sure your home remains rodent-proof, because that’s the most effective long-term control,” Lee advised. “If you do find signs, take action to get rid of the rodents that are living indoors and discourage others from hanging around outside. Then rodent-proof your house and clear out any sanitation problems in your yard.”

More information about house-loving rodents and their prevention is available from any county’s Extension office or on K-State Research and Extension’s Web site (http://www.oznet.ksu.edu) under “mice” and “rodent control.”

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward, Communications Specialist
kward@oznet.ksu.edu
K-State Research& Extension News