Mice and Rats in the Home

If you've seen one small, scampering critter, there's a good chance that the little guy (or gal) has skittered out of sight by now. If so, your immediate problem — removing a mouse or rat from your line of sight — no longer exists.

However, know that one mouse is usually only evidence of the problem. You can rest assured that there's probably more than one. In fact, there could be many.

Depending on where you live, rats can also be a problem. Their habits, breeding patterns, the problems they cause, and the steps for controlling and eradicating them are similar to what is done for mice, but there are some differences between the two.

For simplicity's sake, from here on out we'll refer to both mice and rats generically as "rodents." However, more often than not, you'll be dealing with a mouse, as they're the most common intruders, and the one you're most likely to encounter.

Other small animals can also invade your home. Raccoons, for example, can enter homes through windows, chimneys, and roof vents. Squirrels can also gain entry in a variety of ways. For more detailed information on dealing with these animals, see Animals in the Home.

Meet the Enemy

Mice and rats are often referred to as commensal rodents in recognition of their close association with humans. Because of their affinity for the luxuries available in human dwellings, they are particularly troublesome pests. People spend a lot of money getting rid of them. And getting rid of them. And getting rid of them.

Once rodents take up residence in your house, it can be difficult to control them. But it's not impossible. Diligent use of traps or rodenticides will kill them.

The House Mouse

Known formally as Mus musculus, the house mouse is the most common rodent pest in the United States.

A female mouse can have between 5 and 10 litters every year, with five or six babies in each litter. Young mice are capable of reproducing when they're six weeks old, and mice typically live to between 9 and 12 months old.

Do the math, and you'll quickly see how one pair of mice turns into many more. In fact, one pair of mice can produce more than 15,000 offspring in a year. Definitely a scary number.

The Rat on Rats

In the United States, the roof rat (Rattus rattus) and the Norway rat (Rattus norvegicus, also called the brown rat or sewer rat) are the two most common rat pests.

As their name suggests, roof rats claim roofs as their home turf. They're excellent climbers, and often gain entrance to houses by scurrying along overhanging tree limbs to a roof. They can also climb up almost every type of siding material, including smoother ones like stucco. These animals also like to live high up, and typically take up residence in attics or cabinets. They enter homes through bathroom vents, gable vents, spaces around soffits, exhaust pipe holes, spaces between fascia boards and roofs — just about any vulnerable spot. They can even chew holes through roofs.

Norway rats, which are ground nesters and often dig burrows in gardens and along foundations, can enter homes through cracks and holes in crawl spaces, slabs, a foundation block, you name it. Once inside, they lay low, preferring to nest in kitchens and bathrooms.

In the United States, Norway rats are more common in the North, roof rats in the South. Of the two, roof rats are less common and less aggressive. Like mice, rats are prolific breeders, with short gestation periods and large litters. They can live as long as three years.

Other common names for Norway rats are dump rats, river rats, sewer rats, and city rats.