Rats and mice are pests of residential and commercial buildings. The most common rats are the Norway rat and the roof rat. The house mouse is more widely distributed than the two rat species and more common as an indoor pest. Deer mice invade houses in fall, but they usually do not remain as permanent pests. The success of these rodents as pests is based on their ability to enter structures through small openings, utilize nearly all human food to live and reproduce, and be very wary of attempts to control them.
Norway rats and roof rats have different habitats and preferences. Roof rats prefer warm temperatures and occur primarily in coastal regions. They range along the eastern and western coasts, through the Gulf Coast states, and in Hawaii. However, in the last 10 years, they have been moving farther inland and may occur along with Norway rats in some locations. When these two species occupy the same location, they separate themselves to limit competition for food and harborage. Roof rats will nest, in above-ground locations and Norway rats at ground level, typically in burrows.
The little brown bat and big brown bat are common in urban and suburban areas. While they are disliked or even feared by some people, they have an important role in the environment. These bats eat a large number of insects; a colony of bats can eat about 150 pounds of insects from May to September. However, their beneﬁts often are discounted when they roost in buildings and present a health problem, because they can; carry rabies.
Bat control or exclusion measures are limited and closely regulated by state agencies. In general, control measures cannot be enacted during summer.
Squirrels often are considered cute when they are chasing each other across the grass or up trees in the yard. But these rodents can become nuisance pests in many situations. The gray squirrel is becoming dominant in many regions of the country; mild winters and the reproductive ability of these animals have increased their numbers. The most serious damage occurs when they enter roof spaces or attics by climbing the sides of houses or entering from a nearby tree. Once inside, they can damage electric wires and disrupt insulation. Their activity in attics and wall voids is an additional problem to homeowners.