Mice & Rats
Common House Mouse
Next to humans, the common house mouse is the most prevalent mammalian species in the world. An adult house mouse is about 2-1/2" to 3-3/4" in length and will weigh about .5 to 1.1 ounces. They have four toes on the front feet and five toes on the back feet. The life span of these mice is about one to two years, in which a female can have 6-10 litters that usually contains about 5-7 pups, but can contain anywhere from 2-13 pups per litter. They are light brown to black, and their ears are moderately large and very distinct. Their tail is somewhat naked and about as long as their whole body. Because they are so small, this helps them to fit in the smallest of cracks and crevices. In favorable conditions (i.e. clutter grocery stores, unsanitary restaurants, unkempt residential garages, etc.) mice populations can grow rapidly. When inside a structure with favorable conditions mice can breed throughout the year. At low temperatures they produce fewer offspring and they are smaller in size. Outdoors they are seasonal breeders with peak times during spring and fall. A house mouse, despite it's name, commonly exists outside in fields, wooded areas, yards, ditches, etc. Here they will feed on various plant seeds and insects, and constructs a nest in ground burrows, tree cavities, vegetative debris, etc. When inside, they will build nests inside the base of cabinets, wall voids, stove and dishwasher voids, etc. For a nest they will use such material as cardboard, plastic, fabric, leaves, string, paper, etc. Research has shown that a pregnant female will make as many as 150 trips in one night to collect these materials for her nest.
The deer mouse is the most widely distributed and abundant mammal in North America. They are most common around homes and buildings in rural and semi-rural areas, not typically in urban areas. In color, deer mice resemble the common white tailed deer, this is where their name comes from. Their fur varies from grayish brown to a golden brown. They measure about 6" in length, including their tail. The life span of a deer mouse is 2-24 months. In this time they can have any where from 2-4 litters, and these litters can contain about 3-5 pups. Deer mice are nocturnal, meaning they are active at night. Outdoors they will nest in or around fence posts, tree hollows, log piles, beneath decks, barns, etc. Outdoors they have been found to be particularly a nuisance because inside garages they will nest in cars, trucks, and farm equipment. Indoors they can be found in basements, attics, storage boxes, furniture, wall voids, etc. Nests can be relatively large at about 8-16 inches in diameter, and often globular shaped. They do not stay in these nests for long because they will contaminate their nests themselves, forcing them to relocate and rebuild every few weeks. When traveling, they tend to leap rather than run. It has been recorded that a Deer Mouse can move at a speed of 8 feet per second. Deer mice will feed on insects, insect larvae, nuts, seeds, berries, and meaty items such as dead mice, snails, slugs, and young birds. Since they are nocturnal, feeding peak is at dusk or dawn. In winter the mice may not leave the nest for several days at a time and feeding on stored food.
This is the most common rat in Iowa. It is relatively large, measuring at about 16" from nose to tail and weighs about 12-16 ounces. The Norway Rat is typically a grayish brown, but it can vary from a pure gray to a blackish, or even a reddish-brown. The reproductive peak for this rat is during the spring and fall. A female can have about 8-12 pups in a litter. Wild rats may only live 5 to 12 months, whereas a rat in captivity may live up to 3 years. Outside these rats are found living in woods and fields. They are a ground dwelling mammal and will dig and construct its nests beneath heavy or large rocks, beneath slabs and along building foundations. The Norway Rat is well adapted to water and is a good swimmer. Because of this you will typically find nests around rivers, streams, lakes, inlets, and bays. They will feed on fish, frogs, other aquatic animals, insects, birds, other mammals, nuts, berries, fruits, plant seeds, and other natural foods. Inside, these pests will live in wall voids, ceiling voids, attics, crawl spaces, etc. When inside they will feed on just about anything that people or other animals consume, combined with any natural foods found outside. Norway rats will consume about 10 percent of their body weight daily. They will carry or hoard food to their nest or hiding place, which if inside, food can be found inside wall voids, furniture, appliances, etc. These rats will stay within 25-100 feet of its nest. Research has found that when a rat is taken from its nest and was put in places that were foreign to them, they have been recaptured up to 4 miles away from the point of release. This shows how likely it is for a Norway Rat to follow various pathways such as sewer lines, drainage ditches, overhead utility lines, etc. to establish new infestations in previously non-infested areas.