Norway rats are highly adapted to living closely in and around human buildings in both city and countryside.
Muridae
The Muridae family of Old World rats are now found everywhere around the world except Antarctica. These rats and mice can be both serious pests and useful laboratory animals. Genus Rattus (“true rats”) includes the brown or Norway rat, black or roof rat, and the Polynesian rat. Several species of the genus Sigmodon, the cotton rats, are native to North and South America.
The Old World rats were introduced to North America during the earliest days of exploration and colonization. Although there are native rats such as the wood or pack rat, cotton rats, and kangaroo rats, the invasive rats are by far the most common and troublesome rodents to homeowners and farmers.
Norway and black rats live around residential, industrial, and farm sites; cropland; and parklands, especially near ponds, rivers, and waterways. Rapid breeders, they quickly infest an area. They often transmit bacteria, viruses, parasites, and other diseases that can contaminate food and buildings.
To deal with their constantly growing teeth, rats must continually gnaw. They use their oversized front teeth to chew foodstuffs and housing or bedding materials, often causing great damage to structures.
Although they have poor eyesight and are colorblind, rats use their good senses of hearing, smell, taste, and touch to locate food. Capable of breeding year-round in warmer areas, they produce 5 to 8 pups per litter and 4 to 5 litters per year.
Hunting and foraging. Rats are usually nocturnal, beginning to search for food after sunset. They will hoard food to eat later, caching it in a variety of locations. Rats are omnivores, eating fruits, seeds, insects, snails, garbage, foodstuffs, and animal feed. As opportunistic animals, they will also eat eggs, meat, and fish. They require daily access to water.
Rats contaminate food; spread disease (plague, salmonella, leptospirosis, and tularemia); inflict serious damage to buildings and wiring; prey on poultry, eggs, and newborn animals; and destroy crop and landscape plants.
Norway and black rats are not protected, and any legal means may be used to control them.
While cats cannot usually hunt rats successfully, the ratting dog breeds are dedicated to the pursuit of rats and have long been welcome in barns and farmyards. No electronic frightening or ultrasonic devices have long-term effectiveness, as rats become habituated to them.
Any lethal control of rats will not solve an established problem unless you implement prevention methods to control what is attracting them. Any use of poisons carries a danger to children, pets, livestock animals, and other species. All rodent baits should be considered toxic to dogs, cats, and wildlife. Rats are leery of new objects and will often avoid traps or bait stations for several days.
(Rattus norvegicus)
Norway rats are highly adapted to living closely in and around human buildings in both city and countryside.
The Norway or brown rat, also called the sewer or wharf rat, is not a native of Norway, despite the belief that it arrived in England from that country. Sturdy and comparatively large, Norway rats weigh up to 18 ounces. They can be as long as 16 inches, including the nearly hairless tail, which is slightly shorter than the length of the head and body. They are primarily grayish brown although black, white, and mottled rats are seen, and they have small ears and a blunt snout.
Norway rats are adaptable to most climates. Usually found on ground or lower floors of buildings, they live primarily in burrows.
▲ Norway Rat
The Norway rat is found in the entire continental United States and Canada except Alberta. Alberta has successfully and proactively eliminated rats for more than 50 years.
(Rattus rattus)
Black rats can be distinguished from their Norway cousins by their larger ears and pointed snout.
The black or roof rat is similar in length, but its hairless tail is longer than the Norway’s, and its body is slenderer and darker. Black rats weigh up to 10 ounces. Their ears are large, and the face has a pointed snout. Excellent climbers, they are more likely to be found in trees and rafters and on wires and roofs than are Norway rats.
Black rats are limited to warmer climates around coastal cities, where they frequently enter buildings through the roof and live in utility spaces and false ceilings or attics, as well as in trees, brush, and ivy.
▲ Black Rat
The black rat is limited to the lower half of the eastern coast, the Gulf states into Texas, and the entire Pacific coast. Isolated groups may be found elsewhere at times.
(Sigmodon hispidus)
These rats were named for their habit of building nests out of cotton. Native to North and South America, cotton rats range from southern Virginia through the Gulf Coast states; west to northern Missouri, Nebraska, and Kansas, through southeastern Colorado, New Mexico, and southeastern Arizona and California.
The cotton rat is 10 inches long, including its bare tail. It is smaller than the Norway rat, with a shorter tail, grizzled black or gray fur, and large ears hidden in fur. Active day and night, cotton rats are herbivores that eat green vegetation, quail eggs, and more rarely insects or small animals. They will damage grass, alfalfa and grain crops, fruits, berries, nuts, and vegetables such as peanuts, sweet potatoes, and melons. Cotton rats cut plants off at the base, chop them into smaller pieces, and leave small pieces of grass or stems in piles along their grassy runs. Nests are found in grassy or overgrown fields, ditches, or fencerows. They will also infest outbuildings.
Solid sheet-metal barriers 18 inches tall and buried 6 inches deep will exclude cotton rats. They are a host for airborne hantavirus; handle droppings carefully and wear a protective mask.
Poultry, eggs, newborn animals
Night
Front 1⁄2–7⁄8 inch long, 1⁄2– 3⁄4 inch wide; rear 3⁄4–13⁄8 inches long, 5⁄8–11⁄4 inches wide.
Walking stride 3–5 inches; bound stride 6–21 inches
Small unconnected ovals, 1⁄4–1 inch long, 1⁄8–1⁄4 inch in diameter
