Norway Rats: Facts, Identification & Control
Norway rats are large rodents that may weigh in excess of 500 grams. They can reach lengths of 40 cm,and their tails alone may measure 21 cm. The body of the Norway rat is covered in shaggy fur that is brown or gray in color. The ears and tail are covered in scales, and the tail is shorter than the head and body. Droppings are capsule-shaped.
Behavior, Diet & Habits
Norway rats typically nest in underground burrows from which they enter buildings in search of food. They tend to remain in hiding during the day.
Norway rats are omnivorous and feed on a variety of food sources. If given the choice, they will consume meats, fruits, grains and nuts. Dead animals also serve as a food source for these rats, and they are capable of catching small fish and rodents. They require water to drink, and they make their colony as close to a water source as possible. Norway rats live in communities with dominant and subordinate members, though they are not truly social like ants.
The Norway rat reaches sexual maturity in two to five months and can breed any month of the year. Litters may number from four to 22. Females can have three to 12 litters per year. Adults generally live up to one year in the wild.
Signs of a Norway Rat Infestation
Norway rats are not usually seen exposed unless driven out of their hiding spaces because of limited space or disturbances. Sightings during the day often indicate a potentially large infestations. Outdoor burrows surrounding the building may be an indication of Norway rat nesting. Other signs of Norway rats are their gnaw marks on food and objects such as utility lines. Rub marks or grease stains caused by rats running along an edge also can indicate activity. In general, the darker the stain, the greater the activity. Perhaps one of the most well-known signs is their droppings. Norway rat droppings are blunt and 18 to20 cm long. They can be scattered along frequently traveled rodent pathways.
Sometimes called “Norway wood rats” or “Norwegian water rats,” Norway rats are prevalent throughout North America. Arriving on ships from Great Britain circa 1775, these rodents quickly spread throughout the American Midwest. By the 1800s, they were present as far as Ontario, Canada.
Today, Norway rats thrive in a variety of human habitats. While it is believed that Norway rats originally lived only within temperate forest regions, they are extremely adaptive and now thrive comfortably in densely populated cities. Outside, they can be found burrowing in the soil beneath buildings, in embankments and near tree roots. Inside, they live in basements, crawlspaces, attics and sewers. They can be carriers of various diseases.