Norway Rat (Rattus norvegicus)
Quick Look Pest Stats
Color: Brown with scattered black hairs; gray-white underside
Shape: Long with blunt muzzle
Size: 7 – 9 1/2″ Long
Region: Found throughout the U.S.
Norway rats are believed to be of Asian origin, but are now found throughout the world. These rats can cause damage to properties and structures through their gnawing. Norway rats have smaller eyes and ears and shorter tails.
Outdoors: Norway rats live in fields, farmlands and in structures. These rats frequently burrow in soil near riverbanks, in garbage and woodpiles, and under concrete slabs. Indoors: They often nest in basements, piles of debris or undisturbed materials. These rodents can gain entry to a home through a hole the size of a quarter.
Norway rats are primarily nocturnal and often enter a home in the fall when outside food sources become scarce. These rats are known to gnaw through almost anything, including plastic or lead pipes, to obtain food or water. Norway rats eat anything, but they prefer: meat, fish, cereal, dry dog food.
Norway rats are social rodents and build burrows close to one another. These rats mature in 2-5 months, and live as an adult for 6-12 months, longer in captivity. Pregnancy lasts 3 weeks. Newborns get hair after 1 week, open their eyes in 2 weeks, and are weaned at 3-4 weeks. A female has 3-6 litters per year, 7-8 young per litter, with an average of 20 young weaned per year. They have keen hearing, smell, taste, and touch, with their long whiskers, but poor vision, and are also color blind. They can run, climb, jump, and swim. They are nocturnal, and explore a lot, but they are cautious and shy away from newly introduced objects.
Norway rats can cause damage to structures through their gnawing and eating. These rats are also vectors of diseases including plague, jaundice, rat-bite fever, cowpox virus, trichinosis and salmonellosis. In addition, Norway rats can contaminate food and introduce fleas into a home.
Signs of a Norway rat infestation include; rodent droppings, gnaw marks, damaged goods and greasy rub marks caused by their oily fur.
Norway rats are often drawn to piles of wood, so homeowners should keep firewood stored well away from the structure and remove debris piles to reduce nesting spots. For proper Norway rat control, seal any holes on the outside of the home with silicone caulk. Eliminate sources of moisture, especially in crawl spaces and basements.