FACTS AND INFORMATION ABOUT NORWAY RATS

Norway rats (Rattus norvegicus), have many other names, including “Norwegian water rat”, “Norway wood rat”, “brown rat”, “house rat”, “barn rat”, “sewer rat” and “gray rat”. These are disease carrying rodents who have adapted well over time and have successfully learned to thrive living among humans. Norway rats originated from Great Britain, and arrived in North America via ships during the 1775 American Revolutionary War. They spread west, and arrived in Ontario, Canada in the 1800s.

Norway rats are large, stocky, rodents with long tails (up to 21 cm long). Their bodies can grow up as big as 40 cm long and weigh as much as 1 pound. They are notably larger than roof rats. Their shaggy fur is typically gray or brown in colouring. Both their tail and ears are covered with scales. Their teeth continually grow, and they use gnawing to help them maintain their teeth.

Norway rats are not social, but they do live in colonies with a caste system of dominant and subordinate members. Norway rats can climb, but they prefer ground nests, and inhabit lower levels of buildings. Common habitats include underground in burrows around tree roots, embankments, concrete slabs and under buildings They also live round docks, in warehouses, sewers, woodpiles, basements, cellars and crawlspaces, barns, kennels, and livestock facilities.

They enter homes and buildings in their pursuit for food and water. These rodents are quick, and can gain entry through climbing, jumping or swimming. Like roof rats, these rodents can squeeze through quarter-sized holes due to their small bones and flexible body. If a Norway rat can get its head through a hole, crack or crevice, it can collapse its body and pull itself through the opening.

Norway rats are omnivorous. While they favour meats, grains, fruits and nuts, they will eat just about anything, including dog food, greasy foods and dead animals. Norway rats are very resourceful, and can even catch other small rodents or small fish for food. Very important to their survival is drinking water – they need to drink. Nests are usually built as close as possible to a water source.

Like a roof rat, a Norway rat reaches its sexual maturity between 2-5 months, and can breed all year. A female Norway rat produces 3 to 12 litters a year, with litter sizes varying greatly (from 4 to 20+ babies born). Also like roof rats, the Norway rat's life span is around 1-year long.

Norway rats are damaging rodents. They chew through electrical wires, which can cause electrical shortages, and electrical fires. They cause structural damage to buildings through their gnawing and burrowing underground. They cause serious damage to walls, ceilings, floors, window sills, and doors by gnawing holes through them, as well as by burrowing and nesting in insulated attics and in walls.

These rodents can transmit a variety of diseases to humans or livestock, including Rat-Bite Fever (RBF), murine typhus, leptospirosis, trichinosis and food poisoning. Norway rats are not typically associated with carrying plague disease, like roof rats, and other rodents

Being nocturnal, Norway rats stay hidden in their nests during the day. If nests are disturbed (usually by constructions or renovations), or colonies get too large, these rodents can become exposed during the day. Here are some signs that you have a Norway rat infestation:

• Sighting live rats during the day.
• Finding urine or scattered ¾ inch capsule-shaped rat droppings.
• Uncovering nests indoors.
• Locating outdoor burrows surrounding your home or building.
• Discovering their rub marks or grease stains along interior edges.
• Finding gnaw marks on food or even on utility lines.

To help prevent Norway rats from invading your home or business, or to help get rid of them, it is crucial to eliminate their access to food, water and shelter. Here are some tips:

• Empty indoor garbage cans regularly, and store outdoors away from homes and buildings.
• Use secure lids on all garbage cans (indoors and outdoors).
• Keep dry foods, including pet food and bird seed, in tightly sealed containers.
• Regularly clean and sanitize your kitchen, and other eating areas.
• Fix plumbing leaks in and around your home or building.
• Refrain from using water features and bird baths close to your home or business.
• Maintain lawns to prevent tall grass or heavily weeded areas from developing close to your home or buildings.
• Trim trees, shrubs, bushes back, and away from your home or business.
• Store woodpiles away from homes or buildings.
• Don’t leave window open, especially at night, without tightly, hole-free, fitting screens.
• Install, repair or replace broken screens over windows and vents.
• Seal up cracks and crevices around your windows, doors, eaves, chimney, and any other entry point
• Install, repair or replace damaged weather stripping.

Learn more about getting rid of Norway rats.

If you uncover a Norway rat infestation contact a licensed pest professional, who can help you get rid of Norway rats.