Norway rats, often called brown rats or sewer rats, can be brown or gray in color. They are larger and more bulky than roof rats, weighing between 7 to 18 ounces, their tail is nearly hairless and shorter than body and head combined. The body of the Norway rat is covered with coarse shaggy fur. They have a blunt nose, and small ears with short hairs that does not cover the eyes.
Norway rats are primarily nocturnal and tend to remain in hiding during the day. Unlike roof rats, they prefer to inhabit sewers and the lower floors of multistory buildings in urban areas. They live very close to people and normally nest in burrows that are found along building foundations, beneath wood piles, rubbish in the gardens and fields. They thrive in the sanitary sewer system feeding on human wastes. They have been known to come up toilets inside the buildings, and exit the sanitary sewer systems through sewer breaks. Norway rats usually travel an area of about 100 to 150 feet in diameter and seldom travel more than 300 feet from their burrows.

Norway rats will eat nearly any type of foods; however, they prefer a balanced diet of cereal grains, meats, fish, nuts, and fruits. They require 0.5 to 1 ounce of water daily when feeding on dry foods but require less when moist foods are available. Norway rats frequent household garbage due to the choice of a balanced diet and the availability of moist foods. They are usually active around dusk and may be seen during the daylight in cases of heavy infestations. Their droppings are blunt and about the same shape and size of a dry raisin.

Norway rats mature sexually at 3 months of age. The female average 4 to 6 litters of 6 to 12 young per litter a year. The average lifespan of an urban Norway rat is one year.

Sanitation and exclusion are the most effective measures you can take to reduce rodent populations. When there is evidence of rodent activity like droppings, rub-marks, gnaw marks, and noises of gnawing, scratching or running, it is likely that a rat infestation already exists. Trapping or outdoor baiting is usually necessary to reduce the number of rats immediately. Trapping is the most effective and safe method to use in homes.

Wooden snap traps are effective and can be purchased at most hardware stores. Traps can be baited with a variety of foods; peanut butter is the most popular because it is easy to use and attractive to mice and other rodents. There are a number of different types of traps on the market with varying methods of capture.

Proper trap placement is very important. Set traps along rodent runways and travel paths where you frequently see rodents or find droppings. For Norway rats, set the traps close to walls, behind objects, in dark corners, and in places where signs (droppings, rub-marks) have been observed. Position traps along a wall at right angles, with the trigger end nearly touching the wall. If the traps are set parallel to the wall, they should be in pairs to intercept rodents traveling from either direction. Glue traps can be used but are less effective than snap traps. More traps often leads to greater success.

Structural modifications provide the most permanent and secure strategy for rodent proofing. Build a rat-proof structures for storing food, bird seed, and dog food in containers with tight-fitting lids. Seal all openings larger than ¼ inch to exclude both rats and mice. Repair all broken ventilation screens around the foundation and under the eaves. Norway rats can gnaw away plastic sheeting, wood and other less sturdy materials. Metal sheeting is recommended for framing doors and windows; coarse steel wool, wire screens, and lightweight sheet metal are excellent for plugging gaps and holes caused by Norway rats. Call our District or submit an online request for an inspection and assessment if you are struggling with Norway rat control.

Ref: http://ipm.ucanr.edu/PMG/PESTNOTES/pn74106.html

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A Guide to Norway Rat

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