The Norway rat is the largest of commensal rodents. They have rather poor vision and are color blind; but their senses of hearing, smell, touch and taste are keenly developed. Touch is via their long whiskers. They are good runners, climbers, jumpers and swimmers. Rats are primarily nocturnal in habit and they are cautious. They shy away from new objects and changes. They will feed on meat, fish and grains. Norway rats will travel between 100-150 feet from their nest for food and water.
Outdoors, Norway rats prefer to nest in burrows in the soil. An opening of greater than 1/2 inch is required for entry into buildings. Indoors, Norway rats usually nest in basements and the lower portions of buildings in piles of debris or merchandise as long as it is not disturbed. Occasionally they are found in attics, but prefer lower ground levels.
The disease most commonly thought of involving rats is the plague, which is transmitted via fleas leaving an infected rat and attacking a man. Recently, the plague has started to appear in several areas throughout the United States. A case involving a man in Oregon was reported just last summer of 2018.
Signs of Infestation of the Norway Rat
Gnaw Marks: New gnawing or holes tend to be rough; whereas, old gnawings are smooth from wear and old holes are often greasy.
Droppings: Fresh droppings are soft and moist; whereas, old droppings are dried and hard. Adult Norway Rats droppings are about 3/4 inch with blunt ends VDS adult roof rats that are about 1/2 inch with pointed ends.
Tracks/Footprints: Front foot is 4-toed and the print is in front of the usually longer hind print with 5-toes. Fresh tracks are clear and sharp; whereas, old tracks are at least partially obscured by dust.
Rub Marks: Fresh marks are soft, greasy and easily smeared; whereas, old marks are with the grease dry and flaky.
Burrows: Found in earthen banks, under concrete slabs and under walls. If active, they will be free of dust and cobwebs. The main opening is usually with hard packed soil and rub marks may be visible.
Runways: They consistently follow the same paths, usually along walls, among stacked merchandise, etc. Active runways will be greasy in appearance, free of dust and cobwebs, with fresh tracks and/or droppings.
Damaged Goods: Norway Rats prefer seeds, meat, fish and cereal; whereas roof rats prefer seeds, fruits, vegetables and cereals.