Norway Rats


Reviled as the most destructive mammal pest, Norway rats compromise the well-being of humans and cause costly damage to manmade structures. They can live as long as two years in the wild and produce as many as 20 young in that span of time. Norway rats are mostly active at night, have poor eyesight, and rely on their other senses to guide them. Actually quite intelligent, Norway rats quickly detect and avoid unfamiliar objects that show up in their chosen environment, such as traps and baits. Their rapid rate of reproduction and elusive nature make them particularly challenging to control.
Rats living in your crawl space or walls? Disappearing pet food? Dead rats or rat dropping in your attic? These may well be signs of a rat infestation.

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Biology & Behavior

The Norway rat is the common domestic rat in Utah. It has course hair, close set ears, and its muzzle is blunt. The tail is dark on top and light on the underneath side. The tail is shorter than the combined length of the head and body. ​The fur is grey brown on back and grey white on the belly. The adults weight between 0.12 and 0.20 ounces and the combined length of the head and body is 7.5 to 10 inches long. The tail length is between 6 and 8.5 inches. The feces are capsule shaped and about 0.75 inch long. ​Norway rats can be found in warehouses, farm buildings, houses, sewers, rubbish, dumps, wood piles, and building foundations. They are good climbers and they can jump 24 inches vertically. The Norway rat has relatively poor vision but keen sense of smell, touch, taste, and hearing. Long whiskers on the snout serve the sense of touch. Their home is often 100 to 200 feet. ​Norway rats and other domestic rodents are mainly nocturnal, but they may go about in undisturbed places during the day. They feed on virtually anything edible. Norway rats are unable to vomit, they must drink water to survive.



Rats urinate often, creating stains and offensive odors. A single rodent will produce about 25,000 feces droppings in a year. They also do damage to electrical wiring by chewing off the insulation. It is estimated that 25% of fires are caused by rats.​ Rats burrow holes in yards and chew entry points of homes and buildings.​ Rat bites and scratches can result in disease and rat-bite fever. Rat urine is responsible for the spread of leptospirosis, which can result in liver and kidney damage. It can also be contracted through handling or inhalation of scat. Complications include renal and liver failure, as well as cardiovascular problems. ​

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