Norway Rat

What it does

Norway rats are mainly nocturnal, cautious, and wary of new objects, which can make trapping slow. They are strong burrowers and swimmers but poorer climbers than roof rats, staying low in basements, crawl spaces, and burrows. They gnaw constantly to keep their ever-growing incisors worn down, damaging wood, plastic, pipes, and electrical wiring.

Where it lives

They nest in burrows in soil along foundations, under woodpiles and slabs, and in sewers, as well as inside basements, crawl spaces, and the lower levels of buildings. They stay close to food and water. Norway rats live throughout the US, most abundant in cities, ports, farms, and older neighborhoods.

How it breeds

Norway rats breed year-round where conditions allow. Females mature in a few months and can produce several litters a year, averaging six to twelve pups each. Populations grow quickly when food and harborage are plentiful, so a small problem can escalate within a season if entry points and food sources are not addressed.

What it eats

Norway rats are omnivores that prefer cereal grains, meats, and pet food but will eat almost anything, including garbage and fresh produce. They need daily access to water. They tend to feed at established sites and follow the same routes between harborage and food.

Identification

A Norway rat has a heavy, thick body 7 to 9.5 inches long, coarse brown-gray fur, a pale belly, a blunt nose, small ears, and a scaly tail shorter than its head and body. Droppings are large and capsule-shaped, about 3/4 inch with blunt ends. Compared with the roof rat, it is bulkier with a shorter tail and smaller ears.

Signs of an infestation

• Large capsule-shaped droppings with blunt ends, up to 3/4 inch
• Gnaw marks on wood, wiring, pipes, and food packaging
• Smooth, greasy rub marks along walls and beams
• Burrow openings in soil near foundations, slabs, or woodpiles
• Scratching or gnawing sounds in walls and floors at night
• Runways and worn paths through grass or along walls

Prevention tips

• Seal exterior gaps 1/2 inch or larger with steel, hardware cloth, or concrete
• Store food, grain, and pet food in sealed metal or heavy containers
• Keep garbage in rat-proof bins with tight lids
• Remove clutter, woodpiles, and debris that offer harborage
• Trim vegetation and eliminate standing water and outdoor food sources

Professional solutions

Small numbers may be reduced with well-placed snap traps and tamper-resistant bait stations plus sealing entry points, but Norway rats are wary and infestations often outpace DIY efforts. A professional can identify burrows and entry points, apply an integrated trapping and baiting program, and rodent-proof the structure. Always follow the EPA label on any rodenticide and keep baits away from children and pets.