Norway Rats. How to Find the Burrow and Stop Them

Think big and blunt. The Norway rat, also called the brown rat, sewer rat or barn rat, is larger and stockier than the roof rat.¹ Adults weigh 7 to 18 ounces. The muzzle is blunt, the belly is mostly gray and the ears do not reach the eyes when folded forward.¹

Pull the tail over the back. A Norway rat's tail reaches the middle of the skull and is dark above and pale below.¹ A roof rat's tail is longer and dark all over. Compare in the roof rat guide.

Weight separates a rat from a mouse, since a Norway rat weighs 7 to 18 ounces.¹ See the house mouse guide if what you found is small.

A female Norway rat has an average of 4 to 6 litters a year and can wean 20 or more young annually.¹

Nests may be lined with leaves, shredded paper, cloth or other fibrous material.¹

Nightly trips can run 100 to 500 feet from the nest, but when food and nest are close, rats stay close to reduce risk.¹ That means a rat inside your basement probably has a burrow within a few yards. Find the burrow and you find the colony.

Norway rats work close to the ground. Look low.

• Burrows along building foundations, beneath rubbish or woodpiles, under garbage cans and compost piles, and among garden plants.¹
• Droppings near food storage, pet food bowls and food prep areas.¹
• Nests behind boxes, in cluttered garages and in woodpiles.¹
• Noises from the attic or drop ceilings.¹
• Dead rats carried around by pet cats and dogs.¹

Indoors, expect the basement or ground floor first.¹ Ceiling voids are not uncommon either. Walk the outside of the house first, because the burrow is usually the thing you can see and the thing you can fix.¹

Norway rats contaminate food and damage buildings. They can transmit typhus, leptospirosis, rat bite fever and foodborne illness such as salmonella, E. coli and campylobacter. They have also been linked to medically significant allergic responses in people.¹

Plague is rarely found in roof and Norway rats. Commensal rats do not carry or transmit rabies.¹

Norway rats and black rats are the natural hosts for Seoul virus. Infection in people is generally less severe than other hantaviruses, but it can still be serious. In 2017 CDC found 31 infected ratteries in 11 states and 17 infected people.⁴

Wear gloves when you handle dead rats and read the hantavirus cleanup steps.

Remove the way in and the food, then trap. Snap traps are the safest, most effective and cheapest option. For Norway rats, put traps close to walls, behind objects, in dark corners and where you find droppings. Use a pea-sized amount of bait, set traps 10 to 20 feet apart and use a dozen or more in a heavy infestation. Keep traps away from children and pets.¹

Poison is a second tool. Tamper-proof bait stations exist, and every rodenticide is toxic to pets, wildlife and people. Seal the building first so poisoned rats do not come inside to die.¹ EPA says consumer products come as ready-to-use bait stations.³

Call a pro if you have a burrow under a slab, traps that keep failing, or rats in the ceiling. Ask who does the sealing and the follow-up.

A typical rat job costs $150 to $600, or about $400 for a 2,000 square foot home. Large infestations or big properties can reach about $6,500.²

Standard removal with baits, traps and follow-ups runs $145 to $572. Sealing entry points is $150 to $650 and an initial inspection is $90 to $150.² DIY snap traps cost $2 to $5 each.²

Where the rats live matters. Walls and crawl spaces are harder to reach, and a poorly kept property costs more to work on.² Get three quotes and ask each company how it will seal the burrows and entry holes.

Rats go where food is easy.

• Seal cracks and openings larger than 1/4 inch with steel wool, wire screen or sheet metal. Rats chew plastic, foam, wood and caulk.¹
• Fit door sweeps and weather stripping.¹
• Store garbage, compost and pet food in tight containers. Rats can gnaw through plastic, so choose rigid metal where you can.¹
• Pick up fallen fruit and nuts and clear garden debris.¹
• Keep woodpiles and trash away from the foundation, since burrows start there.¹

UC IPM gives no off season for Norway rats. With 4 to 6 litters a year, expect pressure in every month.¹

Where they live changes more than when. Norway rats dig burrows along foundations, beneath rubbish and woodpiles and around gardens and fields, and indoors they stay in basements and on ground floors.¹

Check those spots in every month. The best time to seal is now, before a burrow gets a second litter. Walk the foundation and woodpiles once a season and look for fresh holes.

Norway rats are the rat to expect in Ohio. They live throughout the 48 contiguous states.¹ The Ohio Department of Health notes that antibody to a Hantaan-related virus turned up in wild rats collected in Columbus and Cincinnati in 1983.⁴

Ohio law requires pest management companies to be licensed through the Ohio Department of Agriculture. Ask for the license, a certificate of insurance and a workers' compensation certificate, and get at least three bids.⁵

A person hired to apply pesticide on someone else's property needs a commercial applicator license, which means passing the Commercial Core exam and a category exam.⁶

In California, both Norway rats and roof rats are present in almost all cities.¹ If you trap a rat, check its tail against the photos to learn which one you have.¹

Bait rules are tight. Bait used in and around structures generally must sit in bait stations within 50 feet of a structure, and most first- and second-generation anticoagulants are prohibited for most uses.¹

Use the Structural Pest Control Board's online services to verify a company or an individual before you sign.⁷ See the roof rat guide if the rat is in your attic.