Quick answer
A Norway rat is a large, heavy-bodied brown rat, the species Rattus norvegicus, that digs burrows along foundations, under woodpiles and in yards, and moves into basements and ground floors for food and shelter.
Adults weigh 7 to 18 ounces, and their tail is shorter than the head and body, which is the quickest way to tell them from the slimmer, climbing roof rat.
Quick facts
The key facts about Norway Rat, with sources:
- Scientific name
- Rattus norvegicus, also called the brown or sewer rat 4
- Weight
- 7–18 ounces 1
- Length
- Body up to about 11 inches; about 16 inches with the tail 3
- Tail
- Shorter than head and body; reaches about mid-skull when pulled forward 1
- Breeding
- Averages 4–6 litters a year; can wean 20 or more young a year 1
- Foraging range
- About 100–500 feet from the nest 1
Key takeaways
- The Norway rat is the big, ground-dwelling rat found across the lower 48 states.
- It digs burrows along foundations and under clutter, then moves into basements and crawl spaces.
- Blunt droppings up to an inch long and burrow holes near walls are its clearest signs.
- It can undermine slabs and chew copper, lead, plastic and wood, so damage goes beyond food.
- Control means removing food and harborage, sealing gaps and trapping, in that order of lasting value.
What a Norway rat is
The Norway rat is the rat most people picture: a thick, brown-gray body, a blunt nose, small ears and a scaly tail.
UC IPM describes it as larger and stockier than the roof rat, with a mostly gray belly 1.
Cornell says adults can reach 11 inches in body length and about 16 inches with the tail 3.
The name is misleading. Arizona Extension notes this rat is one of three commensal rodents brought to North America on ships in the 1600s and 1700s, and it also goes by sewer rat 4. “Commensal” means it lives with people and depends on our food and buildings.
It is a ground-level animal, so Norway rats burrow along foundations, under rubbish and woodpiles and around gardens. Indoors they mostly stay in basements and on ground floors 1. They are strong swimmers, which is how they use sewers 1.
Water matters to them, and Cornell says Norway rats need to drink standing water every day 3. Leaky hose bibs, pet bowls, drains and ponds all help them settle near a home.
How Norway rats live around a home
A Norway rat colony follows a predictable daily pattern, which is why traps and sealing work when placed right.
- Burrow: Rats dig tunnels next to foundations, under slabs, sheds, garbage cans and compost piles. Nests are lined with leaves, shredded paper or cloth 1.
- Forage at night: Both rat species are mostly active at night 1. Norway rats forage about 100 to 500 feet from the nest but stay close when food is nearby 1.
- Eat what is plentiful: They prefer cereal grains, meat, fish and nuts, and tend to eat whatever is abundant, often right where they find it 1.
- Drink daily: They visit a source of standing water every day, which keeps them close to leaks and drains 3.
- Breed: A female averages 4 to 6 litters a year and can wean 20 or more young 1.
- FoodGarbage, pet food, birdseed, compost
- WaterDrinks standing water daily
- CoverWoodpiles, dense shrubs, rubbish
- EntryGaps of 1/2 inch under doors
Take away any one of these and the colony shrinks; take away all four and traps finish the job. Source: [1] [3]
Norway rat and the animals it gets confused with
| Animal | Body and tail | Droppings | Where it nests |
|---|---|---|---|
| Norway rat | Stocky; tail shorter than head and body 1 | Blunt, 3/4–1 in. 4 | Burrows in soil, basements 1 |
| Roof rat | Slim; tail longer than head and body 1 | Pointed, 1/4–1/2 in. 4 | Trees, attics, upper walls 1 |
| House mouse | 5–7 in. total including tail 2 | 1/8–1/4 in. 3 | Walls, drawers, boxes 2 |
| Pack rat (woodrat) | Hairy, bicolored tail 4 | Blunt, 1/2–3/4 in. 4 | Stick piles near rocks and plants 4 |
Pack rats are native animals with different habits, and in the Southwest they are common look-alikes. If you are not sure, our pest identifier can help narrow it down.
Example: sizing the search area around one burrow
This is an illustration built from published figures, not a survey of a real yard. It shows why rat work covers more ground than mouse work.
| Question | Published figure | What it means for the search |
|---|---|---|
| How far will they travel for food? | About 100–500 feet 1 | Check neighbors’ compost, bins and sheds, not only your own yard |
| How far does a house mouse travel? | Seldom past 30 feet 2 | A mouse search is a few rooms; a rat search is the block |
| How far apart should traps go? | 10–20 feet apart 1 | A 100-foot wall run may need 5 to 10 traps |
| How many traps for heavy activity? | A dozen or more 1 | Plan for many traps at once, not one or two |
The lesson: one burrow by your foundation may be fed from food 300 feet away. Fixing the food source can matter as much as the traps.
Where you will see the term
On an inspection report, the technician should name the species. “Rats” is not enough, because Norway and roof rats need traps set in different places. Look for notes on burrows, runways, rub marks and entry points.
On a quote, look for separate lines for trapping, exclusion and follow-up visits, and for any burrow work outdoors. Our page on pest control treatment plans explains what each should cover.
On a bait label, the target pest is printed. Products labeled for house mice only should not be used for rats.
On a city notice, Norway rats are often the reason for rules on garbage cans, lids and yard debris.
Warning signs of Norway rats
UC IPM and Cornell list these signs of an infestation, so check the foundation line, garage, basement and anywhere food is stored.
- Burrow holes under garbage cans, compost piles, slabs or along the foundation 1.
- Droppings 3/4 to 1 inch long with blunt ends, near food or pet food 31.
- Gnaw marks about 3.5 to 4 mm wide per pair of teeth 3.
- Tracks with feet 3/4 to 1 1/4 inches long, sometimes with a wavy tail drag in dust 3.
- Nests behind boxes, in cluttered garages or in woodpiles 1.
- Noises at night from basements, crawl spaces or ground-floor walls.
Disease and cleanup
UC IPM says rats can spread leptospirosis, typhus, rat bite fever and foodborne germs such as salmonella and E. coli 1. Do not handle rats bare-handed.
Air the area for 30 minutes, wear gloves, soak droppings with disinfectant and wipe them up; never sweep or vacuum 7. For a bite, wash it and see a doctor.
What each control step does well
Strengths
- UC IPM calls snap traps the safest, most effective and most economical way to trap rats 1.
- Traps set close to walls, behind objects and in dark corners match how Norway rats move 1.
- Removing food, water and cover makes every other step work better.
- Sealing gaps with metal stops new rats from moving in 1.
Weak spots
- Rats can chew through plastic, foam, wood and caulk, so soft patches fail 1.
- The CDC says not to use glue or live traps, which can make rodents urinate and spread germs 6.
- Baits take time, and secondary poisoning can kill pets and wildlife that eat poisoned rats 10.
- Burrows in a neighbor’s yard can keep feeding rats back to you.
Why Norway rats are hard to clear
They cover a lot of ground, and with a range of up to 500 feet, the source of a problem is often outside your lot 1.
They are strong and persistent chewers, and UC IPM says Norway rats gnaw copper, lead, plastic and wood 1. A gap patched with foam or caulk alone tends to reopen.
They dig, and their burrows along a foundation can undermine slabs and walks 1, and a sealed wall can be bypassed by a tunnel under it.
They breed steadily, since four to six litters a year means a missed few can restock the area within months 1.
What drives the cost of Norway rat control
We do not publish rat control prices, because a fair figure needs many dated local quotes, but these are the factors that move a quote up or down.
The size of the area and the number of burrows set how many traps and visits are needed.
Exclusion work, such as metal on vents, door edges and pipe gaps, adds labor and materials. Slab or foundation damage may need a contractor on top of pest work. Cleanup of nests and droppings in a crawl space adds time.
Our rodent exclusion planner helps you list gaps before you call, and the pest control cost guide explains how quotes are put together.
Ask what any guarantee covers, how long it lasts and whether it needs ongoing service to stay valid.
How a professional Norway rat job usually works
A licensed company usually works in this order, which mirrors the CDC’s seal up, trap up, clean up approach 567.
- Inspect inside and out: Map burrows, runways, droppings, rub marks and every gap. Rats can squeeze under a door through a 1/2-inch gap 1.
- Cut food, water and cover: Lids on bins, pet food indoors, woodpiles off the ground, shrubs at least 2 feet from the house 1.
- Trap: Set snap traps 10 to 20 feet apart along walls and in dark corners, with a pea-sized bait 1.
- Seal: Use galvanized 1/2-inch mesh on vents and sheet metal on gnawed door edges; avoid chicken wire 1. See rodent exclusion for details on materials and methods.
- Clean up: Disinfect droppings and nesting material the way the CDC describes, using gloves and a wet method 7.
- Follow up: Check traps daily at first, then look for new burrows and fresh signs.
Home rat control does not need a permit, but the company and its applicators must hold a state license, and our pest control licensing page explains how that works.
Keeping Norway rats away
- Use bins with tight lids and keep them off bare soil where rats like to burrow.
- Fix dripping faucets and empty standing water, since Norway rats drink daily 3.
- Store pet food and birdseed in metal containers; clean up spilled seed.
- Keep woodpiles and lumber off the ground and away from the foundation.
- Check the foundation line monthly for fresh burrow holes and fill them in.
Fill a burrow to test it
Loosely fill a suspected burrow with soil or paper and check the next day. If it is open again, rats are using it. This is a simple activity check many extension services teach.
Good sanitation is the cheapest rat control there is. Our pest risk checklist covers the rest of the yard.
When to call a professional
Call when you see rats in daylight, find burrows along the foundation, or find droppings inside the home, because daytime sightings can mean the colony is crowded.
Call if rats have chewed gas lines or wires. UC IPM notes rats may chew natural gas lines and car wiring 1. Contact the utility or an electrician for repairs as well.
Call if a slab, step or walkway is sinking near burrows, because that structural damage needs a contractor as well as pest control. Our rodent control service page explains what a full job includes.
Rules that apply to rat control
Federal (EPA, FIFRA): The EPA registers all rodenticides under federal law. Following its 2008 risk mitigation decision, consumer products must be ready-to-use bait stations with block or paste bait, and second-generation anticoagulants are no longer registered for consumer products 8.
Professional second-generation products must be sold in containers of at least 16 pounds 8.
Endangered species: On November 22, 2024, the EPA released its final biological evaluation and Rodenticide Strategy for 11 rodenticides. The strategy itself imposes no new limits; measures apply in specific areas as each product goes through registration review 9.
State: States license applicators and can go further than federal rules. California bans most anticoagulant uses, and most structural bait must be in stations within 50 feet of a structure 1.
Poisoning: NPIC warns that pets and wildlife can be poisoned by eating bait or a poisoned rat, so a suspected exposure needs a fast call to a vet or poison center 10.
Norway rat vs roof rat at a glance
| Trait | Norway rat | Roof rat |
|---|---|---|
| Build | Large and stocky 1 | Smaller and sleek 1 |
| Muzzle | Blunt 1 | Pointed 1 |
| Nesting | Burrows; basements and ground floors 1 | Above ground; attics and trees 1 |
| Food | Grains, meat, fish, nuts 1 | Fruit, nuts, berries, snails 1 |
| Litters | 4–6 a year 1 | 3–5 a year 1 |
| Where to trap | Floor level, along walls 1 | Off the ground on ledges and beams 1 |
The trap placement row is the one that decides whether a job works. Our rodent droppings page covers the dropping differences in detail.
Common Norway rat myths
- Myth Rats carry rabies.
- Reality UC IPM says commensal rats do not carry or transmit rabies 1.
- Myth Chicken wire will keep rats out.
- Reality UC IPM says to avoid lightweight chicken wire and use 1/2-inch galvanized mesh 1.
- Myth Caulk or foam seals a rat hole.
- Reality Rats can chew through plastic, foam, wood and caulk 1.
- Myth A big trap baited with a lot of food works best.
- Reality UC IPM advises only a pea-sized amount of bait 1.
- Myth Rat poison is the fastest fix.
- Reality Baits take days and can poison pets and wildlife that eat the rat 10.
Where the Norway rat is, and is not, the main rat
UC IPM says Norway rats live throughout the 48 contiguous states 1.
Arizona is the notable exception in practice: Arizona Extension reports the Norway rat is not well established there, though it is confirmed in the Phoenix area from time to time, while the roof rat has spread through Phoenix, Tucson and Yuma since 2001 4.
In the Southwest, check whether you have a roof rat or a native pack rat before treating. Rules on which baits may be used also vary by state, so check your state pesticide agency.
When it matters to you, and what to do next
A single burrow outside with no signs indoors is a job you can start yourself: remove food and cover, fill the hole and watch it. When burrows reopen, droppings show up indoors or rats appear in daylight, call a licensed company for inspection, trapping and sealing.
Avoid putting poison bait out on your own near a home with children, pets or wildlife. Federal rules already limit consumer products to bait stations for a reason 8.
When comparing companies, ask how they tell Norway from roof rats, where they will set traps, what materials they use to seal and how follow-up works. See choosing a pest control company for more questions.
Quick decision guide
For one outdoor burrow, clean up and monitor. For reopened burrows or indoor droppings, book a licensed inspection and exclusion. If a gas line is chewed, leave and call the gas utility. If a child or pet ate bait, call Poison Help at 1-800-222-1222.
Questions about Norway Rat
How can I tell a Norway rat from a roof rat?
Look at the tail and the overall build of the body. A Norway rat is stocky with a blunt nose, and its tail is shorter than its head and body.
A roof rat is slimmer with a pointed nose and a tail longer than its head and body, per UC IPM. Norway rats live low and burrow; roof rats climb and nest high.
How big do Norway rats get?
Adult Norway rats weigh 7 to 18 ounces, according to UC IPM. Cornell says the body can reach 11 inches, or about 16 inches including the tail. That makes them the largest common rat in U.S. homes, and it is why mouse traps and mouse bait stations are the wrong size for them.
Where do Norway rats live?
Norway rats live in burrows along building foundations, under rubbish and woodpiles and around gardens, per UC IPM. Indoors they mostly use basements, crawl spaces and ground floors. They also live in sewers, since they swim well. UC IPM says they are found across the 48 contiguous states.
What do Norway rat droppings look like?
Norway rat droppings are dark, capsule-shaped and blunt at the ends, about 3/4 to 1 inch long, per Cornell and Arizona Extension. That is much larger than mouse droppings at 1/8 to 1/4 inch, and blunter than roof rat droppings, which are pointed and up to about 1/2 inch.
Do Norway rats carry diseases?
Yes, Norway rats carry several diseases. UC IPM lists typhus, leptospirosis, rat bite fever and foodborne germs such as salmonella, E. coli and campylobacter, although they do not carry rabies. Avoid touching rats or droppings, and clean up with gloves and disinfectant as the CDC describes, and see a doctor after any rat bite.
How small a gap can a rat get through?
UC IPM says rats, especially young ones, can squeeze under a door through a gap of only 1/2 inch. It advises sealing all holes larger than 1/4 inch, since young mice and rats use the smaller ones. Use metal, not foam or caulk alone, because rats chew through soft materials.
Why do I see rats during the day?
Rats are mostly active at night, so daytime sightings can mean the population is large and competition for food is pushing some out early. It can also mean a nearby food source is easy to reach. Daytime activity is a good reason to call a licensed company for a full inspection.
Can Norway rats damage my house?
Yes, they can cause serious damage. UC IPM says Norway rats can undermine foundations and slabs by burrowing, and they gnaw copper, lead, plastic and wood. Rats also chew vehicle wiring and may chew gas lines. Have any chewed wiring checked by an electrician and any gas line damage handled by the utility.
What is the best trap for Norway rats?
A rat-sized snap trap is usually the best choice. UC IPM calls snap traps the safest, most effective and most economical option. Set them close to walls, behind objects and in dark corners, 10 to 20 feet apart, with a pea-sized bait. The CDC advises against glue traps and live traps.
Is it safe to use rat poison at home?
Consumer rat poisons must come in ready-to-use bait stations, under EPA rules, and must be used exactly as the label says. Poison still carries risks: NPIC notes secondary poisoning of pets and wildlife that eat poisoned rats. If a child or pet may have eaten bait, call Poison Help at 1-800-222-1222.
Sources
- UC Statewide IPM Program, Pest Notes: Rats (Publication 74106), retrieved .
- UC Statewide IPM Program, Pest Notes: House Mouse (Publication 7483), retrieved .
- Cornell CALS Integrated Pest Management, Mouse and Rat Biology and Behavior, retrieved .
- University of Arizona Cooperative Extension, Roof Rats: Identification, Ecology, and Signs (AZ1775, 2018), retrieved .
- U.S. CDC, Seal Up to Prevent Rodent Infestations, retrieved .
- U.S. CDC, Trap Up to Control Rodent Infestations, retrieved .
- U.S. CDC, How to Clean Up After Rodents, retrieved .
- U.S. EPA, Restrictions on Rodenticide Products, retrieved .
- U.S. EPA, Strategy to Protect Endangered Species from Rodenticides, retrieved .
- National Pesticide Information Center, Rodenticides Fact Sheet, retrieved .
Expert review
Written by the HyrePest Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Identification, behavior, breeding, damage, trapping and exclusion facts follow UC IPM Pest Notes 74106.
Body length, droppings, tracks, gnaw width and water needs are from Cornell IPM; droppings ranges, history and Arizona status from Arizona Extension AZ1775. Cleanup, sealing and trap guidance are from the CDC. Product rules are from the EPA and NPIC.
Suggest a correction. We fix errors and say what changed.