Rattus norvegicus
Rodent
7 to 10 inches body, plus 6 to 8 inch tail (shorter than body)
Brown to grayish-brown back, lighter gray or white belly
1 to 2 years in the wild
About the Norway Rat
The Norway rat (also called brown rat or sewer rat) is Michigan's largest commensal rodent. Norway rats spread leptospirosis, salmonella, rat-bite fever, and hantavirus. They gnaw through lead, aluminum, concrete, and even low-grade steel, causing structural damage and electrical fires.
Habits & Behavior
Norway rats are burrowers. They dig 6 to 18 inches underground along foundations, under slabs, and beneath sheds. They prefer ground-level nesting over attics and enter structures through foundation gaps, sewer line breaks, and unsealed utility penetrations. They need about 1 ounce of water daily and travel 100 to 150 feet from the nest.
Signs of a Norway Rat Infestation
Capsule-shaped droppings 1/2 to 3/4 inch long with blunt ends
3 to 4 inch diameter burrow holes near the foundation, under decks, in garden beds
Heavy greasy rub marks 1 to 3 inches wide along travel paths
Gnaw marks on wood, PVC pipes, electrical wiring, concrete block
Loud thumping or scratching in walls, ceilings, or crawlspaces at night
Visible runways of flattened grass 2 to 4 inches wide along fence lines
Norway Rat Pressure in Michigan
Norway rats in Metro Detroit cluster around Detroit River waterfront, Downriver communities, Hamtramck, Highland Park, and dense commercial corridors. They exploit aging sewer infrastructure and enter buildings through broken sewer lines. Construction projects displace established colonies into adjacent neighborhoods.
How BTR Treats Norway Rat Infestations
BTR uses a burrow-baiting program combined with exterior tamper-resistant bait stations. Active burrows are treated with locked bait, then observed for reactivation. Exterior perimeter stations maintain pressure. Interior snap traps address any rats that enter the structure. Most Metro Detroit Norway rat jobs require 4 to 6 visits across 8 weeks because colonies are large.
Prevention Tips
Never store pet food, trash bags, or bird seed in the garage or outdoors. Eliminate standing water. Cap sewer stack vents. Repair broken sewer laterals. Seal weep holes with hardware cloth. Trim dense vegetation 18 inches from all foundations.
Frequently Asked Questions About Norway Rats
What is the difference between a Norway rat and a roof rat?
Norway rats are larger, heavier, with shorter tails than body length and blunt noses. They burrow at ground level. Roof rats are smaller, sleeker, with tails longer than body length and pointed noses. They nest in attics and trees. Michigan has almost exclusively Norway rats; roof rats are rare north of Ohio.
How fast do rats reproduce?
A single female Norway rat produces 3 to 6 litters of 6 to 12 pups per year. Pups reach sexual maturity in 8 to 12 weeks. One breeding pair can produce 1,000 descendants in a year under ideal conditions.
Can rats come up through the toilet?
Yes, though it is rare. Norway rats are strong swimmers and can navigate sewer pipes. Installing a backflow preventer valve or rat blocker in the sewer lateral eliminates this risk.
Are rats dangerous to humans?
Yes. Norway rats carry leptospirosis, salmonella, rat-bite fever, hantavirus, and trichinosis. Their urine and droppings contaminate surfaces. Rat bites occur when humans startle rats in enclosed spaces. Children are at higher risk due to smaller size.
How much does BTR charge for rat removal?
Call (734) 338-1828 for a free inspection and quote. Pricing depends on property size, colony size, and exclusion work required. Most Metro Detroit Norway rat programs include 4 to 6 visits across 8 weeks.
Norway Rat Problem? BTR Can Help Today
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