Norway rat (brown rat) facts & identification

Norway rats (Rattus norvegicus), also known as brown rats, are one of the most common and adaptable rodents in North America. Known for their strong burrowing habits and knack for survival, Norway rats have spread across the globe, thriving in cities, farms, and fields.

Norway rats in the US

Introduced to North America in the 18th century, Norway rats are now widespread across the United States. Often referred to as “sewer rats” due to their prevalence in urban sewer systems, they are adaptable to various environments, particularly areas with ample food and water sources. Though they originated in northern China, they have become highly prevalent in urban areas and can frequently be found in proximity to human habitats, including homes, businesses, and farms.

Signs of a Norway rat infestation

Early detection of a Norway rat infestation can help prevent serious damage and health risks. Here are the key signs of rats to watch for in your home or property.

• Droppings: Dark, capsule-shaped droppings roughly 3/4 inch in length.
• Gnaw marks: Norway rats have strong, continuous-growth teeth, resulting in gnaw marks on wood, wires, pipes, and plastic.
• Burrows: Commonly found in gardens, near foundations, under sidewalks, and in basements.
• Grease marks: These can appear on walls, floors, or pathways where rats repeatedly travel, leaving greasy streaks from their fur.
• Footprints and tail marks: In dusty areas, you may see tracks or drag marks from their tails.

Nests: Norway rats create nests in burrows lined with shredded paper, cloth, and other debris.

Habitat, diet, life cycle & behaviors

Norway rats are incredibly adaptable and can live in various environments provided they have sufficient access to food, water, and shelter. Their behaviors and diet make them well-suited to life near humans, particularly in urban areas.

Where do Norway rats live?

Norway rats are versatile in their habitats but generally prefer ground-level or burrowed spaces. Unlike black rats, which are climbers, Norway rats are usually burrowers, nesting in the ground, beneath structures, in sewers, and occasionally indoors in basements or crawl spaces. They thrive in dark, secluded areas with nearby food sources and are known to create intricate tunnel systems in dirt or woodpiles.

Diet

Norway rats are omnivores with a preference for high-calorie foods. They scavenge for food sources like grains, fruits, meats, and garbage. As opportunistic foragers, they often depend on human waste and are known to consume nearly anything edible, making them highly adaptable in both rural and urban settings.

Life cycle

The life cycle of a Norway rat is relatively short, typically around one year in the wild. Female Norway rats can produce litters multiple times a year, with gestation periods lasting about 21-24 days. Norway rats reach sexual maturity in just 2-3 months, allowing populations to grow rapidly in favorable conditions. Their short life cycle and high reproductive rate make them challenging to control once an infestation takes hold.

Behaviors

Norway rats are nocturnal and polygynandrous, meaning they have multiple mating partners within their colony. They are territorial and aggressive, known to gnaw through materials to access food or shelter. Norway rats often forage within a close range of their nests, establishing trails and avoiding new or open spaces. Their gnawing behaviors help wear down their continuously growing teeth, and may can cause significant damage to structures, wires, and household items.

Are Norway rats dangerous?

Yes, Norway rats pose various health and safety risks. They are known carriers of diseases such as salmonellosis, leptospirosis, and trichinosis, which can spread to humans through contaminated food or water sources. Their droppings and urine can introduce pathogens, and their fur can carry parasites like fleas, which may spread diseases, including typhus and the plague.

Additionally, Norway rats can cause structural damage through gnawing, which may result in costly repairs or even fires if electrical wires are compromised. For these reasons, it’s crucial to take rat infestations seriously and seek appropriate control measures when necessary.

How to get rid of Norway rats

Effectively managing Norway rat infestations requires a combination of sanitation, exclusion, and pest control measures.

• Eliminate food and water sources: Keep food sealed, clean up spills immediately, and remove pet food after feeding.
• Seal entry points: Use steel wool, hardware cloth, and caulk to seal gaps or cracks in your home's foundation, walls, and roof. Rats can squeeze through surprisingly small spaces, so thorough inspection and sealing are key.
• Use traps and rodenticides: Place snap traps or bait stations in areas with signs of rat activity. Use bait stations carefully, as rodenticides can be dangerous to humans and pets.
• Professional pest control: For severe infestations, consider hiring a pest control professional like Ehrlich for rat extermination. We can assess the severity of the issue and implement effective rat control techniques.

Norway rat prevention tips

Preventing Norway rats from entering your property is often easier than removing an established infestation. Start by securely storing food in metal or glass containers with tight lids, especially in vulnerable areas like garages and basements. Proper waste management is also essential—regularly dispose of trash and keep garbage cans covered and positioned away from your home. Clear outdoor areas of any potential food sources, such as birdseed, pet food, and fallen fruits, to eliminate attractants.

Maintaining your landscaping can also help; keep shrubs, plants, and woodpiles away from the foundation to reduce hiding spots. Finally, routinely inspect your foundation, walls, and roof for any cracks or holes, sealing up any gaps that could serve as entry points for rats.

Keep reading our blogs for more rat information, details of common rats in the US, and advice on how to get rid of rats.

Need help with rat pest control?

Norway rat infestations can quickly become a serious concern. From health risks to property damage, these pests are not to be taken lightly.

If you’re dealing with a Norway rat infestation or want to take preventative steps, Ehrlich can provide peace of mind and effective solutions. Contact us today.

Frequently Asked Questions