The Norway rat is an invasive species that damages property, spreads diseases, and ruins human and pet food. They are omnivores, meaning they eat anything. This includes meat, like eggs and other small animals, as well as grains, seeds, and vegetables, meaning these rats can also destroy crops.
Why Are Norway Rats in Your House a Problem?
Norway rats are carriers of multiple diseases that can be transmitted to humans, pets, and livestock through a rat bite or the fleas, ticks, and mites living on their bodies. Diseases may include rat bite fever, salmonellosis, and tularemia.
Norway rats have teeth that continually grow throughout their short lifespan. To keep their teeth from causing pain, rats must gnaw on hard materials, including wood, plastic, vinyl, drywall, and some thin metals. They usually find these materials on your house, leading to severe damage to your property. While Norway rats don’t need a reason to chew holes into your siding, windowsills, or doors, they may do so seeking food or a place to nest.
Because Norway rats in your house can fit through holes the size of a quarter, they can easily travel throughout your house and attic and build nests in your walls, pipes, vents, and ducts. Clogging vents, gutters, pipes, and chewing electrical wires are a few examples of the water and fire hazards rats can cause.
Rats build burrows, creating tunnels under homes, driveways, sheds, and other structures. Burrows cause unstable foundations, risking your and your home’s safety.
Signs of Norway Rat Problems
Norway rats never live alone. Instead, they live in large groups or colonies, consisting of as few as 15 and as many as 150. Some females may spend time in a nest alone when birthing a litter. However, Norway rats tend to share nursing duties. It is common for females to nurse pups that are not their own.
If you find evidence of one Norway rat, you likely have a rat colony in your house.
Homeowners may not always recognize signs of Norway rats because these pests avoid detection. Once a Norway rat builds a nest, it will stay within 45 meters of it. Rats will spend a good deal of time exploring and creating travel routes and looking for food and water.
Rats memorize their travel routes and generally avoid any new foods or objects placed in their path, including traps with bait. Homeowners using toxic bait cause Norway rats to become sick and, ultimately, bait-shy. In addition, they are nocturnal creatures, making it hard for humans to see them in action. Therefore, knowing other problem signs is crucial.
Norway rats in a house leave droppings and urine trails everywhere they travel. They drop feces and urine along baseboards, countertops, cabinets, and appliances. Wherever they go for food, water, and shelter, you will find rat droppings.
Norway rat droppings are typically ¾” long and ¼” in diameter. When the droppings are soft, they are likely fresh. If hard, dry, and crumbly, they are likely old droppings. Both versions create health risks for you.
Norway rats leave tracks in multiple ways with their feet, tails, and fur. Each type of track can be seen easily when looking for them. They have four front toes and five back toes. They walk on the front parts of their feet, so only that part leaves a print mark. Their greasy bodies rub against your walls, floors, cabinets, and appliances, leaving black marks. Tails also leave marks as they travel, touching numerous spots throughout your home.
Norway rats can chew on and through most materials. You may see gnaw marks on wires, wood, siding, carpets, etc. Tooth marks are noticeable; you will likely find shavings or debris under their gnaw marks. When gnawing, the Norway rat typically produces circles no more than two inches in diameter. However, the depth of the opening may become a tunnel, like from the outside of your home, through your siding and drywall, and into your attic.
Typical Nesting Areas
Norway rats find hiding places inside your home where they feel safe and warm. They usually build nests within 45 meters their food sources but get very creative in where they nest.
Below are the most common places Norway rats live in a house:
There are specific noticeable signs when a Norway rat is living in your attic. They tend to burrow in insulation and shred insulation to add it to their nests. If they have babies, they create a nest big enough for at least five pups. Norway rats in your house may find spaces in vents, ducts, storage bins, old chests, or trusses when not nesting in insulation. Noise may also alert you to an attic infestation. More on this below.
A sign that a Norway rat is living in your walls is the noise they make, usually when you are trying to fall asleep. Noticeable sounds include chirping, chattering, grunting, squeaking, shuffling, running, and gnawing. You may also see indentations in your drywall where they have chewed it on the other side, or the drywall may appear stained due to urine and feces.
Crawlspaces underneath your home or building typically have dirt floors and no lighting, making it the perfect spot for a Norway rat to build a nest. You may even find a colony of Norway rats in your crawlspace since they tend to live in groups when there is enough room. Access to your crawlspace allows them to burrow under your foundation, making it unstable.
Some basements provide excellent homes for Norway rats, especially when trash bins and bulk foods are stored there. An infestation is noticeable if you see droppings that make paths or piles of droppings near food sources. These animals will also create runways with the foods they steal. Walking into your basement, you may notice a strong, musky odor, signaling a rat problem.
Norway rats are attracted to cluttered yards with multiple food sources. They eat bird seed from feeders, steal garden crops, and chew through garbage cans to get the trash inside. You will find nests in piles of wood or rocks, under decks or porches, or in small open spaces around your home. Rats will even build a nest under your vehicle’s hood, creating driving hazards.
One of the most noticeable signs of Norway rats in your yard is the burrows they create, which look like tiny holes on the surface but are actually long tunnels. An infestation can mean many tunnels and potentially hazardous terrain. Imagine your home sitting on top of hundreds of tunnels, not solid ground.
Getting Rid of Norway Rats
There are several effective methods for getting rid of Norway rats, all of which should be done by trained professionals because they know the correct methods to address infestations. There is rarely just one rat in the area. Additionally, there is a risk of worsening the infestation if initial methods do not work. Professionals know how to eliminate an infestation the first time successfully. Below are some examples.
The size of the infestation determines the number of traps to use and the right bait. Snap traps are usually the first line of treatment. One trap for an infestation of twenty will not go well. Even with the correct number of traps, the process can take up to two weeks.
With both traps and stations like those detailed below, expect Norway rats to take several days to adjust to something new in their environment. Professionals recommend placing bait traps somewhere between the rats’ nest and food source, but not directly in their path. Place them along baseboards or near burrows.
Baits for Norway rats can include tiny portions of peanut butter, meat, chocolate, gummies, cheese, or fruit. Because rats are omnivores, they are not picky eaters.
Setting baits and traps without implementing exclusions means you will soon have another rat infestation. Exclusions are what keep Norway rats from entering your home in the future. Exclusions are best when done by a professional who can adequately seal every opening ½” or larger with heavy-duty materials that the Norway rat cannot chew through, like concrete or thick metal.
Bait Stations for Ongoing Rodent Control
With larger infestations, bait stations may be a better option. It may take over two weeks to eliminate all the Norway rats in your house. Bait stations are boxes that allow rodents to enter. Once inside, they consume toxic bait. Most Norway rats do not leave the box, but if they can, they carry the toxic materials back to their nests, where other rats will also consume them.