Written by Rose Pest Solutions’ Technical Coordinator, Allison Beach, B.C.E.-Intern
Chicago is the second rattiest city in the United States according to researchers at Orkin (and was the first for ten years before that!). Rats are a growing concern for homeowners, business owners, and neighborhoods across the region. Between fluctuating weather, urban infrastructure, and natural habitat, Midwest cities give rats everything they need to thrive. Understanding why they’re here (and how to spot the warning signs early) is the key to keeping your home, business and community protected.
One rat species in particular dominates the Chicago region:
The Norway rat (also called brown rat) is the most common rat in the Midwest. Norway rats prefer ground-level burrows and often invade basements and lower floors. They’re strong climbers, excellent swimmers, and very destructive.
Why Cities (Like Chicago) are an Ideal Environment for Rats
Rats are opportunistic survivors, meaning they will take advantage of any available resources nearby. Urban areas provide several environmental and structural features that make them especially appealing:
- Abundant food sources from residential garbage, urban dumpsters, parks, and restaurants.
- Old housing with structural gaps, aging foundations, and aging sewer systems that offer easy shelter.
- Dense urban neighborhoods where homes sit close together, giving rats connected pathways.
- Heavy construction that disrupts burrows (and displaces rats).
- Waterfronts and river systems (rats thrive near water and will actively seek moisture). In fact, rats need to drink one-half to a full ounce of water per day.
Urban areas typically experience elevated rodent pressures, especially around garbage storage areas and commercial districts. For more commercial context, visit our commercial pest control page.
How Does Weather Impact Rat Behavior?
As temperatures drop, rats become far more aggressive in their search for warmth, shelter, and steady food sources. Because Midwest winters are long, unpredictable, and cold, rats become more determined to get indoors. Unfortunately, once inside a structure they rarely leave on their own.
Once sustained cold hits, rats move indoors. A rat can enter a warm structure through a hole the size of a quarter. Heated homes, restaurants, and commercial buildings offer the warmth and moisture they need to survive. Activity increases in basements, crawl spaces, storage rooms, and around utility systems because these spaces stay warm and undisturbed. When temperatures drop, rats rely heavily on human-made food waste (garbage bins, alley dumpsters, pet food bowls, and compost piles), causing them to venture closer to homes and businesses.
Can Rats be Dangerous?
Yes, rats can be dangerous to humans. Rat waste can contain harmful bacteria like E. coli or Salmonella, potentially causing food poisoning symptoms if accidentally ingested. Norway rats can cause allergic reactions, as well as trigger asthmatic attacks through particles of waste or dander becoming airborne.
Rats can carry other harmful pathogens and parasites that can cause disease. Norway rats are able to transmit the pathogens that cause hantavirus pulmonary syndrome, leptospirosis, and can transmit rat-bite fever through their saliva.
It’s estimated that 20-25% of all fires of unknown origin may be caused by rodents (rats included) gnawing on electrical wires. Rats in your structure could mean possible damage or even a fire hazard living within your walls. Rat nesting materials can also cause structural damage or potentially dangerous vehicle issues.
Signs of Rat Activity
If you suspect rats in or around your structure, look for these most common indicators:
- Droppings shaped like dark capsules (1/2 to ¾ inch) behind appliances, in basements, attics, garages, or near food sources
- Gnaw marks (about 4mm wide and in a straight line) on wood, wiring, or stored items. Damaged food packaging in pantries or storage areas can also signal that rats are nearby
- Unfamiliar scratching, running or squeaking noises in walls, ceilings, or basements (especially at night)
- Grease marks or smudges along walls or baseboards. Many rats following the same path may leave these greasy marks
- Burrows near foundations, sheds, garages, or landscaping
- Unusual pet behavior. Pets often detect rats first, so pay attention if your dog or cat is behaving strangely
Even a single sign can point to a much larger problem, since rats rarely travel alone.
Common Rat Attractants Found in Neighborhoods
Norway rats thrive where food, water, and shelter are easily available and in close proximity. It’s easy for homeowners to accidentally attract rodents to their structure through the following:
- Garbage cans without secure lids or with holes that only need to be the size of a quarter.
- Bird feeders (dropped seeds are a major food source for mice and rats near homes).
- Pet food left outdoors
- Cluttered yards, sheds, and garages (cluttered objects provide a perfect space for rats to hide)
- Outdoor grills and cooking areas
- Compost piles
- Woodpiles or other debris stacked against a home
- Standing water from gutters, planters, or leaky hoses
Reducing these attractants is the first step to Norway rat prevention.
Rats are adaptable, intelligent, and fast breeders, making professional help critical when signs appear. Whether you’re dealing with a sudden winter invasion or ongoing outdoor activity, an expert inspection can uncover entry points, eliminate nests, and prevent future problems. Rose Pest Solutions has been protecting Midwest homes from rodents since 1860. If you’re seeing activity or suspect rodents around your property, we’re here to help.
