Five clear signs of a rodent infestation
Rodents are an unfortunate reality for many households in the Netherlands. If you are living in an older, poorly isolated house or apartment in the city center, close to a canal, lake, or river or in a densely populated area of the city near a food market, popular shopping areas, or housing with shared infrastructure, alongside cafes, bars, and restaurants, remember, those are all ideal conditions for rodents to thrive (often unnoticed at first). Many people only realize they have mice or rats at home when the problem has already escalated, and a full-scale infestation is taking place.
Female rats can start breeding as early as 5 to 9 weeks old. They can have up to 7 litters a year, with 6 to 12 pups per litter. As pregnancy lasts only 21–23 days, and females can get pregnant again immediately after giving birth, a single pair of rats can create a serious problem within a very short period of time, and produce over 1,000 offspring in a year.
Fortunately, rats usually leave clear warning signs early on. Knowing what to look for can help you act quickly and avoid serious hygiene and safety risks for you and your loved ones. Below are five common signs that may indicate rodent infestation in your home.
1. Unusual noises, especially after dark
One of the earliest signs of rodents in a house is sound, so listen carefully. Rats and mice are mostly active at night, so homeowners often hear scratching, scurrying, or gnawing noises once the house has gone quiet. These sounds typically come from walls, ceilings, lofts, crawl spaces, or behind kitchen units.
In many Dutch houses — especially older terraced homes and canal properties — hollow walls, wooden floors, and shared foundations allow rats to move around unnoticed. If you regularly hear movement at night, it’s a strong indication that rodents may already be inside the building.
2. Droppings
Rat droppings are one of the most obvious physical signs of an infestation. They are usually dark in color and found where rats feed. Kitchens, pantries, cupboards, but also basements and storage areas where rats might travel through are common places where droppings appear. If droppings keep reappearing after cleaning, this usually means rats are actively present.
Please, take even a small number of droppings seriously. Rats contaminate surfaces with urine and bacteria, which can pose health risks. They can spead life-threatening viruses, for intance, hantavirus. As reported by BBC, the virus is usually spread from rodents, but according to the World Health Organization, in rare instances, it could spread among “really close contacts”, like in the recent case aboard the Dutch cruise ship, MV Hondius, taking lives of three passengers back in May 2026.
3. Chewed materials and visible damage
Rats gnaw constantly to keep their teeth from growing too long. Inside homes, this behavior often leads to visible damage. Food packaging that looks torn or bitten into is a common clue. Rats can also chew wood, plastic, insulation, and even electrical cables.
Pay a close look to potential entry points: those are often found around old pipe penetrations, drains, floor wall junctions, or poorly sealed ventilation openings. Damage to cables is especially concerning, as it increases the risk of electrical faults or fire.
4. Smear marks along walls
Rats tend to follow the same routes repeatedly as they move through a home. Over time, the natural oils and dirt in their fur leave dark, greasy marks along walls, skirting boards, and narrow passageways.
These smear marks are often subtle at first but become more visible with increased activity. They are commonly found near entry points, behind appliances, or along basement walls.
5. Persistent smells or signs of nesting
An unusual, unpleasant smell can sometimes point to a rat problem. Strong ammonia like odours may come from rat urine, while a musty smell can indicate nesting areas. In more serious cases, a dead rat trapped in a wall or crawl space can cause a noticeable and persistent odour.
Remember, rats are multiplying quickly and building nests using soft, shredded materials such as paper, cardboard, insulation, or fabric. If you discover piles of chewed material in remote, undisturbed parts of your home, it may indicate that rats have established a nesting site nearby.
Urban environments in the Netherlands offer rats easy access to food, warmth, and shelter. A recent study, as highlighted in reports on the Science Advances article, linked climate change and rising city temperatures directly to larger rat infestations. Shorter and warmer winters allow rodents to skip traditional seasonal slowdowns in terms of reproduction and basically year-round foraging. This is a perfect set of conditions for explosive expansion. Once inside a building, they reproduce quickly and adapt easily. DIY solutions may offer short-term relief, but they rarely address how rats are entering the property or where they are nesting.
That’s why early professional assessment is important. A structured, Integrated Pest Management (IPM) approach focuses not only on control but also on prevention and long-term protection—especially important in older residential buildings. If you recognize one or more of the signs listed above, it’s best to act as soon as possible. A professional inspection can confirm whether rats are present, identify entry points, assess the scale of the issue, and provide a clear, realistic plan to resolve it.
Get in touch with iRotec to request a professional inspection and take the first step towards regaining peace of mind and control over your home.