The stone marten: what does it look like?
As a pest controller with more than 20 years of experience, I get the same question every autumn and winter: “Johan, do I have a marten in the attic?” People hear sounds, see tracks, but are often not sure if it is a marten. Let me explain what to look out for.
Appearance: How to recognise a stone marten
A stone marten is a medium-sized predator from the weasel family. It is about 40-50 centimetres long (without tail), and with tail added you get to 65-80 centimetres. That's pretty big - about as long as a small cat, but much slimmer and more agile.
The colour? Dark brown to grey-brown on the back, with a prominent white throat patch that often branches out towards the front legs. That white spot is the main identifying feature. Because a pine marten (which you rarely see in houses) has a yellowish throat patch.
What I often hear from customers: “I thought it was a big rat!” That's right, they are similar in size. But a marten has a longer tail, a pointed snout, and that distinctive white throat patch.
Behaviour: Nocturnal Animal With Personality
Marters are nocturnal animals. During the day they sleep, at night they become active. And believe me, if you have a marten in your attic, you will notice it. They are not subtle. They run, jump, drag stuff, and make a lot of noise.
Just last week, I had a client who couldn't sleep because the marten was running above her bedroom every night. “It sounds like someone is running around,” she said. And that's what it feels like.
Marters are also curious and playful. They do not destroy insulation out of malice - they are just playing, collecting nesting material, or hiding food. But the damage they do is real.
Where to Find Marters?
In the Netherlands, stone martens are mostly found in built-up areas. They have adapted perfectly to living with humans. Favourite places:
Attics: Warm, dry, sheltered, and lots of hiding places. Perfect for a marten.
Barns and outbuildings: Especially if you store stuff there or have animals (chickens, rabbits).
Crawl spaces: Less often, but it happens. Especially if the crawl space is easily accessible.
Cars: Yes, really. Marters crawl into engine compartments and bite through cables and hoses. This is especially a problem during the mating season (June-August).
Why in particular attics? Because they find peace and quiet there, it is warm, and they are safe from larger predators. Plus: many attics have holes and cracks they can get through.
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Tracks and sounds: This is how to recognise a marten
OK, you've probably never seen a marten before. Because they are nocturnal and shy. But they do leave clear marks. And those tracks are often the first evidence that you have a marten. Let me explain what to look out for.
Sounds at night: The Most Noticeable Sign
This is usually how people find out they have a marten. You hear noise in the attic at night. And not just any noise - it sounds like someone is walking around. What can you hear?
Rumbling and tapping: Marters run across the attic. They are not mice or rats - this sounds heavier, louder.
Scratching noises: If they pull off isolation or try to enter somewhere.
Rolling noises: Sometimes they play with things, or roll notes around.
Rustling: When they scavenge through stuff or collect nesting material.
When do you hear this? Usually between 10pm and 5am. With peaks around midnight and early morning. If you hear noise during the day, it is probably not a marten (unless you have disturbed it).
Excrement: The Confirmation
Marters often defecate in fixed places - we call them latrines. And you can usually find those latrines in a corner of the attic, or at an elevated point.
What do marten droppings look like? They are 8-10 centimetres long, about as thick as your thumb, dark grey to black, often twisted (like a sausage), and contain hairs, bones, fruit pits (martens eat a lot of fruit in summer).
Want to know if it's fresh? Fresh droppings are dark and shiny. Old droppings turn grey and crumble. If you see fresh droppings, it means the marten is still there.
Damage to Insulation And Materials
Marters destroy insulation to make nesting material. What you see: large amounts of insulation pulled away, often in a corner or under roof tiles, insulation scattered across the attic, holes in insulation that the marten walks through.
They also bite on things. Cables (this is dangerous!), water hoses, wooden beams (not often, but it happens). In cars, they bite through brake hoses, cooling hoses, and electrical wiring. This can be life-threatening.
Smell
Marters have a pungent, musky smell. It is a bit like the smell of a ferret, but less intense. If your attic smells like musk, and you have no other explanation, it could be a marten.
Note that the smell gets stronger during the mating season (June-August). This is when they mark their territory with scent glands, and you can really smell it.
Paw prints
If you have dust in your attic (and who doesn't?), you can see paw prints. Marten paws are smaller than you think - about 4 by 4 centimetres. They have five clawed toes, and the print looks a bit like that of a small dog, but with sharper claws.
Why does a marten enter your attic?
Good thing you asked! Because martens don't just go anywhere. They are looking for specific things, and if your attic offers them, they are happy to come by. Let me explain why.
What Attracts Marters?
Marters seek three things: shelter, food, and a safe place to sleep. An attic provides all that. Let me explain.
Shelter and warmth: Attics are warm and dry. Perfect for a marten to sleep, especially in winter. They crawl in insulation, under roof tiles, behind stuff. There they are protected from wind, rain, and cold.
Security: In an attic, there are no natural enemies. No foxes, no dogs, no people to bother you. For a marten, this is ideal.
Food nearby: Martens eat mice, rats, birds, insects, eggs, fruit, and rubbish. If your home or garden offers food (e.g. a bin that is not properly sealed, bird food, fruit on the ground, mice in your crawl space), it attracts martens.
What I often see: people have a mouse problem, and then a marten comes because it wants to eat those mice. The marten solves your mouse problem, but creates a new problem.
How Do They Get In?
Marters are agile and can pass through surprisingly small openings. A 5-6 centimetre hole is enough. Where do they enter?
Loose or broken roof tiles: The number one access route. Especially on old roofs with tiles that are not properly fixed.
Holes in the facade: Cracks around gutters, vents without mesh, holes where cables used to go through.
Open skylights or shutters: If you leave a skylight open at night, a marten can climb right in.
Through trees or bushes: Marters are excellent climbers. If there is a tree against your house, they will use it as a ladder to your roof.
Season: When Are They Coming?
Marters are active all year round, but you notice them mainly in two periods:
Autumn and winter (September-March): They look for a warm place to hibernate. This is the busiest time for marten control.
Mating season (June-August): Males are looking for females, and they are extra active and noisy. This is also when they do a lot of damage to cars.
Preventing Marters
Want to prevent martens from entering your attic? My practical tips:
Roof maintenance: Check your roof tiles annually. Make sure they are tight. Replace broken tiles immediately.
Plugging holes: Walk around your house and look for holes, cracks, loose panels. Seal them with sturdy material (sheet metal, mesh, cement). Marters can sometimes gnaw through plastic and wood, so use sturdy stuff.
Shield ventilation openings: Put sturdy mesh (mesh size max 1 cm) in front of vents. Marters can get through otherwise.
Tree pruning: Make sure there are no branches hanging against your house or roof. Keep at least 2 metres away.
Taking away food: Do not leave bird food outside overnight, close rubbish bins tightly, clear away fallen fruit, do not store food in the attic.
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Damage by martens: what's in store for you?
You might be thinking, “It's just a little critter, how bad can it be?” Well, let me be honest: martens can cause enormous damage. I see it every week with clients. And the longer you wait, the worse it gets.
Insulation Material: The Greatest Damage
Marters destroy insulation to make nesting material. They pull it out of the cavity, tear it into pieces, spread it across the attic. What does that mean for you?
Heat loss: If your insulation is gone, your energy costs go up. I have had clients paying hundreds of euros more a year on heating.
Replacement cost: Installing new insulation costs money. Easily €1,000 to €3,000 for an average attic.
Moisture problems: If insulation is damaged, it can lead to condensation and moisture problems. And that, in turn, leads to mould.
Last month, I had a client where the marten had destroyed half the insulation. The attic was so cold that there were ice flowers on the windows. He had let that sit for months, and now it was costing him €2,500 to repair.
Cables And Pipes: Danger!
Marters bite on everything. Electrical cables, water hoses, gas hoses. This is not only expensive, but also dangerous. An electrical cable bitten through can cause a short-circuit fire. A water hose bitten through leads to leakage and water damage.
In cars, it is even worse. Brake hoses, cooling hoses, ignition cables - martens bite through them all. I know stories of people who took their car out on the road, and suddenly had no brakes. Life-threatening.
Noise pollution: Sleepless Nights
People often underestimate this. But the noise pollution is enormous. Marters are active at night, and they make a lot of noise. Running, jumping, dragging, scratching. People can't sleep, get cranky, stressed.
I've had clients who hadn't slept well for weeks. Who went to sleep on the sofa because the attic was above their bedroom. Some even got sick from it.
Structural Damage
Marters sometimes gnaw on wooden beams and roof structures. Not often, but it happens. If they damage a beam that is structurally important, it can become dangerous.
They also make holes bigger. A small 5 cm hole becomes a 15 cm hole because of their digging and gnawing. And then other animals can enter: pigeons, crows, rats.
Hygiene And Health
Marten droppings can contain parasites and bacteria. When those droppings dry up and turn into dust, you can breathe it in. This is not healthy, especially for people with asthma or other respiratory problems.
Martens also attract other pests. Their food scraps attract rats and mice. Their droppings attract flies and beetles. Before you know it, you have multiple pests.
That's why I always say: if you have a marten in the attic, tackle it immediately. The longer you wait, the more damage, the more expensive the solution. Call me, and I'll come and take a look and make a plan. That will ultimately save you time, money, and most importantly: stress.
Frequently asked questions about Recognising Marters
These are the questions I get most often about martens in the attic. Is your question not among them? Feel free to call me for personal advice.
A stone marten is about 40-50 cm long (without tail), with brown-grey fur and a distinctive white throat patch that often branches out to the front legs. With tail included, it grows to 65-80 cm. It resembles a cat in size, but is much slimmer and more agile. Its main identifying feature is that white throat patch - a pine marten has a yellowish patch. Marters have a longer snout than cats, and their tail is very fluffy.
Marters make quite a lot of noise for their size. You'll mostly hear thumping and trampling - it sounds heavier than rats or mice, more like someone is walking. You'll also hear scratching and scratching sounds when they pull away insulation, rolling sounds when they play with things, and rustling when they scavenge through stuff. You hear this mostly at night between 10pm and 5am, with peaks around midnight. During the day, they are quiet because they are sleeping.
Marters are strictly nocturnal animals. They sleep during the day and become active at dusk, usually from 10pm until sunrise around 05am-06am. You mainly notice them in two periods: autumn/winter (September-March) when they seek a warm place to hibernate, and during the mating season (June-August) when they are extra noisy. During these months, I get the most reports of martens in attics.
Marters are opportunistic omnivores. They mainly eat mice, rats, birds (and their eggs), insects, snails, earthworms, fruit (cherries, apples, pears), berries, and rubbish from dustbins. In summer they eat a lot of fruit and insects, in winter more rodents and birds. This is also why they get into houses - if you have mice, that attracts martens. Ironically, the marten solves your mice problem, but creates a new one.
Marters are generally shy and avoid contact with humans. They do not attack unless cornered. If you try to catch or grab a marten, it may bite and scratch - and it hurts, as they have sharp teeth and claws. The real dangers are indirect: they bite through electrical cables (fire hazard), damage water hoses (leakage), and in cars they bite through brake hoses (life-threatening). Their droppings can contain parasites and bacteria. So don't touch them, and leave control to professionals like me.
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