Rats in the compost bin and chicken coop: the garden action plan

"We set up a compost bin two years ago, like the town hall recommended. Since this summer there have been holes all around it, and we saw two of them dash under the hedge." This scenario has become commonplace in the houses of Champigny-sur-Marne, Saint-Maur and Sucy: ever since food-waste sorting became mandatory for all waste producers (the AGEC law, rolled out to everyone on 1 January 2024, article L. 541-21-1 of the French environmental code), home compost bins have multiplied in gardens. And to a brown rat, a compost bin is a heated restaurant, open 24 hours a day, twenty metres from a shelter.

The usual reflex — buying a pack of bait blocks and tucking it behind the compost bin — solves nothing and creates two new problems: a risk to cats, hedgehogs and children, and a colony that rebuilds itself as soon as food remains available. A garden rat is not treated with poison first; it is treated by removing the resource. As long as the compost, the coop's grain and the bird feeder keep working, you are feeding them faster than you are killing them.

This guide sets out, in order, what to inspect, what to fix on a household compost bin and chicken coop, and at what point chemical control becomes legitimate.

Why a suburban garden is the perfect target

The brown rat (Rattus norvegicus), the dominant species in the Île-de-France region, is a burrowing rodent. Unlike the black rat, it lives at ground level and underground: sewers, riverbanks, embankments, burrows dug under a slab or a woodpile. It needs three things, and only three:

1. Regular food: a reliable source less than 50 metres from its burrow.
2. Water: a pot saucer, an uncovered rainwater butt, a chicken drinker, a blocked gutter.
3. Undisturbed shelter: dense vegetation, a stack of logs, a garden shed sitting on breeze blocks, a compost bin, a tarpaulin on the ground.

A house with a vegetable patch, chickens and compost ticks all three boxes. Add the proximity of the Marne, ageing sewerage networks and building works that periodically reopen the main sewers, and you get the typical set-up behind the calls we receive in autumn. The timing is no accident: in October and November, wild food becomes scarce, that year's young disperse, and colonies look for fixed spots to see out the winter.

A few useful biological benchmarks

A female brown rat can produce 4 to 6 litters a year, of 6 to 12 young each, reaching sexual maturity at around 10 to 12 weeks. In other words: two rats tolerated in September means about ten by January. Reaction time matters more than the method you choose.

Recognising an established colony in the garden

You rarely see the rats themselves — if they are moving about in broad daylight, that is already a sign of a dense or disturbed population. What you are looking for is the evidence.

A simple, free test: sprinkle a little flour or talc in front of a suspect hole in the evening and photograph it in the morning. Footprints and a tail drag mark confirm an active burrow. Filling the hole with compacted soil and finding it reopened the next day is another reliable test.

Remember to time-stamp your photos. They will prove useful if the source turns out to be next door or on a patch of waste ground — a documented file is the only thing that gets a municipal public health department moving, as explained in our guide on rats coming from the street or a neighbouring plot.

The compost bin: five fixes that change everything

A compost bin does not attract rats by nature. It attracts them when it is badly designed, badly fed and badly maintained. Here is what makes the difference in practice.

1. Cut out meat and fatty waste

No meat, no fish, no cheese, no leftovers from cooked dishes, no bread, no pet kibble. These are by far the most attractive inputs for a brown rat, and they don't compost well anyway. Peelings, coffee grounds, crushed eggshells and green waste pose no major problem.

2. Close off the bottom

This is the point most often overlooked. A plastic compost bin sitting on bare soil gets colonised from below: the rat digs and emerges directly into the heap, out of sight. The proven solution is to set the bin on 6 mm galvanised wire mesh (a 1 cm mesh still lets mice and young rats through), turned up 10 cm at the sides and fixed in place. Standard chicken wire, with its 25 mm mesh, is of absolutely no use here.

3. Balance it and keep it damp

Compost that is too dry becomes a cosy nest — insulating material, quiet and dry. Balanced compost (alternating nitrogen-rich green material and carbon-rich brown material, wood chippings, dead leaves, brown cardboard) that is dampened regularly heats up and becomes hostile. Turning the heap every two to three weeks with a compost fork disturbs it enough to discourage settlement.

4. Choose the right kit if you are starting again

For a garden that has already had visitors, a tumbling compost bin on a stand or a solid-walled bin with a lockable lid solves 80% of the problem: no contact with the ground, no access from below, and a lid that cannot be lifted. It costs more than a bin made of planks, but far less than a full rat-control intervention.

5. Move it away and clear around it

Place the compost bin at least 5 metres from the house, never against a wall or the shed. Clear 50 cm all around it: a brown rat hates crossing bare, well-lit ground.

The chicken coop: the real magnet in the garden

Between a well-kept compost bin and a badly kept coop, it's the second that causes the trouble. Pellets and cereals are a dense calorie source, permanently available, and often stored in a paper sack sitting straight on a shed floor.

What to fix, in order of effectiveness:

• Never leave food out overnight. Bring the feeder in once the hens have gone to roost, or use a pest-proof treadle feeder (the hen's weight opens the flap; a rat isn't heavy enough to trigger it). This is the best value measure of the lot.
• Store pellets in a rigid container. A sack, even a closed one, will be gnawed open in a single night. A sealed drum with a screw-on lid or a metal bin with a weighted lid settles the matter. The same goes for sunflower seeds and fat balls meant for the birds.
• Seal the base of the run. The mesh should be buried in an L shape, 30 cm deep and 20 cm outwards, with fine mesh over the first metre of height. Rats dig under runs; climbing them is not their first choice.
• Collect eggs every day. A brown rat will eat eggs and may attack chicks; its role as a predator is real, not a myth.
• Keep an eye on the drinker. A shallow drinker kept permanently full is a colony water point. Go for a siphon-type drinker, and empty anything left standing.

The same reasoning applies to bird feeders: whatever falls to the ground feeds rodents, not blue tits. A catch tray under the feeder, or removing the feeder for as long as the problem lasts, changes things radically. The same principle applies to pet bowls, a subject we covered in detail in this article on kibble, litter trays and bowls.

Removing shelter and access to the house

Once the food is secured, the next steps are making the ground uncomfortable and then blocking the route from the garden into the building — because a rat deprived of compost goes looking for the kitchen.

To do before the first frosts:

• Dismantle and raise the log pile onto a support 30 to 40 cm off the ground, away from the wall. A wood store sitting straight on the soil against the façade is a ready-made burrow.
• Cut back long grass, clear away tarpaulins and sheets lying on the ground, and turn over large empty pots.
• Clear up fallen fruit under trees and empty out any standing water.
• Check the base of the house: loose air vents, unsealed cable entries, a worn garage door threshold. A brown rat gets through a 2 cm opening, a mouse through 6 mm.
• Seal gaps with woven stainless steel mesh or stainless steel wool plus mortar. Expanding foam on its own is gnawed through in a few nights.
• Check the bottom of downpipes, wastewater inspection chambers and access covers: a cracked chamber is a direct doorway from the sewer network. If signs appear inside the house, our guide on rodents in the loft and insulation sets out the rest of the protocol.

Traps and rodenticides: what a private individual can legally do

Once the resources are cut off, reducing the population is possible — and far more effective, because baits and traps finally become the only easy food in the garden.

Mechanical trapping

For a recent, limited presence (one or two individuals, no multiple burrows), metal snap rat traps remain the cleanest method: no toxic residue, visual confirmation of the catch, and no risk of secondary poisoning for a cat or a bird of prey. Three rules: set the traps along the runs rather than in the middle of the garden; protect them under a crate with an opening cut in it, or in a station, so no pet can reach them; and leave them baited but not set for 3 to 4 nights before arming them. The brown rat is neophobic: it avoids any new object for several days.

Rodenticides

Anticoagulant-based baits are biocidal products governed by European Regulation No. 528/2012 and monitored in France by ANSES. For a private individual, the practical rules are strict:

• Always in a secured, lockable bait station, never loose blocks left in the open, never loose grain.
• Never within reach of children, pets or wildlife.
• No permanent "preventive" use: ANSES and the plans to reduce pesticide use explicitly target continuous treatments, which encourage resistance and the secondary poisoning of predators (owls, hedgehogs, cats).
• Collect and dispose of carcasses wearing gloves, in a sealed bag, with household waste.

Remember that anticoagulants take several days to kill, and that the poisoned animal itself becomes a poison for whatever eats it. That is why, in a garden with cats, chickens and hedgehogs, mechanical trapping is very often the right choice — and poison a decision to take with a professional. Our prices and the services page set out what an intervention of this kind involves.

When to stop DIY and make the call

There are clear signals:

• more than two or three active burrows on the plot, or holes that reappear after being filled in;
• rats visible during the day;
• signs inside the house, garage or crawl space;
• an outside source (waste ground, building site, neighbour, riverbank) that is beyond your control;
• a gnawed cable, a pierced conduit, the beginnings of material damage — in which case also read what home insurance really covers before you repair anything;
• a health risk: leptospirosis, transmitted via rodent urine in water and mud, justifies wearing gloves and boots whenever you handle contaminated compost, a flooded shelter or a damp cellar after the Marne has burst its banks.

A professional does not simply put down bait: they map the burrows and runs, identify the origin (sewer network, party wall, chicken coop), place secured stations in the right spots, come back to check bait consumption, and provide you with a useful report if the source is on someone else's property or if you need to approach the municipal hygiene and health department.

The calendar to remember

The thread running through all of this is always the same: food, water, shelter. Remove one and the pressure drops; remove all three and the colony moves off of its own accord to find something better elsewhere.

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Are you finding burrows, a tunnelled compost heap or tracks around the chicken coop in the Val-de-Marne? Describe the situation and send your photos via our contact page for a diagnosis, or use the emergency page if rodents have already got into the house. We work in Champigny-sur-Marne, Saint-Maur-des-Fossés, Créteil, Nogent, Vitry and neighbouring towns — the full list is on the service areas page.