What's the difference between rat and mouse droppings?

Mouse droppings are 3-5mm long, pellet-shaped. Rat droppings are 10-20mm long, capsule-shaped. Both are dark brown to black. Mouse droppings tend to be scattered (kitchen drawers, cupboards); rat droppings tend to cluster along runways.

How big a gap do mice need to enter a property?

5mm — about the diameter of a biro. Young mice can squeeze through smaller. This is why proofing matters: traps catch the mice in residence, but the next mouse will walk in through the same gap.

Is rodent control safe around pets and wildlife?

Only when done properly. Professional pest controllers use locked, tamper-resistant bait stations outdoors that pets can't access. The bigger ecological concern is secondary poisoning — predators eating poisoned rodents. The CRRU Stewardship Regime exists to manage this risk; every controller in our network is CRRU-compliant.

What is the CRRU Stewardship Regime?

The Campaign for Responsible Rodenticide Use is the UK industry stewardship body for professional rodenticides. From 1 January 2026, all professional Second-Generation Anti-coagulant Rodenticide (SGAR) users must hold current stewardship-specific training certification (less than 5 years old) or be members of a CRRU-approved CPD scheme. Sellers won't supply non-certified users.

Do ultrasonic rodent repellers work?

Not really. Extensive university and commercial testing shows little to no meaningful effect on established rodent populations. Some short-term avoidance is reported but rodents habituate quickly. Spend the money on wire wool and brush strips instead.

My cat ignores the mice — what should I do?

Don't rely on the cat. Many domestic cats either ignore rodents or only catch the bold ones — leaving the cautious majority of the population. A cat is a useful deterrent for casual incursions but is not a substitute for proofing and (where needed) professional treatment.

Rats and Mice in Cornwall Properties: Signs, Prevention, and When to Call a Pro

Rats and mice are the most common indoor pest in Cornwall — and the one where DIY most reliably fails because of the missing ingredient: proofing. This guide walks through how to spot the signs, the practical steps that genuinely keep rodents out, what's changed in 2026 with the CRRU Stewardship Regime, and where the line is between a DIY job and a professional pest control programme.

How to know if you have rats or mice

Telltale signs:

Droppings — the most reliable indicator. Mouse droppings are 3-5mm long, pellet-shaped, dark brown or black, scattered in kitchen drawers, cupboards, under sinks, around food storage. Rat droppings are 10-20mm, capsule-shaped, dark, usually clustered along runways.
Sounds — scratching, scuttling, gnawing in lofts, stud walls, behind kitchen units. Mice are lighter and faster; rats are heavier with the occasional thump. Activity is mostly at night and early morning.
Gnaw damage — corners of food packaging, soap, candles, paper, plastic. Mice nibble; rats can gnaw through plasterboard, plastic pipes, even soft mortar.
Smell — a distinctive musky odour where mice are nesting (urine plus glandular secretion). Strongest in confined spaces.
Runways — greasy marks along skirtings, behind furniture, on top of cupboards, where rodents run the same path repeatedly
Pets behaving oddly — cats fixated on one corner of a room, dogs barking at walls at 3am, ferrets going mad in a loft

If you've spotted droppings but aren't sure rat or mouse: measure one. Photograph it on a coin or against a tape. A pest controller can confirm at the first survey visit.

Cornwall-specific risk patterns

Cornwall has its own rodent pressure:

Rural cottages — stone-and-mortar construction, old air bricks, original cellars, generations-deep ingress points. Rural Cornwall pest controllers often spend more time on proofing than treatment.
Holiday lets — guests' food waste, irregular occupancy, changeover cleaning windows that don't always catch the signs. Year-round food supply sustains rodent populations.
HMOs and student lets — shared kitchens, multiple cooking patterns, bin storage shared between properties. Falmouth, Penryn and Truro see a regular wave of HMO mouse treatments at student handover (September-October).
Coastal harbour villages — Mevagissey, Mousehole, Newlyn, Port Isaac all have older fishing-village terrace housing where ingress is built into the construction
Farm-adjacent properties — mice from feed stores and barns cross gardens and into nearby houses, especially in autumn as field food becomes scarcer
Bodmin Moor and the Lizard — outbuildings and isolated farmhouses with multiple harbourage points

The proofing checklist (a 6-step approach)

Effective long-term rodent control is 80% proofing, 20% killing. If you do nothing else, do this:

Step 1: Walk the perimeter

Start outside with a torch and a phone camera. Walk slowly round the entire building. Look for any gap a 1p coin can fit through — that's enough for a mouse. Mice need only a 5mm gap; young mice can squeeze through smaller. Pay special attention to:

Where pipes enter walls (water, gas, electrical, waste, satellite/aerial cables)
Around air bricks (often the biggest single ingress point)
Behind soil stacks where they meet the wall
Under door thresholds, especially external doors
Round the meter cupboard and any other utility access
Where the cladding or render meets the foundation
Roof level — soffit gaps, missing tiles, broken pointing at gable ends

Photograph each gap as you go. This becomes your worklist.

Step 2: Seal pipe penetrations with wire wool

Coarse-grade wire wool, packed tightly into any gap around pipes. Mice can chew through expanding foam alone — wire wool gives them something they can't gnaw through. Top with foam or sealant if cosmetics matter, but the wire wool is doing the work.

Step 3: Mesh the air bricks

Air bricks must stay open for ventilation (it's why they're there). The holes are usually big enough for mice. Fit stainless-steel mesh (6mm hole maximum) over each air brick on the outside, secured with masonry screws or external sealant. Critically: do not block the air flow — that risks damp and condensation issues. Mesh, don't seal.

Step 4: Brush-strip the doors

External doors, especially older Cornwall cottage doors, often have a 5-15mm gap at the bottom — easily mouse-passable. Fit a brush strip or rubber threshold seal. Same for any access door to a loft from a garage or outbuilding. Internal door gaps matter less unless there's a known rodent route between rooms.

Step 5: Sort the bins and feed stores

Rodents follow food. Outdoor bins must have locking lids — gulls, foxes and rats all open swing-tops. Animal feed (chicken, horse, dog food in outbuildings) must be stored in sealed plastic or metal bins, never in paper or polythene sacks — rats and mice chew straight through. Compost bins should be enclosed types with a lid and a sealed base; open compost heaps are five-star rodent accommodation.

Step 6: Check inside annually and after building work

Pull out kitchen kickboards once a year and look for droppings or runways. Check the loft annually. After any building work — new pipework, kitchen refit, extension, roof work — re-walk the inspection. Every new penetration is a potential ingress point.

When to escalate to a professional

Self-managed prevention is fine for low-grade activity. Escalate to a pest controller if:

You're seeing droppings in food-prep areas — Salmonella, E. coli and other contamination risks aren't theoretical
You can hear activity at night for more than a week — a population is established
You've found dead rodents — there are usually 5-10 alive for every one dead
You're a landlord and a tenant has reported the issue — Homes (Fitness for Human Habitation) Act 2018 places a duty on you
It's a food business or holiday let — EHO and review-driven reputational risks demand documented treatment
DIY traps and bait have failed — a professional has stronger products, more locations, and the proofing knowledge

The CRRU Stewardship Regime — 2026 changes

The Campaign for Responsible Rodenticide Use (CRRU UK) governs how Second-Generation Anti-coagulant Rodenticides (SGARs) — the strongest professional products — are used in the UK. The 2026 changes:

From 1 January 2026, all purchasers and users of professional SGARs must hold either a current CRRU-approved training certificate (less than 5 years old) or be members of a CRRU-approved CPD scheme
This is not optional — sellers won't supply non-certified users
The change applies to pest controllers, gamekeepers and farmers
For non-professional users (homeowner DIY), only low-strength First-Generation products are now sold over the counter

Why this matters to you: every Cornwall pest controller in our network is CRRU-compliant. Anyone offering professional rodent treatment in 2026 who can't show CRRU certification is not legally able to supply or use professional-strength products. We verify before referring.

Wildlife considerations — owls, badgers, foxes, family cats

The reason CRRU exists is secondary poisoning. Owls, foxes, badgers, weasels, stoats and the family cat all hunt rats and mice. If a rodent dies in a hedge after consuming SGAR bait, the predator that eats it gets a sublethal dose. Multiple sublethal doses over time can kill the predator. This is a documented problem in UK barn owls and red kites in particular.

What a good Cornwall pest controller does:

Uses locked, tamper-resistant bait stations outdoors — mandatory under CRRU
Considers non-toxic monitoring blocks first to confirm activity before any SGAR is deployed
Prefers traps and proofing over poison for wildlife-sensitive sites (woodland edges, holiday lets with garden wildlife, smallholdings)
Removes carcasses promptly to reduce secondary kill
Discusses alternatives if the customer has strong concerns about wildlife

Common misconceptions

"Mothballs will keep mice away" — there's no good evidence this works at typical household concentrations
"Peppermint oil deters rodents" — similar; small lab effects, no meaningful field result
"Ultrasonic repellers work" — extensive testing shows little to no effect on established populations
"Cats solve the problem" — sometimes; many house cats ignore mice or only catch the bold individuals. A cat is not a substitute for proofing.
"It's just one mouse" — almost never. By the time you see one, there are usually 10-20.

If you've got an active infestation now

The fastest route to clearance is usually: submit a postcode and a quick description via the form on our homepage. We match you with a CRRU-compliant Cornwall pest controller in your area; they survey, treat over 2-3 visits, and write up the proofing work that stops it coming back. Total cost typically £150-£400 depending on severity and access.