Rat or Mouse? Droppings, Noises and Other Tells
By Henry, Taff Pest Control · Reviewed August 2026
Half our rodent calls start the same way: “something’s scratching, and I don’t know if it’s rats or mice.” It’s a better question than most people realise, because rat or mouse changes the method, the number of visits, and what proofing can genuinely promise. The good news: the two leave quite different evidence, and you can usually tell which you’ve got without ever seeing the animal.
Quickest route of all: photograph what you’ve found and WhatsApp it over. We’ll tell you which it is in a minute, free. But if you’d rather do the detective work yourself, here’s how we read it.
Rat or mouse droppings: the raisin and the rice grain
Droppings are the first thing we look for and the most reliable tell. Rat droppings are dark, tapered and about the size of a raisin. Mouse droppings are the size of a grain of rice: small, scattered, and usually far more numerous, because a mouse produces dozens a night and drops them wherever it roams.
Location talks too. Rats follow the same few routes, so their droppings concentrate: along one wall, behind one kickboard. Mouse droppings turn up everywhere the mouse has wandered: cutlery drawers, worktops, under the toaster.
Freshness matters as much as size: dark and soft-looking means current activity, grey and crumbly means history. Old droppings alone don’t prove you have a problem today; they prove you had one.
The noises: scuttle versus rustle
Rats are heavy enough to announce themselves: a purposeful scuttle or dragging sound in the ceiling or under the floor, once the house goes quiet. Mice are a faint, light scratching or rustling, often in the same spot behind a cupboard or wall.
One caution that saves people money: loud scampering in the loft during the day is more likely squirrels, a different animal, a different law, and a different job entirely.
The other tells
Smear marks mean rats. Grey-black grease smudges along skirtings, pipes and hole edges are left by rats hugging their fixed routes. Mice don’t leave them to any noticeable degree, so if you can see smears, think rat.
Hole size. Rats need a gap you could fit a fist near; outside, they dig fist-sized burrow entrances by sheds, decking and drains. A mouse fits through a gap the width of a biro, which is why you can have mice with no visible hole at all.
Gnawing. Both gnaw constantly; rats leave coarse, obvious damage on wood and plastic, and chewed cables are the sign that turns a rat job urgent. Mouse gnawing is finer, and nibbled packets in the cupboard is classic mouse.
Where they came from. Rats in Cardiff very often arrive underground: defective drains, and above all extensions built over old drain runs nobody remembered were there. Mice arrive at ground level, through the gaps every building has.
| Tell | Rat | Mouse |
|---|---|---|
| Droppings | Raisin-sized, tapered, concentrated | Rice-grain, scattered, numerous |
| Noise | Heavy scuttle, night | Faint rustle or scratching |
| Smear marks | Yes: grey-black, along routes | Rarely visible |
| Way in | Drains, fist-sized gaps, burrows | Biro-width gaps at ground level |
| Behaviour | Cautious, fixed routes | Curious, roams widely |
Why the answer changes the job
This is the part the identification guides skip: rat and mouse jobs are different work.
Rats are cautious animals on fixed routes, so the job is iterative detective work: finding and eliminating entry points one by one, with traps leading and rodenticide rare (and usually advised against indoors, because poison in a wall cavity is a smell you don’t forget). Minimum three visits, often more, and the proofing story is strong: rat routes can genuinely be found and closed.
Mice are the reverse. The treatment side is more straightforward (thorough baiting, typically two to three visits, more where they’re established), but the proofing promise is smaller: with a biro-width way in, “every hole closed” isn’t a promise anyone can keep. The infestation gets dealt with thoroughly and the obvious routes get closed; anyone promising total mouse-proofing is overpromising.
Either way, the wrong first move is the same: don’t scatter shop poison and don’t block the holes yet. Both make the professional job slower. There’s a fuller list of evidence on the signs of rats guide.
Common questions
Can I have rats and mice at the same time?
It’s unusual, because rats predate mice and the smaller animal tends to keep well clear. Where both show up, it’s usually different parts of the property. Mixed evidence is worth a photo before anyone names a price.
Do mice grow into rats?
No. Different species, not sizes of the same thing. A large mouse is still a mouse; a young rat has an oversized head and feet it hasn’t grown into. The droppings settle it faster than the animal will.
I found droppings but never hear anything, still a problem?
Check freshness first: grey, crumbly droppings may be history rather than news. Fresh-looking ones with no noise just mean a quiet route, and mice especially are easy to sleep through. Photograph them and get a proper read.
Which is worse to have?
Neither is good news, but rats bring the bigger risks (cable damage, drain involvement) while mice are usually the longer nuisance. The truth is that “dealt with early” beats either label: both get worse with time, not better.
Worth reading: once you know which animal it is, our guide to how pest control is priced lays out the visits each job takes.
Still not sure which you’ve got? Send us the photo (droppings, damage, whatever you’ve found) and we’ll tell you which animal, for nothing.