Size and appearance
- Mice are small, with a body of roughly 6 to 9cm, large ears relative to their head, a pointed nose and a thin tail
- Rats are much bigger, with a body of roughly 20 to 25cm, smaller ears, a blunt nose and a thick, scaly tail
A "baby rat" in the house is usually a mouse. Young rats have larger feet and heads in proportion to their bodies.
Droppings
- Mouse droppings are small, dark and rice-shaped, about 3 to 6mm long
- Rat droppings are larger and capsule-shaped, often 12mm or more
Droppings are often the quickest way to tell. See our guide to mouse droppings for more.
Noises and nesting
Mice make light scratching and scuttling sounds and nest close to food, in cupboards, walls and lofts. Rats make heavier scratching, gnawing or thumping noises and often burrow outside, under sheds, decking and foundations, entering the building when they are looking for food.
Gnawing and damage
Both gnaw, but rats cause more serious damage and can chew through pipes, cables and even soft masonry. Mice nibble small amounts of food and packaging and gnaw to reach food.
Behaviour
Mice are curious and will investigate new objects, which makes them easier to trap. Rats are cautious and wary of new objects, so traps often need to be introduced gradually.
Health risks
Both can contaminate food and surfaces. Rats can carry Weil's disease (leptospirosis), which can be spread through contact with their urine. Always wear gloves when cleaning up after either, and wash your hands afterwards.
Why it matters
Mice and rats need different traps, baits and proofing, and rats usually need professional treatment. If you are unsure, take a photo of droppings or damage and ask an expert. For a mouse problem, our guide to how to get rid of mice is a good place to start. For rats, read what do rats look like.
Frequently asked questions
Can I have both mice and rats?
Yes, although they tend to compete, and one species usually dominates a site.
Are baby rats the same as mice?
No. Young rats are bigger than adult mice and have proportionally larger feet and heads.
Which is more dangerous, a mouse or a rat?
Both can spread bacteria. Rats are bigger, cause more damage and carry a wider range of risks, so they should be dealt with promptly by a professional.
Not sure what you have?
Visit anticimex.co.uk and our team can identify the problem and advise on the right treatment.