Here are a few tell-tale signs you might be harbouring some furry little freeloaders.

Sounds

One of the first things you are likely to notice is sounds. Mice are nocturnal, so you will most often hear them scurrying about in the walls or ceilings at night when the house is quiet.

Droppings and Urine

Mice find their way around by following a trail of mouse urine. A mouse highway.
So if you are a homeowner suffering from a mice infestation, you are sure to find droppings and urine in cupboards, kitchen counters (back near the walls), the backs of drawers, under appliances—virtually anywhere mice tend to travel.

Gnaw Marks

Like all rodents, mice have to continuously gnaw to keep their teeth (incisors) short. And if your new furry friends have found their way into your home, it is only a matter of time before they begin chewing up everything in sight.
https://www.pestsolutions.ca/how-to-tell-there-is-a-mouse-in-your-surrey-house/