Mice in a crawl space may reveal themselves through scratching sounds at night, droppings, chewed openings

https://tysonhogy375.capitaljays.com/posts/why-you-need-to-clean-your-crawl-space-right-now-3

Mice in a crawl space may reveal themselves through scratching sounds at night, droppings, chewed openings, nesting material, or even unusual pet attention.