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

https://waylonhaay445.cavandoragh.org/why-san-diego-rats-invade-attics-in-the-summer-1

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