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

https://edwinaoyv652.opalvector.com/posts/how-rodents-sneak-into-san-diego-rooflines-4

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