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

https://waylonvkhp072.quantlynix.com/posts/why-pest-control-fails-without-attic-air-sealing-4

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