[stumpstalker]

An (unarmed) cat is maybe all you really need.

I know a fellow who had a big, old female cat with him up on the couch when he was watching TV. It was sound asleep when a mouse did exactly what is described: it came out of some opening into the room and ran along the wall.

My friend was impressed with how quickly that cat awoke, leaped to the floor in a flash, ran and grabbed the Mouse and dispatched it. And, he thought it was just an old, slow house cat.

The mouse, as quiet as it likely was, still must have generated a particular sound that triggered something in the cat that it was genetically encoded to be alerted by.