When I was growing up, my parents found evidence of mice in the house. No good! Out came the Havahart trap. Got a mouse almost immediately. We had a decent bit of land, 1.5 acres or so and far longer than it was wide. So she took it way out to the back of our property and released it.
Repeat the next day, and the next. The next week and the next. A couple of dozen trappings later, it didn’t make sense. They’d found like one dropping in a drawer, we obviously weren’t infested…
So the next time the trap was sprung, mom grabbed a green felt marker. Field mice have a white belly, so she stuck the pen up through the bars of the cage and gave it a little green dot in the middle of its white fur.
You see where this is going! Every time the trap was sprung, it was the same mouse, green dot on its belly, finding its way back from the edge of the yard. My parents did a search of the foundation, spotted the little gap it was using, and sealed it up. And that, finally, was the end of that.
