My brother once found a shrew in his trash compactor. He took it outside and let it go. An hour later, he heard a noise in the trash compactor again. Found a shrew again. Put a dab of red printers ink on it's back and turned it loose further from the house. A couple hours later, he heard a rustle in the trash compactor. Yup, same shrew. He drove it across the river and set it free in a field. That did the trick. Never came back.