I've lived in my current home for 3 years. Saw evidence that some had been there while the house was empty, but we never saw anything once we moved in. Until I started hatching chicks. And I thought that was the cause, because I saw some droppings in that room. Caught about 5, then never saw any more. Then my hubby realized that we brought some boxes of stuff home from camp, and we believe we carried them in. :/