Question: how do you know if you have rats in the attic?
Answer: Droppings and Urine. The most obvious indicator of a rat infestation in the attic is the presence of feces and urine. ... 
Chewing. Another sign of a rat infestation in the attic is chewed-up debris. ... 
Night Activity. Rats, like most rodents, are nocturnal, meaning they come at night to search for food and water.