Rats and Mice are Rodents. The word "rodent" means "to gnaw" and this is a textbook example of rodent gnawing. Like its cousin, The Beaver, Norway Rats have superb incisors for cutting through surfaces that are not as hard as their teeth. This old tree stump is an example of this. We will cut it out and permanently repair it with stainless steel mesh and efficiently remove the animals inside. Problem solved.
Call EHS Pest for a permanent solution that involves exclusion but doesn't involve chemicals.