Norway rats are ground-dwelling rodents that build burrows near structures and can enter through openings at or below ground level. They are strong diggers and often establish nests close to food sources. 

Homeowners may notice burrows near the foundation, larger droppings, gnaw marks, or movement in lower levels of the home. They may also hear activity in walls or beneath floors. Because of their size and strength, Norway rats can cause significant damage by gnawing on wood, insulation, and wiring. They may also contaminate food and surfaces as they move through a structure. 

Infestations often grow over time as rats expand their burrow systems and nesting areas. Their ability to reproduce and remain hidden makes them difficult to control without targeted intervention. Without addressing entry points and nesting areas, activity is likely to continue and worsen.