What kind of markings might indicate the presence of rodents in a building?

Gnaw marks on wooden surfaces are a strong indicator of rodent presence, specifically because rodents have continuously growing incisor teeth that require them to gnaw on various materials to keep them from overgrowing. Wood provides both a source of material for gnawing and potential nesting sites, leading to visible marks where rodents have chewed. These gnaw marks can take the form of small notches along edges or larger grooves, highly suggesting that rodents have been active in the area.

Other options, while they may hint at issues, are not as definitive. Footprints on the floor, for instance, could be caused by various animals or even human activity, making them less specific. Scratches on furniture could result from a multitude of other pests or household activities, and piles of dust do not specifically indicate rodent activity; they might simply indicate a lack of cleaning. Therefore, gnaw marks are the most distinctive and reliable sign of rodents in a building.