Which of the following can damage food supplies as a rodent sign?

Gnaw marks indicate that rodents, such as mice and rats, have been actively feeding or nesting in an area. These marks are a direct sign of activity and can signify potential damage to food supplies. Rodents have strong teeth that allow them to gnaw through various materials, including packaging that protects food. The presence of gnaw marks indicates that the rodents could have access to the food, leading to contamination or destruction of the food supplies, which is a significant concern in pest management.

In contrast, mouse tracks, while they show where rodents have traveled, do not directly indicate damage to food. Pheromone trails are chemical signals used by rodents for communication and do not cause damage themselves. Chewed clothing may signify rodent activity, but it does not specifically relate to food supplies like gnaw marks do. Thus, gnaw marks are the most relevant indicator of potential harm to food due to rodent presence.