Rodents’ most characteristic feature is their set of teeth. The large, curved set of teeth, two in the upper mouth and two in the lower mouth, separated from the rest of the teeth by a large, toothless space. Rodents primarily gnaw with the lower front teeth in the lower part of the mouth while the upper front teeth to a high degree serve to position the head while gnawing. The shape and size of holes from teeth in food can reveal what kind of animal that has been eating the food. In adult mice, the total width of the front teeth is approximately 1.5 mm and in rats approximately 3 mm.

The house mouse and the yellow-necked mouse are often found indoors. Other species of mice can go indoors, but do not thrive there for long. Of our two rat species, the brown rat is the most common, while the black rat sometimes is found in ports.