If a rodent did not gnaw daily on hard food or other hard objects, its front teeth, called incisors, would continue to grow. The rodent could not then chew or even open its mouth. It would starve to death. If you keep a rodent, such as a mouse or rat, in a cage, it will gnaw on hard objects just to wear down its teeth. The hard object is often the cage itself.
Rodents have bulbous eyes.
Bulbous eyes bulge out like domes from the sides of the rodent's heads. Their bulbous eyes let them see in front and behind themselves without moving their heads. This helps them look out for their many enemies. Most rodents have large eyes, especially the ones who are more active at night. The families of wild rodents living in North America include squirrels, chipmunks, rats, mice, beavers, lemmings, muskrats, voles, and porcupines.