Rodent, << ROH duhnt, >> is an animal with front teeth especially suited to gnawing hard objects. Squirrels, beavers, and rats are rodents. Squirrels can break the shells of nuts with their front teeth. Beavers can gnaw through tree trunks, and rats can gnaw through some wood and plaster walls. The many kinds of rodents include gophers, hamsters, mice, and porcupines.
All rodents have two top and two bottom front teeth called incisors. They wear away at the tips, but do not wear out until late in the animal’s lifetime because they keep growing until the animal is old. The incisors wear faster in the back than in front. As a result, they have a chisellike edge, well-suited to gnawing. Rodents also have back teeth consisting of molars and premolars that they use for chewing. The space between the incisors and back teeth is called the diastema.
Rodents are mammals (animals that feed their young milk). There are more individual rodents than there are individuals of all other kinds of mammals combined. Rodents live in almost all parts of the world.
Mice are the smallest rodents and capybaras of South America are the largest. Some capybaras are up to 4 feet (1.2 meters) long. Most rodents are herbivorous (plant eaters). But rats and other rodents eat almost any food.
Rodents are both helpful and harmful to people. Some rodents eat harmful insects and weeds, and some have valuable fur. Scientists use mice and rats in research. But some rodents damage crops and other property. Many rodents also carry serious diseases, such as plague and typhus.
