The order of rodents includes a number of small, furry mammals that can make pleasant companions. Rodents include a great variety of species with many different forms, habits, and habitats. The strange quality that unites all rodents is that their sharp front teeth never stop growing; they wear the teeth down to a constant length through gnawing at tough food and digging through the ground. Rodents are all relatively small and tend to be skittish, which is reasonable considering how many predators consider them prey.