Almost half of all species of mammals are rodents , more than 2000 species! Rodents are found throughout the world, except Antarctica, New Zealand, and some remote islands. Rodents are extraordinarily diverse in their body shapes, diets, and lifestyles. They range in size from pygmy mice, which weigh 4 grams, to capybaras, which weigh over 70 kg.
Rodents are so diverse that there are almost no ecological features that they all share. However, all rodents do share several physical features. Rodents have teeth that are specialized for gnawing, they have a single pair of upper and lower incisors (front teeth) that grow throughout their lives. These teeth have a layer of enamel on their front surfaces but none on their back surfaces. Because of this, as the teeth rub together they are each sharpened by the other to a chisel-like point. This self-sharpening system and their powerful gnawing abilities are one of the keys to their success.
Rodents are found in all terrestrial habitats worldwide.