With over 2000 living species placed in about 30 families, rodents are by far the largest order of mammals (well over 40 percent of mammalian species belong to the order Rodentia). Rodents range in size from pygmy mice weighing 5 grams to capybaras, the largest of which weigh over 70 kilograms. They are found around the world, except in Antarctica, New Zealand, and on some Oceanic islands. Ecologically, they are incredibly diverse. Some species spend their entire lives above the ground in the canopy of rainforests; others seldom emerge from beneath the ground. Some species are highly aquatic, while others are equally specialized for life in deserts. Many are omnivorous to some degree; others are highly specialized, eating, for example, only a few species of invertebrates or fungi.