Examples of animals classified as mammals include elephants, dogs, whales and rhinoceroses. Humans, koala bears and horses are other examples of animals in the class Mammalia. Characteristics of mammals include milk glands for feeding young, fur or hair and being warm-blooded.
The majority of animals in the class Mammalia have teeth, although the anteater is a mammal despite its lack of them. Mammals inhabit a wide range of environments, including the oceans, land and below the ground. The blue whale, which can grow over 80 feet in body length, is the largest known ocean mammal, while the elephant is the largest mammal that lives on land. After the elephant, the rhinoceros and the hippopotamus are the largest land mammals.
There are three main subcategories of mammals: live-young, marsupials and egg-laying species. Live-young mammals are also called placental mammals, and their young are born live rather than in eggs. A marsupial carries its young in a pouch on its body. Examples of mammals that are marsupials include kangaroos and opossums. Egg-laying mammals are also called monotremes, and some examples are long-nosed spiny anteaters and platypuses.
Mammals may be carnivores, herbivores or omnivores. Carnivores have diets of only meat, while herbivores feed on plants. Omnivores, such as humans, eat a combination of meat and plants.