Mammals

the highest class of vertebrates. It contains all those animals that suckle their young and no others. With the exception of a small group of Australian animals represented by the duckbill, all mammals bring forth their young alive. They are warm-blooded and breathe air. Their skin is more or less hairy, rarely naked. Some of the principal families included in the mammals are man, the monkeys, the bats, the hedgehogs, the shrews, the moles, the bears, the raccoons, the dogs, the cats, the weasels, the seals, the hares, the squirrels, the porcupines, the rats and mice, the sloths, the cattle, the goats, the sheep, the antelopes, the giraffes, the deer, the camels, the horses, the elephant kind, the swine, the seal, the whale kind, the ant-eater, the opposum, the kangaroo, and the duckbill. There are over 3,000 different species of animals that suckle their young. The greater number of mammals live on land, but some, like the walrus, seal, whale, manatee, and dugong, are adapted to a life in the water. One mammal, the bat, is aerial. See the articles describing the various families of mammalia enumerated above.