Mammals—a group that include humans—are warm-blooded animals with hair and vertebrates, or backbones. Unlike other classes of animals, female mammals produce milk to nourish their young. Almost all mammals give birth to live young (except for the platypus and echidna, which lay eggs).
Scientists have identified more than 5,400 mammal species on Earth, roughly one-fifth of which are known to be threatened or extinct. One of the most threatened order of mammals is the primate, which includes monkeys and apes. The United States has more than 400 mammal species. Of those mammals, nearly a quarter are listed on the U.S. endangered species list for reasons including habitat loss, climate change, pollution, and disease.
Nocturnal, flying mammals that eat fruits and insects
|Jamaican Fruit-Eating Bat
|Little Brown Bat
Gnawing mammals with a single pair of incisors
|Black-Tailed Prairie Dog
|Red Tree Vole
Gnawing mammals with two pairs of incisors
Moles and Armadillos
Meat-eating mammals, such as bears, felines, and canines
|Hawaiian Monk Seal
|North American River Otter
Hooved mammals with four legs
Cetaceans and Sirenians
Aquatic mammals with paddle-shaped forelimbs
|West Indian Manatee
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