World

Our planet is home to approximately 5,000 species of living mammals that display enormous variety. Too see them all in the wild you would have to visit the shores of oceans, travel from Arctic tundra to tropical swamps, and explore rainforest, open praire, barren desert, high mountains, tropical grasslands, and city sewers. Many bats or mice could fit in easily in the palm of a toddler's hand. A large polar bear on the other hand, stands 10 feet tall on two legs and weight as much as ten men, while the blue whale is the largest animal ever to have lived on earth.
Some mammals are held up as symbols of nobility and strength; others are reviled as vermin or feared predators. Loved or loathed, few are regarded with ambivalence - way or other, mammals always seem to elicit an emotional response. Perhaps this is because as mammals ourselves we can at least partially relate to their view of the world - we experience the same drives to obtain food and shelter and protect ourselves from attack. We, too, compete with others of our kind but sometime rely on close alliances with others to survive. Above all, we, too, go through an extended period of parental care and experience the same urge to protect and provide for our young, which like mammals, begin life dependent on milk produced by theirmother in mammary glands. Like all mammals our bodies are warm. It is this ability to generate boday heat internally (by metabolizing food), that has allowed mammals to populate nearly every habitat on earth, from desert to pole.