US State Animals and Mammals

Official Mammal and Animal State Designations

The evolution of the class Mammalia has produced tremendous diversity in form and habit. Living kinds range in size from a bat weighing less than a gram and tiny shrews weighing but a few grams to the largest animal that has ever lived, the blue whale, which reaches a length of more than 100 feet and a weight of 200 tons. Every major habitat has been exploited by mammals that swim, fly, run, burrow, glide, or climb.

There are approximately 5,000 species of living mammals, arranged in about 125 families and 29 orders (familial and ordinal groupings sometimes vary among authorities).

The greatest present-day diversity is seen in continental tropical regions, although members of the class Mammalia live on (or in seas adjacent to) all major landmasses. South America (the Neotropics), for example, was separated from North America (the Nearctic) from about 65 million to 2.5 million years ago. Mammalian groups that had reached South America before the break between the continents, or some that “island-hopped” after the break, evolved independently from relatives that remained in North America. Some of the latter became extinct as the result of competition with more advanced groups, whereas those in South America flourished, some radiating to the extent that they have successfully competed with invaders since the rejoining of the two continents.

In contrast, North America and Eurasia (the Palearctic) are separate landmasses but have closely related faunas as the result of having been connected several times during the Pleistocene Epoch (1,800,000 to 10,000 years ago) and earlier across the Bering Strait. Their faunas frequently are thought of as representing not two distinct units but one, related to such a degree that a single name, Holarctic, is applied to it.

US State Animals and Mammals