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The American bison (''Bison bison''), also commonly known as the American buffalo, is a North American species of bison that once roamed the grasslands of North America in massive herds. They became nearly extinct by a combination of commercial hunting and slaughter in the 19th century and introduction of bovine diseases from domestic cattle, and have made a recent resurgence largely restricted to a few national parks and reserves. Their historical range roughly comprised a triangle between the Great Bear Lake in Canada's far northwest, south to the Mexican states of Durango and Nuevo León, and east to the Atlantic Seaboard of the United States (nearly to the Atlantic tidewater in some areas) from New York to Georgia and per some sources down to Florida. Bison were seen in North Carolina near Buffalo Ford on the Catawba River as late as 1750.〔(Project Gutenburg E Book - ''The Extermination of the American Bison'' )〕〔(【引用サイトリンク】title=American Buffalo (''Bison bison'') species page )〕〔 Retrieved on February 24, 2013.〕 Two subspecies or ecotypes have been described: the plains bison (''Bison bison bison''), smaller in size and with a more rounded hump, and the wood bison (''Bison bison athabascae'')—the larger of the two and having a taller, square hump. Furthermore, it has been suggested that the plains bison consists of a northern (''Bison bison montanae'') and a southern subspecies, bringing the total to three.〔 However, this is generally not supported. The wood bison is one of the largest wild species of bovid in the world, surpassed by only the Asian gaur and wild water buffalo. It is the largest extant land animal in the Americas. ==Description== A bison has a shaggy, long, dark brown winter coat, and a lighter weight, lighter brown summer coat. As is typical in ungulates, the male bison are slightly larger than the female and, in some cases, can be considerably heavier. Plains bison are often in the smaller range of sizes, and Wood bison in the larger range. Head-and-body length ranges from long, the tail adding . Shoulder height in the species can range from . Weight can range from 〔(The Animal Files )〕 The heaviest wild bull ever recorded weighed . When raised in captivity and farmed for meat, the bison can grow unnaturally heavy and the largest semi-domestic bison weighed .〔 The heads and forequarters are massive, and both sexes have short, curved horns that can grow up to long, which they use in fighting for status within the herd and for defense. Bison are herbivores, grazing on the grasses and sedges of the North American prairies. Their daily schedule involves two-hour periods of grazing, resting and cud chewing, then moving to a new location to graze again. Bison mate in August and September; gestation is 285 days. A single reddish-brown calf nurses until the next calf is born. If the cow is not pregnant, a calf will nurse for 18 months. At three years of age, bison cows are mature enough to produce a calf. Bison bulls of that age may try to mate with cows, but if more mature bulls are present, they may not be able to compete until they reach five years of age. Bison have a life expectancy of approximately 15 years in the wild and up to 25 years in captivity. For the first two months of life, calves are lighter in color than mature bison. One very rare condition is the white buffalo, in which the calf turns entirely white. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「american bison」の詳細全文を読む スポンサード リンク
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