The American bison (Bison bison; : bison), commonly known as the American buffalo, or simply buffalo (not to be confused with true buffalo), is a species of bison that is endemic to North America. It is one of two extant species of bison, along with the European bison. Its historical range circa 9000 BC is referred to as the great bison belt, a tract of rich grassland spanning from Alaska south to the Gulf of Mexico, and east to the Atlantic Seaboard (nearly to the Atlantic tidewater in some areas), as far north as New York, south to Georgia, and according to some sources, further south to northern Florida, with sightings in North Carolina near Buffalo Ford on the Catawba River as late as 1750.
Two subspecies or ecotypes have been described: the plains bison (B. b. bison), smaller and with a more rounded hump; and the wood bison (B. b. athabascae), the larger of the two and having a taller, square hump. There has been a proposal to divide the plains bison into subspecies of northern (B. b. montanae) and southern (B. b. bison), With wild animals weighing up to , the bison is among the heaviest extant land animals in North America and the heaviest herbivore.
Once roaming in vast herds, the species nearly became extinct by a combination of commercial hunting and slaughter in the 19th century and introduction of bovine diseases from domestic cattle. With an estimated population of 60 million in the late 18th century, the species was reduced to 541 animals by 1889 as part of the subjugation of the Native Americans, because the American bison was a major resource for their traditional way of life (food source, hides for clothing and shelter, and horns and bones for tools).
Spanning back millennia, Indigenous peoples of the Great Plains have had cultural and spiritual connections to the American bison. It is the national mammal of the United States.
Etymology
thumb|left|Adult male (behind) and adult female (in front), in [[Yellowstone National Park]]
In American English, both buffalo and bison are considered correct terms for the American bison. However, in British English, the word buffalo is reserved for the African buffalo and water buffalo and not used for the bison.
In English usage, the term buffalo was used to refer to the American mammal as early as 1625. The word bison was applied in the 1690s. Buffel in turn comes from Portuguese bufalo (water buffalo), which comes from Latin bufalus (an antelope, gazelle, or wild ox), from Greek boubalos. The same Greek word boubalos is also the origin for the Bubal hartebeest.
Bison was borrowed from French bison in the early 17th century, from Latin bison (aurochs), from a Proto-Germanic word similar to wisent and, per Etymonline, first applied to American buffalo in the 1690s.
In Plains Indian languages in general, male and female bison are distinguished, with each having a different designation rather than there being a single generic word covering both sexes. Thus:
- in Arapaho: (bison cow), (bison bull)
- in Lakota: (bison cow), (bison bull)
Such a distinction is not a general feature of the language (for example, Arapaho possesses gender-neutral terms for other large mammals such as elk, mule deer, etc.), and so presumably is due to the special significance of the bison in Plains Indian life and culture.
Description
thumb|right|Male plains bison in the [[Wichita Mountains of Oklahoma]]
thumb|Skeleton of plains bison.
thumb|Plains bison galloping, photos by [[Eadweard Muybridge, first published in 1887 in Animal Locomotion]]
A bison has a shaggy, long, dark-brown winter coat, and a lighter-weight, lighter-brown summer coat. Male bison are significantly larger and heavier than females. Typically weights can range from , with medians of (B.b. bison) and (B.b.athabascae) in males, and with medians of in females, while there had been bulls estimated to be . Elk Island National Park, which has wild populations of both wood and plains bison, has recorded maximum weights for bull bison of (plains) and (wood), but noted that three-quarters of all bison over were wood bison. When raised in captivity and farmed for meat, the bison can grow unnaturally heavy and the largest semidomestic bison weighed . to width, 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. Sexually mature young bulls may try to start mating with cows by the age of two or three years, but if more mature bulls are present, they may not be able to compete until they reach five years of age.
For the first two months of life, calves are lighter in color than mature bison. Though extremely rare, white buffalos exist.
Evolution
Bison are members of the tribe Bovini. Genetic evidence from nuclear DNA indicates that the closest living relatives of bison are yaks, with bison being nested within the genus Bos, rendering Bos without including bison paraphyletic. While nuclear DNA indicates that the two living bison species are each other's closest living relatives, the mitochondrial DNA of European bison is more closely related to that of domestic cattle and aurochs, which is suggested to be the result of either incomplete lineage sorting or ancient introgression.
Bison first appeared in Asia during the Early Pleistocene, around 2.6 million years ago. Bison only arrived in North America 195,000 to 135,000 years ago, during the late Middle Pleistocene, descending from the widespread Siberian steppe bison (Bison priscus), which had migrated through Beringia. Following their first appearance in North America, the bison rapidly differentiated into new species, such as the largest of all bison, the long-horned Bison latifrons, along with Bison antiquus. The first appearance of bison in North America is considered to define the regional Rancholabrean faunal stage, due to its major impact on the ecology of the continent. Modern American bison are thought to have evolved from B. antiquus at the end of the Late Pleistocene - beginning of the Holocene, with likely intermediates between the species referred to as Bison "occidentalis". The North American bison population experienced demographic stability during the Middle Holocene but began a slow decline in the Late Holocene beginning about 2,700 BP.
Differences from European bison
thumb|left|An adult European bison
Although they are superficially similar, the American and European bison exhibit a number of physical and behavioral differences. Adult American bison are slightly heavier on average because of their less rangy build and have shorter legs, which render them slightly shorter at the shoulder. American bison tend to graze more and browse less than their European relatives because their necks are set differently. Compared to the nose of the American bison, that of the European species is set farther forward than the forehead when the neck is in a neutral position. The body of the American bison is hairier, though its tail has less hair than that of the European bison. The horns of the European bison point forward through the plane of its face, making it more adept at fighting through the interlocking of horns in the same manner as domestic cattle, unlike the American bison, which favors charging. American bison are more easily tamed than the European and breed more readily with domestic cattle.
Crossbreeding with cattle
During the population bottleneck, after the great slaughter of American bison during the 19th century, the number of bison remaining alive in North America declined to as low as 541. During that period, a handful of ranchers gathered remnants of the existing herds to save the species from extinction. These ranchers bred some of the bison with cattle in an effort to produce "cattalo" or "beefalo". Accidental crossings were also known to occur. Generally, male domestic bulls were crossed with bison cows, producing offspring of which only the females were fertile. The crossbred animals did not demonstrate any form of hybrid vigor, so the practice was abandoned. The proportion of cattle DNA that has been measured in introgressed individuals and bison herds today is typically quite low, ranging from 0.56 to 1.8%. Many claimed "beefalo", even those regarded as pedigree, have no detectable bison ancestry. In the United States, many ranchers are now using DNA testing to cull the residual cattle genetics from their bison herds. The U.S. National Bison Association has adopted a code of ethics which prohibits its members from deliberately crossbreeding bison with any other species.
Range and population
thumb|Bison herd grazing at the [[CSKT Bison Range in Montana]]
Population estimates in 2010 ranged from 400,000 to 500,000, with approximately 20,500 animals in 62 conservation herds and the remainder in approximately 6,400 commercial herds. According to the IUCN, roughly 15,000 bison are considered wild, free-range bison not primarily confined by fencing.
The Nature Conservancy (TNC) has reintroduced bison to over a dozen nature preserves around the United States. In October 2016, TNC established its easternmost bison herd in the country, at Kankakee Sands nature preserve in Morocco, Newton County, Indiana. In 2014, U.S. Tribes and Canadian First Nations signed a treaty to help with the restoration of bison, the first to be signed in nearly 150 years.
Habitat and trails
thumb|right|Bison sparring in [[Grand Teton National Park in Moose, Wyoming ]]
American bison live in river valleys, and on prairies and plains. Typical habitat is open or semiopen grasslands, as well as sagebrush, semiarid lands, and scrublands. Some lightly wooded areas are also known historically to have supported bison. Bison also graze in hilly or mountainous areas where the slopes are not steep. Though not particularly known as high-altitude animals, bison in the Yellowstone Park bison herd are frequently found at elevations above , and the Henry Mountains bison herd is found on the plains around the Henry Mountains, Utah, as well as in mountain valleys of the Henry Mountains to an altitude of . Reintroduced plains bison in Banff National Park have been observed to roam mountainous areas, including high ridges and steep drainages. Archaeological finds indicate some bison spent their lives within mountain ranges while others may have migrated in and out.
Those in Yukon, Canada, typically summer in alpine plateaus above treeline. The first thoroughfares of North America, except for the time-obliterated paths of mastodon or muskox and the routes of the mound builders, were the traces made by bison and deer in seasonal migration and between feeding grounds and salt licks. Many of these routes, hammered by countless hoofs instinctively following watersheds and the crests of ridges in avoidance of lower places' summer muck and winter snowdrifts, and often following the routes of least resistance across rolling terrain, were followed by the aboriginal North Americans as routes to hunting grounds and as warriors' paths. They were invaluable to explorers and were adopted by pioneers.
Bison traces were characteristically north and south along seasonal migration routes, but several key east–west buffalo trails were used later as routes for railways. Some of these include the Cumberland Gap through the Blue Ridge Mountains to upper Kentucky. A heavily used trace crossed the Ohio River at the Falls of the Ohio and ran west, crossing the Wabash River near Vincennes, Indiana. In Senator Thomas Hart Benton's phrase saluting these sagacious path-makers, the bison paved the way for the railroads to the Pacific.
Mexico
thumb|Bison herd grazing in [[Chihuahua (state)|Chihuahua, Mexico]]
The southern extent of the historic range of the American bison includes northern Mexico and adjoining areas in the United States as documented by archeological records and historical accounts from Mexican archives from 700 CE to the 19th century. The Janos-Hidalgo bison herd has ranged between Chihuahua, Mexico, and New Mexico, United States, since at least the 1920s. The persistence of this herd suggests that habitat for bison is suitable in northern Mexico. In 2009, genetically pure bison were reintroduced to the Janos Biosphere Reserve in northern Chihuahua adding to the Mexican bison population. In 2020, the second herd was formed in Maderas del Carmen. A private reserve named Jagüey de Ferniza has kept bison since before the above-mentioned reintroductions in Coahuila.
Introductions to Siberia
thumb|Wood bison introduction program in Sakha Republic
Since 2006, an outherd of wood bison sent from Alberta's Elk Island National Park was established in Yakutia, Russia as a practice of pleistocene rewilding; wood bison are the most similar to the extinct steppe bison species (Bison priscus sp.). The bison are adapting well to the cold climate, and Yakutia's Red List officially registered the species in 2019; a second herd was formed in 2020.
Plains bison were also translocated into the Pleistocene Park, as more-favored wood bison could not be acquired.
Behavior and ecology
thumb|right|Grazing in winter, Yellowstone National Park: Bison use their heads to clear out snow for the grass
Bison are migratory and herd migrations can be directional as well as altitudinal in some areas. Bison have usual daily movements between foraging sites during the summer. In the Hayden Valley, Wyoming, bison have been recorded traveling, on average, per day. On shortgrass pasture, bison predominately consume warm-season grasses. On mixed prairie, cool-season grasses, including some sedges, apparently compose 79–96% of their diet. In montane and northern areas, sedges are selected throughout the year. However, female herds may also contain a few older males. During the breeding season, dominant bulls maintain a small harem of females for mating. Individual bulls "tend" cows until allowed to mate, by following them around and chasing away rival males. The tending bull shields the female's vision with his body so she will not see any other challenging males. A challenging bull may bellow or roar to get a female's attention, and the tending bull has to bellow or roar back. More subordinate bulls mate with any remaining estrous cow that has not mated yet. Male bison play no part in raising the young.
right|thumb|Calf
left|thumb|A cow suckling calf at the [[Cologne Zoological Garden in Cologne, Germany]]
Bison herds have dominance hierarchies that exist for both males and females. A bison's dominance is related to its birth date. Bison born earlier in the breeding season are more likely to be larger and more dominant as adults.
Bison have a life expectancy around 15 years in the wild and up to 25 years in captivity. However, males and females from a hunted population also subject to wolf predation in northern Canada have been reported to live to 22 and 25 years of age, respectively.
Bison have been observed to display homosexual behaviors, males much more so than females. In the case of males, it is unlikely to be related to dominance, but rather to social bonding or gaining sexual experience.
Horning
Bison mate in late spring and summer in more open plain areas. During fall and winter, bison tend to gather in more wooded areas. During this time, bison partake in horning behaviors. They rub their horns against trees, young saplings, and even utility poles. Aromatic trees like cedars and pine seem to be preferred. Horning appears to be associated with insect defense, as it occurs most often in the fall when the insect population is at its highest. Cedar and pines emit an aroma after bison horn them and this seems to be used as a deterrent for insects. Bison wallowing has important ecosystem engineering effects and enhances plant and animal diversity on prairies.
Predation
thumb|right|American bison standing its ground against a [[northwestern wolf|wolf pack]]
right|thumb|A [[grizzly bear feeding on an American bison carcass]]
While often secure from predation because of their size and strength, in some areas, vulnerable individuals are regularly preyed upon by wolves. Wolf predation typically peaks in late winter, when elk migrates south and bison are distressed with heavy snows and shortages of food sources, with attacks usually being concentrated on weakened and injured cows and calves. Wolves more actively target herds with calves than those without. The length of a predation episode varies, ranging from a few minutes to over nine hours. Bison calves use five apparent defense strategies in protecting themselves from wolves: running to a cow, running to a herd, running to the nearest bull, running in the front or center of a stampeding herd, and entering a lake or river or other body of water. When fleeing wolves in open areas, cows with young calves take the lead, while bulls take to the rear of the herds to guard the cows' escape. Bison typically ignore wolves not displaying hunting behavior. Wolf packs specializing in bison tend to have more males because their larger size than females allows them to wrestle prey to the ground more effectively. Healthy, mature bulls in herds rarely fall prey.
Grizzly bears are known to feed on carcass and may steal wolves' kills. Grizzlies can sometimes kill calves as well as old, injured, or sick adult bison, but direct killing of adult bison is rare even when grizzlies target lone and injured young individuals. Attacking a healthy bison is risky for a bear, who itself may be killed instead.
Dangers to humans
Bison are among the most dangerous animals encountered by visitors to the various North American national parks and will attack humans if provoked. They appear slow because of their lethargic movements but can easily outrun humans; bison have been observed running as fast as . Bison may approach people for curiosity. Close encounters, including to touch the animals, can be dangerous, and gunshots do not startle them.
thumb|right|Tourists approach dangerously close to a wild herd of American bison to take a photograph in Yellowstone National Park, Wyoming
Between 1980 and 1999, more than three times as many people in Yellowstone National Park were injured by bison than by bears. During this period, bison charged and injured 79 people, with injuries ranging from goring puncture wounds and broken bones to bruises and abrasions. Bears injured 24 people during the same time. Three people died from the injuries inflicted—one person by bison in 1983, and two people by bears in 1984 and 1986.
Genetics
thumb|Map from 1889 by [[William Temple Hornaday, illustrating his book, The Extermination of the American Bison|left]]
A major problem that bison face today is a lack of genetic diversity due to the population bottleneck the species experienced during its near-extinction in the late 1800s. Another genetic issue is the entry of genes from domestic cattle into the bison population, through hybridization. Moreover, when they do interbreed, crossbreed animals in the first generation tend to look very much like purebred bison, so appearance is completely unreliable as a means of determining which is a purebred bison, a crossbred cow and a crossbred bison. Many ranchers have deliberately crossbred their cattle with bison, and some natural hybridization could be expected in areas where cattle and bison occur in the same range. Since cattle and bison eat similar food and tolerate similar conditions, they have often been in the same range together in the past, and opportunity for crossbreeding may sometimes have been common.
thumb|Hybrid between the domestic cow and the American bison
In recent decades, tests were developed to determine the source of mitochondrial DNA in cattle and bison, and most private "buffalo" herds were actually crossbred with cattle, and even most state and federal buffalo herds had some cattle DNA. With the advent of nuclear microsatellite DNA testing, the number of herds known to contain cattle genes has increased. As of 2011, though about 500,000 bison existed on private ranches and in public herds, perhaps only 15,000 to 25,000 of these bison were pure and not actually bison–cattle hybrids. DNA from domestic cattle (Bos taurus) has been found in almost all examined bison herds.
Significant public bison herds that do not appear to have hybridized domestic cattle genes are the Yellowstone Park bison herd, the Henry Mountains bison herd, which was started with bison taken from Yellowstone Park, the Wind Cave bison herd, and the Wood Buffalo National Park bison herd and subsidiary herds started from it, in Canada.
A landmark study of bison genetics performed by James Derr of Texas A&M University corroborated this. The Derr study was undertaken in an attempt to determine what genetic problems bison might face as they repopulate former areas, and it noted that bison seem to be adapting successfully, despite their apparent genetic bottleneck. One possible explanation for this might be the small amount of domestic cattle genes that are now in most bison populations, though this is not the only possible explanation for bison success.
thumb|A [[wood bison around the Coal River in Canada]]
In the study, cattle genes were also found in small amounts throughout most national, state, and private herds. "The hybridization experiments conducted by some of the owners of the five foundation herds of the late 1800s, have left a legacy of a small amount of cattle genetics in many of our existing bison herds," said Derr. "All of the state owned bison herds tested (except for possibly one) contain animals with domestic cattle mtDNA."
Population bottleneck and near extinction
Bison went from numbering an estimated 60 million individuals