Bison

• 1. Introduction

  ›

  In 1889, an estimated 1,091 American bison were left alive, counting both wild animals and captive ones. The bison is a large, shaggy grazer, and that figure marked the low point of its modern history. How did a continent's most familiar animal fall so far? Why do Americans call it by another animal's name? And what does it take to pull a species back from the edge, when the survivors are not always what they appear to be?

  65666768

• 2. A Name Borrowed

  ›

  The word bison first described a European animal, not an American one. In the 2nd century AD, the Greek writers Pausanias and Oppian wrote of the creature as bisōn. The Roman authors Pliny the Elder and Gaius Julius Solinus used the Latin bĭson. The Germanic word wisent shares a common origin with it, which is why the European bison still carries that second name. In 1827, Charles Hamilton Smith turned the Latin word into a formal genus name.

  The word buffalo reached English by a different road. In 1616, Samuel de Champlain applied the French term buffle to the animal, in an account published in 1619. His information came from members of the Nipissing First Nation, who showed him skins and a drawing. They told him they travelled 40 days from east of Lake Huron to trade with another nation that hunted the animals.

  The label fits the biology poorly. The two true buffalo are the Asian water buffalo and the African buffalo, and the bison is only distantly related to either. Even so, buffalo has a longer history in English than bison, which was first recorded in 1774. Because of standard American usage, many dictionaries accept buffalo as a name for the American animal. Who the bison truly belongs with is a stranger question, and it took DNA to begin answering it.

  5758596061

• 3. A Family Tree Rewritten

  ›

  Between 5 and 10 million years ago, the bovine tribe split in two. One branch led to the buffalos. The other led toward the bison and taurine cattle. Nuclear DNA now shows that the closest living relatives of bison are yaks, and that bison sit inside the genus Bos. For that reason, the old practice of giving bison a genus of their own no longer holds up. In 2021, the American Society of Mammalogists treated Bison as a subgenus and placed both species back into Bos.

  The oldest members of the bison line lived in Asia. Bison sivalensis, from the Indian Subcontinent, and Bison palaeosinensis, from China, date to roughly 3.4-2.6 million years ago. Researchers place them in the subgenus Eobison. The oldest Eobison remains in Europe belong to Bison georgicus, found at Dmanisi, Georgia, and dated to around 1.76 million years ago. The whole line is thought to descend from an extinct genus called Leptobos. More advanced bison appeared around 1.2 million years ago, including the widespread Bison schoetensacki.

  Sometime between 195,000 and 135,000 years ago, the steppe bison, Bison priscus, crossed the Bering land bridge into North America. It became the ancestor of the large Bison latifrons and the smaller Bison antiquus, which died out at the end of the Late Pleistocene. Modern American bison are thought to descend from Bison antiquus, through an intermediate form called Bison occidentalis. Meanwhile, the European bison, Bison bonasus, appeared in Europe and lived alongside the steppe bison there. The steppe bison itself lasted into the early-mid Holocene in Alaska-Yukon and eastern Siberia.

  One genetic puzzle remains open. Nuclear DNA says the two living species are each other's closest relatives. Yet the mitochondrial DNA of the European bison sits closer to that of domestic cattle and aurochs. The mitochondrial DNA of the American bison, by contrast, resembles that of yaks. Researchers suggest incomplete lineage sorting or ancient introgression, which means gene flow between lineages. Whatever the answer, the two living species differ in ways a trained observer can count, right down to the ribs.

  2331322120

• 4. Two Continents, Two Bison

  ›

  An American bison has 15 ribs, while a European bison has 14. The lower spine reverses the pattern: American bison have four lumbar vertebrae, and European bison have five. The reason is that the first lumbar vertebra of an American bison carries ribs. It is therefore counted as a 15th thoracic vertebra, against 14 in the wisent.

  In size, the two animals are close rivals. American bison reach up to 2 m in height and 3.5 m in length, and weigh from around 400 to 1,270 kg. European bison reach up to 2.1 m in height and 2.9 m in length, and weigh from 800 to 1000 kg. Both are broad, muscular, cloven-hoofed animals with shaggy coats. The American animal is less slim and has shorter legs, while the European animal tends to stand taller.

  Feeding habits shaped the heads. American bison graze more and browse less than the wisent, and their heads hang lower as a result. The American body is typically hairier, though its tail carries less hair than the wisent's tail. Horns differ too. The wisent's horns point through the plane of the face, which suits fighting by interlocking horns, much as domestic cattle do. The American bison favours butting.

  Habitat divides them as well. American bison live in river valleys, prairies and plains, in open or semiopen grassland, sagebrush, semiarid land and scrub. Some lightly wooded areas have supported them, and they graze hills where the slopes are not steep. The Yellowstone herd is often found above 8000 ft. The Henry Mountains herd in Utah ranges up to 10000 ft.

  European bison favour lightly to fully wooded country, with shrubs and bushes, though they sometimes live on grassland. In Poloniny National Park, in the Carpathian Mountains of Poland and Slovakia, a herd of cattle-wisent crossbreeds called zubron is maintained.

  316385148

• 5. Life in the Herd

  ›

  A young bull leaves the female herd at two or three years of age and joins a herd of males. Male herds are usually smaller than female ones, and mature bulls rarely travel alone. Bison are nomadic grazers that move in herds. Toward the end of summer, the sexes necessarily mix for the reproductive season.

  The rut runs from June through September, with peak activity in July and August. Older bulls rejoin the herd then, and fights often break out between bulls. The whole herd grows restless. Observers describe the animals in this season as belligerent, unpredictable and most dangerous.

  At other times, a bison can look peaceful, unconcerned or even lazy. It may still attack without warning or any apparent reason. Bison can run at speeds up to 35 mph and cover long distances at a lumbering gallop. Both males and females carry horns. The massive head works as a battering ram, typically weighing 2000 to 2700 lb and moving at 30 mph. The hind legs can kill or maim as well. Early naturalists considered the bison savage and fearless, able to best any foe in prime condition except a brown bear or a pack of wolves.

  On the prairie, a wallow is a shallow depression in the soil, either wet or dry. Bison roll in it and cover themselves with mud or dust. Researchers have proposed many reasons: grooming during moulting, rivalry between males, group cohesion, play, relief from biting insects, fewer ticks and lice, and temperature control. Wallowing carries a risk, because anthrax can occur naturally in soil and may infect a rolling bison.

  Bison are ruminants, with a specialized stomach that ferments cellulose before digestion. They were once thought to eat almost only grasses and sedges. They are now known to eat a wide variety of plants, including woody plants. Through the year they shift toward whichever plants offer the most protein or energy, and they return to the same species year after year. Protein in those plants is highest in spring and lowest in winter. In Yellowstone, bison browse willows and cottonwoods in summer as well as winter. They also concentrate on recently burned areas, where regrowth offers better forage. The wisent browses shrubs and low trees more often than the American bison does.

  After her third year, a cow can begin reproducing, and she may continue beyond age 19. She bears a calf each year as long as her nutrition is sufficient, but not after years of poor weight gain. Heavier cows produce heavier calves. Calf weights fall for cows older than 8.

  Because of their size, bison have few predators. Five exceptions are humans, grey wolves, cougars, grizzly bears and coyotes. Wolves usually need a pack, though single wolves have been reported killing bison. Grizzly bears sometimes drive off the pack and eat the wolves' kill, and grizzlies and coyotes also take calves. In the deep past, the list was longer: lions, cave lions, tigers, dire wolves, Smilodon, Homotherium, cave hyenas and Neanderthals. Humans therefore appear on the bison's list of enemies twice, in the Neanderthals of prehistory and in the hunters of recent centuries.

  3435444550

• 6. Sacred and Slaughtered

  ›

  For the Indigenous peoples of the Plains, the bison was the principal food source. Native Americans valued their relationship with the animal and saw it as sacred. They treated it respectfully to ensure its abundance and longevity. The Lakota teacher and elder John Fire Lame Deer described that relationship in his biography. In his words, "The buffalo gave us everything we needed. Without it we were nothing."

  Lame Deer went on to list the uses, one by one. Tipis were made of the skin, and the hide served as bed, blanket and winter coat. It also became a drum and water bags. A red-hot stone dropped into the stomach made a soup kettle. Horns became spoons, and bones became knives, awls and needles. Sinews made bowstrings and thread. Ribs were shaped into sleds for children, and hoofs into rattles. The skull, with the pipe leaning against it, served as a sacred altar. As he put it, "Not the smallest part of it was wasted." He argued that killing off the buffalo also killed the real, natural, wild Indian.

  At the start of the 19th century, tens of millions of bison roamed North America. Before the late 19th century, the population likely reached perhaps as many as 60 million. European colonists were almost exclusively responsible for the near extinction that followed. They slaughtered an estimated 50 million bison during the century, although the causes and numbers are disputed. Railroads advertised "hunting by rail". When trains met large herds beside or across the tracks, men fired from the roof or windows and left countless animals to rot where they fell.

  Part of the motive was political. The U.S. government wanted to limit the range and power of the Indigenous plains peoples, whose diets and cultures depended on the herds. The hunting reduced the population to hundreds. In one count, the survivors in North America numbered as few as 541.

  6362656764

• 7. Recovery's Fine Print

  ›

  A handful of ranchers gathered the remnants of the herds to save the species from extinction. Some of them bred bison with cattle, hoping to produce a animal they called "cattleo", known today as beefalo. Domestic bulls were usually crossed with bison cows, and only the female offspring were fertile. The hybrids showed no hybrid vigor, so the practice was abandoned. American bison are more easily tamed than wisent and breed with domestic cattle more readily, so accidental crossings also occurred.

  Other crosses were tried in Germany, where wisent-American bison hybrids proved fully fertile, and a herd of such animals is kept in Russia. First-generation crosses do not occur naturally and require caesarean delivery, and first-generation males are infertile. Today, the U.S. National Bison Association has a code of ethics that bars members from deliberately crossbreeding bison with any other species. Many ranchers use DNA testing to cull leftover cattle genetics. Measured cattle DNA in affected individuals and herds is typically low, ranging from 0.56 to 1.8%.

  Repopulation began in 1910, through enforced protection of government herds and extensive ranching. The effort has continued with excellent success, and the population now stands at nearly 150,000. The bison is officially no longer considered endangered. Genetically, though, most of those animals are hybrids with domestic cattle. Only two populations, in Yellowstone National Park and Elk Island National Park in Canada, remain genetically pure. They account for only about 5% of American bison, which reflects the loss of most of the species' genetic diversity. Another estimate puts genetically pure Plains bison at only about 20,000, in fragmented herds that all need active conservation.

  Other purebred herds live on public lands. Wind Cave National Park in South Dakota, Blue Mounds State Park in Minnesota and Grasslands National Park in Saskatchewan hold important herds. In 2015, genetic testing of mitochondrial and nuclear DNA identified a purebred herd of 350 animals in the Henry Mountains of southern Utah. That study also found the herd free of brucellosis, a bacterial disease that arrived in North America with domestic cattle.

  The wood bison, the generally more northern of the two North American subspecies, is endangered in Canada and threatened in the United States. Beefalo ranchers have made numerous attempts to have it removed entirely from the Endangered Species List. The other subspecies is the Plains bison.

  Disease is a constant worry. In American bison, malignant catarrhal fever is a main illness, and brucellosis is a serious concern in the Yellowstone herd. On Antelope Island, bison are regularly inoculated against brucellosis, parasites, Clostridium infection, infectious bovine rhinotracheitis and bovine vibriosis. European bison suffer mainly from foot-and-mouth disease and balanoposthitis.

  The wisent has its own improbable refuge. The Chernobyl Exclusion Zone has become a kind of wildlife preserve for wisent and other rare megafauna, including Przewalski's horse. Poaching has become a threat there in the 21st century. Inbreeding in a small population causes genetic defects and weakens immunity. Male wisent also face posthitis, an incurable and often fatal disease that is seen as a large threat to the remaining wild population.

  2729858889

• 8. Fences and Farms

  ›

  In Montana, free-ranging bison on public land are legally shot. The stated reasons are disease transmission to cattle and damage to public property. Across most of their historical range, landowners have sought limits on free-roaming bison, and herds on private land must be fenced. In 2013, Montana passed legislative measures concerning bison. Native American tribes opposed them because they impinged on sovereign tribal rights. Steve Bullock, then the state's governor, vetoed three such bills. The question remains contested between Native American tribes and private landowners.

  The earliest plausible account of captive bison comes from the zoo at Tenochtitlan, the Aztec capital. It held an animal the Spaniards called "the Mexican bull". In 1552, Francisco Lopez de Gomara described Plains Indians herding and leading bison like cattle, in his controversial book Historia general de las Indias. Gomara never visited the Americas, and he likely misread early accounts through the familiar herding customs of the Old World.

  Today, most of the world's bison are raised for meat or fur clothing, and increasingly for hides and wool products. The meat tastes much like beef but has less fat and cholesterol and more protein. A market even exists for kosher bison meat. Beefalo are advertised as a bison-cattle hybrid, but many beefalo, including the original pedigree founding herd, have no detectable bison ancestry.

  In the 1990s, Ted Turner found limited success selling high-quality cuts such as bison steaks and tenderloin to restaurants. The trouble was the rest of the animal. About 400 pounds of usable meat per bison suits hamburger and hot dogs, a market described as almost nonexistent. In 2003, the United States Department of Agriculture bought $10 million worth of frozen overstock to save the industry, which later recovered through better consumer marketing. Ted's Montana Grill added bison to its menus, and Ruby Tuesday first offered it in 2005.

  Canadian bison farming began commercially in the mid-1980s. The first census, in 1996, counted 45,235 bison on 745 farms. By the 2006 census, the count had grown to 195,728 bison on 1,898 farms. Several pet food companies, among them Natural Balance Pet Foods, Freshpet and Blue Buffalo, use bison as a red meat alternative in dog food.

  The largest bison population on U.S. public land, an estimated 4,900 animals in July 2015, lives in Yellowstone National Park. Visitors there suffered 33 bison-related injuries during 1983-1985, which led the park to start education campaigns. After years of success, five injuries occurred in 2015, because visitors did not keep the required distance of 75 ft (23 m) while hiking or taking pictures.

  4042757880