The largest terrestrial animal in North America, bison once roamed in herds numbering in the millions dominating prairie and forest ecosystems. Now reduced to a fraction of their current range and population, bison survive mainly in conservation herds. Yellowstone is the only place in the lower 48 states to have a continuously free-ranging bison population since prehistoric times. In the 1800s, market hunting and the US Army nearly caused the extinction of the bison. By 1902, poachers reduced Yellowstone’s herd to about two dozen animals. The US Army, which administered Yellowstone at the beginning of the 20th century, protected these bison from further poaching. Bison from private herds were used to establish a herd in northern Yellowstone. For decades, bison numbers were reduced due to the belief that they, along with elk and pronghorn, were over-grazing the park. By 1968, herd reductions of bison ceased. Reductions began again in the 2000s due to increasing numbers and litigation about migration into Montana. An estimated 20 to 30 million bison once roamed in North America from the Appalachians to the Rockies, and from the Gulf Coast to Alaska. Habitat loss and unregulated hunting reduced the population to under 2,000 animals by 1889. Today, approximately 500,000 bison live across North America, mostly on farms and ranches. Fewer than 30,000 wild bison live in conservation herds in national and state parks and reserves. Today’s bison ancestors appeared on the planet 5-10 million years ago (homo sapiens have only been dated back to 200,000 years) after splitting with the bovine lineage that eventually became the beef cow. Bison lived amongst mammoths, sabertooth tigers, and giant sloths. Today’s bison are much smaller than their larger ancestors and their main natural predators are wolves and mountain lions. Bison live in large numbers so as to provide safety and create more random harvesting by predators. They circle up when predators are present and push the calves into the center of the group. They are extremely aggressive animals using their horns, heavy heads, kicking action of their hooves and their thick skin to fight off attacks. We have found coyote skeletons with half of the skull sheared off, presumably by bison attacking them to protect the herd, and have never lost a bison of any age to a coyote attack.

Bison are the largest land-dwelling mammal in North America. Males (2,000 lbs/900 kg) are larger than females (1,100 lbs/500 kg) and both are generally dark chocolate-brown in color, with long hair on their forelegs, head, and shoulders, but short, dense hair (1 in/3 cm) on their flanks and hindquarters. Calves of the year are born after 9 to 9-½ months of gestation. They are reddish-tan at birth and begin turning brown after 2-½ months. Both sexes have relatively short horns that curve upward, with males averaging slightly longer than those of adult females. All bison have a protruding shoulder hump. Large shoulder and neck muscles allow bison to swing their heads from side-to-side to clear snow from foraging patches, unlike other ungulates that scrape snow away with their front feet. Bison are agile, strong swimmers, and can run 35 miles per hour (55 kph). They can jump over objects about 5 feet (1.5 m) high and have excellent hearing, vision, and sense of smell.

At one time, bison were widespread from Alaska to northern Mexico, but the current range occupied by conservation herds has diminished to one percent of its original status. Today, herds can be found in parts of Alberta, British Columbia, Manitoba, Northwest Territories, Ontario, and Saskatchewan in Canada, as well as Arizona, California, Idaho, Montana, South Dakota, Utah, Alaska and possibly Texas in the United States. Modern conservation herds are substantially fragmented. Originally, bison were found primarily in the grasslands and prairie of North America. Today, bison distribution is greatly limited due to population decline and their movements are greatly regulated. Within the national parks, bison are found at all elevations. Yellowstone bison historically occupied approximately 7,720 square miles (20,000 km2) in the headwaters of the Yellowstone and Madison rivers. Today, this range is primarily restricted to Yellowstone National Park and some adjacent areas of Montana. The bison population lives and breeds in the central and northern regions of the park. The northern breeding herd congregates in the Lamar Valley and on adjacent plateaus for the breeding season. During the remainder of the year, these bison use grasslands, wet meadows, and sage-steppe habitats in the Yellowstone River drainage, which extends 62 miles (100 km) between Cooke City and the Paradise Valley north of Gardiner, Montana. The northern range is drier and warmer than the rest of the park, and generally has shallower snow than in the interior of the park. The central breeding herd occupies the central plateau of the park, from the Pelican and Hayden valleys with a maximum elevation of 7,875 feet (2,400 m) in the east to the lower-elevation and thermally- influenced Madison headwaters area in the west. Winters are often severe, with deep snows and temperatures reaching -44°F (-42°C). This area contains a high proportion of moist meadows composed of grasses, sedges, and willows, with upland grasses in drier areas. Bison from the central herd congregate in the Hayden Valley for breeding. Most of these bison move among the Madison, Fire-hole, Hayden, and Pelican valleys during the rest of the year. However, increasing numbers of bison are traveling to the northern portion of the park and mixing with the northern herd. Some of these bison do not return to the Hayden Valley for the subsequent breeding season, and instead breed and rear young in their new range.

The largest terrestrial animals in North America, bison are characterized by a hump over the front shoulders and slimmer hindquarters. Both male and female bison have a single set of short, sharply pointed, hollow horns that curve outward and up from the sides of the massive head. The head, neck, forelegs, and front parts of the body have a thick coat of long, dark hair. The adult bull adds to this thick coat with a black beard about one foot long. The rear part of the body is covered with much shorter hair. The shaggy head is the most heavily insulated part of their body, which has adapted as such to withstand blizzards as the animal stands facing into the wind. Heavy coats are shed in the spring as the animals roll to loosen the hair, which falls off in gobs.

Bison are usually found in bands arranged by sex, age, season, and habitat. Older bulls are often solitary. Both cows and bulls live in a dominance hierarchy, which is established early in life. Most of the year, females with young form small bands, and immature bulls may stay with them. The bands may congregate in large herds in the spring or fall to search for food or water. Mature males have their own groups that may reach up to 30 individuals. Grazing takes place during several periods each day and is conducted in loose groups. When bison travel, they form a line. Bison are also adept swimmers, able to cross streams and rivers without difficulty.

Most other ungulates of the Greater Yellowstone Ecosystem follow the “green wave” of sprouting plants and grasses during spring because young plants are highly nutritious. Bison begin spring by leaving winter ranges in sync with the green wave but let it pass them by as they migrate and graze, not reaching summer ranges until weeks after green-up. Bison can move out-of-sync with forage green-up because they engineer the ecosystem. Rather than just moving to find the best foods, bison create high-quality foods by how they move and graze. When bison let the green wave pass them by, they spend their time returning to graze the same areas repeatedly at high intensity. The behavior keeps plants growing, although the plants never appear more than a few inches tall, and allows bison to keep getting highly nutritious foods. In winter, bison will move from their summer ranges to lower elevation as snow accumulates and dense snowpack develops. Bison migrate up to 70 miles between summer and winter ranges. Most animals travel about 1,000 miles over the course of the year by repeatedly leaving and returning to the same areas. This means bison travel a greater distance than any other ungulate in the Greater Yellowstone Ecosystem.

Before 1800, bison roamed the Great Plains in vast numbers; estimates range from 30 to 100 million. While most were west of the Mississippi ranging to the Rocky Mountains, some were found east of the river in forested areas. Bison were once a major source of meat and hides in the United States; they formed the basis of the economy for a number of Native American tribes. However, by the 1890s, there were fewer than 1,000 of these animals left on the continent. The U.S. government slaughtered many bison in an organized effort to destroy the livelihood of Plains Indians. Conservation threats to American bison include habitat loss, hybridization in managed populations and low genetic diversity among individual herds. While bison have made a comeback since their population was devastated over 100 years ago, the species is still heavily dependent on conservation action for survival. Of the remaining American bison population, approximately 500,000 individuals are managed as livestock by private commercial ventures, while conservation herds are comprised of around 30,000 individuals. According to IUCN Red List guidelines, commercial herds are not eligible for inclusion in the IUCN’s scope of wildlife conservation, so the IUCN status of bison reflects only those found in the 65 known free-ranging or partially-free-ranging herds. Buffalo are Old World animals (Cape buffalo, water buffalo) and bison are only found in Europe and the United States. The taxonomy of bison has been under debate, and through DNA analysis it was determined that the two American subspecies—plains bison (Bos bison bison) and wood bison (Bos bison athabascae) are the same species. Many biologists have seen evidence that supports including the European bison, Bos bonasus, as the same species as the American bison. If proven true, this would have major conservation implications. Yellowstone has played a key role in the conservation of wild bison in North America. If fact, we’ve been so successful that we now face the challenge of helping to manage a rapidly growing population of migratory bison that frequently roam beyond our borders onto private land and land managed by other agencies. Read more about the history of bison management and the challenges of maintaining a wild, migratory population of bison in a modern landscape.

• Bison have an excellent sense of hearing and smell, but cannot see very well, so an entire herd can stampede if it is startled. Bison have cloven hoofs, and can reach speeds of 30 miles per hour (48 kilometers per hour).
  
• Bison shed their heavy winter coats in the spring, rolling on the ground to loosen the hair, which falls off in gobs.

A mature bull can reach 5.5 to 6.5 feet (1.9 meters) high at the hump and nine to 12.5 feet (2.7 to 3.8 meters) in length. Females are normally smaller, at 7 to 10 feet in length (2.2 to 3.2 meters) and 5 feet high at the hump (1.5 meters). Bison can weigh 1,800 to 2,400 pounds (816 to 1,088 kilograms). Male (bull) weighs up to 2,000 pounds, female (cow) weighs up to 1,000 pounds. May live 12–15 years, a few live as long as 20 years. Feed primarily on grasses and sedges. Mate in late July through August; give birth to one calf in late April or May. Can be aggressive, are agile, and can run up to 30 miles per hour. Bison are mostly active during the day and at dusk, but may be active through the night. They are social animals that often form herds, which appear to be directed by older females. Group sizes average about 20 bison during winter, but increase in summer to an average of about 200, with a maximum of about 1,000 during the breeding season (known as the rut) in July and August. Bison are sexually mature at age two. Although female bison may breed at these younger ages, older males (>7 years) participate in most of the breeding. During the rut mature males display their dominance by bellowing, wallowing, and engaging in fights with other bulls. The winners earn the right to mate with receptive females. Once a bull has found a female who is close to estrus, he will stay by her side until she is ready to mate. Then he moves on to another female. Following courtship, mature males separate and spend the rest of the year alone or in small groups. Group sizes decrease through autumn and into winter, reaching their lowest level of the year during March and April. Bison are grazing animals that feed on native prairie grasses mostly. They have a strong herd instinct and tend to graze and travel in large groups. Their mob-like behavior creates a heavy hoof action and substantial manure spreading which is very good for the rejuvenation of prairie and pasture grasses and an integral part of the ecology of open grassland soils. They have a very thick winter coat that sheds away to a slick seal-like undercoat during the summer months. They manage their hair growth, shedding and conditioning by creating wallows, which are large dust baths that they will roll around in. Wallows usually then remain free of vegetation since they are used often and by each animal. All bison are born orange and turn brown just about the time that they are old enough to survive without nursing milk from their mother. All males are called bulls and all females are called cows, and there is no difference between a bison and an American buffalo. The first explorers called them buffalo, not really knowing exactly what they were with the word le boeuf meaning cow, ox or beef in French helped to further confuse the naming. The only true buffalo that exist in the world are African Cape Buffalo and Water Buffalo, and water buffalo number in the hundreds of millions worldwide and are recently being introduced into human and pet foods in the US as “buffalo” further complicating things. Bison are now the U.S. National Mammal as of 2016. Bison have humps in order to anchor their unusually large heads. The large head is used as a snow plow to move snow drifts away from grass that they can smell 3-4 feet down under the snow. Their hair coat can be so thick as to create a snow and ice insulation on their backs that does not melt. They have very large guts (called rumen) that are capable of holding a 3 day quantity of food while it slowly digests and crates massive amounts of heat (like a compost pile) that keeps the animal warm during the coldest northern winters in the upper reaches of Canada and Alaska. Bison do not need or use any shelter.

Bison are year round grazers. They feed primarily on grasses, but will also consume flowering plants, lichens and woody plant leaves depending upon availability. To find grass in winter they sweep their heads from side to side to clear the snow. On average, bison ingest 1.6 percent of their body mass per day of dry vegetation. Bison require water every day as well. At the Smithsonian National Zoo, bison consume a diet of orchard grass hay and herbivore pellets. Yellowstone bison feed primarily on grasses, sedges, and other grass-like plants (more than 90% of their diets) in open grassland and meadow communities throughout the year. They also eat forbs (weeds and herbaceous, broad-leafed plants) and browse (the leaves, stems, and twigs of woody plants) through the year, but those usually comprise less than 5% of the diet. They typically forage for 9 to 11 hours daily. Bison are ruminants with a multiple-chambered stomach that includes microorganisms such as bacteria and protozoa to enable them to effectively digest plant material. Bison alternate between eating and ruminating, which is regurgitating partially digested food and chewing it again, to allow microorganisms to further break down plant material into volatile fatty acids and other compounds. Their large digestive tract allows them to digest lower quality foods with greater efficiency than other ungulates such as cattle, deer, or elk. All ruminant animals harvest and consume large quantities of forage in order to feed a wide variety of microbial “bugs” in their gut consisting of fungi, bacteria, protozoa and a variety of other microorganisms. The bugs then break down and digest forages in the first, second and third stomachs. The ruminant then digests this large assortment of bugs in the fourth chamber of their stomach. They ultimately digest this massive quantity of microorganisms and survive off these animal and plant proteins, meaning that ruminant animals are not actually vegetarians. In fact, there are no mammals that are actually vegetarians, despite the fact that they harvest plant materials as a source of food for these “bugs”. The “bugs” that feed off the plant material that the bison harvests to feed them are passed from adult to calf through saliva, whether it be licking on each other, or feeding in the same spot with saliva that drips out of the adult and is then consumed by the calf grazing side-by-side to its mother. This is one reason why it takes about 6 months for a calf to develop its own rumen capable of sustaining a whole biological grass-consuming factory in its stomach, and requires the animal proteins found in the milk in the meantime. 

Bison communicate through grunts to maintain contact with each other, and will snort to warn intruders. Male bison display their fitness by charging and butting heads with other bulls. They also bellow hoarsely, lower their heads, and paw the earth defiantly, but they rarely fight to the death. They have an excellent sense of hearing and smell, but cannot see very well, so an entire herd can stampede if it is startled. Bison have cloven hoofs, and can reach speeds of 30 miles per hour. Wolves and grizzly bears are the only large predators of adult bison. Dead bison provide an important source of food for scavengers and other carnivores. Bison will rub against trees, rocks, or in dirt wallows in an attempt to get rid of insect pests. Birds such as the magpie perch on a bison to feed on insects in its coat. The cowbird will also follow close behind a bison, feeding on insects disturbed by its steps. Bison are wild animals and will remain that way for a very long time. It takes 8,000-10,000 years to domesticate an animal, and not all animal species will allow themselves to be domesticated, such as the zebra. It is only because of modern technology that we are able to keep them fenced in using special wildlife fencing that is much taller than cattle fencing and quite expensive. The corral is more than twice as fortified as one that would be used for cattle and we have built it so that the animals cannot do damage to the workers or each other. As mentioned, they are very aggressive and can be very dangerous, and they never become tame or friendly. Bison can run 40 miles per hour, use their horns as weapons and can jump 5 feet from a standing position. Thomas Jefferson once tried to keep a bison at Monticello using 18th-century fencing technology and it lasted about 3 hours before the animal busted out and was gone. There are three types of modern bison worldwide. One life in Northern Europe is quite rare, smaller in stature, and called a wisent. The woods bison lives mostly in Canada and has a very small population worldwide. The most common bison is the plains bison which exists in both the US and Canada naturally. All bison at Virginia Bison Co. are plains bison. Bison are capable of breeding with beef cattle, and while this is not practiced anymore, it was a common way to build a small bison herd back before the 1970’s when bison were much more rare. One bison bull could be bred to beef cows and produce a 50% bison-cattle hybrid (called cattalo or beefalo), then that 50% hybrid could be bred to another bison to get a 75%, and after a few more breedings like this the farmer ended up with mostly bison genetics. Cross breeding bison and cattle only produces a difficult animal to handle without providing any of the low-fat and low cholesterol meat that you get from bison. This practice of cross-breeding for the past 100 years has resulted in a small percentage of cattle genetics that many bison carry today.

Females are sexually mature at 2 to 3 years of age. While males reach maturity around age three, they generally do not breed until six years of age. Mating season runs from late June through September, and gestation can last around 285 days. Breeding bulls will protect their chosen females and, with little time to eat, may lose more than 200 pounds during the breeding season. A single yellow-red calf will be born away from the herd in a secluded area. After a few days, the calf can keep up with the herd and follows its mother until the following spring. Calves are nursed for seven to eight months and are fully weaned by the end of the first year. Bison are seasonal producers (unlike cattle and sheep which can breed any month of the year) and go into a breeding season, called rutting, in mid-summer that usually ends around August. Any cows that do not get pregnant but are in good body condition can remain fertile into the early fall, so that sometimes we get calves born the following fall instead of spring like normal. Spring is natures regular cycle for calves to be born as that is when the grass is plentiful for cows to produce milk. Bison are much like deer and elk in their natural breeding and feeding cycles. Bison produce a small quantity of milk that is very thick, rich and sticky compared with cattle milk. It is impossible to milk bison due to the danger and stress on the cow and the quantity of milk produced makes this uneconomical to even consider. Buffalo mozzarella is made from water buffalo, but not bison. Due to the seasonality of bison breeding, the meats are all harvested in the fall and sold through the year frozen. There are feedlots around the country attempting to provide year-round fresh bison meat, but they are achieving this by harvesting some animals early, some animals late, taking advantage of the longer growth cycle of female bison in the feedlot, and playing feedlot grain mixture tricks. None of this is very cost effective and those high costs are being passed along to the consumer. Virginia Bison Co. has opted to maintain a natural seasonal flow in production and to have all meats flash frozen at the time of harvesting to be sold the following months frozen.

Founder Number: 73 |  Sources: 3 | Years: 1963, 1983 | Census: 875 | He: 0.578 | Number of Alleles: 4.56 | Cluster: A

Founder Number: 21 |Sources: 4 |Years: 1913–1952 |Census: 380 |He: 0.595 |Number of Alleles: 4.40 |Cluster: A

Founder Number: 32 |Sources: 2 |Years: 1948, 1964 |Census: 600 |He: 0.561 |Number of Alleles: 4.08 |Cluster: —

Founder Number: 50 | Sources: 7 |Years: 1908–1984 |Census: 350 |He: 0.647 |Number of Alleles: 5.00 |Cluster: 6

Founder Number: 33 |Sources: 3 |Years: 1996–1998 |Census: 63 |He: 0.639 |Number of Alleles: 4.96 |Cluster: —

Founder Number: 19 |Sources: 5 |Years: 1919–1997 |Census: 35 |He: 0.566 |Number of Alleles: 3.62 |Cluster: A

Founder Number: 20 |Sources: 1 |Years: 1962 |Census: 312 |He: 0.522 |Number of Alleles: 3.56 |Cluster: A

Founder Number: 29 |Sources: 1 |Years: 1956 |Census: 371 |He: 0.582 |Number of Alleles: 4.30 |Cluster: A

Founder Number: 17 | Sources: 2 |Years: 1907, 1940 |Census: 600 |He: 0.652 |Number of Alleles: 4.85 |Cluster: 2

Founder Number: 20 |Sources: 2 |Years: 1913, 1916 |Census: 350 |He: 0.591 |Number of Alleles: 4.16 |Cluster: 1Provide the answer to the question here.

Founder Number: 46a |Sources: 3 |Years: 1902 |Census: 3000 |He: 0.625 |Number of Alleles: 4.84 |Cluster: 7