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American Bison

(Bison bison) North America's Largest Land Animal
bisonThe American bison, also known as the American buffalo, is considered North America's largest land animal. Bison, which nearly went extinct in the 19th century, have rebounded in recent decades. They are herbivores who live in mixed-grass prairie, but are also found in short and tallgrass prairie.
For the first several months of life, bison are dark orange/brown in color but as they grow older, their color changes to dark brown. Bison, like many large animals, grow quickly and may weigh 400 pounds or more by their first birthday. An adult male can weigh up to 2,000 pounds. Both male and female bison have short black horns that grow out from the sides of the head then curve up in, ending with pointed tips.
Bison usually live in herds of four to 20, with males and females remaining separate except during the breeding season. Occasionally small herds cluster together to form large herds of several thousand that will stampede if frightened. The bison's large size, however, does not indicate a lack of speed. When galloping, they can reach speeds of 32 miles per hour.

Bison as a Symbol
Wyoming State flag Interior Department logo

Bison have been an important icon throughout history. From prehistoric cave drawings to modern currency, the image of the bison has long symbolized power and freedom. Bison images have served as corporate logos, mascots and as prominent elements on official government seals. Bison play a crucial role in many Native American societies. They regard these majestic animals with respect and reverence and, at one time, relied on bison for their livelihood.

Back from the Brink: Saving the Bison
The American bison population is estimated to have been between 30 and 60 million in 1830. By 1889, the vast herds that once roamed the prairies of the United States had been reduced to fewer than 1,000 animals. Bison were hunted to near extinction by settlers for sport, hides, and meat and to destroy the food supply of Native Americans. In 1889, William T. Hornaday, then-superintendent of the National Zoo, summed up the situation. "The wild buffalo is practically gone forever, and in a few more years...nothing will remain of him save his old, well-worn trails along the water-courses." However, with protection, the species has not disappeared and, in fact, has proven to be resilient.
Did You Know?
Bison horns are actually bone covered in a material similar to our own fingernails, called keratin.
When North America was first settled, some 50 million bison roamed the continent!

Former Smithsonian Secretary, S.P. Langley, advocated the establishment of the National Zoo to serve as a "refuge for vanishing races of the continent." In 1889 Congress obliged Langley with the establishment of the National Zoo. In 1891, several bison, as well as other North American mammals, were moved from the National Mall, to become the Zoo's first residents. Thanks to conservation efforts, zoo-breeding and reintroduction programs, bison have made a dramatic comeback. Today there are an estimated 200,000 bison in national parks, wildlife refuges, and on private ranches.
Climatic conditions on the prairies can be harsh, ranging from bitter cold temperatures and winds in winter, to sizzling hot and dry conditions in summer. American bison behaviors change to withstand these seasonal extremes in the heart of their North American home.

Summer: Male bison, also known as bulls, display their immense power and strength in mid-summer, when the breeding season begins. They advertise their strength to potential mates and competitors through a bellowing mating call and ritualized displays.
They paw the ground, gouge hunks of sod out of the earth, make rumbling guttural calls and roll in bare patches of soil. It is also not uncommont to find two bulls "smashing heads." Competing males will sometimes engage in fierce, head-to-head combat. Their skulls are padded with thick flesh to absorb the impact of the full-force collisions. Dominant males court receptive females for several hours, sometimes days, until they are ready to mate.

bisonFall: After breeding season passes, bison break into smaller herds. The groups are composed either of females, "cows," and their calves, or all males. Some males, however, remain solitary. Mature bulls generally live away from the rest of the herd, recuperating from the rigors of the breeding season.
As the temperatures cool and the days shorten, bison grow their characteristic thick, winter coats.

Winter: Like some other large mammals, bison do not migrate to warmer climates or hibernate during winter conditions. Even when they are coated with snow on the outside, their thick insulating winter coats provide warmth on the inside. However, cold temperatures take a toll on the bison. Because it is difficult to find food under the deep snow, bison depend on stored fat to help them survive the harsh weather. Even so, it is a lack of food, not predators, that is the greatest threat to a full-grown bison.

Spring: As the snow melts and the ground thaws, the vegetation renews itself. Springtime also means new calves. Around mid-April to late May, after a pregnancy of about nine months, bison give birth to a single calf (twins are rare) weighing 30 to 65 pounds (15 to 30 kg). The nutrient-rich plants help the mothers produce ample amounts of milk for their growing calves. Mothers and calves travel together in small herds sometimes referred to as "maternity clubs." Calves remain under their mother's care for about a year. They must then prepare for the upcoming winter by themselves.

Key Terms and Common Behaviors
Chewing: Bison spend much of their time chewing cud. Cud is partially digested vegetation, previously swallowed and then regurgitated from the bison's rumen for further processing.

Rumen: A part of the stomach. Bacteria here break down tough grasses and plants.
Scratching: Rubbing and scratching facilitates the shedding of fur in spring and soothes insect bites.

Shedding: Bison lose their wooly winter coat as the weather turns warmer. While it may look ragged, shedding helps them stay cool. In spring, birds use bison hair to line their nests.

Wallowing: Bison roll in dust or mud to stay cool and keep insects away.

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