Bison, buffalo, and tatanka are names given to the massive animal with a huge hump covered with long wool, a dense layer of hair on the forehead half covering the eyes, short legs, and squat body.  In appearance, it seems that this animal would be vulnerable to nature and predators, yet it has survived for centuries.  Why?  Because it has a number of unique characteristics which helped it adapt to and survive in the terrain and climate of the Great Plains while at the same time benefiting the environment.         

The large body (bulls weigh 1800 pounds of more and stand as high as six feet, cows weigh as much as 1000 pounds and stand five feet high) has distinctive features. The large flat-faced head has a double layer of bone to protect the brain and act as a shock absorber. Bison horns are rounded and curve upward. As the bison grows older, the horns get more curved, making it difficult to win while fighting and allowing younger animals to become dominant and take over the herd.  Bison eyes are set far apart and appear brown during the day and reflect light at night, emitting a reddish glow. Bison are somewhat dim-sighted. Although the ears are buried in the hair, bison have excellent hearing and an even better developed sense of smell. They can hear and smell an enemy up to three miles away. Bison have no upper front teeth but have a heavy blackish tongue which helps to grab grass and put it into the mouth where the bottom teeth grind it against the upper back teeth. The grass is swallowed whole and digested in the four-chambered stomach. Behind the head is the hump made of a mass of bone, gristle, and muscle to support the large head. The hump is actually an elongated extension of the vertebrae in the spine.  The front legs are positioned deep and down while the back legs are cut high in the flanks. This allows the bison to run fast and swim easily. The tail is short with a tufted tip. Because bison can only feel the flies bothering them on the rear, the tail does not have to be as long as other animals.  It is also used as a warning; it stands straight up when a bison is agitated and about to charge.

Bison have body adaptations which help them escape prairie fires and predators. There is an extra rib which gives them more chest capacity for breathing when running. The long, heavy tongue hangs out when running to open the windpipe for better breathing. This gives bison the capacity to run as fast as 35 miles per hour when stampeding.  They do not charge wildly, but, led by a mature cow, head for a protected destination, a stand of trees, or secluded meadow. The positioning of the legs allows bison to stop and wheel about on either the front or the back legs. They are also able to leap over obstacles such as fences five to six feet high while on the run or while standing still by the obstacle.  The natural noise of bison is quiet, peaceful grunts except during the rut.

The grazing habits of bison help them survive. They do not overeat, but rather eat only what they need and then quit. Because their food stays in their intestines 3-5 hours longer than cattle, bison are better able to get the nutritional value out of the vegetation eaten. Bison’s’ nutrient requirement is only 4-5% protein so they are able to subsist on the dry, short grasses further west in the Dakotas, Wyoming, and Montana.  Bison have a big “eat” in the morning and another one in late afternoon about sundown. During the day, they lie down on the top of a hill to get the air movement and digest their food.  Bison also eat willow tree leaves which are a natural wormer for them. 

Bison are well adapted to the extreme shifts in temperatures and blizzards of the plains. Bison’s’ hides are thick but porous with an elastic-like feature. This allows bison to sweat and remain cool in the summer, yet warm in the winter. A layer of fat between the meat and hide acts as extra insulation to a bison’s body. In late fall and early winter, bison develop a rich, full, dark brown coat in preparation for coming cold. Bison are double protected as this brown wooly under fur is covered by a layer of coarse guard hair which helps the snow blow off  the bison’s’ bodies. Both layers are shed in late winter or early spring into mid-summer. During very cold weather, bison’s’ metabolism slows down, lowering their nutrition requirements so they need less food during winter. Bison feed on exposed grass, clipping it down to near the level of snow. In deeper snow, bison use their heads and horns to swing from side to side pushing snow away and then shove deeper with their noses to clear a trench down to the grass. Using this method, bison can feed in snow four feet deep. One can tell if the winter was snowy or not by the beard. If the snow was deep, the beard is nearly worn off from pushing aside snow. During severe blizzards, they face into the wind which keeps snow and ice blown off of their noses, thus preventing suffocation.

The natural healing process helps bison. If a bison suffers a broken leg, he will lie down and rest until the leg is healed. If cut, bison do not get infection nor will insects bother the injury.    

The reproduction process of bison also aids in survival of the species.  There is a natural breeding cycle called the rut beginning as early as the end of June and continuing into September. This allows the bulls to be with the cows year around without the risk of getting bred at any time throughout the year. The calves, born in late April to early May when the first spring lush growth of grass occurs, are able to run about immediately after birth. Cows have the ability to delay calving for up to three days should there be a late winter storm or rainy weather.  When food is abundant, cows have a calf every year; if food is scarce and cows must expend a great amount of energy just to survive, calves are often born every other year.  When calves are born, they are a reddish brown which blends with the old prairie grasses still standing. This camouflages the babies from predators which can only see in black and white so the calf appears gray. Calves are born with a heavy coat which protects them if a late storm occurs. They keep this coat all their first year; it gets thicker and acts as insulation and protects the calves from flies. 

Bison are family oriented and have a herd instinct which protects them. From late fall to spring, bison separate into bull groups (5 to 20 animals) and cow/calf herds (20 to 70 animals), sometimes intermingling, sometimes splitting apart.  However, bulls do separate themselves from the main herd during the calving season.  Cows keep their calves near them nearly all the time, and the cow/calf herd consists of the cows and their offspring from the past several years. 

Dominance rules in the herds and enables survival.  Cows fight each other all year around, and each herd has a lead cow which dominates and is experienced in knowing the whereabouts of good grass, a water supply, and salt licks. When predators approach, the mothers gather the calves in the middle of the herd, and they and other older bison face outward to take on predators that are then limited to preying on the old and injured.  Bulls fight only during the rutting season as they try to establish dominance in the herd and possession of cows. During the rest of the year, the bulls mingle together as a herd.

Bison also have characteristics which have been beneficial to the environment in which they live. Hair, filled with seeds, is shed and this helps scatter those seeds.  Bison have sharp hooves which poke into the ground to aerate it, break the crust so rain can be absorbed, push seeds into the soil, and chop up vegetable matter to return to the soil as organic matter. Herds generally do not walk in a trail following each other, but rather cover a wide area which doesn’t pack the soil. 

The environment is also adapted to the bison’s needs. They inhabit the same locale as prairie dogs, foxes, and coyotes. Prairie dogs supply natural minerals that bison like to lick.  The soil from the mounds and dens is soft and provides a place to roll in the dirt which may become a wallow or indentation in the ground. This rolling is a way to scratch their backs and sides and rub off the lice. In the spring, this rolling loosens the hair and in the summer gets dirt on their hides to keep off flies and insects.

Because of certain characteristics, bison have been able to survive in and help their natural surroundings.  The structure of the body and internal body structures and organs have given bison the capabilities to live and survive under adverse and dangerous conditions. The reproductive cycle and herd instinct have enabled bison to increase in numbers and protect the young.  The bison is able to utilize as well as benefit the land.  The many features of bison assure its survival in the natural environment of the Great Plains.

Please click on the following slideshow for pictures:

  Survival Characteristics of the Bison