American bison

The American bison (*Bison bison*) is a massive mammal native to North America.

It is often called the American buffalo, though this name can be confusing. In American English, both terms are considered correct. However, in British English, the word buffalo refers to the African buffalo or the water buffalo. The bison is the national mammal of the United States.

These animals are vital to the ecology of the continent. They once occupied a massive area called the great bison belt. This grassland stretched from Alaska down to the Gulf of Mexico. It reached from the Atlantic Seaboard to the west. This historical range included areas like New York and Georgia.

Biologists describe two main subspecies of the American bison. The first is the plains bison (*B. b. bison*). It is the smaller of the two and has a rounded hump.

The second is the wood bison (*B. b. athabascae*). This subspecies is larger and has a taller, square hump. The wood bison is one of the largest wild bovids in the world. It is surpassed in size only by the Asian gaur. Some scientists have suggested splitting the plains bison into northern and southern groups. However, this idea currently has limited scientific support.

Bison are impressive in their physical scale and strength. They are the heaviest and longest land animals in North America. They are also the second tallest, following only the moose.

Males are much larger and heavier than females. A male plains bison can reach a weight of 1,000 kilograms. Wood bison can be even heavier. Their heights at the withers can reach 2 meters. Both sexes possess short, curved horns. These horns can grow up to 30 centimeters long. Bison use these horns to defend themselves or fight for status in the herd.

As herbivores, bison follow a strict daily routine to survive. They graze on grasses and sedges found in prairies and river valleys.

Their day is split into two-hour cycles. They spend these periods grazing, resting, and chewing cud. After resting, they move to a new location to feed again. This constant movement helps them manage the vast grasslands. For the first two months of life, calves have a lighter color than adults. While extremely rare, some white bison have also been seen.

Bison have a deep evolutionary history spanning millions of years. They first appeared in Asia during the Early Pleistocene, about 2.6 million years ago. They migrated to North America between 195,000 and 135,000 years ago. They descended from the Siberian steppe bison by traveling through Beringia.

Once in North America, they evolved into many different species. One was the massive long-horned bison. Modern bison likely evolved from *Bison antiquus*. The arrival of bison in North America was so impactful that it defines the Rancholabrean faunal stage. This shows how much they shaped the environment.

The population of the American bison faced a near-extinction event. In the late 18th century, there were an estimated 60 million bison. By 1889, the population had crashed to only 541 animals. This decline was caused by commercial hunting and slaughter. It was also caused by diseases from domestic cattle. This period was part of the subjugation of Native Americans. The bison was a vital resource for Indigenous peoples of the Great Plains. They relied on the animals for food, clothing, and shelter. They also used horns and bones to create tools.

Today, the bison is a symbol of successful conservation. Recovery efforts in the mid-20th century helped the numbers grow. As of March 2019, there were roughly 31,000 wild bison. They now roam freely in parts of the United States, Canada, and Mexico.

Some populations are kept in national parks or conservation herds. Others live in private commercial herds. Some bison have even been introduced to Russia in the Ingilor Nature Park. In 2014, U.S. Tribes and Canadian First Nations signed a treaty to help restore bison populations. This marked the first such treaty in nearly 150 years.