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American bison: the story on HearLore | HearLore
American bison
Bison first appeared in Asia during the Early Pleistocene, around 2.6 million years ago. They arrived in North America between 195,000 and 135,000 years ago, descending from the Siberian steppe bison that migrated through Beringia. This migration marked a major shift in the continent's ecology, defining the Rancholabrean faunal stage. Following their arrival, the species rapidly differentiated into new forms like Bison latifrons and Bison antiquus. Modern American bison evolved from Bison antiquus at the end of the Late Pleistocene. The population experienced demographic stability during the Middle Holocene before beginning a slow decline about 2,700 years before present.
Physical Characteristics And Subspecies
Two subspecies have been described: the plains bison and the wood bison. The plains bison is smaller with a more rounded hump, while the wood bison is larger with a taller, square hump. Male bison are significantly heavier than females, reaching weights up to 2,000 pounds for plains bison and over 2,500 pounds for wood bison. Head-rump lengths can reach 10 feet for males and 8 feet for females. Heights at the withers range from 5.5 to 6.5 feet. The wood bison is one of the largest wild bovids in the world, surpassed only by the Asian gaur. Among North American land animals, it is the heaviest and longest, standing second tallest after the moose. Their coats change seasonally, featuring shaggy dark-brown winter fur and lighter brown summer coats.
When did the American bison first appear in North America?
The American bison arrived in North America between 195,000 and 135,000 years ago. They descended from the Siberian steppe bison that migrated through Beringia during this period.
What are the physical differences between plains bison and wood bison?
Plains bison are smaller with a more rounded hump while wood bison are larger with a taller square hump. Male wood bison can reach weights over 2,500 pounds and stand as tall as 6.5 feet at the withers.
How many American bison existed before the population decline of the 18th century?
An estimated population of 60 million American bison existed in the late 18th century before declining sharply. Commercial hunting reduced numbers to just 541 animals by 1889.
Why do modern American bison populations lack genetic diversity?
Modern American bison populations lack genetic diversity due to a severe bottleneck where only around 100 individuals survived. Ranchers bred some bison with cattle to produce cattalo or beefalo which introduced cattle DNA into the gene pool.
When did conservation efforts begin to restore American bison numbers?
Conservation efforts began expanding in the mid-20th century leading to a resurgence to roughly 31,000 wild bison as of March 2019. The Nature Conservancy reintroduced bison to over a dozen nature preserves around the United States starting in recent decades.
The historical range circa 9000 BC spanned from Alaska south to the Gulf of Mexico and east to the Atlantic Seaboard. Sightings occurred as far north as New York and as far south as northern Florida. Some sources document sightings near Buffalo Ford on the Catawba River in North Carolina as late as 1750. These herds shaped the ecosystem through grazing patterns that influenced vegetation growth. Bison traces became the first thoroughfares of North America, followed by aboriginal peoples and later pioneers. Key routes included the Cumberland Gap and trails crossing the Ohio River. These paths were adopted by railroads, with Senator Thomas Hart Benton noting that bison paved the way to the Pacific. They lived in river valleys, prairies, and mountainous areas like Yellowstone Park at elevations above 8,000 feet.
The Near Extinction Event
An estimated population of 60 million existed in the late 18th century before declining sharply. Commercial hunting and slaughter in the 19th century reduced numbers to just 541 animals by 1889. This culling was part of a strategy to subjugate Native Americans who relied on the animal for food, hides, and tools. The bottleneck resulted in a founding population of around 100 individuals split into six herds. Five were managed by private ranchers while one survived in Yellowstone National Park. Each privately ranched herd had an effective population size of only 5 to 7 individuals. The Texas State Bison Herd started with five wild-caught calves in the mid-1880s. By 1929, Charles Goodnight died and the herd changed hands multiple times. Conservation efforts began expanding in the mid-20th century, leading to a resurgence to roughly 31,000 wild bison as of March 2019.
Genetic Bottlenecks And Hybridization
A major problem facing modern bison is a lack of genetic diversity due to the population bottleneck experienced during the near-extinction. During that period, ranchers bred some bison with cattle to produce cattalo or beefalo. Male domestic bulls crossed with bison cows produced offspring where only females were fertile. The proportion of cattle DNA measured in introgressed individuals ranges from 0.56 to 1.8 percent. Many claimed beefalo have no detectable bison ancestry. As of 2011, perhaps only 15,000 to 25,000 of the 500,000 existing bison were pure. DNA testing revealed that almost all examined herds contained cattle genes. The Texas State Bison Herd had an average heterozygosity level of 0.38 compared to 0.63 for Yellowstone. This low diversity led to a coefficient of inbreeding of 0.367. Simulations predicted a 99% chance of extinction within 41 years without outside intervention. Conservationists added new individuals to increase survival chances.
Cultural Significance To Indigenous Peoples
Indigenous peoples of the Great Plains maintained cultural and spiritual connections to the American bison for millennia. Buffalo hunting provided more than 150 uses including food, clothing, shelter, tools, and ceremonial items. For some tribes, bison are known as the first people. Crow chief Plenty Coups described the loss: When the buffalo went away the hearts of my people fell to the ground. Spiritual loss was rampant during the slaughter era. Sioux and other tribes participated in the Ghost Dance to boost morale. Among many tribes, especially Plains Indians, the animal is considered sacred. The birth of a white buffalo signals the return of White Buffalo Calf Woman. The Mandan and Hidatsa honored the White Buffalo Cow Society. The Inter Tribal Bison Council formed in 1990 comprises 56 tribes representing over 15,000 bison. These groups focus on reestablishing herds on tribal lands to promote culture and restore ecosystems.
Modern Conservation And Reintroduction Efforts
Population estimates in 2010 ranged from 400,000 to 500,000 with approximately 20,500 animals in conservation herds. The Nature Conservancy reintroduced bison to over a dozen nature preserves around the United States. In October 2016, they established their easternmost herd at Kankakee Sands in Indiana. U.S. Tribes and Canadian First Nations signed a treaty in 2014 to help restore bison populations. Genetically pure bison were reintroduced to the Janos Biosphere Reserve in northern Chihuahua in 2009. A second herd was formed in Maderas del Carmen in 2020. Since 2006, wood bison from Alberta's Elk Island National Park have been introduced to Yakutia, Russia. Yakutia's Red List officially registered the species in 2019. The 2020 Bison Conservation Initiative aims to translocate up to three bison every five to ten years between Department of Interior herds. Free-roaming herds exist in places like Yellowstone Park, Henry Mountains, Wind Cave National Park, and Fort Peck Indian Reservation.