American Bison (Bison bison)

American Bison: Icon of the American Plains

Majestic, powerful, and resilient, the American bison stands as a symbol of wilderness and conservation success after being brought back from the brink of extinction in the late 19th century.

Taxonomy and Classification

The American bison (Bison bison) belongs to the family Bovidae, which includes cattle, sheep, goats, and antelopes. Despite often being called "buffalo" in North America, true buffalo species (water buffalo and Cape buffalo) are native to Africa and Asia and are only distantly related to bison.

Scientists recognize two subspecies of American bison:

Plains bison (B. b. bison) - The more numerous subspecies historically found across the Great Plains
Wood bison (B. b. athabascae) - Larger and darker, native to boreal forest regions of Canada and Alaska

The American bison's closest living relative is the European bison or wisent (Bison bonasus), which faced its own near-extinction event but has since been reestablished in parts of Eastern Europe. Genetic studies suggest that bison are more closely related to yaks, cattle, and gaur than to true buffalo species.

Physical Characteristics

The American bison is the largest land mammal in North America, with a distinctive appearance that makes it instantly recognizable.

Size and Weight: Adult males (bulls) typically weigh 1,000-2,000 pounds (450-900 kg), though exceptional individuals may reach 2,500 pounds (1,134 kg). Females (cows) are smaller, usually weighing 800-1,200 pounds (360-540 kg). Body length ranges from 7-12 feet (2.1-3.7 m), with a shoulder height of 5-6.5 feet (1.5-2 m).

Distinctive Features:

Massive head with short, curved black horns present in both sexes
Pronounced shoulder hump formed by elongated vertebral spines
Dense, shaggy dark brown fur on the head, neck, shoulders, and front legs
Shorter, lighter fur on the rear portions of the body
Beard and mane, particularly prominent in males
Short tail with a tuft of hair at the end

Physical Adaptations: Bison possess several adaptations for their environment:

Massive head used as a snow plow in winter to access buried vegetation
Thick wool undercoat and long guard hairs for extreme cold protection
Muscular hump that supports the heavy head and provides attachment points for powerful neck muscles
Acute senses of smell and hearing to detect predators
Surprising speed and agility for their size, capable of sustained speeds of 35 mph (56 km/h)

Differences Between Subspecies: Wood bison differ from plains bison in several ways:

Generally larger and heavier
Darker fur coloration
Higher, more pronounced shoulder hump
Less hair on the forelegs, beard, and neck
Different habitat preferences and adaptations

The bison's distinctive appearance evolved in response to the harsh conditions of North American grasslands and winters, with their forward-heavy build allowing them to face into blizzards rather than turning away from them.

Range and Habitat

The historical range and current distribution of American bison represent one of the most dramatic changes in wildlife distribution in North American history.

Historical Range: Before European settlement, an estimated 30-60 million bison roamed across North America:

Plains bison occupied the Great Plains from Canada to Mexico and from the Rocky Mountains to the eastern woodlands
Wood bison inhabited boreal forests and mountain meadows in northwestern Canada and Alaska
Small populations extended into the eastern United States, Florida, and the desert Southwest
The core range covered approximately one-third of the North American continent

Current Distribution: Today, bison occupy less than 1% of their historical range:

Yellowstone National Park maintains the largest wild, free-ranging population
Other significant conservation herds exist in Badlands, Grand Teton, and Wind Cave National Parks
Wood bison populations in Wood Buffalo National Park and other Canadian preserves
Numerous private ranches and tribal lands across the western United States and Canada
Small reintroduced populations in various nature preserves and wildlife refuges

Habitat Preferences: Bison are adaptable to various environments:

Plains bison: Shortgrass, mixed-grass, and tallgrass prairies; open woodlands; shrublands
Wood bison: Boreal forests, aspen parklands, meadows, and muskeg areas
Both subspecies require open areas for grazing, access to water, and some shelter
Can survive in diverse climates from desert margins to subarctic regions

Habitat Requirements: Key elements of bison habitat include:

Abundant grasses and sedges that form the bulk of their diet
Water sources for drinking and wallowing
Open spaces that allow for herd movement and social interactions
Some topographic variation providing shelter from extreme weather
Sufficient space to accommodate seasonal movements and migrations

The restoration of bison to portions of their former range represents one of conservation's greatest challenges and opportunities, with efforts ongoing to establish new conservation herds in suitable habitats across North America.

Behavior and Social Structure

Bison are highly social animals with complex behaviors and interactions that evolved in the context of large herds on open grasslands.

Social Organization: Bison typically form two types of groups:

Cow-calf groups: Consisting of adult females, calves, yearlings, and some young males
Bull groups: Composed of adult males outside the breeding season
During the rut (breeding season), mature bulls join cow-calf groups
Historical herds could number in the thousands or even millions
Modern conservation herds typically range from dozens to several thousand individuals

Daily Activity: Bison divide their day between several activities:

Grazing (7-11 hours daily)
Ruminating (digesting food)
Resting and sleeping
Wallowing (rolling in dirt depressions)
Social interactions and play
Movement between grazing areas

Communication: Bison use various methods to communicate:

Vocalizations: Grunts, snorts, and bellows, particularly during the rut
Body language: Tail position, head movements, and posture
Physical displays: Wallowing, horning trees and ground, and mock fighting
Scent marking: Urination and wallowing spread individual scents

Distinctive Behaviors:

Wallowing: Creating and using dirt depressions for dust bathing, which helps with parasite control, thermoregulation, and social signaling
Horning: Using horns to rub against trees or dig in the soil
Rutting behavior: Bulls bellowing, displaying, and fighting for breeding opportunities
Group defense: Forming circles around vulnerable calves when threatened
Migration: Historically undertook seasonal movements following optimal grazing conditions

Intelligence and Learning: Bison demonstrate considerable intelligence:

Strong spatial memory for water sources and migration routes
Recognition of individual herd members
Ability to communicate danger through the herd
Problem-solving skills for accessing food and water
Teaching behaviors between generations, particularly mother to calf

The social nature of bison played a crucial role in their survival strategy, with group living providing protection from predators and allowing for the transfer of knowledge about resources and threats across generations.

Reproduction and Life Cycle

The reproductive cycle of bison is synchronized with seasonal patterns to ensure calves are born when conditions are optimal for survival.

Breeding Season: The rut typically occurs from July to September:

Bulls join cow-calf groups and compete for breeding opportunities
Males engage in dominance displays including bellowing, wallowing, and head-shaking
Serious fights between bulls may occur, with opponents charging and clashing heads
Dominant bulls may defend a small harem of cows or follow receptive females
Bulls rarely breed for more than a few seasons due to the physical demands of competition

Gestation and Birth: Following a gestation period of approximately 9-9.5 months:

Calves are typically born in spring (April-May) when grass is most nutritious
Cows usually separate briefly from the herd to give birth
Most cows have a single calf, with twins being extremely rare
Newborn calves weigh 30-70 pounds (14-32 kg)
Calves are reddish-orange at birth, earning them the nickname "red dogs"
They can stand within 30 minutes and run within hours of birth

Calf Development: Young bison develop rapidly:

Begin grazing alongside nursing at about 5-7 days old
Coat darkens to brown within a few months
Weaned at 7-12 months
Young males typically leave their maternal group at 2-3 years
Females often remain with their maternal herd
Sexual maturity reached at 2-4 years for females, 6-7 years for males
Social maturity and full size achieved several years after sexual maturity

Reproductive Lifespan: Bison are relatively long-lived for large herbivores:

Females may reproduce for 15-20 years
Males typically have a shorter reproductive period (3-5 prime breeding years)
Average lifespan in the wild is 12-20 years
Some individuals may live into their 30s, particularly in protected settings

Reproductive Challenges: Several factors can affect bison reproduction:

Hybridization with domestic cattle in some herds
Disease impacts on pregnancy and calf survival
Nutritional stress during drought or harsh winters
Limited genetic diversity in small, isolated herds

The reproductive strategy of bison—producing robust calves that can quickly keep up with the herd—evolved in response to predation pressure and the migratory nature of historical bison populations.

Diet and Feeding Habits

Bison are primarily grazers with a specialized digestive system that allows them to extract nutrients from grasses and sedges that would be indigestible to many other mammals.

Dietary Composition: The bison diet consists primarily of:

Grasses (80-90% of diet), particularly native prairie species
Sedges and rushes, especially in wetter areas
Forbs (flowering plants) seasonally
Browse (leaves and twigs) in limited amounts, particularly wood bison
Lichen and moss in northern habitats during winter

Seasonal Variations: Diet changes throughout the year:

Spring: New growth grasses and sedges high in protein
Summer: Diverse grasses and some forbs
Fall: Mature grasses, preparing for winter by maximizing intake
Winter: Dried grasses, sedges, and woody vegetation when necessary

Feeding Adaptations: Bison possess several specialized adaptations:

Broad muzzle for efficient gathering of grasses
Four-chambered stomach as a ruminant for fermenting fibrous plant material
Ability to digest lower-quality forage than cattle
Efficient water utilization allowing them to go longer between drinking
Ability to use their massive heads to clear snow for winter grazing

Grazing Impact: Bison grazing has significant ecological effects:

Creates patches of different vegetation heights and ages
Stimulates new plant growth through moderate grazing
Distributes seeds through their digestive system
Wallowing creates depressions that collect water and support unique plant communities
Dung provides nutrient cycling and habitat for insects and decomposers

As a keystone species, bison grazing patterns historically shaped the plant communities of North American grasslands, creating a mosaic of habitat types that supported diverse wildlife populations.

Predators and Threats

Throughout their evolutionary history, bison faced various threats, though their size, speed, and herding behavior provided significant protection.

Historical Predators: Before European settlement, bison were preyed upon by:

Gray wolves - Hunted in packs, primarily targeting calves, old, or injured individuals
Plains grizzly bears - Occasionally hunted calves or injured adults
Mountain lions - Rarely took calves or weakened adults
Indigenous human hunters - Sustainably harvested bison for thousands of years

The Great Slaughter: The most devastating threat came in the 19th century:

Commercial hunting for hides and tongues began in the 1830s
Industrial-scale slaughter accelerated after the Civil War
Construction of railroads provided access and transportation
Military strategy to eliminate Native American food sources
By 1884, fewer than 1,000 bison remained from tens of millions
Represents one of history's most dramatic wildlife population collapses

Modern Threats: Today's bison face different challenges:

Habitat fragmentation - Limited space for herds to roam naturally
Genetic issues - Inbreeding in small, isolated populations
Hybridization - Cattle gene introgression in many conservation herds
Disease - Particularly brucellosis and bovine tuberculosis
Policy conflicts - Challenges with managing bison that leave protected areas
Climate change - Altering grassland ecosystems and water availability

Disease Concerns: Several diseases affect bison management:

Brucellosis - A bacterial disease that can cause abortion in bison, cattle, and elk
Bovine tuberculosis - Respiratory disease that can spread between wildlife and livestock
Malignant catarrhal fever - Viral disease transmitted from sheep
Anthrax - Bacterial disease that can cause sudden death in bison

While natural predation is minimal in today's fragmented landscapes, disease management and genetic conservation have become the primary challenges for maintaining healthy bison populations in the 21st century.

Conservation and Recovery

The story of bison conservation represents both one of the greatest wildlife tragedies and one of the most remarkable recovery efforts in North American history.

Early Conservation Efforts: By the late 1800s, with bison nearly extinct, several key initiatives began:

Private individuals like Charles Goodnight and Charles "Buffalo" Jones captured and bred surviving bison
The New York Zoological Society (now Wildlife Conservation Society) established a captive breeding program
The American Bison Society was founded in 1905 by William Hornaday and Theodore Roosevelt
In 1908, the National Bison Range was established in Montana
Yellowstone National Park protected its small remaining wild herd

Recovery Progress: From fewer than 1,000 individuals in the 1880s:

Current North American population exceeds 500,000 bison
Approximately 30,000 are in conservation herds managed for ecological restoration
The remainder are in private commercial herds raised for meat production
Yellowstone herd has grown to approximately 5,000 animals
Wood bison have been successfully reintroduced to Alaska after being extirpated

Conservation Challenges: Despite population recovery, several issues remain:

Genetic integrity - Many herds have some level of cattle gene introgression
Ecological function - Most herds are too small or confined to fulfill their ecological role
Disease management - Particularly brucellosis in the Greater Yellowstone Ecosystem
Limited range - Bison occupy less than 1% of their historical range
Social acceptance - Concerns from ranching communities about disease and competition

Current Initiatives: Modern bison conservation focuses on:

Establishing new conservation herds on public and tribal lands
Developing metapopulation management strategies to maintain genetic diversity
Restoring bison to their ecological role as a keystone species
Addressing disease concerns through research and management
Building social acceptance for bison restoration
Tribal leadership in bison restoration through the InterTribal Buffalo Council

While bison have been saved from extinction, the greater challenge of restoring them as a functional, ecologically significant species across substantial portions of their former range remains a work in progress.

Cultural Significance

Few animals have shaped North American culture as profoundly as the American bison, particularly for Indigenous peoples of the Great Plains.

Indigenous Relationships: For thousands of years, many Native American tribes developed deep cultural connections with bison:

Central to subsistence, providing food, shelter, tools, and clothing
Featured prominently in spiritual practices, ceremonies, and creation stories
Hunting methods and knowledge passed through generations
Sustainable management through controlled burns and other practices
The near-extinction of bison devastated many tribal cultures and economies

Modern Tribal Restoration: Today, Native American tribes lead bison restoration efforts:

The InterTribal Buffalo Council represents over 80 tribes working to restore bison
Tribal herds now manage approximately 20,000 bison
Cultural revitalization connected to bison restoration
Traditional ecological knowledge informing modern management
Economic development through bison-related enterprises

American Symbolism: Bison have become powerful national symbols:

Featured on the official seal of the Department of the Interior
Depicted on coins, including the Buffalo Nickel (1913-1938) and the American Buffalo Gold Coin
Adopted as the national mammal of the United States in 2016
State mammal for Kansas, Oklahoma, and Wyoming
Mascot for numerous sports teams, schools, and organizations

In Popular Culture: Bison remain culturally significant in modern America:

Iconic images in western art, from traditional paintings to contemporary works
Featured in literature, film, and music about the American West
Symbol of wilderness, freedom, and the frontier experience
Growing interest in bison meat as a sustainable, healthy protein source
Tourism draw for national parks and wildlife refuges

The cultural significance of bison continues to evolve, with growing recognition of both their historical importance and their potential role in future conservation and sustainable land management across North America.

Viewing Opportunities

For wildlife enthusiasts interested in observing American bison in natural settings, several locations across North America offer reliable viewing opportunities.

National Parks: The U.S. National Park System protects several significant bison herds:

Yellowstone National Park (Wyoming/Montana/Idaho) - Home to America's largest wild bison population, with excellent viewing in Lamar and Hayden Valleys
Grand Teton National Park (Wyoming) - Bison often visible in the Antelope Flats area
Theodore Roosevelt National Park (North Dakota) - Both North and South Units offer good viewing opportunities
Badlands National Park (South Dakota) - Bison roam throughout the park's mixed-grass prairie
Wind Cave National Park (South Dakota) - Maintains a genetically important conservation herd

Other Public Lands: Several other protected areas offer bison viewing:

National Bison Range (Montana) - Established specifically for bison conservation
Custer State Park (South Dakota) - Home to one of the world's largest publicly owned bison herds
Wichita Mountains Wildlife Refuge (Oklahoma) - One of the oldest bison conservation herds
Tallgrass Prairie Preserve (Oklahoma) - The Nature Conservancy's herd in a restored tallgrass ecosystem
Elk Island National Park (Alberta, Canada) - Source herd for many bison restoration projects
Wood Buffalo National Park (Alberta/NWT, Canada) - World's largest free-roaming wood bison population

Viewing Tips: For successful bison watching:

Dawn and dusk typically offer the best viewing opportunities
Use binoculars or spotting scopes for distant observation
Remain in vehicles when bison are near roads
Maintain a minimum distance of 25 yards (23 meters) when outside vehicles
Be aware that bison can run three times faster than humans
Watch for warning signs like tail raising, head shaking, or pawing the ground
Visit during the rut (July-August) to observe dramatic bull behaviors

Safety Considerations: Despite their calm appearance, bison are wild animals:

More visitors are injured by bison than by bears in Yellowstone National Park
Never approach bison for photographs or any other reason
Keep children and pets close and under control
Use telephoto lenses for photography
Follow all park regulations and ranger instructions

Observing bison in their natural habitat provides not only spectacular wildlife viewing but also a connection to the historical landscape of North America and a testament to successful conservation efforts.

Quick Facts

Scientific name: Bison bison
Family: Bovidae
Subspecies: Plains bison (B. b. bison) and Wood bison (B. b. athabascae)
Weight: Bulls 1,000-2,000 pounds (450-900 kg), Cows 800-1,200 pounds (360-540 kg)
Shoulder height: 5-6.5 feet (1.5-2 m)
Length: 7-12 feet (2.1-3.7 m)
Lifespan: 12-20 years in the wild, up to 30+ years in captivity
Top speed: 35-40 mph (56-64 km/h)
Historical population: 30-60 million
Current population: Approximately 500,000 (about 30,000 in conservation herds)
Conservation status: Near Threatened (IUCN Red List)
Diet: Primarily grasses and sedges
Gestation period: 9-9.5 months
Number of calves: Usually one
Predators: Historically wolves and humans; few natural predators today
Designated as: National Mammal of the United States (2016)