10 Fascinating Facts About Bison

American bison, also called buffalo, freely roamed North America numbering an estimated 40 million in 1800. Today, the International Union for Conservation of Nature and Natural Resources (IUCN) lists them as a species near threatened by extinction. They make up one of two species of bison — the other being European bison — and are divided into two subspecies: plains and wood bison.

The mighty buffalo lend their name to mountains, rivers, sports teams, and cities. They are an iconic animal of the American plains, but how much do you know about them? Here are 10 fascinating facts about the majestic animals.

1. Bison Are Fast

Bison may look like they're lumber, but they're quite agile and fast, able to run an impressive 30 to 45 mph and jump as high as six vertical feet. Because tourists underestimate their speed and overestimate their docility, bison have injured more people than any other species in Yellowstone National Park. Unlike other herbivores, bison aren't slow to use their agility and size to attack perceived predators.

2. Their Coats Are Extraordinarily Thick

Uniquely, bison don't burn extra calories to stay warm in below-zero temperatures. Their coats' thickness insulates them from harsh winter weather with two layers of hair and a thick hide. The coarse outer layer serves as protection from cold and moisture. The inner layer consists of fine fibers, creating an insulation that traps air and warmth. Bison have 10 times more hair per square inch than domestic cattle. Their coats are so effective against cold that snow remains on top of the bison without melting.

On particularly frigid days, the animals face into the wind with their heads down, presenting the thickest part of the coat to break the fierce prairie cold.

3. They Are Key to a Healthy Plains Ecosystem

As a keystone species, bison play a vital role in creating and maintaining ecosystem biodiversity. They graze native grasses, their hooves turn up the soil, and their droppings fertilize it. Even the wallowing of bison changes and balances the tall grass prairie's biodiversity by affecting the insect populations. Prairie dogs and other animals prefer to live in areas grazed by bison so they can spot predators more easily. One endangered species of butterfly is becoming more abundant since the reintroduction of bison to their range. Bisons' grazing has created conditions favorable for plants these butterflies use as a food source.

4. They Were Almost Extinct

During the 1800s, several factors led to the near extinction of the American bison, with only around 325 remaining in 1884. Most commonly cited is the widespread slaughter of buffalo by white settlers. Removal of the Indigenous people's food source, cultural heritage, and trade goods was used as a war tactic. During Westward Expansion, what was once open rangelands was fenced off to roaming bison, restricting their habitats. This continues to limit their recovery today.

Other threats include diseases and drought that leave bison weakened and subject to predation by wolves. Yellowstone National Park is the only location in the entire continent where bison have lived continuously since prehistoric times.

5. They Are Considered Ecologically Extinct

The number of American bison in free-ranging or managed conservation herds is stable as of 2020, with IUCN estimating between 11,248 and 13,123 adult animals within that population. Unfortunately, most of those bison don't live in herds large enough for long-term viability. These small herds create a situation where bison are considered "ecologically extinct." That is to say they're not yet extinct but lacking the genetic diversity needed to maintain their population.

6. They Are North America's Largest Mammal

The bison's size is difficult to comprehend. A typical bull (male) is between 11 and 12.5 feet long. Cows (females) are smaller, ranging between 7.5 feet and 10.5 feet in length. They stand between five feet to just over six feet at the shoulder. The woods bison subspecies is the larger of the two, with the bulls weighing more than 2,000 pounds.

7. Calves Change Colors

Most bison today aren't pure bison; only about 8,000 individuals or 1.6 percent of the species' total population is not hybridized to some degree with cattle. Hybridization, in which domestic cattle are sometime involved, results in black, brown, or even white bison calves.

Pure bison calves are generally red when they are born, and as they grow, their coat darkens. This process begins after two months and completes at the four-month mark. White calves are albino, leucistic, or true white bison. Albino calves lack all pigment and have pink eyes, leucistic have blue eyes, and white bison are simply born with genetically white coats. The true white calves tend to morph colors, just like the typical red calves. White calves are considered sacred by many Indigenous peoples of North America.

8. Their Conservation Is at Risk

Despite being listed as near threatened by the IUCN, conservation of the species is complicated. Some laws in North America categorize bison as livestock while others categorize them as wildlife. Breeding them for commercial purposes doesn't serve the species' conservation because of selective breeding for docility and meat quality. Hybridization through purposeful and accidental breeding with cattle further limits the conservation gene pool.

Bison need large tracks of land in which to range, breed, and migrate. In North America, there's little support for the re-wilding of such a large animal. Despite the lesser amount of wilderness in Europe, public acceptance of this strategy has been a success story for European bison.

9. Both Males and Females Have Horns

You can't tell whether a bison is male or female by the horns, but you can tell their age. Both sexes have horns beginning around two years old. They then have a stage called a "spike-horn," where the horns develop at a 45-degree angle. This lasts until they are around four years old. Horns start black but turn grey as the buffalo ages. Adult horns curve upward, and the tips start to become blunted and shorter after about age eight.

10. They Make a Variety of Sounds

Despite their similarity to cows, they don't make noises like domestic cattle. Bison don't moo or low; instead, they bellow, grunt, growl, and snort. The snorts and growls can sound similar to truck or lawnmower engines. The grunts sound like a pig's. Bellows are particularly common during rut or breeding season. Bison communicate with calves and cows using a variety of snorts, growls, and rumbling alarm calls. Calves make some bleating sounds in response to being called by their mothers.