(ALL INTERNAL RIGHTS, LIMITED EXTERNAL RIGHTS) Bison (Bison bison) grazing on the Zapata Ranch with the Great Sand Dunes NP and Sangre de Cristo mountains in the background, Colorado USA. PHOTO CREDIT: © Nick Hall
NCM130709_310 (ALL INTERNAL RIGHTS, LIMITED EXTERNAL RIGHTS) Bison (Bison bison) grazing on the Zapata Ranch with the Great Sand Dunes NP and Sangre de Cristo mountains in the background, Colorado USA. PHOTO CREDIT: © Nick Hall © Nick Hall

Animals we Protect

American Bison

Bison Bison

Meet the American Bison

The largest land mammal in North America, adult males may stand as tall as six feet at the shoulders and weigh 1000-2000 pounds. Bison are grazers, traveling between pastures in groups ranging from family units to large herds. They feed in the morning and evening, mostly on grasses and sedges, and rest during the day, chewing cud or wallowing in mud to rid themselves of parasites.

During mating season, which begins in July and can last until September, bulls will fight amongst themselves for cows. After a nine-month gestation, a single calf is born per cow. The calf suckles for 12 months and remains with its mother until sexual maturity, which occurs around 3 years of age for females and 6 years for males.

Protecting the American Bison 

Once a staple for some Native Americans, millions of American bison roamed from Canada to Mexico and New York to California, until wholesale slaughter by American settlers brought them to the brink of extinction in the early 20th century. At the end of the slaughter, less than 100 free-roaming bison remained in the world.

Thanks in large part to the efforts of the American Bison Society, the species has rebounded, and herds have been built up in preserves, where they live in a semi-wild state. However, genetic diversity remains a concern because the population was bred from such reduced numbers. Individuals also mate with vastly different success rates, further limiting the available gene pool.

The Nature Conservancy is working at a handful of preserves in Central North America to bring bison back to its natural landscape. One reason for this is that bison are actually quite good for grasslands. 

Today about 350,000 bison live in the U.S. and they can be found in all 50 states. Conservancy preserves across the country are currently home to approximately 5,500 of these amazing animals.