Wildlife and Photography
American Bison Calving Season in the Black Hills
Nature has synchronized the American bison springtime calving season
I have traveled throughout the lower 48 states of the United States. Throughout the country, I seek beautiful landscapes, vibrant cities, solitude, and wildlife. Still, I return to Yellowstone National Park and Custer State Park over and over again.
When my son asked why I visit Yellowstone and Custer so often, I didn’t need to think for long. Both parks have fascinating landscapes and forests. Yellowstone adds geothermal features. But neither park’s scenery competes with the crags of Grand Teton or the gorges of Grand Canyon. The answer is simple. I return for the dynamic wild animals.
Wildlife managers have established large bison herds at Yellowstone and Custer. The parks also feature elk, deer, bighorn sheep, coyotes, and mountain goats. Wolves, black bears, and grizzly bears roam Yellowstone as well. The parks abound with birds and other animals, too.
Custer State Park is home to about 1,400 American bison (Bison bison), often called buffalo. The park encompasses 71,000 acres (28,373 hectares) in the Black Hills of South Dakota.
Bison bulls and cows mate in summer or fall after cows enter estrus. The cow carries a single fetus for nine months. They give birth to calves between mid-April and early July each year.
Calves are born with their eyes open. They weigh from 33 to 55 pounds (15 to 25 kilograms). Calves walk and graze within a week of birth and follow their mothers and the herd over long distances.
According to the U.S. National Park Service, 80% of bison have a birthday in April or May. This year, I visited Custer State Park and adjacent Wind Cave National Park from May 19 through 20. Indeed, it appeared that most calves within the parks were born in April.
At Fisherman’s Flat within Custer’s Wildlife Loop Road, I observed a herd of about 200 animals. Several dozen calves within the herd appeared to be about the same size. This indicates that they they were born at roughly the same time.
Some scientists believe that the birth synchrony of bison is due to climate. Climatic effects on food quality and availability may determine when cows enter estrus. Predation may also play a role.
Custer State Park is filled with beauty and the wonders of wild animals. I hope that my journeys take me their again soon.
More Wildlife Stories
Discover The Bison Herds of North America
Discover the Bison Herds of Iowa
References
Journal of Mammology — Birth Synchrony in American Bison (Bison bison): Response to Predation or Season? Allen T. Rutberg
South Dakota Game, Fish, & Parks — Custer State Park
U.S. National Park Service — Bison Bellows: Birth Synchrony — Why Now?
Wikipedia — Bison
Wikipedia — Custer State Park