Custer State Park, located within South Dakota’s Black Hills, is a 71,000-acre wildlife sanctuary. It is home to one of the largest publicly owned bison herds in the world. Managing this free-roaming herd balances the health of the animals with the sustainability of the native grasslands. The number of bison is not static, fluctuating throughout the year as new calves are born and animals are moved or sold.
The Current Herd Population
The bison population in Custer State Park is actively managed to maintain a specific target range. The park’s goal for the post-management winter season is typically 950 to 1,000 animals. The population swells considerably each spring with the birth of hundreds of calves.
The annual roundup counts the herd at its maximum size before the required reduction process begins. For instance, a recent roundup gathered 1,485 animals, including 488 calves. Maintaining a manageable herd size is necessary to ensure the long-term health of the ecosystem.
Ecological Management and Carrying Capacity
Controlling the bison population is a deliberate ecological strategy rooted in the concept of carrying capacity. This refers to the maximum number of animals the park’s land can sustain without causing permanent damage to the ecosystem. If the herd grew unchecked, the bison would quickly overgraze the native prairie grasses.
Overgrazing depletes the forage base, negatively impacting the bison and other grazing wildlife like elk and pronghorn. Park managers assess the condition of the grasslands annually, factoring in precipitation levels and forage availability. This scientific assessment determines how many bison must be removed to restore balance and prevent the degradation of soil and plant life.
The Annual Bison Roundup
The primary tool used to manage the herd size and health is the Annual Bison Roundup, held every fall, usually in late September. This event involves park staff, cowboys, and cowgirls driving the herd into a centralized set of corrals. The roundup is necessary for animal husbandry and population control.
Once contained, every animal undergoes a thorough health check, receiving vaccinations and necessary testing. Calves are branded and tagged for identification, allowing staff to track the herd’s lineage and demographics. After the assessments, “surplus” animals are sorted and prepared for auction, which typically occurs in November. The sale maintains the target population size and helps fund the park’s wildlife management programs.
Historical Context of the Custer Herd
The Custer State Park herd represents a success in American conservation, given the species’ near-total annihilation in the 19th century. By 1889, only a few hundred bison remained across the continent due to market hunting and habitat loss. The park’s herd was established in 1914, before the area was officially designated a state park.
A small group of 36 bison was purchased from a private herd near Pierre, South Dakota, to reintroduce the species to the Black Hills region. These animals successfully restored a breeding population to their native lands. This initial restoration effort laid the groundwork for the large, genetically important herd that exists in the park today.