Antelope Island State Park, situated within the Great Salt Lake in Utah, provides a unique and isolated environment for one of North America’s most significant wildlife populations. The island is the largest landmass within the lake and serves as a major habitat for various species, most notably its famous bison herd. This herd is recognized as one of the continent’s largest and oldest publicly owned, free-ranging groups of bison. The careful management of this population is a complex effort aimed at balancing the health of the animals with the delicate ecosystem of the island itself.
Historical Introduction of the Antelope Island Herd
The bison currently roaming Antelope Island are not descendants of animals that historically inhabited the land. The herd’s origin dates back to 1893 when a group of 12 bison was introduced to the island by a private consortium. Ogden rancher William Glasmann and Antelope Island owner John Dooly were the principals in this venture, which was initially driven by commercial interests like tourism and hunting. The isolation of the island proved instrumental in the herd’s survival and growth. The Antelope Island bison developed a distinct and valuable genetic heritage, making the herd an important resource for conservation efforts and the establishment of other herds across North America.
The Current Population Count and Fluctuations
The Utah Division of Parks and Recreation actively manages the herd size, which generally varies between 550 and 700 animals annually. This fluctuation is largely driven by the annual calving season, which adds a significant number of new animals to the population each spring.
The island’s ecosystem has a limited carrying capacity. To prevent overgrazing and ensure the health of coexisting species like pronghorn and mule deer, park managers maintain a target population of approximately 500 to 550 bison. Since the island lacks any natural predators capable of controlling the animals, this target size necessitates human intervention to balance the food supply with the needs of the entire ecosystem.
Managing the Herd: The Annual Bison Roundup
The method used to maintain the target population size is the Antelope Island Annual Bison Roundup, a large-scale event held every fall, typically in late October or early November. Hundreds of horseback riders participate in herding the animals from the southern reaches of the island toward the corrals at the historic Fielding Garr Ranch on the north end. This process is the first phase of a multi-day operation focused on herd health and population control.
Once secured in the corrals, the bison undergo the “Working of the Bison,” where each animal receives a thorough veterinary check. During this time, they are also weighed, vaccinated, and tagged with Radio Frequency Identification (RFID) chips. These health checks ensure the continued disease-free status of the herd, which adds to its value as a foundation stock for other conservation efforts.
The final action of the management cycle is the removal of excess animals to bring the herd size back down to the target range of 500 to 550. These surplus bison are sold at a public auction, with the revenue directly supporting the park’s Wildlife and Habitat Management Program. This cyclical management ensures the long-term viability of the bison herd and protects the fragile natural resources of Antelope Island.