Three hundred riders on horseback drove Antelope Island State Park's bison herd into corrals Saturday, Oct. 24, launching the annual roundup that keeps the island's population in check.

Of those 300 riders, 200 were public volunteers who signed up through an online reservation system that filled up in minutes, ABC4 reported. The rest were staff from the Utah Division of State Parks.

The island, a short drive from Farmington across the Davis County causeway, can sustain a herd of about 500 to 550 bison year-round. With no natural predators on the island, the herd grows each calving season. Utah State Parks spokesperson Ally O'Rullian told ABC4 the herd reaches roughly 700 to 750 after calves are born, though the state parks roundup page describes the herd as nearly 800.

Either way, the park has to thin the numbers.

About 200 bison will be sold in an online public auction on Tuesday, Nov. 3, beginning at 10 a.m., according to KSL. Viewers can watch the auction at the visitor center's new movie theater. A portion of the auction revenue goes toward habitat work and bison infrastructure, according to Utah State Parks.

Before the ride began Saturday morning, riders gathered for a safety briefing. Rios Pacheco of the Northwest Band of the Shoshone Nation offered a blessing. Then hooves hit the trail.

Charlotte Vaughan, a first-time rider, showed up despite a recent horse accident that put her in the hospital for five days. "I just got in a horse accident a few days, a few weeks ago … It's all wrapped, and I was coming no matter what," she told ABC4.

Matt Jensen, riding in the roundup for a seventh year, brought his dad and his daughter. His father was on his eighth ride. His daughter was on her sixth.

The roundup is phase one. Phase two, called the Working of the Bison, runs Oct. 27 through Oct. 29. During those three days, park staff sort the animals one at a time for vaccinations, pregnancy checks and individual health screenings. Each bison gets an RFID tag, a radio-frequency identification chip, linked to its health records. Free public tours are available all three days, according to Utah State Parks.

O'Rullian told KSL the number of bison sold varies year to year. A little more than 250 were auctioned in 2025.

The registration fee for riders was $100 per person and included camping, a souvenir bandana and a chili dinner Saturday evening. Riders had to be 18 or older.

Coming up at Antelope Island:

  • Oct. 27–29: Working of the Bison, with free public tours. Group reservations available by emailing the park.
  • Nov. 3, 10 a.m.: Online public bison auction. Bidder information is available through the state parks roundup page.