Photos: Tallgrass Prairie Preserve's 31st bison roundup

Ranch hands and members of the Nature Conservancy gathered early Sunday morning at the Joseph H. Williams Tallgrass Prairie Preserve for the 31st bison roundup.

The annual event helps control diseases in the bison population and identifies surplus animals born in the herd. The bison get their blood drawn, receive vaccinations and get their weight documented. Some excess bison are donated to the InterTribal Buffalo Council to be reintroduced on tribal lands; others may be sold.

"I've been around cattle operations my whole life, and the bison are different," said Harvey Payne, community relation coordinator with the Nature Conservancy. "They accumulate stress — they didn't evolve going through a set of corrals; they don't like anything about it.

"So we put them through a working chute. We try to have them in that chute for less than a minute," Payne said about processing 300 to 500 bison a day before they are released into a 1,400-acre pasture.

The processing stage of the roundup at the Mary L. Pasture takes about a week, but the earlier stages involve getting the bison to the pasture from the nearly 40,000-acre preserve with siren-equipped feed trucks starting in late September or early October.

"We've learned something every year. The bison are very intelligent, and a lot of times it's a cat and mouse game," Payne said about the roundup experience.