Bison calf after receiving a health checkup at Tallgrass Prairie Preserve annual Bison Roundup.
Bison calf at roundup. Bison calf after receiving a health checkup at Tallgrass Prairie Preserve annual Bison Roundup. © David Smith


Bison Get Clean Bill of Health at Tallgrass Prairie Preserve

Despite droughts, chilling winters, and anything else Mother Nature sends their way, this resilient bison herd is healthy and going on strong.

Pawhusa, OK

Since 1993, bison at the Joseph H. Williams Tallgrass Prairie Preserve are gathered to perform various scientific studies and receive vaccinations to ensure the health of the herd. This year, 2,508 bison received a clean bill of health at the 25th annual Bison Roundup.

Consisting of almost 40,000 acres near Pawhuska in Osage County, the Tallgrass Prairie Preserve is the largest protected remnant of tallgrass prairie left in the world!

The roundup, which takes about a week, is the only time the bison are gathered and confined on the prairie. During the roundup, all heifer calves were vaccinated against brucellosis and all keeper animals were vaccinated for several bovine diseases and treated for parasites. For research and record-keeping purposes, each individual bison in the herd is identified with an ear-tag transponder.

A bison leaves the examination chute where it received its annual health checkup.
CLEAN BILL OF HEALTH After receiving its health checkup, Perry Collins releases a bison from the examination chute during the 2018 Tallgrass Prairie Preserve Bison Roundup. © David Smith

A total of 705 bison were sold this year in order to keep the size of the herd within the appropriate ecological stocking rate. Bulls are sold at 6-7 years of age, since after this they tend to become more aggressive and dangerous. Cows are sold at 10-12 years of age. The largest bison that came across the scales at this year’s roundup was a 1,795-lb. bull born in 2010. The infographic below shows this year’s roundup statistics.

The Tallgrass Prairie Preserve bison herd started in 1993 with 300 and reached its target size in 2008 of 2,700 for the summer (includes calves) and 2,100 for the winter (after roundup).

The preserve is open daily from dawn to dusk and provides hiking trails and 10-mile bison loop. Plan your trip to see this healthy herd of bison!

Results from the 2018 Bison Roundup at Tallgrass Prairie Preserve in Pawhuska, OK.
2018 BISON HERD STATS Results from the 2018 Bison Roundup at the Tallgrass Prairie Preserve in Pawhuska, OK.

The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world's toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. Working in 79 countries and territories, we use a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit or follow @nature_press on Twitter.