Folks up at the Tall Grass Prairie Preserve near Pawhuska are gearing up for their annual Bison Round-Up.

There are about 2,500 bison that roam free on the Tall Grass Prairie, and over the last couple of weeks, they've all been brought to a smaller pasture for their yearly checkup.

Starting next week, preserve staff and local wranglers will round up the bison into corrals so they can weigh them, give them vaccines, and check on their general health. The preserve says the largest bison last year was a 1,830-pound bull born in 2012.

The round-up also gives the preserve a chance to count the herd and see how many newborns they have. It says the herd needs to stay at a certain size for the area they roam, so any extra bison will be auctioned off. Last year 306 were sold.

Since the bison are wild animals, this is the only human contact they get all year. After the round-up, the bison will be free to roam 23,000 acres of the nearly 40,000-acre preserve.