Riders herd bison during the annual bison roundup at Antelope Island, Utah. (AP)
The riders gather the bison to give them medicine and keep track of their numbers. (AP)
A bison peers through the grass on Antelope Island in Utah. (AP)
Hundreds of people on horseback ride in the annual roundup of bison. (AP)
A worker puts a radio collar on an older bison cow. It will help track her health. (AP)
A large herd of bison lives on an island in the Great Salt Lake. People round up the herd every year.
Each bison gets a checkup. Some are sold. The rest stay on the island. But there will be another roundup next year.