The U.S. Fish and Wildlife Service (FWS) manages almost 1,400 bison spread out amongst seven herds located in Iowa, Colorado, Oklahoma, Montana, Nebraska and North Dakota. About 70 of these bison live at the Neal Smith Wildlife Refuge in Prairie City.
FWS aims to preserve the species genetic diversity with as little human intervention as possible by allowing the forces of natural selection determine which bison live and die. However, because herds are isolated from each other the agency conducts genetic testing to prevent inbreeding.
To obtain DNA samples bison are sent through a series of gates at a yearly bison roundup. Bison with rare genes stay at the refuge while those with more common DNA are culled from the herd.
This year 12 bison leave Prairie City. Two go to Jester Park in Polk County and 10 are sold to the Oneida Tribe in Wisconsin as the tribe eats a traditional diet. The rest of the herd are released back into the refuge for another Iowa winter.