Bison Roundup at the Rocky Mountain Arsenal National Wildlife Refuge

COMMERCE CITY, CO. - DECEMBER 17: Jason Marheine takes a tail hair sample during the annual bison roundup at the Rocky Mountain Arsenal National Wildlife Refuge in Commerce City, CO December 17, 2013. The U. S. Fish & Wildlife Service is processing the herd of 87 bison taking blood samples, checking identity chips and plucking tail hairs for genetic testing. The herd currently resides on 2300 acres and federal biologists are tasked with deciding which 27 bison must be cut from the arsenal herd to avoid degrading the prairie. (Photo By Craig F. Walker / The Denver Post)