Went to the east end of the Lamar Valley in Yellowstone NP to shoot some animals. The bison are getting ready for the rutt as the the bulls are grunting loudly. No head butting yet as they haven't gathered their harems yet but I'll be back to capture that. This is a bison calf whose fur is turning from baby red to a dark winter brown. Pentax K-5 + K 400mm f/5.6 MF lens.