As I watched this bull approach a resting cow and “check her out”, I was thinking of the Little Feat, Fat Man in the Bathtub with the Blues" lyrics. Where the rest of the line is, “…come back Monday, come back Tuesday, then I might.” This was taken in the open area between Gardiner and the Yellowstone entrance booth as this bull guarded his harem of a dozen cows. Given the previous two posts showing male/female interactions, I felt compelled to continue the theme. 
(7D2, 100-400 IS II @ 321 mm, 1/640 s, f/9, iso 800, tripod)
Its a nicely balanced composition with excellent detail. Very nice shot!
The earth tones are really nice as are all the details in the scene. This is being super picky; and I only noticed it when I opened the large version; but the OOF bit of brush on the lower part of the bull’s hind leg caught my eye right away. Maybe clone it out if you are so inclined. Anyway, great shot.