Mule deer are generally easy to identify due to their large mule-like ears (generally 3/4 the length of the head).
They usually have a distinctive black forehead, or mask, that contrasts sharply with a light grey face. The lighter facial coloration makes the eye rings and muzzle markings seem less obvious.
Mule deer are brownish-gray in color, have a white rump patch and a small white tail with a black tip.
Normally the Lamar Valley is home to a large herd of Bison but during this trip they and moved further into the park. It appears this big bull is being attracted to this cow who may be in estrus.