On November 10, 2004, a park crew involved in chronic wasting disease management observed a doe white-tailed deer (Odocoileus virginianus) on the east side of Deer Mountain in Rocky Mountain National Park. She was seen at 8,630 ft. altitude in antelope bitterbrush and ponderosa pine, and was standing with a group of mule deer (Odocoileus hemionus). While white-tailed deer are listed on the park Mammals List, they are very rare. This observation is remarkable because it is only the third time white-tailed deer have been reliably reported in the park. The previous reports were in 1984 and 1990.
How did the crew know this doe was a white-tailed deer rather than a mule deer? Tails, ears, and antlers are the main distinguishing characteristics of these two species.White-tailed deer have a broad white flag-like tail that they hold erect when alarmed and when running. Mule deer have smaller, proportionately narrower black-tipped tails that they raise when alarmed. Click on "more" of the upper and middle photos to the right to compare tails . Mule deer have disproportionately large ears - thus their common name - mule deer.
A final characteristic that aids in field identification of bucks is the form of their antlers. Mule deer antlers are dichotomous meaning they branch into equal Y-shaped parts. Click on the caption of the bottom right picture to see an example of dichotomous antlers. In white-tailed deer antlers the tines (points) are smaller branches off a larger main stem.