Elk are very closely related to the red deer. They are in fact so similar that some claim they should be treated as the same species. This is not surprising though because of their many shared traits. Some of these shared traits include the appearance of antlers, their similar diet, their outer covering and the roaming that both animals exhibit. Both of these species also use their antlers for defense and for fending of other males from their mates. During mating season males will use their antlers to try and show dominance over other males. This is used to show which male is the most dominant. The strong similarities have shown elk to be classified closely to the Olgocene genus which contain the deer(Whitehead 1972). The major difference is that elk are larger is size than the red deer. The elk are believed to have their common ancestors from Eurasia. Then, it is believed, that they spread out to fill most of the niches in Eurasia and North America. The common ancestor is believed to have been much larger as evidence has pointed to a reduction of size over time since the beginning of the species (Red Deer).

 Many of the different types of elk are split up because of different types of DNA. Some of its closest relatives are the:  Cervus elaphus elaphus, Cervus elaphus xanthopygus, the Cervus elaphus kansuensis, the Cervus songaricus, the Cervus wardi, and the Cervus macneilli. All of these animals can be found in the same genus and actually have very similar characteristics (Murie 1951). The elk even have the same rut time as the red deer which shows that they are closely related. It is not known if a deer and a Roosevelt elk can mate so the major similarities are morphological and cladistical. The Roosevelt elk has the closet relationship to the Rocky Mountain elk. This is mainly because the territory of the Roosevelt elk is close to the territory of the Rocky Mountain elk. When concluding that these elk had the most similar DNA one can expect that they share a common ancestor that also lives in North America at one time.

Many once thought that Roosevelt elk and Rocky mountain elk were the same species. The elk were soon compared side by side and found to have many differences. The major difference between the Roosevelt elk and the Rocky mountain elk is that the Roosevelt elk is typically bigger topping out the scales at 1,000 pounds. They also have larger antlers which can also be another defining characteristic. Not only do Roosevelt elk have larger antlers but actually larger skulls. This is understandable because of the larger size. Another morphological difference is the color change between the two types of elks. The Roosevelt elk has a darker coloration to it than is close relative the Rocky mountain elk. The last major difference is actually where they live. They live in a separate environment than do the rocky mountain elk which has caused differences in their DNA.