Meet the Mule Deer, Western Cousin of the Whitetail

June 18, 2024 By: Ben Westfall

The white-tailed deer is often referred to as “North America’s favorite game animal,” and while that may be true, there are multiple whitetail subspecies and other deer species in North America that we enjoy pursuing, observing and managing. Mule deer (Odocoileus hemionus) are another extremely popular big game animal with ample opportunities for hunting in the western United States.

Mule Deer Origins

Deer have been present in North America for quite some time, with fossil records indicating that whitetails have been here for about four million years! Mule deer are likely much “younger” and, according to the most widely accepted theory, have only been around in their current form for about 10,000 years, which makes them the most recent deer species to appear on our landscape. Although parts of their range do overlap and both are native to North America, mule deer are found exclusively in the western half of the United States and Canada while whitetails are present just about everywhere on the continent (and even into central and south America).

Muley Description

Once considered a subspecies of whitetail, mule deer and whitetails can in fact hybridize, but the phenomenon is rare. They are closely related but differ in their appearance, behavior, and geographical distribution. “Muleys” get their name from the seemingly disproportional size of their ears that resemble, you guessed it, a mule. This particular species is just a little bit larger than their eastern cousins, packing on about 50 extra pounds at maturity for both bucks and does. This puts muleys at about 200 pounds for males and 150 pounds for females on average, but it is not uncommon to see much larger individuals across their range. One of the most prominent distinguishing features is the mule deer’s thin, rope-like black-tipped tail which is much different than the famous bushy white tail of their kindred counterparts.

Another unique attribute that sets them apart is they way they traverse the landscape. Rather than running or galloping like a whitetail that just caught you playing on your phone in the stand, mule deer exhibit what’s called “stotting” or “pronking,” which is the act of springing into the air with all four feet coming down together. If you’ve never seen it, I encourage you to look it up as it’s really quite graceful for such a large animal.

One of the most prominent distinguishing features is the mule deer’s thin, rope-like black-tipped tail which is much different than the famous bushy white tail of their kindred counterparts.

Mule Deer vs Whitetails

When it comes to their biology and behavior, they share many similarities with whitetails. They exhibit similar rut timing and behavior. Gestation is roughly the same at about 200 days. They shed their antlers in the winter. Diets are similar in many places, and they are ruminants with a four-chambered stomach. One major difference is that mule deer exhibit migration behavior and will often move from low elevation winter ranges to high elevation summer ranges to avoid deep snow and utilize abundant forage during the summer. Because of this, muleys also tend to have larger home ranges than your average whitetail. 

According to the Mule Deer Working Group, these migrations are extremely important for their survival and can be dangerous due to vehicle collisions, fences, urban expansion, and other forms of human disturbance. In recent years, advances in GPS technology have allowed researchers to better understand mule deer movement, behavior and survival leading to incredible progress in improving mule deer management and protecting migration corridors. In 2018, Secretarial Order 3362 was passed to emphasize the importance of conserving and improving mule deer and other wildlife habitat. Since it’s inception, a partnership led by the Bureau of Land Management has improved 3 million acres of big game habitat, removed or modified 1,250 miles of fencing to improve migration, and surpassed $30 million in funding for research projects, data analysis, mapping, and habitat improvements. 

mule deer

Mule deer tend to have small or even no brow tines and exhibit bifurcated antler branching, or tines that split once off of a main beam, and then again toward the tips. Whitetails tines grow parallel from the main beam.

Muley Populations

Overall, mule deer are abundant and classified as a species of least concern, which means that their numbers are sufficient in the wild. According to the Mule Deer Working Group, half of the member agencies in the Western Association of Fish and Wildlife Agencies report stable or increasing mule deer populations and many mule deer populations are managed largely by hunter harvest.

According to data we collected from western states, the 2022 U.S. mule deer harvest was just over 240,000. In comparison, U.S. hunters harvest around 6 million whitetails annually! To learn more about the annual mule deer harvest, check out page 52 of NDA’s 2024 Deer Report.

The word “deer” has become synonymous with whitetails specifically, but the NDA advocates for all wild deer, and there are so many other unique and interesting deer species that deserve recognition. This is the first installment of a series derived from our Deer Report that aims to spread the word about some of the other interesting and perhaps lesser-known deer species across North America. 

5 More Facts about Mule Deer

  1. The first reported hybridization occurred in 1898 at the Cincinnati Zoo.
  2. Muleys can be aged similar to whitetails using tooth replacement and wear and cementum annuli aging techniques.
  3. Muleys are the largest of the three deer species in the genus Odocoileus.
  4. The oldest wild mule deer aged at Matson’s Lab by cementum annuli analysis was 20 years old.
  5. They can reach speeds of up to 45 mph!

About Ben Westfall:

Ben Westfall is NDA's Conservation Coordinator. Ben received both his bachelor of science and master of science degrees from Southeast Missouri State University with an emphasis on wildlife conservation.