ID Challenge: White-tailed vs Mule Deer

Let’s turn now from the difficulties of distinguishing similar species of birds to a large mammal conundrum. Living on the east coast for most of my life, there was no doubt that the deer eating the flowers in my neighbor’s backyard was a white-tailed deer (Odocoileus virginianus). There simply are no other deer in Virginia. It wasn’t until I visited Yosemite National Park when I was already an adult that I saw a different type of deer for the first time, the mule deer (Odocoiileus hemionus).

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A mule deer during rutting season at Rocky Mountain Arsenal National Wildlife Refuge. Photo by Jamie Simo.

While the mule deer is typically a western species and the white-tailed deer typically an eastern species, the westward expansion of the white-tailed deer due to the replacement of grassland communities with agriculture and trees, has led to areas where the two commingle. At some point, perhaps, the white-tail, due to its greater adaptability (e.g. tendency toward twins rather than single fawns) may eventually out-compete the mule deer entirely, but, for now, both are present in eastern Colorado.

So, you’re hiking in a state park and you’ve come across a small herd of deer. They stare at you. You stare back. Who are you looking at? Is it a white-tail or a mule?

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White-tailed deer. Photo by Jamie Simo.

One way people say to tell is by looking at the size of the ears. The mule deer has enormous ears, like its namesake, while the white-tail’s are smaller. I’ve never found this particularly useful though because, unless they’re right next to each other, I can’t tell whether that’s a really big or just an average-sized ear.

A better way of distinguishing the two species is by their tails. The mule deer has a rather short, white tail with a black tip and its backside is also pretty white. The white-tailed deer, however, has a longer, bushier, browner tail. Its name comes from the way it raises its tail like a flag to expose the white underneath when alarmed.

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White-tailed deer unnerved by my presence in Fort Collins, CO. Photo by Jamie Simo.
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A mule deer chows down on roses near an office building. Photo by Jamie Simo.

Another way to distinguish if you don’t have a good look at the back of the animal, is by the facial pattern. The mule deer has a fairly even-toned pale brown face. This often sets off a darker forehead (sometimes this looks to me like a unibrow or a toupee). The white-tailed deer, however, has a face the same tone as the rest of its coat with white rings around the muzzle and eyes.

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White-tailed deer buck. Photo by Scott Bauer. http://www.ars.usda.gov/is/graphics/photos/may01/k5437-3.htm

If you’re looking at a buck during antler season, you can also tell what species you have by checking to see whether the the points branch off continuously like a tree (mule) or whether they all split off a main “trunk” (white-tailed). Obviously, this only works for males and only during a part of the year though.

After learning this, I’m now confident I know who I’m looking at when I come across any deer while hiking. Hopefully you will be too!

 

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