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).
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?
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.
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.
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!