Mule Deer
Odocoileus hemionus
Summary 5
The mule deer (Odocoileus hemionus) is a deer indigenous to western North America; it is named for its ears, which are large like those of the mule. The several subspecies include the black-tailed deer.
Seasonal Behaviors 6
Does go into estrus for a few days in the fall while the males compete with each other over mates by sparring with their antlers. This period of time is referred to as the "rut". The female may mate with a few males during this time and if she does not become pregnant, she will go into estrus again within a month. In the winter after the mating season the bucks will shed their antlers completely off and start regrowing them for the next year's rut. The gestation period is about 200 days and the fawns will be born in the spring. The doe can give birth from one to four fawns at a time, but two is most common. Fawns are weaned in early fall the same year they are born.
Mule deer females and fawns all live in smaller multi-generational family units. The males tend to be solitary or form small male groupings. When winter arrives and the females are in their gestation period, the small female family groups will combine to form small herds that protect each other. These groups will then break up again when spring arrives.
Identification 6
The white tail and mule deer population overlap here in Colorado. If you find yourself looking at a deer, it is possible that it could be either species. There are a few things to look for when trying to differentiate the two.
The Ears
The mule deer gets its name from its extremely long mule like ears. They are much larger than the ears of a white tail. I find however that if you are out in the field, judging a deer's ear length can be hard without anything to reference.
The Rump
The white tail gets its name from its longer and bushier white-bottomed tail. The mule deer however has a lot of white on its backside. The mule deer's entire rump is white with a smaller white, black tipped tail that hangs over it. I find the white rump to be one of the easier ways to distinguish a mule deer.
- Behavior Mule deer are generally less skittish. At Rocky Mountain when we were walking along a path, we were able to get very close to them without them spooking. White tail tend to be more allusive. If you get to see the deer moving, mule deer can be identified by their hopping while white tails gallop more like a horse.
Sources and Credits
- (c) woodleywonderworks, some rights reserved (CC BY), https://www.flickr.com/photos/wwworks/4962531922/
- (c) Ryan McFarland, some rights reserved (CC BY-NC), uploaded by Ryan McFarland
- (c) Vanessa A Roberts, some rights reserved (CC BY-NC), uploaded by Vanessa A Roberts
- (c) M. Goff, some rights reserved (CC BY-NC-SA), uploaded by M. Goff
- Adapted by Desmon M Dunn from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Odocoileus_hemionus
- (c) Dylan Souza, some rights reserved (CC BY-SA), https://www.inaturalist.org/guide_taxa/1268739
