Have you ever witnessed a deer raising its tail at you while it speedily ran away? Some believe it’s the deer version of flipping the bird, and to be honest it kind of feels that way. Although it may seem like an offensive gesture, in reality the deer tail is a finely tuned appendage that’s used as a primary form of communication to friend and foe alike. In fact, the tail is so important in the evolution of the species, it’s responsible for their name! White-tailed deer are known for the highly visible white color on the underside of their tail and that tell-tale “tail flagging” behavior.
Why a White Tail?
Deer exhibit many physical and behavioral adaptations as a means to survive, including their cryptic coloration, detecting danger with their sharp senses, selecting the most nutritious foods available, and seeking refuge to stay safe, among other assets.
When a deer’s tail is down, in a relaxed position, it conceals the vast majority of white coloration. In fact, their booty looks mostly brown to the average observer. However, when alarmed, a raised tail shows off that white in all its glory. Of course, tail-flagging also exposes the entire rump area, which is also white. Deer have white fur in other locations as well, including the belly, the undersides of their legs and around the neck and face. Most of these areas are hidden during normal activity but become significantly more visible when a deer is alert, its tail is up, and it’s jumping or running at full stride.
The Eyes Have It
Deer have limited vision when it comes to seeing the finer details, but they’re great at catching movement and they see incredibly well in the shorter wavelengths of the color spectrum and in low-light situations, which is when deer are most active. Short wavelength colors include blues, purples and violets, and twilight is the time of day when the reduced sunlight takes on mostly a blue shade. A deer’s white tail, rump and white hairs in other body locations do a phenomenal job absorbing the ambient “blue hour” tones at dawn and dusk and reflects those same colors to other deer. So, although we’re vain enough to think the raised tail is a stiff middle finger destined for our eyes only, biologically speaking, it’s mostly meant as a tool to communicate with other deer.
The white “flag” serves as a warning of imminent danger. All exposed white areas on the body act as a beacon to help other deer locate and follow each other in dense vegetation while fleeing. This is known as herd cohesion. Think of it as a neon sign lighting the way. As a secondary benefit, flagging also provides a clear signal to predators (like you and me) that they’ve been spotted, which may deter continued pursuit. Been there, done that! In particular, the risk of predation to fawns is likely reduced when they flag.
Research shows tail-flagging is performed by deer of all sex and age groups, with does flagging more often than bucks. However, even tiny, spotted fawns that are merely a few hours old use tail-flagging. In fact, in one study the tendency to flag was greatest among young fawns, though eventually fawns flag at a similar rate to older deer around 6 or 7 months of age. The authors of that study theorized that fawns decrease the risk of predation by portraying themselves as part of a larger group in flight. That illusion helps prevent an individual fawn from being targeted. Obviously, they further benefit by sticking with the adults, who are more experienced.
Mule Deer vs. Whitetail Tails
White-tailed deer are an Eastern prey species that spend a lot of time hiding in dense cover. This landscape and the process of natural selection have shaped their physiology and behavior in several ways. For example, their coat color and hair structure are designed to help them thermoregulate and stay concealed during various seasons and life stages, from spotted fawn to big brown adult. These same influences extend to the presence of a white tail and how it’s used, too.
When whitetails sense danger approaching, they typically hold their ground and don’t move until the last second. Once detected, they’ll either sneak away or, more likely, use short, explosive speed to escape, flagging the entire time. Option B is why they have a white tail. White-tailed deer can outrun most predators for short distances. So, in addition to flagging, their speed is yet another important survival adaptation. This combination allows the group to stay together and maintain strength in numbers. However, if an individual deer is singled out of the herd, the likelihood it may be chased to exhaustion increases.
This behavior is totally different compared to their Western counterpart. Mule deer are much more likely to flee at the slightest hint of danger, even if it’s hundreds of yards and several canyons away (been there, done that too). However, the landscape where they flourish is often more open and contains more topographical obstacles, which has similarly impacted their appearance and behavior. Rather than running or galloping away from a threat, “muleys” exit the scene immediately and commonly display what is known as stotting: They repeatedly jump forward in the air with all four hooves rising and falling in unison. This escape method provides greater vantage and stamina, allowing them to put more distance between their location and the source of danger. Of course, one of the most distinctive physical differences is that mule deer have an always-exposed white rump and thin, rope-like tail with a black tip. With little cover and wide-open visibility in the West, there’s no need for a ‘turn on-and-off’ tail like the whitetail’s!
These differences also influence the number of individuals traveling together for each species. Unlike mule deer, whitetails tend to maintain comparatively smaller group sizes. Rarely, you may see several dozen white-tailed deer in a single place at one time, but in those cases, you’re likely observing numerous distinct groups that have honed in on a limited food resource. There are also big differences in how each species defends itself in response to predation. Mule deer increase their group size, form large cohesive patterns and protect themselves in the face of an incoming coyote or wolf attack, whereas whitetails simply beat feet. All of this has led to the need for an adaptive method of non-verbal communication as whitetails escape.
The Tail End
Sure, the deer tail may not get the same attention as their antlers or their nose, but in the end it’s an important appendage that significantly contributes to their short- and long-term survival because it allows whitetails to stay together while fleeing and navigating thick cover
Interested in learning about 18 more fascinating deer behaviors? Check out this video: