Why Do Dogs Need a Tail?

A dog’s tail is vital for balance when moving and as a means of communication.

Posted January 30, 2026 | Reviewed by Abigail Fagan

Most dogs, except in the cases where humans have intervened, have a tail. Many of these tails, like those on a Golden Retriever or an Irish Setter, are quite handsome and pleasing to the human eye, but one must ask the question, “Other than simply being an elegant ornament, does a dog’s tail have any meaningful function?”

It’s a Matter of Balance

Careful kinematic research, such as that done by a Japanese team headed by Naomi Wada, has determined that the dog’s tail was designed to assist the dog with balance. When a dog is running and turns quickly, he throws the front part of his body in the direction he wants to go. This causes his back to bend; however, the forward velocity is such that his hindquarters will tend to continue in the original direction. The momentum can result in the dog’s rear swinging wide, which may slow his rate of movement or even cause the dog to topple over as he tries to make a high-speed turn. The dog’s tail helps to prevent this problem. Moving his tail in the same direction that his body is turning serves as a counterweight, which reduces the tendency to spin off course.

When moving at lower speeds, dogs also use their tails to assist them when walking along narrow or unstable surfaces. By swinging the tail to one side or the other (in the direction opposite to any tilt in his body) the dog helps to maintain his balance. This is much the same way that the circus tight rope performer uses his balance bar. However, the tail is not particularly important on flat surfaces at normal speeds. Then it becomes available for other uses, and evolution has seized upon the opportunity to utilize the tail for communication purposes.

An Emotional Thermometer

Perhaps the most common misinterpretation of dog behavior is the myth that a dog wagging its tail is happy and friendly. While some tail wags are indeed associated with pleasant feelings, others can signal fear , insecurity, a social challenge or a warning not to approach.

The tail’s position—specifically, the height at which it is held—can be considered a sort of emotion measuring meter. A middle height suggests the dog is relaxed. If the tail is held horizontally, the dog is attentive and alert. As the tail position moves further up, it is a sign the dog is becoming more threatening, with a vertical tail being a clearly dominant signal meaning, “I’m boss around here,” or even a warning, “Back off or else.”

As the tail position drops lower, it’s a sign the dog is more submissive, is worried or feels poorly. The extreme expression of this sort is the tail tucked under the body, which is a sign of fear, meaning, “Please don’t hurt me.”

Tail Movements Matter

Dogs’ vision is much more sensitive to movement than to details or colors, so a moving tail is very visible to other dogs. Evolution has made tails even more visible by providing some with a light or dark tip or a lighter underside to improve the visibility of tail motions.

The speed of the wag indicates how excited the dog is. Meanwhile, the breadth of each tail sweep reveals whether the dog’s emotional state is positive or negative, independent of the level of excitement.

There are many combinations, including the following common tail movements:

Left or Right Tendencies Are Meaningful

There is another, more subtle, dimension to tail movements which is also important, namely side bias . A group of Italian researchers observed that when dogs see their owners, their tails tend to wag vigorously with a bias to the left side of their body (as seen from the front). Such predominantly left-sided wags were accompanied by a tendency for the dogs to approach. When confronted with the sight of an aggressive, unfamiliar dog, their tails wagged with a bias to the right side and they tended to avoid rather than approach. Follow-up research showed that seeing another dog wagging its tail with a leftward tendency tends to evoke positive emotions, while right wagging tendencies trigger negative emotions in dogs that observe it.

What Happens When the Dog’s Tail Is Absent or Very Short?

If the dog’s tail is so important, then the absence of a tail could cause communication problems for a dog when interacting with other canines. Steven Leaver and Tom Reimchen of the University of Victoria in Canada constructed a robot dog that stood 20 inches at the shoulder. It was stuffed with cotton and covered with black synthetic fur so that it looked much like a Labrador Retriever. It could be fitted with a 12-inch long tail or a 3.5-inch, short stubby tail and this tail’s movements could be remotely controlled.

Starting with the long-tailed version, they placed the robot dog in an off-leash exercise area. They found that when the robot’s tail was wagging (non-threatening) other dogs would approach it in a playful manner. However, when its tail was held upright and was motionless (dominant threat signal) the other dogs avoided it, which is what we would expect if the dogs were reading the robot’s tail signals as if it were a real dog. Next, they replaced the robot’s long tail with the short “docked” version and returned it to the exercise area. Now, other dogs approached it cautiously and in a guarded manner, regardless of whether the tail was wagging or not. The researchers concluded that the other dogs were acting as if they could not make up their minds as to whether the robot would receive their approach in a friendly or a hostile manner.

All of this confirms that tail movements and tail positioning are vital channels of communication among dogs, and perhaps we humans should think twice before we dock their tails and deprive them of its benefits—especially if the tail docking is being done solely as a matter of fashion or style.

Facebook image: Juice Dash/Shutterstock

Leonetti, S., Cimarelli, G., Hersh, T. A., & Ravignani, A. (2024). Why do dogs wag their tails?. Biology Letters, 20(1), 20230407.

Wada, N., Hori, H., & Tokuriki, M. (1993). Electromyographic and kinematic studies of tail movements in dogs during treadmill locomotion. Journal of Morphology, 217(1), 105-113.

Siniscalchi, M., Lusito, R., Vallortigara, G., & Quaranta, A. (2013). Seeing left-or right-asymmetric tail wagging produces different emotional responses in dogs. Current Biology, 23(22), 2279-2282.

Coren, S. (2001). How to speak dog: Mastering the art of dog-human communication. New York: Fireside Books, Simon & Schuster (pp. i-xii, 1-274).

Leaver, TE and Reimchen S. (2008). Behavioural responses of Canis familiaris to different tail lengths of a remotely-controlled life-size dog replica. Behaviour 145(3), 377-390.

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Stanley Coren, Ph.D., FRSC. , is a professor of psychology at the University of British Columbia.

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This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.