A dog’s tail is the terminal end of its spinal column, which includes the back bones (vertebrae) and spinal cord (a large, rope-like bundle of nerves). Tail-wagging is actually a very complex behavior and isn’t well-understood. Dog’s use their tails to indicate a number of things, such as social standing and alertness. Different breeds naturally carry their tails in different positions, so broad generalizations about tail carriage aren’t always useful. However, there are some interesting trends:
- - A horizontal tail position, pointing away from the dog but not really stiff, may be a sign of attention.
- - A horizontal tail position, pointing away from the dog straight-out and stiff, is often part of an initial challenge, such as when a dog meets a stranger or confronts an intruder.
- - A tail held up, between the horizontal and vertical position, may be a sign of dominance.
- - A tail held straight up and stiff or curved over the back is usually an expression of confidence and maybe extreme dominance or aggression. Some breeds (such as Shiba Inus, Samoyeds and Akitas) naturally carry their tails in this position.
- - A tail held lower than horizontal, but still away from the hind legs, probably suggests that the dog is relaxed, but it may reflect insecurity or a worried feeling.
- - A tail that is held straight down, close to or between the hind legs, can mean many different things, depending on the rest of the dog’s body language. It may indicate that the dog isn’t feeling well, or is depressed, insecure, submissive, passive or uncomfortable.
- - A tail tightly tucked between the legs usually means “I’m scared! I submit!”
- - Hair standing up along the top of the tail often means that the dog is feeling a bit aggressive: “I’m ready to fight, if you are.” A kinked or sharply bent tail that is held high can also be a sign of aggression.
- - A gently wagging tail suggests a greeting or contentment, while a vigorously wagging tail usually is more suggestive of agitation or aggression.
More About Tail-Wagging...
Enough with the generalizations. Dogs have been wagging their tails since… well, since there have been dogs. These furry appendages serve multiple purposes. The original purpose of the dog's tail probably was for balance. It prevents him from toppling over as he makes sharp turns while running or swimming, acting somewhat like a rudder. The tail also helps with balance when a dog climbs, leaps or walks along narrow structures. Over time, the tail started to play an increasingly important role in canine communication. Dogs obviously wag their tails more than most other domestic animals do, although horses and cattle use their tails to swat away flies and other annoying insects.
People tend to associate a wagging tail with happiness, excitement or pleasure. However, the mystery of tail-wagging is not that simple. Certainly, a wagging tail means something, although we don’t have a large body of scientific information about this subject. It is thought to involve both visual (sight) and olfactory (smell) cues. Dogs are much more in-tune with body language than people are. Tail motion and position are believed to reflect a desire or intent to communicate information to other animal or people, or at least a willingness to interact with them, without regard to whether they are feeling submissive, passive, dominant or aggressive. While some tail-wagging undoubtedly is associated with happiness, this isn’t a reliable generalization, much like a smiling person isn’t always happy or feeling friendly. Because dogs are such social animals and use their tails to communicate strong emotions, such as agitation, annoyance and anger, as well as happiness, parents should teach their children never to approach unfamiliar dogs without permission, whether or not their tails are wagging.
Studies have shown that dogs don’t wag their tails when they are alone, probably because there is no one there to communicate or interact with, so they have no need to. Sometimes, a wagging tail simply signals excitement. Vigorous wagging can reflect extreme excitement, to the point of anger, aggression or fear. Dogs that hold their tail high and wag it rapidly probably express more of their signature aroma from their anal glands and thus indicate a stronger message, whatever their message may be. Another source of scent is a gland on the outer part of the tail, called the supracaudal gland. It’s not clear whether all dogs have retained this scent-producing gland as they have evolved. Course black guard hairs often indicate its location, or where it used to be. Soft or subtle wagging of a low-slung tail is often associated with submission, curiosity, pleasure or a friendly “hello”. A tail clamped tightly between the legs may prevent much of the animal’s signature smell from being released, communicating a more timid message. At least one study suggest that dogs wag their tails more to the right when they are feeling happy or confident, because the left brain (which controls the right side of the body) is involved in behaviors that scientists call "approach" and "energy enrichment." Dogs may wag their tails more to the left when they are feeling frightened, insecure or want to get out of a situation. The right side of a dog's brain controls the left side of its body and is involved in feelings of withdrawal and energy expenditure.
Dogs whose tails are docked, bobbed or otherwise naturally or artificially short may be at a slight disadvantage, because they are less able to communicate with other canines (or people) through tail position, posture and motion and sharing of signature scents than their longer-tailed compatriots. Puppies don't come out of the womb wagging their tails. The majority of them only start wagging after they reach around 4 to 6 weeks of age, when they need to communicate with their litter mates, mother or people. For example, if there's too much "rough-housing" going on, one puppy might wave its tail like a white flag to signal a truce. As they mature, many dogs wag their tails while looking at their owners, asking for food. Researchers have not confirmed whether tail-wagging is voluntary or involuntary. Does a dog think about what he wants to communicate and then decide how to use his tail to communicate it, or does his tail just act independently of conscious thought? It may be a bit of both, much like people and smiling – sometimes it is involuntary, and other times we think about smiling before we do it. Further studies will no doubt disclose other insights into why dogs wag their tails. In the meantime, dog lovers everywhere will continue to debate this intriguing canine behavior.