- Not a substitute for professional veterinary help.
From short and curly to long and floofy, a dog’s tail is a big part of their appearance and personality. But what’s a tail’s purpose? Why do dogs have them, and what do they use them for?
First and foremost, dog tails are powerful tools for communication—though it’s been suggested that they might play a role in scent dispersal and even balance. Not everything a tail does is a conscious effort on a dog’s part, either. Some tail movements are deliberate, but others are involuntary reactions to things a dog is feeling.
With help from Dr. Stacy Kolb, an ER veterinarian at South Carolina Veterinary Specialists & Emergency Care in Columbia and a Thrive Pet Healthcare partner, we discuss what science tells us about why dogs wag their tails.
Dogs Wag Their Tails To Communicate
A wagging tail can signal a huge range of emotions, from happiness and excitement to nervousness and even aggression. “These different expressions are why it’s important to look at a dog’s overall body language to interpret why they may be wagging their tail,” says Dr. Kolb.
Happy
A dog is usually communicating happiness or excitement when they make large, sweeping, relaxed movements back and forth with their tail, either in a neutral or a slightly upright position. Your dog may greet you with this happy tail when you walk in the door or when you’re doing something they love, like playing fetch.
Alert
If a dog is alert, their tail will usually be stiff or slowly wagging while remaining at a mid to low level. You may see this tail position after your dog hears a noise or when they catch a whiff of another animal nearby.
Anxious or fearful
A low or tucked tail might indicate that your dog is feeling worried. Look for other signs of discomfort or anxiety, including flattened ears or excessive lip-licking.
Aggression
A wagging tail can also serve as a warning sign that a dog is likely to escalate to aggression. In this instance, a dog will usually have their tail arched over their back, holding it stiffly or moving it quickly. Other signs to watch for are bared teeth and flattened ears.
Dog Tails & Scent Dispersal
Tail position and wagging is sometimes thought to play a role in scent dispersal. It’s been hypothesized that a dog who tucks their tail is making it more difficult to detect their unique scent, while a dog who carries their tail high with confidence will be easier to sniff out.
Dr. Kolb isn’t so sure. “In times of fear, dogs can express their anal glands, and anywhere the material lands, it will smell; therefore, if it lands in the tail, then the tail can smell, but that is not its intended mechanism,” explains Dr. Kolb.
So as far as modern science can tell, tail wagging probably only helps with scent dispersal if the tail comes in direct contact with the scent.
Do Dog Tails Help With Balance?
Although dog tails were previously thought to aid in balance, a 2023 study found that tails don’t play a major role in keeping a dog upright. “The tail does not play a significant role in balance because they are quadrupeds,” explains Dr. Kolb. “That may change if they require a limb amputation or are born with a limb defect.”
So if your dog doesn’t have a tail or has a docked tail, don’t worry—they can still be the fastest on the agility course. Their social life won’t necessarily suffer either, since they have a lot of other signals they can use to communicate with other dogs, Dr. Kolb reassures.
You’ll see dogs without long tails:
- Wiggling their butts
- Exaggerating facial expressions
- Emphasizing body posture
- Making small physical adjustments (e.g., relying on the body’s proprioceptive senses and inner ear system to take over the role of the tail)
Vera Aksionava via iStock
Did Domesticating Dogs Change Tail Wagging?
There’s significant evidence suggesting that the domestication of dogs may have changed their tail-wagging behaviors. One recent study found that when raising both dog pups and wolf pups in the same exact way, only the dog pups started to wag their tails and offer communicative behaviors. The wolf pups, on the other hand, almost never wagged their tails.
“A majority of tail wagging is a learned response to their owner and the owner’s excitement,” adds Dr. Kolb. “Therefore, domestication may have increased the amount of tail wagging a dog may do, but it is still more natural for some and thus may require further study.”
Domestication syndrome vs. rhythmic wagging hypotheses
Currently, there are two major theories regarding why domesticating dogs could have increased tail wagging. The “domestication syndrome” hypothesis states that the tail wagging we see today may have been an accidental byproduct of other traits that dog breeders were selecting for, such as docility and friendliness.
By contrast, the “rhythmic wagging” hypothesis suggests that throughout history, humans have tended to choose dogs that wagged their tails more because they were inherently attracted to the rhythmic stimuli that tail wagging provided.
Either way, tail wagging has come to be an incredibly valuable communication tool for dogs in their communications—and for humans, if we can learn to read and interpret our friends’ powerful body language.
