People often assume that when a dog has raised hackles that it is displaying dominant aggressive behavior. While this may be the case and one should always be respectful of a dog’s show of reactivity, there are multiple reasons for this phenomena taking place. It is good to become more knowledgeable about dog body language so that we may be able to understand the unspoken signals given off by our canine friends.
In fact, dogs are not the only species to show evidence of what is known as piloerection. Birds, rats, cats, and even humans have an involuntary response of the nervous system where a rush of adrenaline makes the muscles contract causing the hair to stand upright. Have you ever had goose bumps or felt the hair go up on the back of your neck or heard an experience referred to as “hair raising”?
This physical response may be triggered by feelings of fear, aggression, arousal, lack of confidence, anxiety, defensiveness, being startled, or even plain excitement! Hunting dogs have been known to exhibit piloerection when focused with intensity while pointing a bird. Interestingly, the hair raising usually becomes noticeable approximately thirty seconds after exposure to the trigger while taking two minutes to relax.
On a dog you can see the raised hair across the shoulders in a broad swathe. Occasionally you may observe hackles up over the shoulders as well as on the lower back just above the tail. Sometimes you notice a stripe going all the way down the back. Piloerection is more obvious on dogs wit short, stiff coats whereas long, fluffy hair makes it more difficult to spot. Poodles and poodle type coats make it harder to differentiate also
There is not an abundance of data and there can be discrepancies, but it is believed that the dogs who have hackles raised predominantly over the shoulders or withers have a low level of confidence and have fear or even terror. If extreme, they could strike out if cornered or pushed over their threshold.
If the raised hair forms a line all the way down the back and tail, the dog may be more confident in going on the offense in acting out overt aggression.
The third pattern might be the dog who has hackles raised at the shoulders and above tail, but smooth down the center of the back. This dog is thought to be in a conflicted emotional state, thus having the ability to be reactive and unpredictable.
As fascinating as it is to observe piloerection and determine a possible cause, it is more valuable to assess all of the dog’s body language to determine what is going on with the emotional state at hand and how to best deal with it. In my work with dogs, the majority of the potentially aggressive are reacting out of fear. One must be careful as a bite driven by fear can be dangerous, make no mistake! The difference is in how you analyze the problem and design your approach in helping the dog and owner.