There is this notion that dogs with their hackles fully erect are the most dangerous breeds, that they are most likely to be the aggressive types. However, a closer look at some members of the animal kingdom, it seems that hackles are not exclusive to dogs and that they are indeed found in some birds and other mammals, too. So what is the deal with hackles anyway? Are they really an indication of a dog’s aggressive tendencies? Let’s find out more.

What are Hackles?

Hackles are strands of hair or plumage that are known to be attached to an erectile mechanism underneath. In birds, especially roosters, these erectile feathers are found on the side and back of the neck and are especially colorful. Among dogs, hackles are the locks of fur that run from the base of the neck all the way towards the base of the dog’s tail. One can think of dog hackles as fur that are located along the spine of the dog, although it is most pronounced a few inches from the base of its neck up to the level between the shoulder blades or several inches beyond it. These furs also have erectile properties that are not usually seen in fur from other body parts.

hackles in dog's hair

The Process of Piloerection

Have you ever experienced goose bumps? Some folks actually call it goose flesh or even goose pimples. The thing is that goose bumps are the end-result of a process called piloerection or the contraction of the small band of muscle that is attached to every hair follicle. This muscle is called the arrector pili. When it contracts, it pulls the hair follicle causing it to stand up or go erect. Additionally, the tissues surrounding the hair follicle contract creating that characteristic ‘bulge’ or ‘bump’ on the skin. That is why if you have goose bumps, you could easily see small ‘bumps’ on your skin.

The same is true with dog hackles. These furs running along the dog’s backbone also contain the specialized arrector pili muscles that cause goose bumps in people. These muscles are under the influence of the sympathetic nervous system, a branch of the autonomic nervous system which is defined as involuntary. As such, humans and animals that have arrector pili in their skin will not really be able to control when these muscles will contract. As such, there really is no way for you to control your goose bumps in the same way as a dog will not really be able to directly control its hackles from standing erect.

Piloerection and the Fight-or-Flight Response

Since the process of piloerection is under the influence of the sympathetic nervous system, it is often associated with the fight-or-flight response. Technically this is the stress response. Under the General Adaptation Theory, the fight or flight response is taken as the body’s response upon encountering a stressor. It readies the organism to either face the stressor head on (fight) or to move away from it as fast as possible (flight). During this stage of the 3-stage General Adaptation Syndrome, the dog releases epinephrine or adrenaline and cortisol which can help the dog respond to the stressor.

When a dog is presented with a stressor, the sympathetic nervous system is stimulated to prepare it for fight or flight. This is perhaps the reason why people equate raised hackles as a sign of aggression. But given the fact that it is a natural reaction to sympathetic stimulation, raising the hackles can also mean that the dog will be retreating in the face of the stressor.

It is important to understand that stressors can be anything and that it doesn’t necessarily have to be negative. Stress is a reaction to a stressor and is characterized by change. For example, the sight of a favorite treat will get your dog excited. The stressor here is the treat as it is able to elicit a particular response or change. Excitation is pretty much a manifestation of sympathetic stimulation.

The release of adrenaline and cortisol as a result of sympathetic stimulation causes a sudden increase in energy as well as an increase in heart rate. This also leads to the contraction of the different muscles including the arrector pili muscles. The organism’s senses become acutely aware or hyper-vigilant. They focus on certain things. They don’t get easily distracted.

That being said, anything that can stimulate the sympathetic nervous system can also stimulate the fight-or-flight response. Anything that stimulates the fight-or-flight response has the capability to cause piloerection; hence raising the hackles.

hackles on dog's fur

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Interpreting Raised Hackles in Dogs

It is clear that raised hackles are a manifestation of the fight-or-flight response. And since there is a direct causal relationship between stress and piloerection, it is important to understand some of the more common stressors that may affect dogs. Again, it should be understood that these are more in the general terms and that not all dogs may display the fight-or-flight response when faced with such circumstances. Here are some stressors that can stimulate the fight-or-flight response in dogs.

  • Loud noises including noisy household
  • Presence of unfamiliar dogs
  • Presence of unfamiliar persons
  • Over-excitement
  • Feeling trapped such as when placed inside dog crates or on leash
  • Overstimulation especially when playing
  • Frustration

There is one very particular instance when a dog’s hackles are raised and that is when meeting a strange or unfamiliar dog. So what does it mean?

First, it can mean that your dog is ready to ‘fight’, giving it an aggressive stance. However, this is just our own interpretation since the raised hackles may also indicate over-excitement or even curiosity about the new dog on the block.

Second, it can also mean that the dog is frightened or is preparing in the ‘flight’ stage. Dogs that are fearful or are uncertain of something can definitely show raised hackles. Can you remember having goose bumps while watching a horror film?

Third, it can mean your dog is simply over-excited at the prospect of meeting a new dog.

Raised hackles in dogs only indicate that your pet is in a heightened state of arousal. Its sympathetic nervous system is fully at work. The raised hackles are nothing more than the result of the stimulation of this part of the dog’s nervous system. How you interpret it is entirely up to you.

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Sources

  1. Dog Hackles: Hair-Raising Facts, Practical Paw
  2. Raised Hackles, a Sign of Aggression in Dogs?, Master’s Degree Dog Training
  3. The Function of a Dog’s Hackles, Pet Helpful
Olivia Williams
Olivia is our head of content for MyPetNeedsThat.com, mum of one and a true animal lover. With 12 different types of animal in her family, it's never a dull moment. When she isn't walking the dogs, feeding the cats or playing with her pet Parrot Charlie, you will find her product researching and keeping the site freshly updated with the latest products for your pets!

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