Dog hackles; Hair-raising facts

Dog Hackles; Hair-raising facts

Whether you’ve got a feisty Fido or calm canine, you’ve probably, at some point, been aware of your dog’s hackles. For many owners, raising the fur along a dog’s back and shoulders is cause for alarm as most people associate it with aggression.

But raised hackles are a much more sophisticated form of communication than that.  Depending on the situation and the rest of your dog’s body language, the meaning may differ. So here are our hair-raising facts about dog hackles and what they mean.

What are dog’s hackles?

All dogs have hackles, whether you’ve seen them raised or not. They run all the way from a dog’s neck, along the back to the base of the tail.

When a dog’s hackles rise, it is an involuntary reaction to something in the environment. It’s a bit like us getting goosebumps when hearing a great piece of music or see something emotional.

Technically called piloerection, raised hackles can appear in just one area or over the dog’s whole back. Special muscles serve the hair and skin in these areas called arrector pili, capable of lifting the hairs and puffing them out. These muscles are part of the sympathetic branch or fight or flight side of a dog’s autonomic nervous system, meaning that your dog has no active control over them.

The four F’s

Our dogs, like us, experience stress. Sometimes, this is in the form of an unknown dog or a new situation, or loud noise. When something is perceived as a threat, the sympathetic side of the nervous system steps up to prepare the body for action.

Typically this is referred to as the fight or flight response, but these aren’t the only available responses. Dogs also use freeze and fidget responses in answer to stress, but the physiological changes are the same.

When the fight or flight response is activated, adrenaline is released into the body along with stress hormones like cortisol.  The body gets a boost in energy, heart rate quickens, and hackles stand up to communicate arousal.

Common stressors in dogs

What our dogs see as a perceived threat varies from dog to dog. Some dogs are very chilled out, while other dogs are much more anxious. One of the difficulties in identifying what your dog finds stressful is that sometimes it isn’t a single event but rather a build-up of mild stressors over a period of time.

These stacked stressors often cause people to say, “it came out of nowhere” when dogs bite. The truth is that often the dog has been overwhelmed by multiple situations in which they have experienced feelings of excitement, nervousness, surprise, insecurity, or irritation.  But each incident in itself has been below the threshold of immediate threat.

Once a dog has too many of these incidents, they snap, similar to when we say ‘the last straw broke the camel’s back.’

Common stressors for dogs include;

  • Feeling trapped, including being leashed
  • Loud noises
  • Unfamiliar dogs
  • New people
  • Noisy household
  • Overstimulation when playing
  • Over excitement
  • Frustration

But without a doubt, the most common occurrence of raised hackles is when one dog meets another. So what does it mean?


Raised hackles are often associated with a sign of aggression and with good reason. As it is most often seen when dogs meet. Unfortunately, this sometimes leads to a scuffle, and so hackles have been linked to aggressive behavior.

But it is much more likely that your dog feels unsure, excited, or curious when they meet another animal, and the hackles are just a sign of a heightened emotional state.


Linked to the fight and flight response, fear also triggers raised hackles. When dogs are scared, they still experience the involuntary trigger of the sympathetic nervous system.

In some cases, when a dog is unsure of something, as soon as they get close enough to sniff the object, the fear response disappears, and the hackles go down. This reaction happens with new objects, people, or situations and frequently occurs when dogs catch sight of something that looks unusual.


It may seem unlikely, but excitement and fear generate the same response in the body as each other. It’s why a lot of people enjoy horror movies.

Overexcitement can trigger raised hackles in the same way that fear does. This includes play, hunting, chasing, being stroked, and introductions into new environments.

So when a dog raises its hackles, how can you tell if a dog is aggressive, fearful, or excited?

Raised hackles, the whole picture

As your dog can’t control when or if its hackles rise, you must do your best to read the situation. Hackles just let you know that your dog is experiencing arousal in some way. It’s up to you to look at the rest of your dog’s body language and behavior and assess the situation.

If you think your dog is experiencing stress or has become overexcited, remove them from the situation if it’s safe to do so. Understanding a dog’s body language is not always easy, but if your dog looks relaxed and happy, but their hair is standing on end, they are probably just excited.

On the other hand, if your dog’s body is stiff, seems uncomfortable, and has raised hackles when another dog is present, it could mean trouble, and you may want to move them on quickly. Similarly, if your dog is trying to hide behind your legs with hackles raised, they are more likely to be experiencing fear, and you need to reassure them or remove them from the situation.

Dog hackles on dogs

Not all hackles are created equal

If you have trouble reading your dog’s body language, there is another way that you can get information about your dog’s mood.

Although there isn’t much science to back these claims up, there is anecdotal evidence to support that the position of the raised dog’s hair is a determining factor in the mood it represents.

  • Shoulder and neck; Low confidence or fearful – Defensive
  • In a line along the back; Confident – Offensive
  • Shoulders and above tail but smooth back; Conflicted – Unpredictable

You know your dog best. If you think they are in a situation that is making them uncomfortable, take them out of it.

Dog hackles the facts

Despite concerns that raised hackles to mean that a dog is about to get aggressive, it’s not always the case. Any situation that your dog is unsure of is excited by, fearful of, or unhappy with can cause the fur on their back to stand up.

If you’ve never seen your dog’s hackles rise, it doesn’t mean they don’t have them; all dogs do. It’s just much easier to see hackles on dogs with short straight hair than it is to see on any other type of fur.

It’s important to look at the whole picture when a dog’s hackles are raised and not jump to conclusions. Your dog may simply be aroused in some way. You know your dog best so take appropriate action based on what you know of their behavior.

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