Adrienne is a certified dog trainer, behavior consultant, former veterinarian assistant, and author of Brain Training for Dogs.
What Are Hackles?
A dog's hackles consist of the hairs along the backbone. They generally start from the neck area and go up to the tail. These hairs have a piloerection function, meaning that they have a tendency to raise under certain circumstances. All dog breeds have this feature, however, it is easier to see in some than in others.
For example, in long-haired breeds, the effect is more pronounced on the shoulder area because the hair in this area is much longer.
When the hackles raise, they might go from the neck up to the tail, or they may simply just raise in the neck, back, or tail area.
How Does It Work?
Dogs have special muscles in their skin called arrector pili which are attached to their hair follicles and are capable of fluffing the hair by trapping air between the hair shafts.
These muscles are innervated by the sympathetic branch of the autonomic nervous system and are therefore not under conscious control.
The function allows the dog to appear larger, taller and therefore more intimidating than it is. This is a ''fight or flight'' response triggered by adrenaline, similar in some way to the function of fish that ''blow'' themselves up to three times their size to look much bigger in case of a fight.
Porcupines also depend on this function to scare off any predators. This is also seen sometimes in cats that are startled by something. Simply think the classic posture of a "Halloween" cat.
Did You Know?
If the hairs are in the telogen phase (resting phase) when they erect, they will loosen and eventually fall, which explains why so many dogs and cats shed a whole lot when they are stressed.
Why Do the Hackles Raise?
The dog's hackles may be raised for various reasons. One should consider it an involuntary response that cannot be controlled.
Many people assume that it's a sure sign of aggression, but the most common causes are: fear, arousal, surprise, insecurity, excitement, nervousness, or defensive behaviors.
This behavior is often seen in young dogs that are unsure of their environment and are unsure of how to react.
"Hackling" in dogs may be also somewhat similar to a human getting goosebumps. Generally, the meaning of raised hackles is determined by looking at the context and other accompanying body language.
It's not unusual to see the hackles raised when a dog is playing. This can occur from overstimulation. In some cases, the element of surprise may cause a dog to raise hackles such as when another dog pops out of nowhere during a play session.
While raising hackles is an involuntary behavior, it's not a bad idea to intervene to allow the dog to settle down, explains Robin Bennett, CPDT and Susan Briggs, CKO in the book Off-Leash Dog Play: A Complete Guide to Safety and Fun.
Note: Among dog breeds, the Rhodesian Ridgeback displays permanently raised hair on their backs. This is not to be confused with raised hackles. It is just a typical feature of this dog breed.
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
© 2009 Adrienne Farricelli
Adrienne Farricelli (author) on October 05, 2010:
I was aware of this. This is why I explained '' This is not to be confused with raised hackles, this is just a typical feature of this dog breed''. But it never hurts to clarify as I have had people believe they were ''raised hackles! ;)
michael on October 04, 2010:
Actually, a Rhodesian Ridgeback does not have his hackles up permanently. In reality, he has a ridge of hair along his back that grows in the opposite direction.