Piloerection Or Hair Standing On End
This most often shows fear and is a sign to back away
Piloerection, or the hair standing on end is often seen through
the shoulders and down the back of animals. It is a sign
of excitement or arousal and is most often associated with fear.
In addition to the bristling hair, the eyes are usually open
In dogs, it looks aggressive but it is best
to treat this as a sign of fear. The more hair that is standing
on end, the more nervous or fearful the dog is.
Piloerection is more visible on dogs with short, stiff hair. Some
truly frightened dogs can look like brushes.
Involuntary reaction to fear
Piloerection is a function of the nervous system and is an
involuntary reaction to a stimulus such as fear or even cold
weather. Adrenalin triggers contraction of the arrectores
pilorum muscles in the skin. They contract and push up the
hair follicles causing the hair to stand away from the body.
The terms comes from the Latin pilus meaning hair and
erection meaning elevated. Similar displays occur in other
animals including cats. The traditional look of a Halloween cat
with arched back, wide open eyes and hair that bristles from
head to tail is one example. The idea of a bird or a human
having ruffled feathers is another example.
Walk away to be safe
In addition to being an involuntary reaction, piloerection has the
added advantage of making the animal look bigger. This may
cause the source of the fear, another animal or a human, to back
away. When you see this in your dog or cat, you can calm
him down so that fear does not escalate into snarling, lunging,
biting or fighting. If you see this in an animal you do
not know, break off eye contact and slowly back away.