Glossary

Piloerection

The raising of the hair along a dog's neck, shoulders and back, a sign of strong arousal rather than automatic aggression.

Also called: raised hackles, hackles up, raised fur, hair standing up

Piloerection, or "raised hackles", happens when tiny muscles lift the hair along a dog's neck, back and sometimes tail. It is an involuntary response to strong emotion, in the same way that humans get goose bumps. It makes the dog look larger.

It does not mean the dog is going to attack. A dog may raise its hackles from fear, excitement, surprise or uncertainty, as well as in a conflict. Look at everything else: a stiff body, hard stare, growl or forward posture suggest threat, while a lowered body, tucked tail or turning away suggest fear. Give a dog showing raised hackles space and time, and avoid forcing contact.

Last reviewed November 8, 2026

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Related terms

Dog body language The postures, faces and movements dogs use to communicate feelings and intentions without sound. Tail wagging A dog's tail movement, which signals arousal and emotion but does not mean a dog is friendly. Stress signals Small changes in behavior, such as panting without heat, yawning, shaking off or a tucked tail, that show a dog is uneasy. Whale eye A look in which a dog turns its head away but keeps its eyes on something, showing a crescent of white, and is often uneasy.