What is the term for the dog's hair rising along its back, signaling its emotional state?

• A. Piloerection
• B. Trembling
• C. Grooming
• D. Panting

Answer: (A)

Piloerection describes the hair along the dog's back standing upright. This happens when the tiny muscles at the base of each hair follicle contract as part of the autonomic nervous system’s response to arousal. When a dog is frightened, threatened, or highly excited, the hackles rise to make the dog appear larger and to signal heightened readiness. It’s a warning cue that the animal may become aggressive or defensive, so give space and watch for other signs like a stiff posture, direct stare, or raised tail to gauge intent. Other listed behaviors—trembling, grooming, panting—reflect different states (shaking from fear, self-cleaning behavior, or rapid breathing) and don’t indicate hair standing on end.