Raised hackles in dogs are when the hairs on their backs stand up, similar to goosebumps in humans. This response — called piloerection — is an involuntary mammalian response that doesn’t always mean your dog is scared. It simply means your pup is aroused by something and is on high alert: from a smell, a feeling on their paw, or even the temperature changing. A dog’s hair standing on end is a normal reaction to stress or arousal, so pay attention! They may have noticed something you haven’t.