The Root of the Behavior
Breeds with longer hair show hackling more clearly in their shoulders and some breeds such as Poodles can often have piloerection with no one noticing. One breed, the Rhodesian Ridgeback, has permanently displayed raised hackles that is a prominence of his breed rather than a constant piloerection. Many people assume that "hackling" is a sign of aggression and that any dog with raised hackles is looking to fight. In fact, dogs that are raising their hackles are more likely feeling startled, fearful, lacking confidence, nervous, or even excited. Hunting dogs often raise their hackles when they are hyper-focused and pointing at a bird of prey. It is important to learn that all sorts of emotions can bring on the piloerection, and working with your dog through these feelings is essential to having him properly socialized.
Encouraging the Behavior
Regardless of what is going on with your dog and his hackles, you need to remain alert yet calm. Even a dog that is aggressive is often working from fear and needs you to make the situation safe. An aggressive dog needs to be removed from any social gathering that may give him the opportunity to harm himself or others. Work to distract him and lead him away until he can be soothed. However, if your dog seems to have his hackles raised because he is nervous he may just need you to support him through the social situation. A dog that is not properly socialized can become fearful around other people and dogs. Removing him will not help him to become socialized, and dogs that are not properly socialized are more prone to developing aggression. An experienced trainer can help you socialize your dog and decrease the chance of problems in the future.