Dog trainers and behaviorists consider a dog to be “reactive” if it overreacts to certain triggers in its environment. Some dogs react to the sight of another dog, kids, loud noises, or frenetic activity. They often exhibit frightening behavior, such as growling, barking, and lunging. It is often the result of fear, insufficient social experience when young, or exposure to a very scary incident.
If your dog is non-aggressive to other dogs and people when off leash, and reacts badly when on leash, chances are that he or she is “reactive” and not truly aggressive. However, some reactive dogs can, if they are not managed properly, become aggressive if they cannot make the scary thing go away just with an aggressive display, or distance increasing signals, so it is essential that you learn how to help your fearful or reactive dog. Your dog is depending on you to “save” him.
One of the best things you can do to make your dog feel more at ease is to remove pressure from his neck. It can be helpful to use a front-clip no-pull harness, such as the Sensible harness. Using other management tools, such as prong collars, can make things worse – you never want to punish an already frightened dog, or cause pain to a dog that could become aggressive (one possible unintended consequence of sensing pain at the neck when another dog approaches is that some dogs will think that the other dog is causing the neck pain, and grow more fearful, or react with aggression if the approaching dog gets close enough). Allow enough space between your dog and the scary thing so that he doesn’t react in the first place, or get him out of there at the first sign he is reacting. You will need to understand the distance at which your dog reacts in order to further your training, so take careful note. Every dog has their own comfort zone. Some dogs can tolerate another dog almost up to their face, and other dogs react when the other dog is 200 feet away! Remain calm yourself. Don’t clench up on your leash or freeze in place. This only makes your dog think there really is something to be nervous about. Better to walk away then just stand there frozen with your dog reacting. Contact a positive trainer (you can find one at Truly Dog Friendly, Victoria Stilwell Positively, Karen Pryor Academy, Peaceable Paws, or IPDTA) for help, or see if your local SPCA offers positive “Growlies” or “Feisty Fido” type classes.
If you live in a remote area with no trainer nearby, here’s a great little video by another positive trainer on “The Surprise Party Game” that can help you teach your own dog to look to you for guidance when approached by something scary.