A bite seldom "comes out of the blue." The first bite may surprise a novice owner, but to the experienced eye, it's as predictable as a storm rolling in. Our job here is to teach you to recognize that storm while it is still a long way away.
The first thing to know about aggression is that when caught early, it is usually manageable. The second thing to know is that healthy dogs don't "turn on" their owners without warning.
Not every dog that is aggressive will have all of these signs. While some will only have a couple, most will have at least a few. If your dog displays these signs, seek professional advice, join a training class, and educate yourself and then dog.
Watch for:
Ignoring Known Commands
This is so common that most households figure it is just the way dogs are. Not so. Not only is ignoring commands a bad habit, but it can be a strong sign that your dog literally does not think you're worth listening to. And if he won't pay attention to you, an adult, what chance do your children have?
You may have taught him to ignore you by repeating commands, so don't blame him. Aggression most often comes from a dog that sees himself as the head of the household. As long as everything goes his way, he's fine. Cross him, and you'll get growled at or worse.
If your dog ignores you or walks away when you issue a command, take it seriously. Get the whole family involved! Say commands once then calmly follow through. Set up rules that everyone will follow regarding jumping on furniture, eating from the table, and responding to commands. Have him obey you before you obey him. Make sure everyone stops all the free attention he's been getting, or you could be headed for trouble. A united family front is an effective vehicle for change. Exception: Small children. Never ask your child to do something with the dog that you cannot easily do. Adults first, then eldest children and then the little ones with adult back up is the order of dog handling.
Refuses to Lie Down on Command
Here's an even stronger indicator of a potential aggression problem. Lying down is the most submissive posture your dog can assume. If he flat out refuses this command (not just is confused or untrained) or if he has "forgotten it" of late, then trouble may be brewing. Get help. Withdraw all attention unless he is down. If the dog tenses up or growls, stop. Do not continue without qualified help. Also, if this is an overnight change – it could be pain. Speak to your veterinarian.
Bumps into You or Children
Disrespectful dogs will bump into people they feel are below them in the group. If your child is being pushed out of the way at the door, bumped in the hall, or knocked down in the living room, this is no mistake! Teach your puppy to respect your space - those simple games are shown on the MySmartPuppy DVD. Puppies learn them quickly, no reason to live with this annoying and potentially dangerous habit.
Mounts You or the Children
As embarrassing as this is, your dog is not doing it because he thinks you are attractive. He is doing this as an act of dominance. Because it is about power and not about sex, a female dog can be a mounter as well, although that is less common. This neither funny nor acceptable behavior is always a sign that the dog thinks he is in charge. Trouble is most definitely on its way.
Refuses to Give Up Sleeping Areas
Your dog is asleep on the couch. You tell him to get off, and he lowers his head, tensing. You feel threatened. A dominant dog doesn't relinquish sleeping areas to subordinates. And once a dog is elevated on a bed or couch, the likelihood of an aggressive incident increases. It also may put the dog at your child's face level which is not good. A dog who shows any hint of resistance/aggression should stay on the floor.
Stops Eating or Chewing When Approached
Your dog is chewing a toy. You walk toward him, and he stops. He looks at you tensely. If you make a move toward the toy, he tenses up or growls or moves his head between your hand and the toy, blocking you. None of this is not good. Nothing in your house is his. Toys, beds, bowls are all yours. You allow him to use them. He has absolutely no right to claim them as his own or warn you from them.
Hides under Furniture
A dog who heads for cover is a dog who's saying "I'm frightened." Push too hard and you'll could get a bite. Never allow a child to crawl under a piece of furniture toward the hiding dog! On the dog's behalf, this is can be an animal who has been harshly corrected and has lost trust in humans. Move to positive training methods, leave a lead on the dog when you are home with him. Stop all threatening training methods. If he scoots under, call him happily and use the lead to guide him out; then praise him and give him a treat. Chances are he'll learn to relax. This will start rebuilding his faith in you. Prevent the problem by blocking the area with suitcases or boxes.
Growls for Any Reason Other Than Play
Growls are warnings. In play, they warn in fun. The same way kids shout "I'm gonna get you!" dogs growl in play. You can tell this is play because the tail is wagging, and the dog is moving in a playful, relaxed manner. There are also unsure growls, such as the low growl a dog gives an object that he does not recognize. This is not an aggressive growl as much as a commentary. Normally when the object has been thoroughly examined, the growling disappears.
Then there are the other growls, the "don't come closer," "don't bother me," "I don't want to do that" growls. These are bad news. Get help, seek professional assistance, train your dog to respond to commands, make him work for the things he wants, and limit the attention you give him. Teach him that you are his leader and that he is the beloved, cherished, and obedient follower. Aggression is most often a reflection of his general attitude toward you. Once you improve his attitude toward you the aggression will decrease.
Not Neutered
Intact male dogs are responsible for the majority of serious bites in this country. By keeping your dog intact you may well be endangering his welfare. People can feel uncomfortable with neutering their male dogs but often change their minds when they realize that their child's safety can be at stake.
Please keep in mind that aggression either increases or decreases depending on what action you take. The truth is that canine aggression usually works. The dog snarls, you withdraw. He growls and you "leave him alone." This confirms his belief that he can assert himself with humans, making him more likely to be aggressive in the future.
Taking action as soon as you can and seeking qualified professional guidance is the best course of action. Please, do not delay.