There are a couple of different kinds of dog-to-dog aggression: aggression directed at dogs it knows (pack mates) or directed at dogs it does not know.
Pack Mate Aggression
Some of the worst fights involve a kind of sibling rivalry towards another member of a dog’s pack. These fights can be either very short and more of a skirmish or can be very intense and aggressive.
Most of these fights are related to status. Each pack has to have an order to it, and some dogs are natural leaders, others followers. Too many leaders in one pack can be one too many, and the results of infighting can be tragic.
These fights seem to spontaneously happen, and often an owner may report that it started over nothing. No bout of aggression occurs over nothing. Usually, these fights occur over personal space, toys, treats, sleeping spots, or people.
It is very important for owners to treat all dogs fairly within a pack and to never, ever favor one dog over another. Do not give special treatment or items to one dog or another. It is most dangerous when favoring a small dog because a large dog may one day kill that dog during a dispute.
Instead, owners need to acknowledge who the clear leader in the pack is. Who seems to take control of situations? Who do the other dogs look to? This is the dog that cannot be slighted, as he is a natural leader in this pack. It is important to remember to train all the dogs in a group and to have boundaries in the household because even the leader of the dogs needs to follow your lead.
Strange Dog Aggression
Most cases of aggression directed at other dogs stem from lack of exposure to new dogs. While your dog need not play with or even like all the dogs it meets, it does need to be able to handle itself appropriately.
Socialization during puppyhood greatly helps your dog, and it is important that it continues to see dogs throughout its life. Once a puppy leaves its litter, it loses the everyday connection to other dogs. If it does not continue to see other dogs after that point, it may very well lose its ability to communicate effectively with other dogs.
Training classes are just one location, but dogs can be seen at the park, walks around the neighborhood, etc. It is vital for your dog to partake in these experiences. Otherwise, seeing another dog might produce anxiety, and most cases of dog aggression stem from anxiety and being unable to decipher the intentions of a new dog.
Training Your Dog
Basic training is valuable for your dog to help it understand how to conduct itself around other dogs. All dogs should attend dog training classes beginning as puppies to learn basic obedience.
It is always a good idea to have rules about meeting and greeting other dogs. For example, your dog should not automatically assume it needs to greet. Instead, always give your dog permission to greet other dogs instead. There will be times it shouldn’t be touching other dogs, so it is important to establish that in the beginning.
Never allow your dog to lunge at, bark at, climb on, or hump any new dog it meets. This is very excitable or dominant behavior, and while you might know your dog is friendly, a strange dog may view this as very disrespectful behavior and rightly so.
Any time your dog does greet a new dog, watch closely their behavior. Dogs should quickly move to smell one another and giving signals of friendliness. Stiffness, staring, slow tail wagging, and not allowing another dog to sniff it can all be signs of trouble. An uncomfortable dog can suddenly growl or snap. It is better to allow a greeting for just a few seconds and then call your dog back to you and reward it. This gives the second dog a chance to breathe.
Lastly, if your dog already has an established problem with other dogs, professional training assistance may be warranted to help you through it. It will be a plan of interrupting any aggressive behavior by your dog and more importantly, trying to avoid it. Try to not punish your dog for aggressive displays with strange dogs because it could create silent aggression. Instead, work hard to avoid the problem from happening or to immediately interrupt his behavior and redirect his attention back on to you.
Dog-to-dog aggression can certainly be a challenging problem, but with patience, time, and understanding, it can be dealt with head-on.