Sometimes dog behavior is easy to understand: they stand by the door when they need to go out, or they bark at other dogs as a sign of greeting, or the way they always know that its time to be fed. Other times it is much harder to understand what it is that they are trying to tell you when they are panting and pacing or barking for what seems like not reason or especially when they show signs of aggression when that is not their normal behavior.
There are quite a few reasons that dogs show aggression, even unwarranted aggression, and understanding why your dog is acting aggressively even towards you, his owner, can help further your relationship and help you solve the problem.
Your dog might be sick
Like a child who is incapable of telling you what they need until they develop the capacity to communicate, your dog might be confused as to why they are not feeling well and since they are incapable of telling you why, they often respond with aggression. Sickness and illness are also signs of weakness in nature and combative behavior is a natural reaction and form of protection for a dog. They aren’t mad at you, and they haven’t forgotten who you are; they are simply acting on their natural impulses to protect themselves.
Leash aggression and protecting their owners
Some breeds of dog are extremely loyal and when you have them on a leash on a walk they can be in the mindset that they are protecting you. Instead of you taking them for a walk, they are walking with you as your companion and because of this they are on alert for anything that might threaten you and them. Some smaller dogs are especially protective, and that inspires them to be very aggressive towards large breeds of dog, for instance when they are caught off guard.
People can also react with aggression when they are afraid, and, again, this is a natural reaction for a dog. When they feel threatened, or your dog is presented with a situation that they have never found themselves in before, they can think that they are being threatened and react aggressively.
Dogs can be territorial, especially if they are not used to other dogs or animals. Socializing a dog is important if you want them to not react aggressively towards other dogs, humans, or animals. Once a dog has established a territory, it can be extremely hard to stop them from acting aggressively towards anything that threatens their territory.
Toys and possessions
If you have given your dog a toy, treat, bed, blanket, or anything that they can think of as their own, they can become aggressive when those things are threatened. Like territory, once a dog establishes something as its own, it can be hard to stop it from becoming aggressive when it sees anything else try to take or impinge on what the dog thinks of as its possession.
Dogs are pack animals and as such there are established hierarchies within a pack, but domesticated dogs do not always travel in packs and why your dog that is not in a pack is acting aggressively towards other dogs can be attributed to this. Like the breeds that tend to be very loyal, there are also dogs within breeds that can be alpha or dominant. This can depend on birth order, upbringing, or if you have adopted a stray, how they established themselves when they were on the street. They may snap, growl, or bite when they establish dominance.