The most popular theory is that dogs have a pack hierarchy. This theory states that there is an alpha male and/or alpha female that control the rest of the pack. The rest of the pack then has rankings amongst themselves. The theory is that there are 3 different types of hierarchy. Linear, Triangular, and Monarchy. The linear hierarchy is similar to a human hierarchy where there is a clear leader and then other ranks that fall under the leader in command. A good example of this type of hierarchy is the military, or even the Catholic church.
A triangular hierarchy is complex. This type of hierarchy can have many dogs that are higher ranking than others, but there is no clear leader of everyone. So in example, dog A is over dog B. Dog B is over dog C, but dog C is over dog A. This type of hierarchy is also referred to as a circular or (less commonly) a squared hierarchy.
Of course a Monarchy hierarchy is simple. There is an Alpha male and/or female and everyone else in the pack is of equal rank. Therefore, the rest of the pack must fight for resources since no one other than the alpha is actually entitled to it. The alpha is entitled to first dibs.
Although all of these are great theories, and may each be at least a little bit correct, I must say that none of them seem to be right on. I work in a place where the pack is constantly changing. Dogs are coming in, and going home at random times. While they are at the daycare, they have to form a pack or even several packs to get along and coexist. Being that canines are very social animals, the forming of packs is very natural and very important to them. Being in a pack means surviving, so it’s only natural for them to form them.
I must say that during my studies, I have seen traces of all three forms of hierarchy described above. However, I have never in my life with dogs seen any of the hierarchy theories stay consistent. In my experience with dogs, I have found that there always has to be at least one dog that seems in control of every situation. There needs to be a peace keeper, a guide or teacher, a look out, a cop and when puppies are involved, a nanny. These jobs can be spread out between dogs, or done by one dog. Most often, these jobs are spread out between dogs. However, as a human, I have found that I can do them all, and so can certain dogs.
Alpha dogs are simply, in my opinion, the strongest dogs. These are the dogs that are willing to fight for their resources. In the animal kingdom, you have four options. Fight, flight, avoidance, submission. Confident dogs are willing to fight, but they are clever enough not too. This makes them the alpha, because they are so confident that they are often able to intimidate other dogs without having to fight. Other dogs will simply submit with a look, snarl, or growl from this dog.
So, in my opinion, the hierarchy theories may not be entirely accurate. I don’t have any reason to believe at this time that dogs are so complex that they have actual ranks. I believe simply that dogs judge each other based on confidence and power, mental and physical. Ever seen a chihuahua control a great dane? Also knowing that dogs learn best from positive reinforcement, adds to my theory that dogs learn what is acceptable in the pack by doing the behavior and then being rewarded with the strongest dogs, or alpha dogs, blessing. Seeing as how most dogs are bred to please, this makes a lot of sense. Especially with people. Your dog wants to please you as long as he sees you as stronger than him. However the reverse is also true. If your dog sees you as weaker than him, then he will expect you to please him. That last sentence is why I have a job as a behavioral and obedience trainer! Most people that come to me for help training their dog to mind have dogs that see them as weaker. You can definitely tell when a dog sees you as the stronger one, because he will listen to you. After all, the strongest member of the pack is supposed to keep him safe and fed.
I have tried walking into my ring and managing it as a weak personality and as a strong personality. What I found was that I am treated with more respect when I act strong and confident, and was peed on when I was seen as weak. (When a dog marks you, that means that the dog is claiming you as his and/or establishing that there is nothing you can do about it).
Bottom line, dogs respect confidence and strength and reject the weak. Weakness is not something that should be passed on down the bloodline in a dog’s eyes, because the weak will not survive. This is why dogs will attack another dog whom is showing signs of weakness such as whimpering, unsureness, and other physical signs of weakness. The same is true for unstable dogs. Often at the daycare, attendants will try to stick a weak dog into a ring and a stronger dogs will growl and attack that dog upon entry. The strong dog is rejecting the weak or unstable dog, because it will be of no use to the rest of the pack. This behavior from the stronger dog only increases the weak attributes of the weaker dog. In the wild, the weaker dog would be killed for attempting to barge into the middle of a pack of other dogs.
In conclusion, dogs seem to be less organized than the theory of rank suggests. It seems to me that they see each other as individuals that are either strong, or weak. Individuals that are either willing to fight for that bone between their paws, or not. If a dog does not believe himself to be strong enough to fight another dog, he will either flee, avoid, or submit. The "leader" of the pack does not care what the other pack members do, as long as they do not break the rules. Usually the rules set by the alpha are, you can’t have my bone, food, or bed, and you can not mate with my mate. Sometimes the rule is that you can not have my human! However, the theories of rank are partially true. Especially the Triangular hierarchy. Because sometimes, there is no clear alpha. Just some dogs are stronger than others, but no dog is stronger or more confident than all. Whatever the case, make sure your dog(s) see you as the strongest and most confident of your pack.