Three dogs is a lot of dogs. That sounds redundant, but just for good measure; it is a lot of dogs. Enough in fact, that your dogs will be a pack. Not that a single dog, or two dogs won't act at all like a pack, but having three dogs is when they start to take on pack behaviour. Why is it, you may wonder, that three dogs is a pack and two isn't?

Sky, Summer and Star: the Pack
Take your three dogs Sky, Summer, and Star. These three beautiful hounds are a pack because there is an alpha, a beta and an omega. It is the introduction of the omega that rounds out the pack and enables the completion of the pecking order. When you had Sky alone, there was no need for a pecking order.

When you introduced Summer there were two dogs. Summer came in and flaunted her dominant personality. She instigated some minor demonstrations of aggression, and Sky happily took a mellow back seat as the submissive in the pair. In a set of two dogs, there is not technically an alpha and an omega. It is merely just the case that one dog is dominant and one submissive. Because all positions, alpha, beta and omega, will not be filled by only two dogs, there is no pack.

Sky and Summer were companions, not a pack, but once you put Star into the mix, things were different. She was the youngest, a stranger in a strange land. She was not aggressive enough to fight her way up in the pecking order, and so she became the omega, thus beginning your dog's full-blown pack mentality.

Why Does Omega Make the Pack?
You may be wondering why the omega makes the pack? Dog researchers and behaviourists theorise that it has to do with the pack's stability. In order for the group to be stable and maintain itself, there has to be one animal, the omega, who is cast out upon and picked on just a bit. In your dogs, this likely won't necessarily present itself as hostility, but you may notice that Summer and Sky eat first, or sleep farther away from Star than each other. Indeed, you may be encouraging it. If you already assumed that Summer was the Alpha, you already fed her first and then Sky. When Star entered the picture, you may have subconsciously (not wishing to disturb the relationship between you and your existing dogs), fed Star after Summer and Sky.

The omega's role has to do with the diffusion of the pack energy. Her presence will eliminate high tension and aggression by giving it a place to flow: herself. Once again, in your dogs, this is not likely to manifest itself in violence, but rather in indifference or a mild sense of superiority. In the case of wolves, the pack is often rather confrontational towards the omega to keep him or her in her place.

What Does All This Mean to You?
In case you are unaware of what exactly "alpha," "beta" and "omega" mean in reference to your dogs behaviour, here is a quick run down:

Alpha
An alpha, Summer in this case, will be the dominant member of the pack; she is the leader so to speak, just under your partner and you (or if you are single, you alone). Her place is at the top of the pecking order. This means that she will eat first, sleep in the comfiest spot, and get her pick of the best toys.

Beta
The beta, Sky, is the Alpha's second in command, her right hand man, so to speak; Spock to Captain Kirk, if you will. The beta is a bit mellower than the alpha; you will notice almost a stoicism about her demeanour, especially in comparison to the confidence of the alpha. The Beta eats second, and gets the alpha's hand-me-downs, from toys to sleeping spots. Don't start feeling badly for Sky. This is far more exaggerated in wolves, and it is entirely instinctual.

Omega
The omega, Star, is sure to be a bit timid and aloof. She will be the last to eat or play with a toy, and is likely to sleep off by herself. She is a welcome member of the pack, but only with permission. And while today she might play with Summer and Sky, tomorrow may be a different story. It's pack mentality, so let them work it out.

This doesn't mean you should try to favour Star, or give her special treatment. That could, in fact, get her in trouble. Your dogs are your dogs, and they will do their own thing as far as their pack goes. Interfering is unnecessary unless you notice aggression, hostility, or fights that could be dangerous to your dogs' health.

The important thing to remember is to take the appropriate time and steps in introducing a new dog into your home, whether she may be number two, the companion, or number three, making up the pack. That is the best way to ensure that your dogs will figure out their pack dynamic in a peaceful, livable way.