A dog pack is the natural social order for canines throughout history. These animals developed as social beings, unlike cats and other animals that tend to be more solitary. The result is that dogs are accustomed to being one member of a larger community, and this inborn sense of pack mentality helps to dictate a great deal of your pet's behavior. It can be the cause of behavioral problems and can also be used effectively to help train your pet and maintain good behavior as well, provided that you understand the basics of the pack mentality itself.
Being a Member of the Pack
In the wild, dogs have historically grouped together in packs of anywhere from about 5 to about 15 members. These packs tend to function as a group; they'll travel together, hunt and eat together, and socialize with one another. Although in the wild the pack represents a group of dogs that any given animal might interact with, in the case of a family and a modern domesticated dog, the pack will be the humans and other animals around. Therefore, it's important to realize that your dog considers you and anyone else in your home (including other pets like cats) to be a member of his pack, whether or not you're aware of it.
Pack Dynamics
Each pack will have a very specific social order. This is another instinctive concept that is born into every dog, and you will not be able to change it through behavioral training or any other means of modification. The leader of each pack, known as the alpha, is the most dominant member of that group. It roughly corresponds to the largest and most senior member, though this is certainly not always the case. Other animals may routinely challenge the alpha for positioning within the social circle of the pack, and if the alpha is shown to be less than fully dominant, each other member of the pack will recognize a new alpha member.
Pack Behavior and Your Pet
It's important to know that your pet has an idea of the social order of your own family pack. This means that you'll need to be aware of how to make yourself an alpha in his mind. If you're not able to maintain your alpha status and your pet begins to consider himself of a higher rank in the pack than you, you'll have a very difficult time attempting to train him or getting him to behave in the way that you find appropriate. By making sure that your pet follows your training and admonishments and also keeping track of his behavior in relation to other members of the pack, you can monitor him to be sure that you're maintaining your alpha status.
Generally, maintaining height dominance over your pet is a good way to keep yourself as the alpha. Keep your pet in a stay position with a treat a few feet away and stand over him. Do not break eye contact, as this is seen as a sign of less than dominant status. Make sure that he obeys your commands and only gets his treat when you say it's alright. This action, performed repeatedly, can be a useful way of establishing and maintaining dominance.