Dogs are social animals. That's why we make them part of our families. But making a dog part of your family is a big responsibility, not only for his physical welfare, but for his social/emotional well-being.
You know that dogs are natural pack animals. In the wild, they enjoy considerable socialization with their families and extended families. They may hunt on their own, but they meander, play, and sleep with their packs. When they 'move in' with us, we become their packs.
So, when we leave a dog for long periods of time, it upsets their natural order. Some dogs, when their pack leaves, can experience separation anxiety, a very unpleasant, even traumatic experience. I learned this the hard way with one of my own dogs who, after an extensive period of time with me at home, tore down my shades and bit up the molding on my doors in one day (!) when I went back to work. Another very sad day, he tore through a second story screen door, jumped off the balcony, and was found dazed, wandering in the street by a neighbor. Fortunately he survived, but with a broken hip and leg.
Regardless of the age of a new dog in your home, you want to spend several hours a day with her to help her get adjusted to her new surroundings. Activities should include going for walks, playing inside and outside, training, and getting familiar (on a leash) with the areas of your home where she is allowed.
Ideal pen set-up (image)
Having a large 'exercise pen' for your dog and a place to put it inside your house would be best, at least for the first several months with a new puppy or dog. You can furnish the interior with a carpeted crate, water, and a few smelly toys with your scent. (Don't leave anything sharp - and no chew bones. You should be around when your dog has these toys.) Interactive dog toys like these, especially those that hold treats are great. Make the treats very special, not just his regular kibble. My dog loves snuffle mats which you can purchase or make yourself.
Some dog parents find that leaving the television on, especially to Dog TV or Animal Planet, is interesting for their dogs. I purchased a 'dog CD' with music that eliminates tones that are not dog-friendly. Some of this dog music can be streamed.
Others successfully use doggy cams to get their dog's attention and give treats (Make sure it's a special treat!), but some who have tried this approach say they end up confusing their dogs and increasing their anxiety.
Start by leaving your dog alone in his pen for a short time, maybe 15 minutes or a half-hour. When you come home, don't get overly excited about seeing your dog. A calm smile and a "Good boy" is enough. You can let him out of the pen, take him out to do his stuff and let him return. If you are house-breaking your dog, this is the normal routine, and you should return him to his pen when re-entering your home.
But if your dog is already house-broken then, by all means, let him out of the pen when you get home. Just try not to show too much excitement because you want your dog to know that coming and going are both okay. Gradually lengthen the amount of time you spend away from your dog, using the same techniques. When you come home, provide your dog with as much activity and social interaction as possible. This will provide a good time and a release of pent-up energy. Dog trainers recommend that you don't treat your dog when you come home so that your dog will see that you being at home and you coming home are equally okay.
Work your way up to a few hours apart from your dog without her protests. My readings suggest that most dog trainers and psychologists recommend that you leave your dog alone no more that 4 to 6 hours, 6 hours if you have an older dog who is used to being alone and is not very active. As most adults work outside of the house longer than 4 to 6 hours, our dogs may need a break or two from a dog-walker, sitter, or a dog door that will allow them to go out to a confined area to exercise and relieve themselves. Toys with treats inside and dog puzzles provide mental and physical stimulation. A doggy day camp would be a good alternative if your dog gets on with other dogs.
The bottom line is that your dog needs companionship as well as stimulation and exercise to thrive. Try to supply it however you can.