Instructions
Observe Your Dog
A lonely dog will be a little slower and less active than a happy dog. He will lay around more, sleep more, and will less frequently want to play or go for walks. The activities your dog used to like will seem to be less attractive to him.
A lonely dog will have a much lighter appetite. He will not want to eat much, perhaps being unsure when you leave each day when you will return, and leaving a little food just in case. If your dog is eating less, and you don't notice any health problems, it could be a sign of loneliness.
A lonely dog will tend to disobey you or regress in some of its training. The dog may start to chew your belongings, sneak out of your yard, or go to the bathroom inside the house. The dog could be disobeying due to the stress of being alone, or perhaps to purposely disobey you to get your attention. Either way, this acting out can be a sign that your dog needs more companionship.
A dog that needs a companion will seem much sadder than the average dog. He will have sad eyes (and yes, you can tell) and will have a sad demeanor to his walk. Your dog will enjoy fun activities less than most other dogs, and will seem less willing to participate.
If you think your dog might be too lonely, there are a few options to consider. Get another dog or another pet such as a bird or cat. These other animals can keep your dog company while you are gone. Hire a dog walker or pet sitter to come by and visit your dog on a regular basis if you do not want to get another pet. This will help him socialize a bit more. Put your dog into a doggie day care. Here, he will be around people and other dogs all day long, and will be running, playing and socializing. Which ever option you choose, things will improve for you and your dog.
How to Tell If a Dog Needs a Companion
If your dog is your only pet, and you tend to work long hours leaving your dog home alone, he could be getting lonely and depressed. If a dog is lonely, it could benefit greatly by having an extra companion in his life. You may see your dog's mood improve and he may be more obedient. You will enjoy your dog's company more in the precious times you do get to spend with one another.