This is a very difficult situation. A dog may mourn just as a human does. In these cases, time is what cures most cases. If a dog does not show signs of bouncing back and has a severe lack of appetite, medical intervention is necessary. It does not take long for a dog to develop malnutrition or to become dehydrated.
In the beginning stages, it may help a dog to have a piece of clothing
or other object that has the scent of the person or canine friend whom they are missing.
In middle stages, introducing your dog to a new playmate usually helps. In the case of an owner no longer being present, the new owner or remaining owner must take extra time out of each day to bring the dog for walks, do interactive activities such as playing hide n’ seek, Frisbee, catch and so forth. Spending time together will help the dog bond with closer with their main caretaker.
In late stages, with no signs of improvement, medication such as Prozac, given in very low doses has been show to improve a dog’s mental health