Many owners depend on their dogs for emotional support, so it may be hard to imagine they may feel unhappy.
Newsweek asked two animal experts what indications suggest dog sadness and how owners may assist them.
Nebraska veterinarian Grant Little told Newsweek there are several reasons a dog may be melancholy.
Loving a person may hurt a dog as much as losing a companion.
When grieving, Foreman remarked "human company is very important to help them".