Social relationships are adaptive because they are necessary—or at least helpful—as a source of benefits. Those benefits range from basic needs such as food and shelter to other needs such as support, alleviation of stress and mates. Threats to those social relationships may result in jealousy and a behavioral response to that emotion. The purpose of jealous behaviors is to restore or maintain relationships of value that are being challenged.
Dogs rely on humans to meet their physical and emotional needs, so it makes sense to predict that they would respond with jealous behaviors in situations with rivals for that relationship. The most likely rivals for a dog are the other dogs in the household, which is why scientists recently studied dogs’ behavior when guardians paid attention to their other dogs.
via Whisker Therapy