What behavior signifies that a Jack Russell Terrier is excited and happy?

Wagging their tail and jumping with enthusiasm is a clear sign that a Jack Russell Terrier is excited and happy. This behavior is typical of dogs that are in a playful or joyful state, as it indicates high energy and eagerness to engage with their environment or with people. When dogs wag their tails vigorously and jump around, they communicate their enthusiasm and readiness to play or interact.

In contrast, staying still and alert often indicates a dog is focused or potentially assessing their environment. Withdrawing from social interactions suggests a lack of interest or discomfort, which would not be associated with feelings of excitement or happiness. Howling loudly might indicate that the dog is vocalizing its emotions, but it does not specifically convey joy or excitement in the same manner as wagging and jumping do. Therefore, the behavior of wagging and jumping is the clearest indication of a happy and excited Jack Russell Terrier.