Which of the following is indicative of an emotional state in animals?

Tail position is a key indicator of an animal's emotional state because it reflects their mood and can convey a variety of feelings. For instance, a dog with a high, wagging tail may be expressing happiness and excitement, while a tail that is tucked between the legs typically indicates fear or submission. Similarly, a cat’s tail position can indicate their mood: an upright tail may show confidence or contentment, while a puffed-up tail often signals agitation or fear.

While body posture, eye contact, and vocalization also contribute to understanding an animal's emotional state, tail position tends to be a more direct and clear sign that correlates strongly with specific emotions, making it a vital aspect in assessing a pet's feelings in a given situation. Thus, its significance in signaling emotional states is particularly notable in behavioral observations.