Which of the following is a common sign of stress in both cats and dogs?

A tense body is a common sign of stress in both cats and dogs. When animals are feeling anxious or stressed, their body language often becomes tense, which can manifest in several ways. For instance, their muscles may tighten, and they may adopt a posture that appears rigid, which is a physiological response to stress. This may be accompanied by other indicators such as a lowered head, tucked tail, or a lack of usual playfulness.

In contrast, playful behavior is typically a sign of comfort and relaxation rather than stress. Loud vocalization may indicate distress but is not universally recognized as a sign of stress for all animals, as some may vocalize due to excitement or to express other emotions. Relaxed ears signify calmness and comfort, contrasting with the signs exhibited when an animal is under stress. Thus, a tense body serves as a clear and reliable indicator of stress in both cats and dogs.