Which physical response may indicate stress in an animal?

Increased heart rate is a well-documented physiological response that can indicate stress in an animal. When an animal experiences stress, its body activates the fight-or-flight response, which is part of the autonomic nervous system. This reaction triggers the release of stress hormones such as adrenaline, leading to an elevated heart rate. This response can be observed in various situations that may cause anxiety or discomfort for the animal, indicating that it is in a state of heightened arousal or stress.

The other options, such as a calm demeanor, normal breathing, and slow movement, do not typically align with signs of stress. A calm demeanor and normal breathing suggest that the animal is relaxed and not experiencing anxiety. Slow movement might indicate a more sedentary or relaxed state rather than stress. Understanding these physical responses is crucial for interpreting the emotional state of animals and employing appropriate fear-free techniques in a veterinary setting.