Which of the following may indicate that an animal is in pain?

Changes in behavior, such as aggression or hiding, can be significant indicators that an animal is experiencing pain. When an animal is in discomfort, it may react differently than it normally would. Hiding is a common response, as animals often seek to avoid situations where they feel vulnerable. Aggression can also arise as a defensive mechanism; the animal may feel threatened and react to protect itself from perceived dangers.

Increased appetite does not typically signify pain, as animals in distress often show a reduced desire to eat. Excessive grooming may also suggest stress rather than pain specifically, as animals may groom themselves as a coping mechanism. Normal vocalization indicates that an animal is communicating in its usual manner, which typically wouldn’t correlate with pain. In contrast, behavioral changes that indicate agitation, avoidance, or aggression are more directly associated with an animal's struggle to cope with pain or discomfort.