What behavior involves looking around and indicates heightened alertness in animals?

The behavior that involves looking around and indicates heightened alertness in animals is scanning. Scanning is characterized by an animal actively observing its surroundings, which can be a response to potential threats or changes in the environment. This behavior is essential for assessing danger, finding food, and being aware of other animals in the vicinity. It reflects the animal's instinctual need to stay vigilant, especially in situations where it might feel anxious or threatened.

The other behaviors do not align with heightened alertness. Napping suggests a relaxed state, indicating that the animal feels secure enough to rest. Ignoring is typically a sign of disinterest or a relaxed state rather than alertness. Stretching can occur in various contexts, often indicating relaxation, comfort, or preparation for activity rather than a focused alertness toward the environment. Thus, scanning is the best representation of heightened alertness, as it directly relates to an animal's awareness and readiness to respond to its environment.