Why is freezing more likely when an animal cannot locate or escape a threat?

In the context of avoidance behaviour, freezing is a form of passive avoidance characterized by general motor inhibition. When an animal encounters a frightening stimulus that it cannot easily locate or escape, it may shift from active strategies, such as fleeing, toward a state of immobility.1

This response serves as a defensive mechanism to avoid detection by a predator. By suspending all movement, an animal reduces the likelihood of being spotted, as many predators are highly sensitive to the motion of their prey. When escape is not a viable option, this inhibition of movement acts as a final, evolutionarily conserved strategy to survive a threat. In some cases, this state of motor inhibition may progress further into tonic immobility, where the animal becomes unresponsive to external stimuli, potentially causing a predator to lose interest or fail to recognize the animal as viable prey.231