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Why might an animal freeze instead of fleeing from a threat?

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A fluffy gray cat clings to the trunk of a tree, looking upward as it climbs to escape. — Avoidance behaviour Cat fleeing by upward climbing.

An animal may freeze rather than flee from a threat primarily 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 motion. This behavior is often triggered as soon as a predator is detected.12

In some cases, freezing serves as a form of camouflage, especially for animals that resemble their environment, such as stick insects. If a threat is perceived as difficult to locate or impossible to escape, an animal may also resort to freezing as an alternative to fleeing.13

While freezing is a strategy to avoid being seen, it is distinct from tonic immobility, which is typically a reflexive response initiated after an animal has already been caught or held by a predator. In that state, the animal’s sudden motionlessness may distract the predator or cause it to lose interest, providing a final opportunity to escape.2