Why do young fire ants use tonic immobility when raided by neighboring colonies?

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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.

Young fire ants (Solenopsis invicta) utilize tonic immobility as a defensive strategy to escape aggression from raiders belonging to neighboring ant colonies.

This behavior is specifically employed by juvenile ants—typically only days old—because their exoskeletons are softer and leave them more vulnerable to physical attacks. By appearing lifeless, these young ants can avoid the aggression that might otherwise prove fatal. This response is age-dependent within the colony: as the workers mature, their defensive strategies shift, with weeks-old workers opting to flee and months-old workers staying to fight.1