Visual contagion in prey defense signals can enhance honest defense

The co-evolutionary arms race between predators and their prey has led to complex signaling, especially in groups that benefit from the social transmission of alarm signals. In particular, pursuit deterrence signals can allow individuals and groups to indicate, at relatively low cost, that a predator’s further approach is futile. Pursuit deterrence signals are usually more effective if amplified by becoming contagious and rapidly spreading among prey without requiring individual prey to confirm predator presence. However, this can also lead to runaway false signaling. We provide the first evidence of a contagious pursuit deterrence signal in social insects. The Asian honey bee, Apis cerana, performs an I See You (ISY) signal that deters attacking hornets. We show that these signals also attract guard bees to enhance defensive signaling and that the visual movements of appropriate stimuli alone (hornets and ISY signaling bees, but not harmless butterflies) provide sufficient stimuli. Olfaction and other potential cues are not necessary. The ISY signal is visually contagious and is buffered from runaway false signalsbecause it is specifically triggered and, likely, by selection for honesty within the highly cooperative bee colony. These results expand our understanding of contagious signals and how they can be honestly maintained in highly cooperative collectives.