Synchronising anti-predator behavior in the red flour beetle Tribolium castaneum

In many animals, a phenomenon is often observed in which behavior depends on population density and many individuals within the group synchronize their state of behavior to some extent, and theoretical studies have suggested that this synchronization phenomenon is adaptive for predation avoidance. Moreover, death-feigning behavior (DF) has been observed as an anti-predator strategy in many animals. There are large individual differences in the duration of DF, and the optimal duration of DF often varies depending on the situation. Therefore, although it is expected that prey may synchronize with others around them for an optimal DF duration, there are few experimental studies testing this hypothesis. This study investigated whether DF duration varies with and without other individuals, and whether it synchronized with the DF duration of other individuals, in the red flour beetle Tribolium castaneum. This study used populations with genetically longer (L-population) and shorter (S-population) DF duration and measured DF duration when maintained alone and cohabitated with individuals from the L- and S-populations, respectively. The results showed that the DF duration of individuals living alone increased significantly compared to pretreatment. Moreover, individuals that cohabitated with S populations were significantly shorter after cohabitation, but the presence of the L population did not cause any changes in how individuals synchronized their activities. When many individuals had shorter DF durations, DF was synchronized towards shorter durations. This is the first study to illustrate the synchronization of anti-predator behavior in terms of DF behavior.