Data from: Organisation enhances collective vigilance in the hovering guards of Tetragonisca angustula bees

One benefit of group living is vigilance against predators. Previous
studies have investigated the group size effect, where individual
vigilance decreases as group size increases without reducing the overall
ability of the group to detect predators. However, there has been
comparatively little research on whether the positioning of individuals
can improve the collective vigilance of the group. We studied the
coordination of vigilance and its effect on predator detection in the
eusocial bee Tetragonisca angustula. Nests are defended by hovering guards
that detect and intercept intruders before they reach the nest entrance,
in addition to those that stand upon it. We show that hovering guards are
positioned non-randomly, with a strong tendency for equal numbers on both
sides of the entrance. This organisation increases the collective
vigilance of the guard group, as groups distributed in an even ratio,
either side of the entrance, have a greater collective field of view than
groups that deviate from an even ratio. Last, we use a bioassay to show
that when guards are on both sides of the entrance, their ability to
detect intruders before they reach the entrance increases. Overall, our
results provide strong evidence that vigilance is coordinated, and that
this improves nest defence. Whereas other group-living animals are often
selfish in their individual vigilance behaviours, and face competing time
constraints such as foraging, the altruistic nature of eusocial insect
workers has likely facilitated the evolution of coordinated vigilance, as
documented here in T. angustula.