The mystery of swarming honeybees: from individual behaviors to collective decisions

Summary

Thousands of individuals in a honeybee swarm make a collective decision for one among many nest sites discovered. We recorded the waggle dances on swarms in a forested area, where one swarm’s search encompassed about 150 km² and discovered about 50 different sites. We also analyzed swarms in a more controlled situation, with only nest sites which we provided and monitored. Most bees did not visit any site; very few visited more than one. Apparently choices were made with little or no direct comparison, through the interaction of two mechanisms: positive feedback, through recruitment leading to growth in the number of scouts visiting good nest sites, and attrition-reducing activity and recruitment for nonchosen sites. Individual differences between bees substantially affected these dynamics. Scouts varied considerably in the amount of dancing and persistence, but most that danced did so vigorously for a site after their first few visits, then ceased, though continuing to visit. Scouts followed dances of others, and occasionally visited alternative sites, but rarely switched their dancing. Our results suggest that the choice among nest sites relies less on direct comparison of nest sites, and more on inherent processes of feedback and attrition.