How do bees decide when to swarm?
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How Do Bees Decide When to Swarm?
Honey bees exhibit a fascinating and complex decision-making process when it comes to swarming, which involves selecting a new nest site and preparing for the move. This process is driven by collective decision-making among scout bees, who play a crucial role in evaluating potential sites and guiding the swarm.
Scout Bees and Nest Site Evaluation
Scout Bees' Role in Site Selection
Scout bees are responsible for finding and evaluating potential nest sites. They communicate the location, quality, and distance of these sites to the rest of the swarm through a behavior known as the waggle dance. Initially, multiple sites are advertised by different scouts, but over time, the swarm narrows down to a single site . The scouts' dances become more vigorous for higher-quality sites, which helps in the selection process.
Quality and Distance Trade-Off
The decision-making process involves a trade-off between the quality and distance of the candidate sites. When choosing between low-quality sites, swarms prefer moderately distant sites over nearer or farther ones. However, for high-quality sites, nearer locations are preferred. This adaptive decision-making ensures that the swarm selects the best possible site within a reasonable distance.
Consensus and Quorum Sensing
Quorum Sensing Over Consensus
The swarm does not require a full consensus among the scouts to decide on a nest site. Instead, they rely on quorum sensing, where the buildup of a sufficient number of scouts at one site triggers the preparation for liftoff. This quorum is typically around 10-15 bees. This method balances the need for accuracy and speed in decision-making, allowing the swarm to act efficiently without waiting for complete unanimity.
Crescendo of Dancing and Liftoff
As the decision nears completion, there is a noticeable increase in the intensity of the waggle dances. This crescendo signals the swarm to prepare for liftoff. Within about an hour of reaching this peak, the swarm takes off to the chosen site. This final phase ensures that the swarm is ready to move as a cohesive unit.
Mechanisms of Decision Making
Weighted Additive Strategy
The decision-making process in honey bee swarms can be described as a "weighted additive strategy." This strategy involves evaluating all relevant information about potential sites and making a decision based on the combined weight of this information. Despite their small brains, bees distribute the tasks of evaluation and decision-making among many individuals, allowing them to process complex information effectively.
Positive Feedback and Attrition
The swarm's decision-making relies heavily on positive feedback mechanisms, where successful recruitment to a good site increases the number of scouts visiting it. Conversely, attrition occurs as scouts cease dancing for less favorable sites, gradually reducing their support. This dynamic interaction ensures that the best site gains the most support over time.
Conclusion
Honey bee swarming is a remarkable example of collective decision-making. Scout bees play a pivotal role in evaluating and communicating potential nest sites, balancing quality and distance considerations. The process relies on quorum sensing rather than full consensus, with positive feedback and attrition mechanisms driving the final decision. This sophisticated strategy allows honey bee swarms to make adaptive and efficient decisions, ensuring their survival and success in finding new homes.
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