A blog post highlighting the article written by J. C. Makinson, T. M. Schaerf, A. Rattanawannee, B. P. Oldroyd and M. Beekman in Insectes Sociaux

 

Written by Rachael Bonoan

Decision making is hard. Decision making in a group is even harder. The vultures from Disney’s The Jungle Book come to mind. What we gonna do? I don’t know, whatcha wanna do? And so it goes.

Honey bees are an example of a superorganism. Not only do they work together to run their large and complex societies, they also work together to decide on a new home.

When honey bees decide it’s getting too cozy in their hive, half of the bees will leave with the old queen and swarm to an intermediate location. The remaining bees will stay home with a newly raised queen.

While the bees are clustered in their swarm, special members of the colony, aptly named scout bees, check out possible new homes in the area and report back to each other via dancing. In their dances, the scout bees encode the location and quality of each potential new home. Eventually, the scout bees decide on a new home and, after a consensus is reached, the swarm takes off. Before the swarm takes off, it is vital that all the bees agree on where they are going. In European honey bees, we know a lot about this process. Until recently however, we didn’t know how Asian honey bees (Apis dorsata) make this important decision.

Unlike European honey bees, Asian honey bees nest out in the open and their colony’s population size is not constrained by a nest cavity. As such, Asian honey bees tend to swarm to find a home with more food rather than to find a home with more room for all those bees.

Asian honey bees are much quicker at making decisions about a new home than European honey bees (hours vs. days respectively). How do Asian honey bees make a group decision so quickly? Recently, James C. Makinson and colleagues asked the question, how does group decision-making in Asian honey bees differ from group decision-making in European honey bees?

To investigate this question, the research team first created Asian honey bee swarms which were released onto a swarm board. Equipped with a video camera, the researchers filmed the scout bees as they searched for new home sites and made their decision. The researchers measured dance and flight activity, and to get an idea of individual behavior, they labeled the scout bees with colored paint.

Like European honey bees, individual Asian honey bee scouts take flight in between dances, and before lift-off, dances converge in a similar direction. Also, in both species, the duration of a scout’s dance is directly related to the quality of the new home site.

Unlike European honey bees however, Asian honey bee scouts do not exhibit a phenomenon called dance decay when narrowing down their choice. In European honey bees, a scout visits a potential new home multiple times and each time, the duration of her dance shortens. Another scout follows the dancer’s directions to check out the site herself. This recruited scout will also visit the site multiple times; she too will shorten the duration of her dance with each visit. Since scouts do longer dances for more favorable homes from the start, scouts dancing for higher quality homes will continue dancing even after dances for lower quality homes have ceased. Eventually, dance decay results in only dances for the most favorable home site. This is when the bees take off.

Asian honey bees use a different means of coming to a consensus. Makinson and colleagues found that scouts dancing for a “non-chosen” location change their dance direction after observing the dance of a “chosen” location. Thus, Asian honey bee scouts switch their dances—or change their minds—without visiting the potential new home themselves. These “switchers” simply trust what the other scout bees are telling them. This is likely how Asian honey bees make their decision so much faster than European honey bees. It also suggests that checking out the site themselves isn’t as important to Asian honey bees as it is to European honey bees. Based on their nesting behavior, this makes sense. Since European honey bees nest in cavities, the bees check out the cavity to make sure it’s the right shape, size, height, etc. Since Asian honey bees nest in the open, they have less factors to debate about when making their decision.

It seems that Asian honey bees are efficient at group decision-making because they pay attention to only the pertinent information. They don’t let irrelevant factors (in their case, shape, size, height, etc. of the home site) get in the way. They stay focused on the specific task at hand: find a new home.

References

Makinson JC, Schaerf TM, Rattanawanne A, Oldroyd BP, Beekeman M. 2016. How does a swarm of the gian Asian honeybee Apis dorsata reach consensus? A study of the invidual behavior of scout bees. Insectes Sociaux 63: 395-406.

Makinson JC, Schaerf TM, Rattanawanne A, Oldroyd BP, Beekeman M. 2014. Consensus building in giant Asian honeybee, Apis dorsata, swarms on the move. Animal Behavior 93: 191-199.

Seeley TD, Visscher KP, Passino KM. 2006. Group decision making in honey bee swarms. American Scientist 94: 220-229.

 

About the author:
Rachael Bonoan is a PhD student at Tufts University in Medford, Massachusetts, U.S.A. You can tweet to her at @RachaelEBee or check out her website: www.rachaelebonoan.com where she writes her own blog.