How Bees Argue

The book Honeybee Democracy, published in 2010, has been sitting on my shelf for many years. Getting back into the topic of disagreement, I’ve finally read it. And browsing media articles about the book from back then, they just don’t seem to get it right. So let me try to do better.

In late spring and early summer, … colonies [of ordinary honeybees] become overcrowded … and then cast a swarm. … About a third of the worker bees stay at home and rear a new queen … while two-thirds of the workforce – a group of some ten thousand – rushes off with the old queen to create a daughter colony. The migrants travel only 100 feet or so before coalescing into a beardlike cluster, where they literally hang out together for several hours or a few days. .. [They then] field several hundred house [scouts] to explore some 30 square miles … for potential homesites. (p.6)

These 300-500 scouts are the oldest most experienced bees in the swarm. To start, some of them go searching for sites. Initially a scout takes 13-56 minutes to inspect a site, in part via 10-30 walking journeys inside the cavity. After inspecting a site, a scout returns to the main swarm cluster and then usually wanders around its surface doing many brief “waggle dances” which encode the direction and distance of the site. (All scouting activity stops at night, and in the rain.)

Roughly a dozen sites are discovered via scouts searching on their own. Most scouts, however, are recruited to tout a site via watching another scout dance about it, and then heading out to inspect it. Each dance is only seen by a few immediately adjacent bees. These recruited scouts seem to pick a dance at random from among the one’s they’ve seen lately. While initial scouts, those not recruited via a dance, have an 86% chance of touting their site via dances, recruited scouts only have a 55% chance of doing so.

Once recruited to tout a site, each scout alternates between dancing about it at the home cluster and then returning to the site to inspect it again. After the first visit, re-inspections take only 10-20 minutes. The number of dances between site visits declines with the number of visits, and when it gets near zero, after one to six trips, the bee just stops doing any scouting activity.

This decline in touting is accelerated by direct conflict. Bees that tout one site will sometimes head-butt (and beep at) bees touting other sites. After getting hit ten times, a scout usually quits. (From what I’ve read, it isn’t clear to me if any scout, once recruited to tout a site, is ever recruited again later to tout a different site.)

When scouts are inspecting a site, they make sure to touch the other bees inspecting that site. When they see 20-30 scouts inspecting a site at once, that generally implies that a clear majority of the currently active touting scouts are favoring this site. Scouts from this winning site then return to the main cluster and make a special sound which declares the search to be over. Waiting another hour or so gives enough time for scouts to return from other sites, and then the entire cluster heads off together to this new site.

The process I’ve described so far is enough to get all the bees to pick a site together and then go there, but it isn’t enough to make that be a good site. Yet, in fact, bee swarms seem to pick the best site available to them about 95% of the time. Site quality depends on cavity size, entrance size and height, cavity orientation relative to entrance, and wall health. How do they do pick the best site?

Each scout who inspects a site estimates its quality, and encodes that estimate in its dance about that site. These quality estimates are error-prone; there’s only an 80% chance that a scout will rate a much better site as better. The key that enables swarms to pick better sites is this: between their visits to a site, scouts do a lot more dances for sites they estimate to be higher quality. A scout does a total of 30 dances for a lousy site, but 90 dances for great site.

And that’s how bee swarms argue, re picking a new site. The process only includes an elite of the most experienced 3-5% of bees. That elite all starts out with no opinion, and then slowly some of them acquire opinions, at first directly and randomly via inspecting options, and then more indirectly via randomly copying opinions expressed near them. Individual bees may never change their acquired opinions. The key is that when bees have an opinion, they tend to express them more often when those are better opinions. Individual opinions fade with time, and the whole process stops when enough of a random sample of those expresssing opinions all express the same opinion.

Now that I know all this, it isn’t clear how relevant it is for human disagreement. But it does seem a nice simple example to keep in mind. With bees, a community typically goes from wide disagreement to apparent strong agreement, without requiring particular individuals to ever giving up their strongly held opinions.