Honeybees live in a colony that includes two female castes and one male. These we call the workers, the queen and the drones. Names that we give them based on our observations of the colony. The queen is the mother laying the eggs of all three castes, but she doesn’t rule the hive. The colony manages itself, making decisions as a collective. One decision that needs to made with care, quality and precision is that of the swarm when it chooses and decides its new home.
Lindauer noticed in the 1950s that bees that once fed from syrup he had put out for them instead looked more closely and with more interest at the empty hives he had put out near the syrup. What he found was that there are times in the season usually in Spring or early summer when the colony has grown rapidly, there are plenty of stores and the foragers are coming home to find that the house bees aren’t that interested in taking their nectar from them. These foragers become restless, but it seems that this behavior among others is what starts the swarming impulse. What then are the decisions that the colony needs to make in this situation.
- When to swarm?
- The new home for the swarm?
For each of these decisions what are the criteria for making the decision?
1. When to swarm?
This is the process of colony expansion and is important for the continued survival of the honeybee. But what do the bees consider when deciding when to swarm. As already mentioned, the number of bees in the colony, the amount of stores and space that they have left in the current hive. These are all key to making that decision, but the reality is that as beekeepers we don’t know exactly when the bees are going to swarm. Even if we give them plenty of space, the only way we really know when they are preparing to swarm is when they make queen cells for the rearing of new queens. A BBC audio engineer proposed that the colony noise changes as the bees prepare to swarm before they start to make queen cells. The apidictor was created, as yet untested by me even if it does help the beekeeper in predicting the swarming tendency of the colony, we still don’t know what it is that triggers them. Some might say that they will swarm in Spring as a part of their naturally evolved life cycle, however, we see swarms occurring from Spring through to the end of autumn by which time it makes little sense for the bees to be swarming.
Once the bees have decided to swarm they slim the queen down so that she can fly and she also stops laying eggs. In most cases the bees will not cast a swarm until the queen cells have been capped, but this is not always the case. The trigger to swarm is not entirely known.
2. The new home for the swarm?
Once the bees have decided to swarm, around 10,000 bees including the queen leave the hive and locate themselves usually nearby on a tree branch or in a bush. Once in this position they will start the process of looking for a new home. The swarm will remain in this position until they agree on the new home at which point they will set off and move in.
Failing to move the swarm as a single, committed unit risks splitting up the hive and losing the queen. Similarly, making a poor move could expose the hive to predators or extreme temperatures so how do they go about doing it.
Around 3-4% of the swarm population become scouts for a new home. All of the other bees remain in the swarm until the decision on where to move to has been made by the scout bees. These scouts are experienced foragers so are best equipped and most competent to look for a new home in the vicinity. The scout bees will go off individually and look for the ‘ideal’ cavity space for the colony to move to. When a scout finds a cavity it makes many trips along the inside walls of the cavity starting at the entrance and ending at the entrance. Why would the bees make these numerous trips around the inside walls of the cavity unless it is to make an estimate of the size of the cavity, an all important criteria for a new home. In physics there is an acoustic equation using mean free path (l) that can be used to determine the volume of a cavity as follows:
l = 4V/S V is the volume of the cavity, S is the total surface area.
The bees would seem to have evolved a generic algorithm for determining the cavity volume. (The equation is how we as humans might explain how to calculate it). The scout bees will only look for a new home once in their lives, so there is a strong possibility that the algorithm is genetic. There is a possibility that the bees learn about the ideal size of a cavity from their time as a house bee in the home colony.
The optimum volume of a hive is around 40 litres, but bees will select a smaller or larger size if the optimum is not found. The bees also look for an entrance to the cavity to be a hole with a diameter in the region of 3 cm.
These two parameters are critical to making a decision on a new home and the bees follow this criteria closely to ensure that the decision made is of as high a quality as possible.
The bees will also look for leaks that allow in water and drafts, and ideally the only ‘hole’ will be the entrance.
When a scout bee has found a potential home it will return to the swarm and communicate to the other scout bees that are on the surface of the swarm. The bee will ‘dance’ to inform the bees about the cavity that they have found and they have an inbuilt quality system that determines how vigorously they dance, the more vigour indicating a cavity that more closely meets the ideal size. The bees will continue to dance for a while with the vigour of the dance reducing each time at which point they will stop dancing and advertising the location altogether. By this time other scout bees will have been triggered to go and assess the location themselves.
As the process suggests it is vital that the dancing bee is honest about how vigorously it advertises the site that it has found, however as it recruits other scout bees these bees will inspect the site and dance accordingly such that any under or over exaggeration is averaged out.
It needs to be stressed that the vigour with which the bees dance is most important also that scout bees advertising other locations will ‘head butt’ the dancing bees until they stop dancing. This inhibitory action is vital in preventing a decision to take place too quickly.
These actions are key to the decision making of the scout bees as a group. Ultimately any sites that are not of high quality, in other words don’t meet the main criteria that closely will die away in favour of those sites that do more closely meet them.
The actual process of making the decision is that point in time when a high quality location has a critical number of scout bees at the location itself. The decision is hence made by quorum, a critical number is reached. Using this process allows the scout bees time to find several locations, to ensure that a location of a high unbiased quality is chosen.
The scout bees at the chosen location return to the swarm and start rousing the other bees in the swarm to get them ready for take off. Details of all of this process can be found in Tom Seeley’s book Honeybee Democracy
‘The analyses of collective decision-making by honey bee colonies indicate that a group will possess a high level of Swarm Intelligence if among the group’s members there is:
- diversity of knowledge about the available options,
- open and honest sharing of information about the options,
- independence in the members’ evaluations of the options,
- unbiased aggregation of the members’ opinions on the options, and
- leadership that fosters but does not dominate the discussion.’
So how do the bees do it? What kind of brain do they have and can they think?
The bee brain has about 1 million neurons in a volume just under one millimeter cubed, compared to the human brain that has over 85 billion neurons. However, the bees have been shown to have grasped that the same signs mean different things in different mazes – suggesting an understanding of context.
Many cognitive scientists believe that such deliberation reaches its apex in a trait known as metacognition. This ability to introspect and judge the quality of your own thoughts – whether you are certain about something or simply going on a hunch – is often considered to be the keystone of a conscious mind. Identifying metacognition in animals that lack language is a tough challenge but, through a series of canny tests, it has been demonstrated in just a small group of primates and dolphins. There is preliminary evidence that the honeybee may be a member of this select club.
Although bees are quick to pick up new rules, they are soon overwhelmed by large quantities of new information. Honeybees can be trained to associate certain smells with the location of different feeding sites, for instance, but they become less accurate once the number of sites exceeds two. Their inability to form connections between different events will be one of their biggest limitations, says Jeremy Niven, a neuroscientist at the University of Sussex in Brighton, UK. “It gives them less opportunity to make predictions about what’s going to happen in the world around them.”
This lack of parallel processing would explain why a single bee cannot make a decision based on the comparison of sites being proposed by the scout bees and how this process of the colony as whole making the collective decision has evolved, the individual bee in the swarm behaving like a neuron in a brain….
Lars Chittka of Queen Mary University London estimates that we have now recorded around 60 separate behaviours for worker honeybees, including six different kinds of dance (Current Biology, vol 19, p R995). These achievements seem to overshadow the abilities of many mammals. Rabbits are thought to show about 30 distinct behaviours, and the beaver has about 50 in its busy life felling trees, building dams and storing food. Even the bottlenose dolphin’s 120 or so routines are only about twice the number a worker honeybee manages.
I would also add that one of the biggest failures to make an effective decision with humans is not being clear about what it is that needs a decision to be made. Once this is clear then a list of the criteria by which each candidate can be measured is drawn up, then compare each candidate.
In the example of the bees needing to choose a new location to move to they have clear criteria that indicates the quality of a site and they have a way that ensures that they choose the site that matches those criteria as closely as is possible without any bias. There is no need for any hierarchy in making this decision (not that their brain has the capacity for remembering large amounts of data) or indeed for any decisions made by the colony of bees. That is not to say there is not leadership as the scout bees clearly take on this role as individuals initially and then as a collective.
If we as human beings can learn from the bees then the biggest message is about how to make decisions.
Be clear about what it is that needs a decision to be made, list the criteria, then test the candidates against the criteria. It is important that the criteria and the testing of candidates is carried out by unbiased competent people who can be trusted.
As humans we have a greater capacity to remember the details, but the decision needs to be unbiased, need no hierarchy and anyone can be a leader with the given skill-set.
Ultimately the honeybees present to us a high quality decision making process that requires no personality, ego or need for any interjection of power; things that all too often are perceived to be the skill and necessity of the hierarchy or the chosen few. Competence is of course vital as in the bees case it is a matter of survival.
When making decisions about ourselves it helps to be aware of what we value in life. In the case of the honeybee finding a new home this is a life or death scenario. For us as individuals one big decision that we make is what we do with our lives following our education. Often, and for many, an almost impossible decision to have to make. If we spend time becoming aware of what we value in life, then look at the things we can do that fit these values as closely as possible we can apply the same decision making process as the honeybees.