BoundedRationality_TheAdaptiveToolbox.pdf

252 Thomas D. Seeley
group — be communicated to a central decision-making individual, that this individual
then integrates all this information, and finally that it issues instructions
to the other group members (Simon 1981). However, no species of social insect
has evolved anything like a colony-wide nervous system which would allow information
to flow rapidly and efficiently to a central decision maker. Moreover,
there is no individual within a colony capable of processing a huge mass of information.
It is not surprising, therefore, that social insect colonies have evolved
highly distributed mechanisms of group decision making. Given that no one
member of a social insect colony can possess a synoptic knowledge of her coL
ony 's options, or can perform the complex information processing needed to estimate
the utility of each option, it is not surprising that the concepts of bounded
rationality and heuristics are highly relevant to understanding how
superorganisms make their decisions.
HOW HONEYBEE SWARMS CHOOSE A HOME SITE
Natural History
One of the most spectacular and best-studied examples of an animal group functioning
as a collective decision-making agent is a swarm of honeybees choosing
its future home. This phenomenon occurs in the late spring and early summer
when a colony outgrows its hive and proceeds to divide itself by swarming. The
mother queen and approximately half of the worker bees (approximately 10,000
bees) leave the parental hive to establish a new colony, while a daughter queen
and the remaining workers stay behind to perpetuate the old colony. The swarm
bees leave en masse, quickly forming a cloud of bees just outside the parental
hive; they then coalesce into a beard-like cluster at an interim site (usually a
nearby tree branch) where they choose their future dwelling place. The nest-site
selection process starts with several hundred scout bees flying from the swarm
cluster to search for tree cavities and other potential nest sites that meet the bees'
real-estate preferences: cavity volume greater than 20 liters; cavity walls thick
and strong; and a cavity opening smaller than 30 cm 2 , at least 3 meters above the
ground, facing south for sunlight, and located at the floor of the cavity. The
scouts then return to the cluster, report their findings by means of waggle dances,
and work together to decide which one of the dozen or more possible nest sites
that they have discovered should be the swarm's new home. Once the scouts
have completed their deliberations, they stimulate the other members of the
swarm to launch into flight and then steer them to the chosen site (the biology of
swarming is reviewed in Winston 1987).
How exactly do the several hundred scout bees jointly decide which of the
several sites found should be their future home? The first step toward solving
this mystery came in the early 1950s when Martin Lindauer (1955, 1961) discovered
that a scout bee can report the location of a potential nest site to other