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Page last updated at 10:17 GMT, Monday, 15 March 2010
Bee swarms follow 'pied pipers'
By Jody Bourton
Earth News reporter

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Honeybees getting ready to swarm, at 100 minutes the high pitched "piping-signal" is audible above the background buzz.

A tiny group of bees act like "pied pipers" to trigger the onset of bee swarms report scientists.

By buzzing a "piping" signal the bees are able to initiate an explosive departure from the hive.

Bees are known to use signals to tell the colony when to swarm but which bees had the power to make this decision was unclear.

Now scientists have identified a small oligarchy of individual bees that hold the key to swarm behaviour.

The researchers reveal their findings in the journal Behavioral Ecology and Sociobiology.

Exodus

During the reproductive season, large honeybee (Apis mellifera) colonies synchronise an explosive departure of most of their workers and the queen.

This causes a swarm as the honeybees travel to form a new colony in a new location.

Before our studies little was known about how this sudden exodus was coordinated
Dr Juliana Rangel
Cornell University, Ithaca New York, US.

The sudden departure of bees has been known about for centuries and bee keepers have even found ways to avoid it happening and avoid loosing valuable bees.

But scientists have only recently begun to understand how the bees coordinate their departure and mass exodus.

"In this study we wanted to determine what bees are responsible for organising this mass departure, and how they organise this process in an efficient manner," says Dr Juliana Rangel from Cornell University, Ithaca, New York, US.

Dr Rangel undertook the study along with Sean Griffin and Professor Thomas Seeley also from Cornell University.

The bee identity

"Our study is the first one to reveal the identity of the signallers that initiate a swarm's departure from the hive," Dr Rangel says.

The report finds that a small group of experienced forager bees called nest-site scouts produce a "piping-signal" that primes the workers for swarming.

This makes the bees warm up their flight muscles for departure.

They then produce a "buzz-run" signal which releases the departure of the swarm.

BUSY BEES
bee swarm

This small oligarchy of bees make up only 5% of the colony's total population.

The researchers think that the oligarchy in the colony they studied consisted of only 200 individuals in colony size of 8,000.

It is the job of these bees to go out of the hive and search for potential homes for the colony.

When they find somewhere suitable, they return and start the process of swarming by producing the piping signal. They also recruit others by undertaking a waggle dance.

This is a dance-like movement by which the bee communicates the distance and direction of a location to other bees.

"Before our studies little was known about how this sudden exodus was coordinated, and which bees were in charge of this process," Dr Rangel says.

Group control

Animals that travel in groups must synchronise the timing of their movements.

Three different decision making mechanisms are known to coordinate a group's departure Dr Rangel explains.

"In a democracy, the majority of the individuals in the group decide when the move will take place, for example whooper swans and red deer."

"In the other extreme is the despotic mechanism of decision-making, in which only one individual, the group's leader, makes the decision of when to move, for example Hamadryas baboons and African elephants."

Right in the middle lies an oligarchy where a small number of well-informed individuals, makes the decision of when the group should move.

"Decisions of group travel made by an oligarchy are very rare, and very few studies have reported an oligarchic control of group travel," says Dr Rangel.

"This contributes to our knowledge of how a small group of individuals can make important decisions for an entire group."



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