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Zoologger: How to get elected in a termite democracy

Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world

By Michael Marshall

5 January 2011

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If the feeling doesn’t persuade you, the anal fluid will

(Image: Patrick Gleeson/CSIRO)

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Choosing a leader, termite style

(Image: Dr. Judith Korb/University of Osnabrück)

Species: Cryptotermes secundus

Habitat: munching away inside dead trees in the mangrove swamps of northern Australia

Bringing gifts of food, building a house, sitting through interminable romantic comedies: animals will go to great lengths to pass on their genes. The competition for mates is so intense that many individuals die in the process – unless, that is, the animals in question are Cryptotermes secundus termites.

These insects live in colonies ruled by a single king and queen, who do all the breeding. When they die an heir must be found from within the colony’s ranks, but the succession is surprisingly peaceful and orderly. Hardly anyone gets killed.

Family matter

C. secundus are primitive termites, which do not build the great mounds and spires that others do. They live in small colonies of 50 to 100 individuals, all nestled together in a piece of dead wood that serves as both shelter and food.

Apart from the royal pair, the colony is made up of workers and soldiers, who are all siblings. The workers are utterly misnamed: they do not do any work.

Unlike some social animals, individual termites are genetically distinct from each other, so there is plenty of potential for conflict. Clonal animals, as well as the more familiar social insects ants, bees and wasps, tend to be fairly well-disposed towards each other, because preserving their fellows means preserving their own genes, but termites are different.

What’s more, apart from the soldiers, which are sterile, every termite in the nest has the ability to become a breeder. So if the royal pair dies the colony should collapse into violent anarchy, with every worker fighting for itself. This sometimes happens in honeybee colonies when the social order breaks down.

Judith Korb and Katharina Hoffmann of the University of Osnabrück, Germany, wanted to find out how the termites went about resolving the succession question. They collected 17 wild colonies and kept them in wood blocks in their lab where they could monitor them closely. Then they removed the royal pairs and watched how the workers reacted.

Social combat

Within nine days of the royals leaving, some of the workers moulted and acquired the potential to breed. But only about 12 per cent of the workers underwent this transformation: the others stayed as they were. Korb thinks that, when the termites moult, there is a brief period when they can pick up signals from nest-mates and change their status – but because this time is short, only a few become breeders.

The breeders then competed among themselves for the right to reproduce. One element of this was straightforward: they attacked each other until one was wounded, and the injured individual would then be finished off and eaten by workers. “Workers always eat injured individuals,” Korb says: it’s a way of recycling valuable nutrients.

But just as importantly, the breeders became much more social, like politicians canvassing for support. They spent a lot of time feeling other individuals with their antennae: workers and breeders have different chemicals in their cuticle, so feeling each other is a way of finding out who is who.

They also spent much more time than usual feeding their fellows with surplus food, which they squeezed out of their bottoms. This seemingly generous act may actually be a subtle dominance signal, in effect saying: “Look at me, I am so well-fed and powerful I can afford to pass out food.”

There may also be something still more insidious going on: as well as food, the anal secretions might contain hormones or pheromones that stop the recipient from breeding.

Give peace a chance

By insect standards, Korb says, “this is really peaceful. We expected overt conflict, but we didn’t see it.” It’s also efficient: within 11 days of the first breeders emerging, the new royal pair is installed.

Other species are much more competitive. In the closely related Cryptotermes domesticus 35 per cent of workers become breeders, and the struggle to breed is correspondingly brutal.

But it seems the gentler species wins out in the end. In a separate experiment Korb placed colonies of secundus and domesticus together in logs and made them compete. After two years, four out of 16 colonies of secundus had survived, but only one of 16 domesticus were still going. The aggressive termites wasted so much effort, and so many lives, fighting among themselves that in the end they lost out to the peaceful species.

Journal reference: Animal Behaviour, vol 81, p 265

Read previous Zoologger columns: Away in a vermin-infested manger, Child clones shape-shift to escape hunters Weaponised eggs turn predators’ stomachs, The hardest bat in the world, Houdini fly inflates head to break walls, A primate with eyes bigger than its brains, The solar-powered electric hornet, The miniature cuckold fish, Lemmings swap suicide for infanticide, The slow-moving mystery of the sloth’s neck, How weakness makes the crayfish stronger .

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