Survival strategy of tropical ants who form a living raft to avoid drowning

Add to My Stories When you are trying to keep your head above water, the last thing you want is someone grabbing hold of you.
Unless you're an ant, that is, when it turns out the best way to stay afloat is to stick together.
Scientists have revealed how the insects avoid mass drownings in the rainforests by clinging to one another to form huge rafts from their bodies.

Watch the videos below...

Starting point: This video shows 8,000 South American fire ants being dropped into water during an experiment

Spreading out: The ants slowly bind on to each other using their mouths and widen their surface area

Hello sailors: It takes the ants around 100 seconds to spread out to the fullest extent into the life raft, when they use to float around until they find higher ground The remarkable survival strategy belongs to South American fire ants, whose rainforest homes are subject to regular flooding.
As soon as water starts trickling into their nest, the ants spring into action, evacuating their home and drifting along en masse, looking for higher ground.

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Now, American scientists have shown just how they do it.After collecting fire ant colonies from roadsides in Atlanta, they conducted a series of experiments into water repellency, buoyancy and building skills and speed.Some simply involved dropping hundreds, or thousands, of the reddish-brown bugs, on top of water and then using time-lapse photography to track what they did next.In some ca! ses, it took them less than two minutes to clump into floating 'rafts'.

A bug's life: Fire ants have strict societal structures: (L-R) three worker ants, a queen ant and a male

Up close: A floating ant ball drifts on water until it finds sanctuary for the colony

In the wild: The ants in the mass reposition themselves so that no ant is left underwater for too long

The 'rafts' were roughly the shape of a pancake loaded with topping, with approximately half the colony forming a single submersed layer that buoyed the rest.The creatures used their jaws and claws to cling together, in a formation similar to the weaving of a waterproof fabric.The ants that form the base of the raft are usually on top of the water, but if they are knocked underwater, they are able to survive due to pockets of air trapped beneath the surface, it was reported in the journal Proceedings of the National Academy of Sciences.What is more, when the researchers removed ants one by one from the top of the raft, ants on the bottom moved up, to preserve the rafts average thickness.The researchers, from the Georgia Institute of Technology, said this suggests that the submersed ants are able to somehow sense how many 'passengers' are riding along above.Around 100 ants are needed to begin to form a raft and in the wild, the structures can float along for weeks or even months.

View from above: The ants when they are first dropped into the water are in a tighter bunch...

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... y et by the end of the process their circular raft has a much wider circumferenceResearcher Nathan Mlot, a PhD student, said: 'It doesnt matter if you have part of a colony, or the entire colony, all of the rafts are watertight.'But in nature, it is better if the entire colony becomes part of the raft, not just for the strength of the raft, but because ants are social creatures and need to be part of the colony to survive.'
It is thought the ants survive on 'provisions', including parts of other insects, taken from their nests.The queen, and her young are also carried on board and kept safe and dry during the voyage.However, the adhesion process falls apart in soapy water, with lack of water pockets making raft construction impossible.The researchers said that human shipbuilders could learn a thing or two from the humble ant.They said: 'Overlooking its diminutive size and shortcomings in soapy solutions, the ant raft has attractive traits with respect to man-made flotation devices.'It simultaneously provides cohesion, buoyancy and water repellency to its passengers.'It can be constructed quickly, in approximately 100 seconds, without any additional equipment.It can accommodate thousands to millions of passengers with zero casualties.'But, perhaps most strikingly, the ant raft is self-assembling.'Many of these benefits are due to the ant's small size.
'At the scale of millimetres, ants have great strength, high speed and the ability to trap air pockets when submerged, which in turn makes their rafts water repellent.
The fire ant, or Solenopsis invicta, is native to Brazil, but has crept into the southern states of the U.S. in recent years and has also made its way to Australia.
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