Ants build raft to escape flood, protect queen

February 19, 2014
These are ants building a raft. Credit: Jessica Purcell

When facing a flood, ants build rafts and use both the buoyancy of the brood and the recovery ability of workers to minimize injury or death, according to a study published in PLOS ONE on February 19, 2014 by Jessica Purcell from University of Lausanne, Switzerland, and colleagues. Furthermore, the queen ant is placed in the middle and protected on all sides by the rafting ants.

When put in harm's way, are often able to work together to enhance the survival and welfare of the group. Ants living on flood plains are known to link to together to create rafts during floods, but less is known about the composition, shape, and social structure, if any, of these rafts. To better understand this process, scientists collected ants from a flood plain in Switzerland and brought them back to the lab so they could induce flooding in ant populations containing different combinations of worker ants, queens, and broods (containing developing larvae and pupae). During the 'flooding,' they observed where the workers, brood, and queens were positioned in the raft. The flooding also allowed them to observe the buoyancy and recovery ability of the worker ants and brood.

Researchers found that the worker ants and brood were extremely resistant to submersion. The workers protected the most vulnerable and valuable nest mate, the queen, by placing her in the center of the raft, and the used the buoyancy of the brood at the base and recovery ability of workers to create a raft and minimize ant injury or death. Both and brood exhibited high survival rates after they rafted, which suggests that occupying the base of the raft is not as deadly as scientists expected. Placing the brood at the base of the raft may also aid in keeping the nest together during the flood.

Dr. Purcell added, "We expected that individuals submerged on the base of the would face the highest cost, so we were astonished to see the ants systematically place the youngest colony members in that positions. Further experiments revealed that the brood are the most buoyant members of the society and that rafting does not decrease their survival; thus, this configuration benefits the group at minimal cost."

Explore further: Fire ants assemble as a 'super-organism' (w/ video)

More information: Purcell J, Avril A, Jaffuel G, Bates S, Chapuisat M (2014) Ant Brood Function as Life Preservers during Floods. PLOS ONE 9(2): e89211. DOI: 10.1371/journal.pone.0089211

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not rated yet Feb 19, 2014
"The needs of the many outweigh the needs of the few"
- Mr. Spock
Lex Talonis
2.5 / 5 (2) Feb 20, 2014
Yeah but this ant rafting business, has been in SO many documentaries, about so many species of them, so damned often, in so many countries.......

Is this actually news worthy, or have the people in Switzerland just discovered ants?

"Oh my god - ants refuse to sink, drown and die - how amazing! Quick get the semaphore flags out and send the message to the whole world - "Switzerland has ants, and they refuse to obediently drown when forced too.""

4 / 5 (2) Feb 20, 2014
Is this actually news worthy, or have the people in Switzerland just discovered ants?

The linked article is actually quite interesting, too bad articles are often so dumbed down that the important aspects of the linked research works don't come through, leaving only meaningless sensationalist dribble with every "fact" repeated twice and topped by silly titles.
5 / 5 (1) Feb 20, 2014
Is this actually news worthy, or have the people in Switzerland just discovered ants?

It is newsworthy because no one had looked at whether ants structure these rafts with a particular plan in mind. And what they found was quite surprising as one would not have suspected that brood would be put in the most exposed/endangered positions.

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