Last year, I had the good fortune of going on a white water rafting trip. Shivering uncontrollably from the combination of the cold and the danger, it was, all things considered, an amazing adventure. One factor, which at the time, I was very grateful for was the raft – a sturdy construction of rubber and glass fibre. Without it, well, I would just look stupid. It turns out, however, that not everybody needs a raft to go rafting. Ants, in their near-infinite behavioural plasticity, have evolved a way of escaping floods by constructing a raft from their own bodies.
Although this behaviour has been known for some time, one group of scientists decided to study how ants are able to achieve this feat – considering that each individual ant is denser than water and is too large to be supported by surface tension.
The trick, it seems, is teamwork. When ants find themselves in water they readily bunch together, joining up by biting each other with their mandibles and hooking their legs together. This structure was discovered, in a rather frosty manner, by the scientists plunging the ants into liquid nitrogen, freezing them into a solid mass of ants, in order that they could be studied.
This structure isn’t static, it is plastic. Should something disturb the raft such as a strong current or a scientist with a stick [video 1 ], the ants contract their muscles, which pulls the raft into a more rigid structure.
But what about those poor ants on the bottom? Im glad you asked. Well, ants are naturally hydrophobic – their exoskeletons repel water. This enables them to trap a thin layer of air, known as a plastron, around themselves which they can breathe. This plastron also helps the raft remain buoyant. This can only happen if the water is clean. If contaminants are present in the water, the plastron cannot form. The ants at the bottom drown, and the raft itself breaks up. Sounds worse than the Titanic.
These rafts can range from only a few individuals to thousands of colony members. They can self-heal and self-assemble and adapt to the local environmental conditions – all hallmarks of a life. This behaviour does give credence to the idea that ant colonies are super organisms – a lifeform made up of individual animals that behaves as a single creature. Antastic.