Tuesday, 10 May 2011

Eat Your Heart Out Noah: Ants on the High Seas


What do you get when you mix a colony of fire ants, a pool of water and biological engineers? Science! More specifically, you get ant behavior that starts to blur the lines between animal psychology and grade 12 physics.

            We’ve all seen footage of a colony of ants cooperating to move food or construction materials: each ant lending a mandible as one small cog in the colony machine. This metaphor starts to become a little less metaphorical, however, when the construction materials in question are the ants themselves. When they’re not breaking up picnics, it turns out that ants can also build self-assembling rafts with astonishing characteristics.

In a paper published in the May 10th, 2011 edition of the Proceedings of the National Academy of Sciences, a group of engineers and biologists explore the physical dynamics of these bug barges. They collected road-side fire ant colonies, made ant-balls by stirring several thousand ants around in a beaker, and finally poured the insect orbs into tanks of water to observe the effects.What these researchers saw was not panicked dog-paddling and tiny wails of “every ant for themselves!” but rather the colony weaving together to form a waterproof mesh that can float for days, or even weeks. Looking at the microscopic structure of the rafts revealed that the ants both “hold hands” and (gently) grasp other’s limbs in their mandibles to hold the structure together. The ant-raft also responds to such stimuli as being poked with a stick by grasping each other more tightly to form a finer and more waterproof netting.

Yes, I know what you’re thinking: insects floating are not exactly news. Insect exoskeletons are slightly hydrophobic (repel water) and we’ve all seen insects poised delicately on a pond’s surface on a calm day. While it might be underwhelming that the ant rafts are both waterproof and buoyant, the shape and physical dynamics of the raft structure definitely fall into the amazing category. In fact, when forming such floating vessels, individual ants behave less like independent creatures and more like particles in a liquid. The rafts in these experiments were constructed from thousands of ants in a rough ball shape. When placed on the surface of the water, the ants spread out in a matter of minutes to form a pancake-shaped floating raft (picture a ball of silly putty left on a counter in a warm kitchen for a couple of days). In fact, the physical properties of the ant masses were found to be more similar to a physical substance than a conglomeration of multiple sentient beings.

The self-assembling, self-healing, and impressive physical characteristics of the ant rafts in this study have attractive implications for the application of nanorobotics in similar tasks. Once again, Nature’s astounding engineering projects leave our biomimetic scientific efforts scrambling to keep up.

Learn more in this incredible ant raft research paper.
Also check out the amazing video footage

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