While a single locust is inconsequential, a swarm is devastating. But it’s not brotherly instinct that makes them stick together. This talk introduces us to Professor Iain Couzin’s research.
We have spoken of ‘flocks of birds’, ‘swarms of ants and flies’, ‘herds of elephants’ and so on, but as Iain Couzin says, “People do not really know why birds flock together or how fish coordinated their patterns or why locusts swarm. When you see these beautiful patterns, we are very good at capturing that beauty as an emotional expression but we are not really good at measuring that or quantifying it.” Couzin, who studies collective behaviour of animals, working as Assistant Professor in the Department of Ecology and Evolutionary Biology at Princeton University, explains his interest. “I had very little understanding of what science was…I was interested in animals and what particularly fascinated me was patterns…I was drawn to science through patterns, through art.”
Couzin’s initial fascination was for blind ants that swarm Central and South African forests. They are called army ants. Couzin says, “… more than one-and-a-half billion blind ants harvest hundreds of insects and devastate the area where they live, so they have to keep moving. Because of their nomadic life, they build their nest out of their own living bodies, all clinging together…I have seen a five-and-a-half feet wall made by ants clinging to each other and when they have to move they just kind of dissolve…they are all females and work together. Males are produced only when they need to reproduce, so they are kind of expendable…the female are working together… we discovered that much like we have structured lanes on our streets, these ants had evolved lanes for movement long, long ago. The central lane was of ants going back to the colony with food. If we want to build a bridge we may do so in the wrong place, but the ants build and dissolve as is fitting to the place, for even their bridge is built of their own bodies…the trail which ants follow is created by certain chemicals which the leading ants leave behind.”
Couzin studied locusts next. He says locusts are not a problem individually; when they come in swarms they are a catastrophe. Couzin compares the formations of locusts to the way particles combine to make a magnet. But what is it that kept their magnetic pull towards each other and so the formation intact? Couzin found that locusts were actually being eaten by other locusts…when food is short, the locust bites the belly of another locust and begins to eat it. To avoid dying these locusts keep their flight to safe climes in the hope of food. So the pattern formation has a nutritional basis essentially caused by the need to survive, for two reasons: one, the locust tries to bite the belly of the one ahead when food is short; two, if there is enough nutrition also, the locust finds it beneficial to keep behind another just in case food falls short. Couzin hopes this study will help understand why swarms are formed and therefore help farmers get rid of the pests.
Couzin shows that collective activities are not all inspired for the same reasons. “Social insects are more related to their sisters than they would be to their own offspring, and so they have this tight relatedness so they work together, “says Couzin when he talks of ants, whereas the cannibalistic tendencies of the locusts show they have to have relations to the rest of their species.
Couzins has also done some study on human collective behaviour. He says, “Humans, are highly social organisms. Social life is very important to us. We are also very complex and very creative too… but we also, like army ants, form lanes, moving together…we are often not aware of the context…Unlike army ants we have not evolved to that extent and so we are not so efficient in groups. But now we are doing studies on pedestrians and have been filming them. We find they follow the gaze of the other…particularly if we are behind the person…”
Further study may help us manage institutions, where we meet collectively, better.