Cascading Fish
Since moving to Ithaca, I’ve often been captivated by the movement of birds flying in the sky, in triangular formation, cutting through the air, determinedly aimed at an invisible enemy. They’re always beautifully synchronized in their movements and follow the leader’s every move.
Scientists in Sydney were interested in this as well and tried to find out how mosquito fish perform their perfectly synchronized choreography. It appears that these fish depend on their closest neighbors’ movements: they accelerate when the neighbor gets too far and decelerate when it is too close. The speed with which it responds may change but the reaction is consistent.
The article on this story that I have linked at the bottom ended with this observation from the scientists: “It is possible for single neighbor interactions to produce complex schooling patterns.” This whole idea had me thinking about information cascades and network effects. Many creatures with a ‘herd mentality’ exhibit characteristics of information cascades with a take-up threshold of close to 0. There might be a lot of animals in the pack, but only one leader is enough to determine where they all go.
There might be a biological explanation for why they do this, perhaps an evolutionary adaptation that has ensured their survival. However, it still remains a very interesting topic to explore with regards to networks theories. A dictatorship of sorts is upheld through such a system where one individual makes all the decisions and its movements are mimicked. This mimicry is cascaded down the network until every member of the herd/pack moves in unison.
I would be interested to know the commonalities between how different creatures manifest this behavior. Is there a hidden threshold? Could it be something other than a dictatorship?
http://www.dailytelegraph.com.au/a-sydney-study-finds-why-animals-move-in-packs/news-story/72b3628b1617eca6847b5db245d76f80