How to behave in school
Mass animal behaviour is a marvel – but what makes individuals decide which way to go?
A mass of animals flocking, schooling or swarming is one of the grand sights of nature: a flock of magpie geese erupting from an Australian billabong; a bait ball of anchovies about to be engulfed by a humpback whale.
Coordinated behaviour is common in a variety of organisms and it includes such things as insect swarms and bacterial colonies. These are fascinating and often highly visible phenomena.
But the way information spreads and decisions are made in these groups is little understood.
Now, researchers from Southeast University, China, and China University of Mining and Technology have studied synchronised flights of pigeon flocks in an effort to explain the mechanisms behind coordinated behaviour.
Their results have been published in the journal Chaos.
Lead author Duxin Chen, from Southeast University, says that understanding the underlying mechanisms of coordinated behaviour helps us gain a greater understanding of our world.
The best-known work on the subject, published in 1987, suggests the behaviour is subject to three basic rules: avoid collision with your peers, match your speed and direction of motion with the rest of the group, and try to stay near the centre.
The new study, which examines how every individual pigeon in a flock is influenced by the other members, found the dynamics are not so simple.
Using a data mining algorithm named k-nearest as their underlying tool, the researchers studied the flights of three flocks, each composed of 10 pigeons.
Every bird’s position, velocity and acceleration were sampled with time, and the researchers used this data to determine which pigeons have a direct impact on other individuals in the group.
They determined a number of trends in flock motion.
Depending on factors such as the flock’s location, every pigeon has neighbours it influences, and neighbours it’s influenced by. Emphasising the complexity of the interaction, the influencers are likely to change throughout the flight.
“Interestingly, the individuals closer to the mass centre and the average velocity direction are more influential to others, which means location and flight direction are two factors that matter in their interactions,” says Chen.
The authors suggest their method is sufficiently general to study other coordinated behaviours. They plan next to focus on the collective behaviours of immune cells.