The sychronised movement of animal groups like flocking birds, swarming insects, or schooling fish has often lead to the assumption that all of the individuals in the group were more or less the same. With all individuals responding to other members in the group and external stimuli (for example, predators) in pretty much the same way. Marine researchers have recently shown this isn't the case.
Liza aurata photographed in Corsican waters. Photo: Roberto Pillon, wikimedia commons
In the article published in PLOS One yesterday researchers, using high-speed video analysis, found that not all individuals in a school of Golden grey mullet (Liza aurata) respond to a predator threat in the same way. Among his subjects there were leaders, who were consistently first to respond and among the followers fish showed preferences for where they were positioned within the school (front, middle, periphery, or rear) with those at the rear being those with the slowest reaction times.
The authors suggests that certain indviuals are likely to play a key role in the survival of the whole school, and that these difference could also lead to differences in the behaviour of whole schools of fish.
Journal reference: Stefano Marras, Paolo Domenici (2013) Schooling Fish Under Attack Are Not All Equal: Some Lead, Others Follow. PLOS One
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