Princeton University researchers investigating the behaviours of predatory fish have developed a kind of “video game” testing the feeding preferences of the bluegill sunfish.
Describing their research target as “famously ravenous”, the researchers projected simulated prey onto one side of a tank – either as a single target, or in a group. As an added level of difficulty in the “boss battle”, they encoded interactions between members of the simulated groups.
The result was that the bluegills avoided “prey” that were moving in mobile, coordinated groups – far preferring to pick off single prey. As Princeton’s media release (with videos) puts it, the results “show that group formation itself can dissuade a predator, even if the prey — as in the simulation — are completely unaware of the danger”.
Assistant professor of ecology and evolutionary biology Iain Couzin says the research demonstrates that “the specific configuration of animal groups is an evolved defense in its own right”.
The simulated prey were subject to three kinds of interaction rules: they might be attracted to, swim in the same direction as, or ignore nearby individuals – and the simulation allowed the researchers to vary the strength of each trait.
“Effectively, the bluegills were playing an immersive video game in which they hunted”, Couzin explained.
While it’s no surprise that a predator might prefer to “pick off” a stray individual rather than try to attack a group, the simulation goes further: it allows scientists to quantify how individuals’ behavior can influence the safety of the whole group during an attack.
As Julia Parrish of the University of Washington (not part of this experiment) puts it: “This experiment makes some very specific predictions about what's a good configuration and what's not a good configuration, and gives some insight into what the rules of aggregation might be”. ®