The most daring individuals lead schools of sticklebacks.

The most daring individuals lead schools of sticklebacks. Frans Lemmens/Alamy


Bold fish run the school

Sticklebacks’ ‘personalities’ control group dynamics

Individual differences in behaviour, such as boldness and sociability, are common in animals, but how these ‘personalities’ affect group behaviour has remained poorly understood.

Jolle Jolles at the University of Cambridge, UK, and his colleagues observed the behaviour of individual sticklebacks (Gasterosteus aculeatus) in a tank, and then filmed shoals swimming freely and foraging in different environments. Fish that were consistently more sociable tended to swim more slowly and cluster with other fish, while less-sociable fish were more likely to lead the shoal.

When the tank contained hidden patches of food or a refuge, the bolder, more-exploratory fish increased group foraging performance. Using a computer simulation of shoals containing a mix of personality traits, the team found that the same group dynamics emerged. Consistent individual differences in behaviour can affect the structure, leadership and performance of animal groups, the authors say.