For social animals such as schooling fish, the loss of their numbers to human activity could eventually threaten entire populations, according to new research which found that such animals rely heavily on grouping to effectively navigate their environment.

Collective intelligence is vital to certain animals' ability to evaluate and respond to their environment according to the study, which was led by researchers from Princeton University and co-authored by Dr Christos Ioannou, now at the University of Bristol.  Conducted on fish called golden shiners, the research demonstrated that small groups and individuals become disorientated in complex, changing environments.  However, as group size is increased, the fish became highly responsive to their surroundings.

The researchers placed golden shiners in groups as low as one and as high as 256 in experimental tanks featuring a moving light field that was bright on the outer edges and tapered into a dark centre.  To reflect the changing nature of natural environments, they also incorporated small patches of darkness that also moved around randomly.  As the fish pursued the shaded areas, the researchers recorded their movement using computer vision software.  Although the fish sought the shade regardless of group size, their capability to do so increased once groups spanned a large enough area.

The researchers then tracked the motion of individual fish to gauge the role of social influence on their movement.  They found that individuals adjusted their speed according to local light level by moving faster in more brightly lit areas, but without social influence the fish did not necessarily turn toward the darker regions.  Groups, however, readily swam to dark areas and were able to track those preferred regions as they moved.

Dr Ioannou said: "This collective sensing emerged due to the coherent nature of social interactions.  As a result of fish in the shaded areas slowing down, the group rotated toward these shaded areas.  Also, slowing down increased density and resulted in darker regions becoming more attractive to these social animals."    

These findings should prompt a close examination of how endangered group or herd animals are preserved and managed.  If wild animals depend on collective intelligence for migration, breeding and locating essential resources, they could be imperilled by any activity that diminishes or divides the group, such as over-hunting and habitat loss.

Senior researcher, Professor Iain Couzin from Princeton University said: "Processes that increase group fragmentation or reduce population density may initially appear to have little influence, yet a further reduction in group size may suddenly and dramatically impact the capacity of a species to respond effectively to their environment.  If the mechanism we observed is found to be widespread, then we need to be aware of tipping points that could result in the sudden collapse of migratory species."

The work is also among the first to experimentally explain the extent to which collective intelligence – an established advantage of groups, including humans – improves awareness of complex environments.  As it's understood, a group of individual animals gain an advantage by pooling imperfect estimates with those around them, which more or less 'averages' single experiences into surprisingly accurate common knowledge.

With their work, Professor Couzin and his co-authors uncovered an additional layer to understanding collective intelligence.  Even though some individuals have very little ability to estimate how a problem needs to be solved, the group as a whole can find a solution through their social interactions.

The researchers also found that the more numerous the neighbours, the richer the individual — and thus group — knowledge is.  This effect continued to increase up to 256 fish.  As the fish are unlikely to 'know' what size group they're in when there's so many, this demonstrates that collective intelligence is a group-level effect without the individual fish changing their behaviour in larger groups.

These findings correlate with recent research showing that collective intelligence — even in humans — can rely less on the intelligence of each group member than on the effectiveness of their communal interaction.  In humans, research suggests that such cooperation would take the form of open and equal communication among individuals regardless of their respective intelligence.

Paper

'Emergent sensing of complex environments by mobile animal groups' by Andrew Berdahl, Colin J. Torney, Christos C. Ioannou, Jolyon J. Faria, and Iain D. Couzin in Science