Posted on 2 February 2017
Scientists from the Universities of York, Exeter, and the West Indies observed Trinidadian guppies and found the fish developed stronger and more stable social bonds when they thought predators were nearby.
Intriguingly, this also coincided with social groups being smaller – suggesting a possible conflict between being able to form strong social relationships and being able to live in larger social groups.
This is the first experimental evidence that proximity to predators can increase the intensity of animal social relationships.
Previous research has shown guppies recognise other individuals and develop long and stable social relationships.
In this study, fish were kept in pools and some were exposed to model predators, while others were not.
Guppies frequently leave and join new shoals, and the researchers measured social ties by seeing how often the same fish swam together.
While all guppies developed stronger social bonds when faced with predators, the effect was strongest among those most at risk – the larger and bolder individuals.
Many animal species gather in large social groups to gain protection from predators, but the scientists found guppies formed smaller groups as they strengthened their social ties.
“Our research shows that when animals can cooperate in times of danger, they can benefit from forming small groups of trusted friends, at the expense of protection by numbers.”
The paper, entitled ‘Fear of predation drives stable and differentiated social relationships in guppies’, is published in the journal Scientific Reports.
The work was funded by the Leverhulme Trust and the Danish Council for Independent Research.