Scientists were surprised when Trinidadian guppies, a type of tiny fish, defied expectations in a study exploring the “volunteer’s dilemma.” Typically, individuals are less inclined to cooperate in larger groups, as studies have shown in humans. However, the guppies exhibited a different pattern.
The University of Exeter conducted a study on guppies, observing their behavior when faced with a potential predator. The researchers placed a clay model of a pike cichlid, a natural guppy predator, in a tank containing small (five), medium (10), and large (20) groups of guppies.
Contrary to expectations, guppies in larger groups were more likely to approach and inspect the predator. On average, guppies in large groups inspected the predator 14 times during the seven-minute trials, while those in medium groups inspected it only seven times. Guppies in medium groups also spent more time seeking refuge behind plants or near the tank’s edge.
Rebecca Padget, from the Center for Research in Animal Behavior at the University of Exeter, explained that the “volunteer’s dilemma” suggests that individuals in larger groups should be less inclined to cooperate because there is a higher chance that someone else will take the risk. However, the guppies in this study contradicted this prediction.
The researchers speculate that larger groups may contain more cooperative individuals, and others in the group follow their lead. It is also known that after inspecting a predator, guppies return to the group and signal danger to the others.
During the study, an “inspection” was recorded when a guppy approached within 30cm of the predator. This behavior was typically observed in individuals or small sub-groups within the main shoal of guppies.
Source: University of Exeter