While collecting fish samples in the field in Africa recently, behavioral ecologist Shun Satoh made an intriguing discovery. When he gazed towards a group of emperor chichlids, the fish seemed to be more alert and aggressive. This personal intuition became the starting point for a study to determine whether the fish could detect when a diver was directing visual attention toward their offspring.
Usually, aggression in territorial or brood defense among fish varies with the level of threat posed by the intruder or the intruder's species. However, in a new study, published in Royal Society Open Science, “we showed that aggression can also vary depending on where the intruder’s attention is directed,” Satoh told Refractor via email.
Sensitivity to gaze in animals has likely existed for a continuum, ranging from simple gaze avoidance to more sophisticated forms of perspective-taking. However, previous studies have largely limited more complex cognitive abilities – such as attention attribution – to humans and other primates. “Attention attribution is generally understood as the ability to recognize what another individual is attending to,” Satoh explains.
To establish whether emperor cichlids (Boulengerochromis microlepis) possess this ability, Satoh and his colleagues designed an experiment in the fish’s natural habitat in Lake Tanganyika in Zambia. The team used scuba divers and action cameras to assess how cichlids changed their aggressive behavior in different scenarios: when a diver gazed directly at the eggs or fry, looked away from the offspring, turned their entire body away, or stared directly at the guarding parental fish.
Though the cichlids are protective of their eggs, they are not too aggressive or fearful of humans. The results showed that the emperor cichlids attacked significantly more often when the diver looked directly at the eggs than when they averted their gaze or turned away from the brood. The attack rate was similar to when divers stared at the guarding parents.
Male cichlids were more aggressive than the females, though both joined the defense to protect the fry. Interestingly, the fish also spent more time near the divers when they turned completely away.
“Emperor cichlids changed their behavior according to the target of attention, even when the intruder was a human diver,” Satoh told us.
Though this is a preliminary study, it represents another example of more complex cognitive processes that fish might have, likely to the fish's benefit under natural selection, says a biologist, Audrey Looby at the University of Victoria, who wasn’t involved in this work.
“This study also only tested one fish species, meaning this does not necessarily mean that other fish might have the same attention attribution abilities,” she adds.
Looby also highlights the potential effects that scuba diving can have on fish. Though scuba diving is considered non-extractive, unlike fishing, and not much of a threat to the species, this research suggests that it could cause detrimental impacts, says the biologist.
“Cognitive abilities we once regarded as uniquely human may in fact be more evolutionarily flexible and widespread than we expected,” Satoh concludes.
The study has been published in the journal Royal Society Open Science.
