Fish Really Hate Their Mirror Image

Cichlid fish males are not exactly cowards. They are very territorial and highly aggressive, and would gladly pick a fight with any other fish that happens to enter their waters. They are also known for the fact that they readily attack their own reflections, posturing and lunging as in a real battle. But scientists have recently discovered that fighting its own reflection causes “negative” consequences in the animal's brain, as in reactions taking place in areas of its brain that have been associated with fear. A number of other negative reactions are also located in the same area of the vertebrate brain.

The leader of the team that made the findings, Stanford University expert Julie K. Desjardins, says that the results should not be taken as evidence that fish feel fear. However, she and study colleague Russle Fernald, who is also based at Stanford, say that the emotional response the animal produces is indeed of a negative nature. This does not hold true when the cichlid fish fights other males of its species, or of other species, the researchers add. Details of their investigation were published in the May 11 issue of the esteemed scientific journal Biology Letters, Wired reports.

The experts also stress the fact that their study does not imply that the fish recognize their own mirror image. “I want to be clear about that,” explains Reiss. It is however undeniable, the group admits, that the animals are capable of recognizing something is off when they are attacking their own image. What this research does is provide the first scientifically-documented examples of how the fish brain exhibits differential activity patterns when presented with specific images or situations. Some of the animals have thus far proven to be able to recognize their reflection include great apes, elephants, dolphins, pigs and magpies.

Desjardins says that the new investigation raises an alarm signal for all researchers whose work with animals revolves around using mirrors. If some of the creatures that cannot recognize themselves in a reflection still perceive something strange when looking at themselves, then this could skew the end study results. “I think mirrors need to be used with caution,” she warns. Recent studies involving animals and mirrors have, for example, demonstrated that pigs could use reflections to find food concealed after an obstacle, even if they had no direct line-of-sight.