Study suggests they may be the only self-aware fish
All divers who have encountered a manta ray know there is something special about these elasmobranches - and new research reveals that they may very well be self-aware.
The study suggests that they are one of the few creatures that are capable of recognising themselves in a mirror. A rare cognitive feat and an often accepted indication of self-awareness and high levels of intelligence.
Very few animals can gaze into a mirror and know it’s themselves looking back. Gorillas, leopards, dogs, and cats, fail the test, often believing that their reflection is just another animal looking back. Non-human animals that have passed the mirror test include bonobos, chimps, dolphins, elephants, and some birds. According to new research published in the Journal of Ethology, we can now add manta rays to the list. It’s the first time that a fish has been observed to pass the mirror test.
'This new discovery is incredibly important,' says Marc Bekoff, of the University of Colorado in Boulder. 'It shows that we really need to expand the range of animals we study.'
Csilla Ari, of the University of South Florida in Tampa, filmed two giant manta rays in a tank, with and without a mirror inside. The fish changed their behaviour in a way that suggested that they recognised the reflections as themselves as opposed to another manta ray.
They did not show signs of social interaction with the image, which is what you would expect if they perceived it to be another individual. Instead, the rays, which are the fish with the largest brains, repeatedly moved their fins and circled in front of the mirror. This suggests they could see whether their reflection moved when they moved. The frequency of these movements was much higher when the mirror was in the tank than when it was not.
The rays also blew bubbles in front of the mirror, behaviour that Ari had not observed in the rays before.
'The behavioural responses strongly imply the ability for self-awareness, especially considering that similar, or analogous, behavioural responses are considered proof of self-awareness in great apes,' Ari says.
However, other scientists are far from convinced. Gordon G Gallup Jr, of the University at Albany, New York, who originally developed the mirror test, remains sceptical. The unusual movements in front of the mirror might have merely been a sign of curiosity or exploratory behaviour, he says.
Other studies have suggested that dolphins, elephants, monkeys and magpies, and even a robot, can recognise themselves in the mirror. But Gallup says these were usually conducted on just one or two animals and the results were not reproducible.
'Humans, chimpanzees and orangutans are the only species for which there is compelling, reproducible evidence for mirror self-recognition,' he says. This implies that self-awareness may be limited to humans and some great apes.