Giant manta rays have proven to be the first elasmobranch species to recognize themselves in a mirror. These results suggest that manta rays may be self-aware. Only a few animals, mostly primates, have passed the mirror test which is widely used as a tentative test of self-awareness.
University of South Florida researcher Csilla Ari, set up a mirror-test experiment inside the manta enclosure at the Atlantis Aquarium Bahamas. Ari observed two giant manta rays inside the aquarium as they swam past the mirror.
Ari noted that the mantas behavior changed when the was a mirror inside the tank and that the mantas recognized their reflection as their own and not that of another individual. Self-recognition is conventionally identified by the understanding that one’s own mirror reflection does not represent another individual but oneself.
The manta’s showed no signs of social interaction with the reflections, which is what you would expect if they believed it to be another individual. Instead, the rays repeatedly moved their fins and circled in front of the mirror and the frequency of these movements was much higher when the mirror was in the tank than when it was not.
One of the rather interesting finding was that the rays blew bubbles in front of the mirror, a behavior that had never before been observed in manta rays. “The behavioral responses strongly imply the ability for self-awareness, especially considering that similar, or analogous, behavioral responses are considered proof of self-awareness in great apes,” Ari says.
Although manta rays have the largest brain of any fish, not everyone is convinced that the new study proves conclusively that manta rays, or indeed, that the mirror test itself is an appropriate measure of self-awareness.
Gordon G. Gallup Jr, of the University at Albany, New York, who originally developed the mirror test, is also skeptical. The unusual movements in front of the mirror might have merely been a sign of curiosity or exploratory behavior, he says.
Previous studies on dolphins, monkeys, birds and elephants suggest they can recognize themselves in the mirror. However Gallup says these experiments were done with one or two animals and the results were not reproducible.
Especially for animals who use senses other than visions to navigate the world, perhaps the mirror test may not be the most effective test for self-awareness for all animals.[Journal of Ethology]