Very few animals are capable of recognising themselves in the mirror. New research suggests that manta rays are capable of this unique cognitive feat — a possible sign that these fish are self-aware. As children, many of us enjoyed playing in front of the mirror. We'd stick our tongues out at ourselves, make funny faces or try to move faster than our reflections. Scientists say this sort of behaviour is "self-directed", meaning we can adjust our actions to reflect the reality or needs of a situation. Like sticking out our tongues in front of the mirror. Self-directed behaviours are considered a prerequisite for self-awareness — that is, the conscious knowledge we have of ourselves, feelings, motives and desires.
Indeed, very few animals can gaze into a mirror and know it's themselves looking back. Gorillas, leopards, dogs and cats can't quite grasp the concept, often believing that their reflection is just another animal looking back. Non-human animals that have been observed to pass 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 this list. It's the first time that a fish has been observed to pass the mirror test.
C. Ari and D. P. D'Agostino, 2016.
Researchers Csilla Ari and Dominic D'Agostino from the University of South Florida in Tampa observed two captive giant manta rays in a tank, both with and without mirrors inside. When the manta rays saw their reflections, they didn't try to get friendly and socialise with them. And tellingly, the white markings on their back did not change, which is what usually happens when a manta ray meets a new individual.
But the manta rays did exhibit self-directed behaviours consistent with self-awareness. Specifically, the fish made "frequent and unusual" repetitive swimming movements in front of the mirror, suggesting that they were investigating, experimenting — or even playing — with their reflections. Incredibly, the manta rays also blew bubbles in front of the mirror, which is an unusual behaviour for these creatures (perhaps it's the elasmobranch equivalent of sticking one's tongue out).
As the researchers concluded in their study, manta rays may be "the first elasmobranch species to exhibit self-awareness, which would imply their potential for an ability to higher order brain function, and sophisticated cognitive and social skills." The researchers said that future studies should determine whether these self-directed behaviours are typical and frequent among manta rays.
For the researchers, this result did not come as a complete surprise. Manta rays have brains with similar structures and functions found in other vertebrates, including those animals capable of passing the mirror test. Manta rays also have the largest brain of any fish.
It's an exciting result, but one that needs to be taken with a grain of salt. Mirror tests are not definitive tests of self-awareness. Humans and other primates, for example, are very visual; it may be unfair to assess animals using a test that relies on visual acuity (as opposed to some other sense). Also, some animals may be self-aware without being able to identify oneself in an external or foreign medium like a mirror. Self-awareness, it's fair to say, is much more complicated than that.