Whether it's pruning your hair or poking at a pimple on your face, many of us take for granted the ability to recognize one’s self in the mirror. This faculty is hardly universal across species – in fact, it is actually considered a rarity. Now, one paper published in the Journal of Ethology questions whether manta rays can join the brief list of animals who pass the mirror test to be deemed “self-aware.”
Traditionally, the mirror test has been used as a litmus test for self-awareness in animals. However, this basic standard is debated among scientists as to whether it can even be considered a tentative measure of self-awareness.
Nonetheless, for the study, lead author Csilla Ari of the University of South Florida filmed giant manta rays inside a tank with and without a mirror. She then recorded whether their behavior changed in a way that indicates they recognize their appearance.
“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 told New Scientist. For the manta rays, such behaviors meant blowing bubbles, flipping their fins, and repeatedly swimming in front of their reflection.
Manta rays swimming in front of the mirror placed in their tank. Image credit: Csilla Ari et al.
And while manta rays also have the largest brain of all fish species, that in itself doesn’t say much. To date, a range of animals with varying brain sizes have passed the mirror test, including dolphins, elephants, and magpies.
However, just because these animals “pass” the test, doesn’t mean it is proof of higher cognitive self-awareness. “Humans, chimpanzees, and orangutans are the only species for which there is compelling, reproducible evidence for mirror self-recognition,” said Gordon Gallup Jr. of the University of Albany, New York, who developed the mirror test, to New Scientist. And in humans, it isn’t even until the age of two that we recognize ourselves.
The authors add that “the manta rays did not show signs of social interaction with their mirror image,” which excludes the likelihood that they are interacting with what they think to be a fellow manta ray. Instead, they say that the study provides evidence for possible behaviors that are the “prerequisite of self-awareness.”
This means that, for now, there is no definitive answer. If anything, the study highlights the need for a better litmus test for self-awareness in animals.
One of the videos of the manta rays swimming repeatedly in front of the mirror, displaying behavior that suggests cognition such as blowing bubbles, rolling its cephalic fin and exposing body parts to the mirror that would not have been visible otherwise. Csilla Ari PhD