Scientists have filmed giant manta rays checking out their reflections, showing that they could be self-aware. Some, however, remain skeptical and believe that only primates and a small of group of animals could pass the mirror test and maintain self-awareness.

Csilla Ari from the University of South Florida recorded two manta rays in a tank, with and without a mirror placed inside. The change in the fishes' behavior suggested that they saw themselves, not another of their kind, in the reflections.

Instead of initiating social interaction with the reflections, the manta rays repetitively moved their fins and circled in front of the mirror. This somehow confirmed that they are aware that the image in front of them moved when they moved, especially with greater movements they showed when a mirror was inside the tank.

Another behavior Ari had not previously seen in the species: in front of the mirror, the studied rays blew bubbles.

“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 tells New Scientist.

Manta rays have the biggest brain of any fish, and have brains exhibiting similar functions and structures with other vertebrates, including primates that are able to pass the mirror test.

In science, self-directed behaviors – just like children sticking their tongues out at themselves and making funny faces in front of the mirror – are deemed a requirement for self-awareness, or the conscious knowledge of one’s self and feelings.

University of Colorado Boulder’s Marc Bekoff dubbed the discovery “incredibly important.”

However, there are experts who aren’t convinced. Gordon G. Gallup Jr., who comes from University at Albany, SUNY, and the maker of the original mirror test, said the strange behavior when they’re in front of the mirror could mean the manta rays were simply curious or exploring.

For him, humans and some great apes have the only “compelling, reproducible evidence” for recognizing themselves in the mirror. Those suggesting the same for dolphins, magpies and elephants, he added, were typically coming from just an experimental animal or two.

Bekoff argued, however, that the mirror test may not be the be-all, end-all when it comes to self-awareness among animals. It may not apply to creatures who do not mainly navigate using their vision, he said, suggesting techniques such as neuroimaging to confirm self-awareness upon seeing a reflection.

The findings were discussed in the Journal of Ethology.

Photo: Justin Henry | Flickr