You’ve probably heard of the mirror test: place a mirror in front of an animal, and see if they can recognize their reflection. Quick, easy, fun to try on the family dog, and thus far only ever successfully passed by humans, magpies, and a handful of primates, elephants, and cetaceans (Ari & D’Agostino, 2016). Even human children below the age of 18 months have trouble identifying themselves in a mirror (Lewis, 1979). However, according to a study published in the Journal of Ethology this past March, it may be time to add manta rays to the list of animals capable of displaying self-recognition, and if so, they’d be the first fish to accomplish this feat of cognition… ever.
Researchers from the University of South Florida tried out the mirror test on two giant manta rays living at the Bahamas’ Atlantis Aquarium, placing a mirror in their enclosure for a 16-day period, and they witnessed some truly stunning results. The animals were observed to repetitively circle the mirror, lifting their fins and turning sideways to bare their bellies to the reflective surface, but displayed no aggressive behaviors towards the mirror, nor any of the coloring changes previously shown to occur when a ray meets a new individual (Ari, 2014). These behaviors would seem to suggest that the rays were testing whether their reflection moved when they did, and could even have been trying to use it to view areas of their bodies that are normally out of sight. Both of these things would indicate that the rays recognized their mirror images as themselves.
You can watch a sample of these behaviors, below:
Future replication of this research will be necessary to confirm whether the behaviors exhibited by the two animals surveyed in this study are true of their species as a whole, and whether they do in fact represent the act of self-recognition. It’s possible that these behaviors could have arisen from a general sense of curiosity towards the ray’s shiny new toy, rather than anything truly self-oriented. However, these findings would not be completely unprecedented, as giant manta rays do possess the largest brains of any fish species (Ari, 2011). And after this study, it certainly seems that they can put that big brain to use.
Ari, C., D’Agostino, D. P. (2016). Contingency checking and self-directed behaviors in giant manta rays: Do elasmobranches have self-awareness? Journal of Ethology 34, 1-8.
Ari, C. (2014). Rapid coloration changes of manta rays (Mobulidae). Biological Journal of the Linnean Society 113, 180–193.
Ari, C. (2011). Encephalization and brain organization of mobulid rays (Myliobatiformes, Elasmobranchii) with ecological perspectives. Open Anatomy 3, 1–13.
Lewis, M., Brooks-Gunn, J. (1979). Social cognition and the acquisition of self. New York: Plenum Press. p. 296.