Contingency checking and self-directed behaviors in giant manta rays: Do elasmobranchs have self-awareness?
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Elaborate cognitive skills arose independently in different taxonomic groups. Self-recognition is conventionally identified by the understanding that one’s own mirror reflection does not represent another individual but oneself, which has never been proven in any elasmobranch species to date. Manta rays have a high encephalization quotient, similar to those species that have passed the mirror self-recognition test, and possess the largest brain of all fish species. In this study, mirror exposure experiments were conducted on two captive giant manta rays to document their response to their mirror image. The manta rays did not show signs of social interaction with their mirror image. However, frequent unusual and repetitive movements in front of the mirror suggested contingency checking; in addition, unusual self-directed behaviors could be identified when the manta rays were exposed to the mirror. The present study shows evidence for behavioral responses to a mirror that are prerequisite of self-awareness and which has been used to confirm self-recognition in apes.
KeywordsSelf-recognition Mirror test Comparative cognition Mobulidae Cognition
This study was funded by the Save Our Seas Foundation. We are very grateful to Michelle Liu, Dave Wert and the staff of the Aquarium for the possibility and logistical support to conduct this research at the Atlantis Aquarium, Bahamas. The Divers Alert Network Europe and Dr. Huntington Potter provided essential support. The observations during this study were in compliance with all ethical standards and were approved by the Kerzner Marine Foundation and the Atlantis Aquarium, Bahamas. We thank three anonymous reviewers for their thoughtful comments on the manuscript.
Movie 1: Manta ray is swimming through the OA in control conditions without the mirror. (WMV 3509 kb)
Movie 2: Manta ray is swimming through the OA in control conditions after the mirror has been removed. (WMV 2666 kb)
Movie 3: Manta rays perform repetitive turning, circling in front of the mirror. This behavior was performed for 6 min continously during this session. (WMV 4081 kb)
Movie 4: Manta ray rolls cephalic fin and slows down when passing in front of the mirror (9–13 s). (WMV 4840 kb)
Movie 5: Manta ray rolls cephalic fin in front of the mirror (1–3 s). Bubble blowing behavior is presented front of the mirror while displaying the ventral side and staying visually oriented (22–24 s). (WMV 4832 kb)
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