Do Manta Rays sleep?
No one knows. In vertebrates (backboned animals), sleep is characterized by a profound change in brainwaves. This has never been demonstrated experimentally in Mantas or any other elasmobranch (shark or ray). Actively swimming sharks and rays, such as the Manta, are believed to swim constantly, never stopping from birth to death. Although it is feasible that some parts of the brain shut-down while the parts of the brain responsible for coordinating swimming movements stays awake, this has not been demonstrated experimentally.
