Researchers put two electrodes in a pool that a dolphin swam in  When the dolphin swam near the electrodes, the researchers would sometimes create a weak electric field by activating the electrodes  The dolphin would swim away if the electrodes were activated; otherwise it acted normally  The researchers then placed a plastic shield over small organs called vibrissal crypts located on the dolphin' s snout
With the crypts covered, the dolphin no longer swam away when the electrodes were activated
Under normal circumstances, dolphins are unable to sense electric fields.