Christian art took up the Mediterranean dolphin as a figure of the soul's safe passage, showing it on sarcophagi sometimes wound around an anchor, the anchor of hope, the dolphin of the soul carried home, together a discreet emblem of salvation. A very different dolphin belongs to the Amazon: the boto, the pink river dolphin, is believed in riverine Brazilian tradition to take human form at night, appearing as a charming, well-dressed man who seduces women at parties before returning to the water, a belief still current and quite unlike the benign rescuer of the Greeks. The same family of animals thus anchors opposite meanings, guardian of souls in one tradition, dangerous shape-shifter in another.
The dolphin's friendly reputation fed directly into a specific piece of modern regulation: because certain tuna fishing methods, particularly purse-seine nets set around dolphin pods in the eastern Pacific, killed large numbers of dolphins as bycatch through the mid-twentieth century, public pressure led to the US Dolphin Protection Consumer Information Act of 1990, which created the dolphin-safe label now printed on tuna cans, a piece of consumer-facing law that exists because enough people cared, in a way they generally have not for less charismatic bycatch species, specifically about this one animal.