Apparently, this phenomenon occurs because these Julia and Sulphur butterflies require sodium to live.
Far away from a source of salt, they rely on salt-rich turtle tears.
Science aside, it's pretty adorable that they're clearing away the turtle's tears.
OMG LOOK AT THESE BUTTERFLY KISSES! THEY JUST WANT HIM TO BE HAPPY, I KNOW IT!
But one question remains: why are the turtles so sad?