European eels have one of the most baffling reproductive cycles on earth, as every single one of them travels thousands of miles to the Sargasso Sea to breed, yet no human has ever actually seen them mating in the wild.

A closer look

European eels have one of the most baffling reproductive cycles on earth, as every single one of them travels thousands of miles to the Sargasso Sea to breed, yet no human has ever actually seen them mating in the wild. They depart their freshwater rivers, undergo massive physiological changes that dissolve their digestive tracts to make room for reproductive organs, and vanish into the ocean never to return. The newly hatched baby eels then blindly drift back to Europe over several years, guided by nothing but instinct and ocean currents. It is a level of extreme, self-destructive sexual secrecy that puts even the most paranoid celebrity couples to shame, proving that eels are the undisputed champions of maintaining physical privacy