Butterflies Drink Turtle Tears

In the western Amazon, a seemingly gentle scene often plays out with a fascinating scientific explanation. Butterflies can be seen congregating on the heads of reptiles, particularly yellow-spotted river turtles and caiman, carefully extending their proboscis to sip the liquid welling in the animals' eyes. This behavior, known as lachryphagy, or “tear-feeding,” is a crucial survival strategy driven by a regional mineral deficiency. The butterflies are not offering comfort; they are harvesting salt.

The reason for this unusual behavior lies in the geography of the rainforest. The Amazon basin is incredibly distant from the Atlantic Ocean, its primary source of salt, and the Andes Mountains block most salt- and mineral-rich weather from the west. The constant, heavy rainfall further leaches the soil of its minerals. Consequently, sodium is a rare and precious resource for herbivores. While a butterfly’s diet of nectar and fruit (Review) provides plenty of sugar, it lacks the essential salts needed for reproduction and metabolism.

The tears of turtles and other reptiles offer a concentrated, reliable source of sodium and other minerals. The interaction appears to be largely harmless to the host animals, who seem to tolerate their tiny, fluttering visitors with little fuss. For the butterflies, these reptilian salt licks are a vital resource, demonstrating a beautiful and bizarre adaptation to life in an environment poor in essential nutrients.