Observing the Behavior
The sight of butterflies gathering on turtles, often around their eyes, is a unique natural phenomenon observed primarily in the Amazon rainforest. This behavior, sometimes involving dozens of butterflies, occurs on sunny days when freshwater turtles are basking. These turtles are particularly susceptible because some species cannot fully retract their heads into their shells, making them accessible. Researchers have documented at least eight different butterfly species engaging in this tear-drinking activity. The butterflies alight on the turtle’s head, extending their proboscis to sip the liquid directly from the eyes.
The Scientific Reason for Tear-Drinking
This intriguing behavior, known as lachryphagy, is driven by the butterflies’ fundamental need for essential nutrients, particularly sodium. The western Amazon rainforest, where this phenomenon occurs, is naturally low in available sodium due to its distance from the Atlantic Ocean and the Andes Mountains blocking windblown mineral particles. While butterflies primarily feed on nectar, water, and fruit liquids, these sources often lack sufficient sodium for their metabolism and reproduction. Turtle tears provide a rich source of these vital salts, and potentially other minerals like amino acids, which supplement the butterflies’ diet.
Turtles, being carnivores, obtain ample sodium from their meat-based diets. Their kidneys are not highly efficient at excreting excess salt, leading them to eliminate it through their tears via specialized lacrimal glands near their eyes. This makes their tears notably salty and a readily available resource for sodium-deficient butterflies. Male butterflies, in particular, engage in tear-drinking more frequently, as sodium is important for their reproductive fitness and the production of nuptial gifts for females.
Other Animals That Drink Tears
Lachryphagy is not exclusive to butterflies and turtles; it is a broader ecological strategy for nutrient acquisition across various insect groups. Moths have been observed drinking tears from large mammals like deer and crocodiles. Some moths even feed on the tears of sleeping birds.
Bees also exhibit tear-drinking behavior. Stingless bees have been documented collecting tears from humans, chickens, and tortoises in Southeast Asia. These bees seek out salt and proteins from tears and sweat to supplement their diets. Flies and cockroaches also exhibit this behavior, with cockroaches feeding on anole tears for nutrients.
What This Means for Turtles and Ecosystems
The interaction between butterflies and turtles is considered harmless to the turtles. Butterflies are lightweight, and their presence does not disturb the turtles, which appear unbothered by the tear-drinking. This relationship is described as commensalism, where one species benefits (the butterfly) while the other (the turtle) is largely unaffected.
Despite being benign, there are some considerations for the turtles. A large cluster of butterflies around a turtle’s eyes could obstruct its vision, making it more vulnerable to predators. Additionally, butterflies, which engage in “mud-puddling” on contaminated surfaces, could transmit ocular diseases to the turtles. This unique interspecies relationship highlights how organisms adapt to resource scarcity and demonstrates complex nutrient cycling within ecosystems.