On a research expedition in a forest along the Solimões River in central Amazonia, a researcher came across a scene that is part fairy-tale, part horror movie and quite simply peculiar. In the dead of night, ecologist Leandro Moraes gazed upon a moth perched on the neck of a sleeping black-chinned antbird.
With its proboscis extended, the dusty-winged creature was gently slurping up the tears of the slumbering bird. Forty-five minutes later, he encountered another moth feasting on the tears of a different bird, reports Richa Malhotra at Science. Luckily for us, Moraes was also able to capture footage of the creepy-cool, late-night snack.
It’s not too surprising that the moth would drink bird tears. Lepidoptera, the insect family including butterflies and moths, are well-known for flocking to animal secretions to get a dose of salt. The critters are fond of salty mud, puddles of urine, decaying flesh, sweat, tears, blood, and poo, you name it—if there’s salt and protein, they’ll take a sip. In fact, Brandon Specktor at LiveScience reports that the phenomenon is so common in biology that is has a name, lachryphagy.
Sandrine Ceurstemont at National Geographic reports that butterflies and bees have been reported drinking the tears of caiman crocodiles, solitary bees have been recorded drinking the tears of turtles in Ecuador and an erebid moth, Gorgone macarea, in Colombia was documented in 2015 drinking the tears of a ringed kingfisher, another species of bird. Many different species of bees and flies are also known to slurp up eye secretions of different animals in tropical areas of sub-Saharan Africa and Asia.
And the number of new tear-loving species is growing. Michael Engel of the University of Kansas, who has studied the phenomenon, but was not involved in this study, tells Ceurstemont that the lachryphage has rarely been reported in the Amazon, though he suspects it's more common than we currently realize.
“The new discovery helps expand an interesting biogeographic region where tear-feeding should be diverse and yet is scarcely known,” he says.
But drinking the tears of sleeping birds is uncommon, and Moraes’s new study in the journal Ecology is only the third scientific account of bird tear guzzling, Specktor reports for LiveScience. The phenomenon is something of mystery, Moraes tells Ceurstemont. That’s because the area where the interaction was filmed often floods, bringing plenty of salt into the mud that moths and butterflies can access.
That makes it possible that the moth was not after the salt in the bird’s tears but something else. Moraes, who conducts research at the National Institute of Amazonian Research in Manaus, Brazil, says it’s likely it was looking for protein.
Other researchers have hypothesized the same thing, finding that tears have 200 times the protein of other secretions like sweat. Researchers have found that other lachryphagous species, in particular bees, don’t get protein from pollen or carrion as other species do, and instead likely rely on tears for the important nutrient. It’s possible the moth is doing the same, or at least supplementing its diet with the bird tears.
Whatever the case, since moths seem to be the goth hero of the internet right now, this finding certainly expands their street credibility beyond their ceaseless addiction to brightly-lit lamps, which is having an ironic moment in the limelight.