Somewhere in the Brazilian Amazon, this moth is literally drinking the tears out of a bird’s eye in the dead of night. While we at Live Science do not hold any degrees in lepidopterology, we believe we are correct in saying that’s pretty metal.
Actually, drinking the tears of your neighbors is common enough in biology that it has a name: lachryphagy.
Moths and butterflies have often been observed feeding on the tears of crocodiles, turtles, and mammals.
It’s thought to be a way of obtaining salt, an essential nutrient that isn’t present in nectar and can be hard to find elsewhere.
Birds’ tears may be targeted for the same reason.
However, the area where the latest case was witnessed is flooded annually by a nearby river and the water soaks up lots of salt from the soil.
Since salt is readily available, Leandro Moraes, who made the recent discovery published last week in the journalEcology, is puzzled.
“The intriguing thing here is why these moths are complementing their saline diet by drinking tears from birds in such an environment,” says Moraes, a biologist at the National Institute of Amazonian Research in Manaus, Brazil.
For insects like these, a few crocodile tears here or a tipple of turtle tears there can provide a nice source of free sodium and even a bit of protein, Moraes wrote in a new study published Sept. 17 in the journal Ecology.
Large, cold-blooded reptiles make good drinking destinations, as they are prone to going torpid — that is, reducing their metabolisms and lying still for extended periods of time.
A video shot in the Amazon earlier this year illustrates that well, as eight opportunistic butterflies take turns drinking the tears from a river turtle’s eyes.
So, what about birds? According to Moraes, moth-on-bird lachryphagy is a much rarer scenario (his is only the third study showing it happens at all).
You can probably guess why, regardless of whether you’ve ever tried to drink a bird’s tears; birds are just too fast, too small and too good at flying.
Credit: Leandro João Carneiro de Lima Moraes
But in this case, Moraes wrote, the moth’s success may have come down to timing. Moraes filmed at night— a time when the black-chinned antbird (seen in the video) enters a torpid state of its own, becoming virtually immobile as a side effect of lowering its body temperature.
This also makes the bird vulnerable to the appetites of nocturnal moths.
In short succession, Moraes witnessed two separate moths poking their proboscises into two separate antbirds’ eyes — and neither bird put up a fight.
“The bird immobility during these events may be related to the significant decrease in the metabolism of these organisms during the nocturnal period,”
Moraes wrote in his study, “rather than having some direct benefit from that relationship.”
Indeed, it’s unlikely that the birds (or turtles, or crocodiles) get anything out of having their tears harvested.
In fact, Moraes wrote, it might even put them at higher risk of developing ocular diseases when a strange insect dips into their peepers for a drink.
It’s like mama always said: You don’t know where that proboscis has been.
