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Moths Drink Tears of Sleeping Birds

A rare tear-feeding moth discovered in Brazil could help explain the bizarre behavior, reports National Geographic.

A moth was observed drinking a sleeping bird’s tears in the Amazon jungle in Brazil, the first time this behavior has been reported in the country and only the third known case worldwide.

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 journal Ecology, is understandably 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.

However, as flood waters disperse, the salty fluid may be transferred elsewhere leaving the insects at a loss. “Scarcity of resources in a particular region in a specific month may explain why moths are seeking additional sources of nutrients in the tears of birds,” says Moraes.

Moths may also be seeking out another type of nourishment altogether: protein. Although they typically source the substance from plant nectar, tears - which contain albumin and globulin, two types of protein - can act as a supplement. A protein boost can help them fly longer and enhances their reproductive success and lifespan.

“Vertebrate fluids are the main alternative source for obtaining proteins,” says Moraes.

Moths aren’t the only insects to feed on tears, either. According to Michael Engel from the University of Kansas, who reported the first case of a tear-drinking stingless bee in Sri Lanka last year, new cases of different insects sucking up tears are growing.

The behavior, however, has rarely been reported in the Amazon jungle, the biggest tropical rainforest in the world and home to an incredible diversity of animals, including about 1,300 bird species and an estimated 2.5 million types of insects.

A few years ago, an erebid moth was seen feeding on the tears of a roosting ringed kingfisher in the Colombian Amazon, the first case involving birds in this region. Solitary bees were also documented drinking the tears of river turtles in the Ecuadorian Amazon for the first time in 2012.

Most observations of the behavior have been in tropical parts of Africa, Asia, and Madagascar. “The new discovery helps expand an interesting biogeographic region where tear-feeding should be diverse and yet is scarcely known,” says Engel.

As Moraes continues his fieldwork in the Amazon, he will be carefully observing his surroundings. This report is “only a single case involving two Amazonian species, which leads me to imagine what other thousands of unknown ecological relationships exist,” he says.


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