Butterflies And Bees Find Nutrition In Crocodile Tears
Was the crocodile crying for company? Or did it just want to lure some prey? Whatever the reason, it's tears were put to good use when a pair of insects got a much needed boost of minerals and salts from it. A film showing a butterfly (Dryas iulia) and a bee (Centris sp.) sucking the tears of a spectacled caiman (Caiman crocodilus), basking on the banks of the Río Puerto Viejo in northeastern Costa Rica was captured by a team of students, photographers, and aquatic ecologist Carlos de la Rosa on a pleasant December day in 2013.
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The team was travelling by boat when they saw the caiman indulging the insects for around fifteen minutes, according to a press release Thursday. De la Rosa reported the encounter in a peer-reviewed letter in the May 2014 issue of the Ecological Society of America's journal Frontiers in Ecology and the Environment. "It was one of those natural history moments that you long to see up close," said de la Rosa, the director of the La Selva Biological Station for the Organization for Tropical Field Studies in San Pedro, Costa Rica. "But then the question becomes, what's going on in here? Why are these insects tapping into this resource?"
Butterflies need salts and minerals for reproduction. Salt is a scarce resource on land and butterflies are often seen hovering around mud puddles where they get their dose of minerals and salts from the soil. When minerals are scarce in the soil, butterflies and other herbivorous animals sometimes gather salt and other rare minerals and proteins from sweat, tears, urine, and even blood.
De la Rosa has seen butterflies and moths flocking around turtles and caimans to drink their tears in the Amazon, since tears contain salt, specifically sodium, which is quite scant in this area.
But tear-drinking "lachryphagous" behavior in bees is only a recent observation. De la Rosa remembers solitary incidents of bees drinking tears like the 2012 report of a bee sipping the tears of a yellow-spotted river turtle in Ecuador's Yasuní National Park. But he didn't know how common this behavior was in nature. A little research on the subject proved enlightening.
"I did a Google search for images and I found out that it is quite common! A lot of people have recorded butterflies, and some bees, doing this," said de la Rosa.
He also found a detailed study published in the Journal of the Kansas Entomological Society of bees drinking human tears in Thailand and the well-known October 2012 story "Trails and Tribulations" about the Ecuadorian bee and the river turtle by Olivier Dangles and Jérôme Casas in ESA's Frontiers.
All this research makes De la Rosa feel that the living world still holds many surprises for ecologists. He is a specialist in the biology of non-biting midges, and a natural historian, with his eyes always open to new discoveries.
He is also the director at La Selva Biological Station situated in the tropical rain forest in northeastern Costa Rica. He says that there are hundreds of species of aquatic insects in La Selva that are still unnamed and undescribed.
"I have over 450 undescribed species from Costa Rica in my laboratory. If I did nothing for the rest of my life but collaborate with taxonomists and try to describe those, I would never get done," he said.
His job is full of surprises and provides him with unique opportunities to observe the wonders of nature.
"I learned I have to carry a camera with me 24/7, because you never know what you're going to find when you're walking to the office or the dining hall," he said. This proved useful when one day on his way to breakfast he observed a new species of dragonfly that had emerged from its larval form in the small pool of water caught in the cupped leaves of a bromeliad plant. This was most unusual since only one species of dragonflies were not known to live in bromeliads. And de la Rosa discovered the second.
"Those are the kinds of things that, you know, you don't plan for them, you can't plan for them," de la Rosa said. "You just keep your eyes open and have curiosity, and when you see something that doesn't seem to fit, dig.
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