Amazonian Butterflies Drink Turtle Tears

The butterflies are likely attracted to the turtles' tears because the liquid drops contain salt.

The sight of butterflies flocking onto the heads of yellow-spotted river turtles in the western Amazon rain forest is not uncommon, at least if one is able to sneak up on the skittish reptiles. But the reason why butterflies congregate onto the turtles may be stranger than you think: to drink their tears.

The butterflies are likely attracted to the turtles' tears because the liquid drops contain salt, specifically sodium, an important mineral that is scant in the western Amazon, said Phil Torres, a scientist who does much of his research at the Tambopata Research Center in Peru and is associated with Rice University.

Unlike butterflies, turtles get plenty of sodium through their largely carnivorous diet. Meat contains significant levels of the salt, Torres told LiveScience. But herbivores sometimes struggle to get enough sodium and other minerals, he added. "They end up needing this extra mineral source," he said. (Photos: Butterflies Drink Turtle Tears)

PHOTOS: Caterpillar to Butterfly in 3D

Drinking tears Turtle tears are not the only source of such salts for butterflies; the insects also readily get the salt from animal urine, muddy river banks, puddles, sweaty clothes and sweating people, said Geoff Gallice, a graduate student of entomology at the Florida Museum of Natural History, who has witnessed butterflies flocking to turtle tears in the western Amazon rain forest.

This region is lower in sodium than many places on Earth, because it is more than 1,000 miles (1,600 kilometers) from the Atlantic Ocean, a prime source of salt, and is cut off from windblown mineral particles to the west by the Andes Mountains. Dust and minerals make their way into the Amazon from the east, sometimes all the way from north Africa. But much of this material is removed from the air by rain before it reaches the western Amazon, Torres said.

One question that arises: Does the butterfly feeding help, hurt or have no impact on the turtles? Torres said it's not completely clear, but the teary endeavor probably has little impact on the turtles, other than perhaps making them more vulnerable to predators like big cats, since the butterflies can obstruct their vision.

In fact, the turtles - blinded and drowning in butterfly kisses - are sometimes easier to photograph than unadorned animals, which may be able to spot an approaching photographer more easily. The photos were taken by Jeff Cremer, marketing director for Rainforest Expeditions, an ecotourism company that hosts guests in the Peruvian Amazon and organizes trips to the jungle.

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Gallice said, based on his observations, that the feeding likely does little direct harm to the turtles. "The turtles have enough tears to feed the butterflies simply because the butterflies are taking so little," he said. "They simply uptake salts through a process similar to absorption by placing the proboscis on the salt-laden and passively 'feed.'"

Torres has also witnessed bees drinking turtle tears. Bees appear to annoy the turtles more than the butterflies, perhaps due to their buzzing wings, he said.

The lack of salt in the region has driven other animals to exhibit unusual behaviors. For example, macaws visit clay licks to, well, lick clay, which contains sodium and other minerals, Torres said. Certain types of monkeys also eat dirt for the same reason, he added. (The Top 10 Weirdest Animal Discoveries)

Swabbing turtle eyeballs The butterflies also may be seeking other minerals in the turtles' tears, and perhaps even amino acids, the building blocks of proteins, Torres said. He plans to study this in the near future to find out what's going on.

"Potentially, they could be getting other resources out of those eyeballs that we don't even know about," Torres said. "Basically, we have to go start swabbing turtle eyeballs and see what we get."

The tear-drinking phenomenon doesn't appear to take place often outside this region. "I have been studying turtles in the wild - from the northern U.S., Mexico and Amazonas - for over 50 years and have never seen butterflies drinking tears of turtles," said Richard C. Vogt, a researcher at the National Institute of Amazonian Research in Manaus, Brazil.

Juarez Pezzuti, a turtle specialist at Brazil's Federal University of Pará, hasn't seen it either. However, neither he nor Vogt doubt that it happened, and they said it makes sense, as some turtles eliminate excess salt through their tears.

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Butterflies in the Amazon have been observed flocking onto the heads of turtles to drink their tears, which provide the animals with a vital source of the mineral sodium.

Old World Swallowtail Egg

The transformation of a caterpillar into a butterfly is nothing short of magical, and now a new study shows what happens from the inside out. Here we follow the life course of an Old World swallowtail butterfly, which begins life as a colorful marble-looking egg. Adult butterflies lay the eggs, which hatch in about 3-7 days.

Old World Swallowtail Caterpillar

The hatchling is born to eat. It devours plant material over a period of 2-3 weeks, increasing body mass by a few thousand times.

While its colorful body is a standout here, when viewed from a distance, the shades can blend into plant material, helping to camouflage the caterpillar. When viewed up close, the colors can also warn predators that the caterpillar’s body contains unappetizing chemicals that can be toxic. Some species can even deliver poisonous stings.

X-ray: Day 1

After the 2-3 week period of feasting, the caterpillar spins a hard shell around itself, which becomes the chrysalis. This is where the real transformational magic begins, leading step-by-step to a butterfly.

The study, published in the Journal of the Royal Society Interface, used high-resolution computed tomography to capture 3D images of what goes on both inside and outside of the chrysalis. This X-ray shot provides just a glimpse of all the changes taking place inside.

Day 1 From the Inside

This image, resulting from many different X-ray slices showing the chrysalis interior, reveals the developing digestive system and wings. Co-author Russell Garwood, a research fellow at the University of Manchester’s School of Materials, told Discovery News, “What this (also) shows is that at the beginning of pupation the tracheal system -- which the insect uses to breathe -- is already fairly well formed. Either this forms very quickly, or it is carried over from the breathing system of the caterpillar.”

Old World Swallowtail From the Outside

This is the more typical view of a chrysalis, showing its protective outer shell. A mucous-like substance allows it to attach to a plant surface. Note that the color resembles a dead or dying leaf, providing life-saving camouflage during this vulnerable time.

Days 1 Through 13, Step by Step

Most of the major changes occur during the first week of pupation. This image shows the changes that take place from day one through 13.

“You can see that as the butterfly develops, the tracheal system grows in complexity," Garwood said, "so by the end, the adult's has a far larger volume of air tubes, but the same basic layout as the first day -- it just has lots more small branches.”

Day 13

“The red structure in the middle is the midgut -- part of the digestive system, which is also the dark structure you see in the X-rays of the chrysalis,” Garwood shared. “Early in the development this is quite large, like the one we see in the caterpillar, but as it develops it shrinks and moves backwards, and then changes shape over the next few days to the structure we find in the adult form.”

“On day 13,” he said, “the yellow things you can see are structures called malpighian tubules, which help clear waste out of the adult's body (a bit like kidneys).”

Day 14

An X-ray image again shows what the changes look like both from the outside and the inside. By this day of development, the chrysalis is already well on its way to becoming a butterfly.

Day 16

“The light green structure you can see growing in size is an air gap between the chrysalis and the edge of the body of the developing adult,” Garwood said. “You can see that as the adult takes shape within the chrysalis, this air gap expands -- this is because there is a narrowing of the butterfly's body here, which forms throughout development. This is actually the margin between the thorax, which has the wings and legs, and the abdomen, which is the back part of the body.”

Butterfly Complete

After just over two weeks, the chrysalis cracks open, unveiling an Old World swallowtail butterfly. After about one hour of adjustment, its wings are full sized, dry and ready for flying.