Animals

Why Do Some Turtles 'Breathe' Out of Their Butts?

Breathing technique may be an important survival mechanism for species such as the Eastern painted turtle and the Australian Fitzroy river turtle.

Nature has a juvenile sense of humor. That, at first, seems like the only explanation for why certain turtles, among them the Australian Fitzroy river turtle and the North American eastern painted turtle, breathe through their behinds Both turtles can breathe through their mouths if they so chose.

And yet, when scientists placed a small amount of food coloring in the water near these turtles, they found that the turtles were drawing in water from both ends (and sometimes just the hind end.) Technically, this hind end isn't an anus, it's a cloaca - an opening through which the turtle excretes, urinates and lays its eggs. Still, the entire situation begs the question: why? If the turtle can use its butt like a mouth to breathe, why doesn't it just use its mouth to breathe?

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The possible answer to the question lies in the turtle's shell. The shell, which evolved from ribs and vertebrae that flattened out and fused together, does more than keep the turtle safe from bites. When a turtle hibernates, it buries itself in cold water for up to five months. To survive, it has to change a lot of things about the way its body works. Some processes, such as fat burning, go anaerobic - or without oxygen - in a hibernating turtle. Anaerobic processes result in the build up of lactic acid, and anyone who has seen Aliens knows that too much acid isn't good for a body. The turtle's shell can not only store some lactic acid, but release bicarbonates (baking soda to the acid's vinegar) into the turtle's body. It's not just armor plating, it's a chemistry set.

It is, however, a fairly restrictive chemistry set. Without ribs that expand and contract, the turtle has no use for the lung and muscle set-up that most mammals have. Instead it has muscles that pull the body outwards, towards the openings of the shell, to allow it to inhale, and more muscles to squish the turtle's guts against its lungs to make it exhale. The combination makes for a lot of work, which is especially costly if every time you use a muscle your body's acid levels go up and oxygen levels go down.

Compare this to the relatively cheap butt breathing. Sacs next to the cloaca, called bursa, easily expand. The walls of these sacs are lined with blood vessels. Oxygen diffuses through the blood vessels, and the sacs are squeezed out. The entire procedure uses little energy for a turtle that doesn't have a lot to spare. Dignity has to play second-fiddle to survival sometimes.

This article originally appeared on io9.

After hatching, sea turtles spend a minimum of 1–2 years at sea, but it’s been a mystery as to what they do and where they go during this time. A remarkable new study, published in the Proceedings of the Royal Society B, managed to track 17 tiny loggerhead turtles as they braved the elements and escaped predators, like sharks.

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The small turtles were outfitted with lightweight, solar-powered satellite transmitters that gathered data on temperatures and the turtles’ movements. Sun exposure could also be inferred, based on solar-charging rates. Project leader Katherine Mansfield of the University of Florida’s Marine Turtle Research Group and her colleagues collected tiny turtles along the southeast coast of Florida and reared them until they were at least 3.5 months old. Bryan Wallace, an adjunct professor at Duke University’s School of the Environment, said the high-tech transmitters do not interfere with swimming, and might later be affixed to animals like great white sharks to better determine where they go.

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Mansfield told Discovery News that turtles like this, after they go out to sea for at least a couple of years, “start showing up again in near-shore habitats like the Chesapeake Bay, North Carolina’s Sounds, and the Indian River Lagoon on the U.S. East Coast.” This little turtle has a long way to go, however, before hoping to make such destinations.

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Turtles aren’t exactly known for being noisy, and Mansfield said that “as far as we know, they don’t socially interact while at sea -- sorry for all those 'Finding Nemo' fans!” She added, however, that “it is possible that turtles may cluster in some areas where currents push certain habitats together, or when certain temperatures are available.”

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Many turtles follow what is known as the North Atlantic Subtropical Gyre. It's a circular current system that moves clockwise around the North Atlantic as part of the Gulf Stream, "a fast-moving current -- almost like a river within the ocean -- that runs up the East Coast to about Cape Hatteras, where it then veers to the east or northeast,” Mansfield explained.

Not all turtles follow that pattern, though, to get to places like the Azores. “Some may drop out of the currents of the interior of the circle,” she said. “We think they may be doing this to follow either spin-off currents (like eddies) and/or resource availability, like Sargassum (a type of brown seaweed) habitat that is known to drop out of the Gyre circulation into the Sargasso Sea.”

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“I would imagine that life at sea would be very, very dynamic,” Mansfield said. It's no wonder that the little turtles seek out floating seaweed for protection and for clinging on to in choppy water. “A turtle may find a safe habitat to float with one day, but lose it the next,” she said. “This is very different from what we, as humans, try to create in our societies -- a safe place and access to food and shelter.”

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Depending on the species, sea turtles may eat small crustaceans and other organisms typically found floating around in Sargassum seaweed. The researchers also expect that some sea turtles, such as young leatherbacks, feast on jellyfish and other gelatinous items. The main predators of the turtles are likely larger fish and sharks.

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Sea turtles tend to stay close to the surface, a surprising find of the study. This probably helps to keep them warm. Turtles at sea “might be much warmer than we’d previously guessed,” said Nathan Putnam of Oregon State University’s Department of Fisheries and Wildlife. This suggests higher metabolism rates that, in turn, could mean “some turtles, at least, could grow much more rapidly than we thought.”

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“All sea turtle species are considered endangered or threatened throughout their range,” Mansfield said. “In order to effectively conserve and protect a species, it is important to fully understand the animal’s life history -- where they go, how they interact with their environment, when they are found in particular areas or habitats.” She continued, “Our research provides a few new pieces to the ‘lost years’ puzzle. We are hoping that our data will open up more questions about the turtles early in-water behavior.”

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