This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Few reptiles can breathe underwater. Australia is home to one of the exceptions, the white-throated snapping turtle (Elseya albagula), which can extract oxygen from water through its backside via a process called cloacal respiration. This unusual technique, shared by a handful of other turtle and fish species, gave the turtles an evolutionary advantage for millennia, allowing them to hide from predators underwater for days at a time.
Unfortunately, breathing out of your butt requires very specific conditions that no longer exist in the turtles' only habitat, Queensland's Connors River and three nearby catchments. Dams, weirs, agriculture and mining have left the water sluggish and full of sediment. That makes it significantly harder for the turtles—especially vulnerable juveniles—to stay underwater. As a result, predation has increased to the point where populations have crashed. The problem has gotten so bad that less than 1 percent of eggs and young turtles survive to adulthood and the species has now been declared critically endangered by the Australian government
Connors River itself is the healthiest ecosystem in the region with relatively clearer waters and a good rate of water flow—but that may not stay that way forever. Four years ago, when James Cook University researcher Jason Schaffer started studying turtles there, he considered the river to be what he calls "a doomed landscape." A planned dam threatened to destroy the bum-breathing turtle's only safe habitat.
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Schaffer says working in the region "was very hard mentally" because of the dam project. "I worked quite closely with a few landowners who had their properties forcibly acquired by the government and were distressed about the whole situation." Luckily, financing fell through for the project but the potential that it could be resurrected looms over the region. "All the planning has been done and the land has only been leased back to the property owners," he says. "There is a risk that the dam will still go ahead in the future if it again becomes financially viable, and that worries me a bit."
The turtles' critically endangered designation might influence any future efforts to build the dam but many other threats remain. Invasive species such as cats, dogs and foxes, which eat eggs and young turtles, pose one of the greatest risks. The turtles' eggs are particularly vulnerable. Schaffer says the turtles lay their eggs in July but they take about seven months to hatch because they go through a semi-dormant phase called diapause until the summer rainy season begins. "This makes them more vulnerable to predation than a lot of other turtle species," he says. In addition, the nests all too often get trampled by the cattle on the agricultural land that surrounds the rivers.
Man-made construction also poses a threat for the few remaining adults. Dams and weirs effectively trap them in certain locations, preventing turtles from traveling to find mates. Shaffer reports that many turtles try to overcome these obstacles but end up falling when they attempt to cross the weirs; their shells crack or shatter and the animals die.
If they survive, white-throated snapping turtles have very long life spans, perhaps as much as 100 years, but that also works against them. For one thing, the species typically starts breeding at 20 years of age. For another, Schaffer fears their long lives create the perception that they can survive if dams are built and more water is taken from the rivers for use by industry. "What [people] don't realize," he says, "is that almost nothing is surviving. When these aged adults eventually die there is nothing coming up to replace them. Pretty soon we'll blink and there will be no more left—just like that."
Schaffer plans to keep studying the turtles and seeks funding to survey additional populations. He hopes to learn more about their susceptibility to environmental threats. Understanding the consequences of habitat alteration could help to predict the threats that these turtles and other species could face in the future.
There's one more important reason to study the species, he adds: "These turtles breathe out of their ass, which is super awesome."
Photo: Stephen Zozaya, courtesy of James Cook University