Reptiles
Mary River Turtle
Elusor macrurus · also called mary river turtle, punk turtle, green-haired turtle
The Mary River turtle lives in exactly one river in Australia, and it is a strange animal even by turtle standards. Adults often sport a crest of green algae like a mohawk. Their tails are unusually long. And they can breathe underwater through their backsides, staying submerged for days. Yet for decades it was one of the most common pet turtles in the country — collected and sold by the thousand before anyone realised it was a species new to science.
Overview
The Mary River turtle is endemic to the Mary River and its tributaries in south-eastern Queensland. It has a carapace up to about 50 cm, olive to reddish-brown, with chin barbels and a very long tail — up to two-thirds the shell length, unique among Australian turtles. It eats algae, plants, fruit, and small invertebrates.
Breathing through its rear
Inside its cloaca the turtle has blood-rich sacs that can take up oxygen from the water. By pumping water through them it can stay fully submerged for about three days without surfacing.
The green mohawk
Filaments of algae grow readily on its still, submerged body, and along the top of the head they can stand up into a ragged crest — the “punk turtle” look.
Sold before it was named
In the 1960s and 70s, hatchlings were taken from the river by the tens of thousands and sold as “penny turtles,” years before the species was formally described in 1994. Because the turtle does not breed until 25–30 years old, that lost generation left a gap the population is still working through.
Status
The Mary River turtle is Endangered and declining, confined to one river, with an ageing population and very poor hatchling survival. It is also one of the most evolutionarily distinct reptiles alive, the sole species of a genus that split off around 40 million years ago.
Mary River Turtle: common questions
Does the Mary River turtle really breathe through its bottom?
In effect, yes. Inside the cloaca, the single rear opening that turtles use for waste and reproduction, this species has a pair of sac-like structures called bursae whose walls are packed with blood vessels. By pumping water in and out of these sacs, the turtle can extract dissolved oxygen from the water, a process called cloacal respiration. It is not a substitute for lungs, and the turtle still surfaces to breathe air, but in cool, well-oxygenated water it can rely mainly on the cloacal route and stay down for very long periods, with records of around three days submerged, allowing it to feed and rest on the bottom undisturbed.
Why does it have green hair?
The green growth is algae, and it is not unique to this turtle, but the Mary River turtle grows it especially well because it spends so much time sitting still, submerged, in clear flowing water where algae get plenty of light. Filaments settle on the shell, the limbs, and the head, and where they establish along the crown they can stand up into a ragged mohawk. The algae are generally harmless and may even offer a little camouflage, and a turtle that has recently moved or been active often has less of it.
How did a turtle become a common pet before scientists knew it existed?
In the mid twentieth century, collectors gathered vast numbers of turtle hatchlings from the Mary River each nesting season and supplied them to the Australian pet trade, where they were sold cheaply as penny turtles or as generic Australian pond turtles. Buyers and sellers had no idea the little turtles belonged to a species found in only one river and known to no museum. It was not until 1994 that a researcher recognised the animal as new to science and formally described it, by which time the decades of hatchling collection had already done serious damage to the wild population.
Why is the Mary River turtle Endangered?
Several factors compound one another. The historic pet-trade harvest removed almost all the young turtles for years, and because the species takes decades to reach breeding age, the population is now dominated by old adults with few younger animals coming through. Nests laid on riverbanks are heavily raided by foxes, dogs, and goannas, and are trampled by cattle. River regulation, sand mining, weeds, and pollution have degraded the habitat. A large dam was proposed on the Mary River in the 2000s and rejected in 2009, partly because of the risk to this turtle and to the Australian lungfish that shares the river.