Mary River Tortoise
The Mary River turtle is the second largest freshwater turtle and the largest short-necked turtle species in Australia, with records of individuals getting to 50cm long. It has a large, rounded carapace (top of the shell) that gets wider at the rear, and a narrow plastron (the bottom of the shell). Despite these huge proportions, it’s small head and large, powerful back legs make it a very fast swimmer. The rear of the shell is serrated in younger turtles, but this becomes smoother out with age. The chin has a large pair of barbels, with a smaller barbel on each side; these are used for sensing their surroundings in murky water. They also have a very long, thick tail, especially the males (in which it can be up to 70% of the length of the carapace.
Omnivores, with young turtles eating mostly animal matter and slowly transitioning to eating mostly plant matter as adults. Freshwater insects, yabbies, shrimp, prawns, fish, tadpoles and bivalves are taken, but aquatic vegetation makes up around 79% of the diet by weight.
Like all turtles, the Mary River turtle is aquatic and native to freshwater environments. Deep pools along the river are preferred, with plenty of weed beds, submerged rocks and logs for cover and overhanging banks.
It is only found in the Mary River catchment of south east QLD, from the upper reaches near Kenilworth all the way to the salt restriction wall in the lowlands.
Mary River Turtles occupy flowing and well-oxygenated streams in the Mary River basin, and only really come onto land to nest. They are a very slow-maturing species, with females estimated to take around 25 years to reach maturity and males up to 30. They are also one of Australia’s famous ‘bum-breathing turtles’ – special organs inside their cloaca called ‘bursae’ can take oxygen out of the water, and so Mary River turtles can stay submerged for close to 3 days!
The Mary River turtle was only formally described in 1994 by renowned turtle researcher John Cann and was instantly recognised as one of Australia’s most endangered turtle species, only surpassed by the Western swamp turtle (Pseudemydura umbrina). An estimated 150,000 baby turtles taken from the Mary River for the pet trade decades previous is thought to be one of the major contributing factors to the turtle’s decline, as well as changes to water flow, nest predation by foxes and pigs, and tramping of nest sites by cattle.
Australia’s first reptile-focused, non-profit conservation organisation, the Australian Freshwater Turtle Conservation and Research Association, were the first to breed this species in captivity for release into the wild in 2007, and regular releases have occurred in the years since. Zoos and other organisations have also gotten involved in recent times.