Mary River turtle
An adult Mary River turtle. Photo: EHP
Common name: Mary River turtle, Mary River tortoise
Scientific name: Elusor macrurus
Conservation status: The Mary River turtle is Endangered in Queensland (Nature Conservation Act 1992) and Endangered nationally (Environment Protection and Biodiversity Conservation Act 1999). It is also considered a critical priority for conservation under the Department of Environment and Heritage Protection Back on Track species prioritisation framework.
The shell of the adult Mary River turtle is massive, smooth, streamlined, dull and unpatterned with a carapace (upper shell) length reaching 400 mm. Its eyes are dull, and dark. A pale eye ring, which is a feature of a number of other species of turtles, is absent or vague in adults and the eyelid is slightly translucent. The neck has tubercles (small rounded bumps) in two longitudinal rows. There are usually four chin barbels (slender feelers near the mouth) with one large median pair between two much smaller lateral barbels.
The males have a very long tail (up to 70 per cent of the length of the carapace in adults). This is unique among freshwater turtles.
Habitat and distribution
Thie Mary River turtle lives in areas of clear, slow moving water and has been found in areas where the riparian communities are heavily grazed and disturbed.
The Mary River turtle occurs in the Mary River, from Gympie, to the tidal reaches just upstream from Maryborough. It probably nests in suitable places along these parts. It is also found in Tinana Creek upstream of Tallegalla Weir. It probably occurs in all the deeper holes of the Mary River downstream from Kenilworth.
Life history and behaviour
The Mary River turtle is a cloacal ventilator (meaning it takes in oxygen through its bottom - a 'bum breather') and historically these types of freshwater turtle do not do well in large standing water bodies. Cloacal ventilation allows the species to stay under water for days at a time when the water is flowing and well oxygenated. This species likes to bask in sunny locations.
Mature males are aggressive towards each other and live separately in the wild.
Egg morphology and other reproductive characters seem essentially like those of the other turtles in the Family Chelidae with a southern temperate breeding pattern. Nesting occurs in late October and again about one month later.
Juvenile Mary River turtles were subjected to illegal collection for the pet trade throughout the 1960s and 1970s (they were sold as 'penny turtles'). This collection has meant that an entire generation of turtles were removed from the wild leaving a reduced, aging population.
Today nesting is threatened by egg predation from feral animals and goannas, and nest trampling by cattle. This current threat has the potential to remove another generation from the wild population and place the entire species at risk of extinction. Water quality in the streams it inhabits has declined in the past 20 years. Parts of the Mary River catchment have been cleared and heavily grazed, and on these reaches of the river, the turtle is threatened by the effects of increased runoff, siltation and pollution. A reduction in water quality can be attributed to chemical pollution and sediment runoff; commercial sand-mining upstream of turtle populations; and the direct and indirect effects of grazing activity, which may also influence changes in flow rates. Impoundments that are designed without consideration of turtle conservation may also threaten this species by injuring turtles caught in floodways and high velocity water flows. Impoundments may also impact on turtles by changing flow regimes.
Removal of riparian trees prevents recruitment of logs into the instream environment. Emergent logs and log jams may be important elements of the Mary River turtle's microhabitat.
Further information is needed about the distribution and habitat requirements of this species to identify its conservation requirements. EHP has been involved in the release of young Mary River turtles into the Mary River. There have been three releases of young turtles to date with approximately 95 turtles released in 2009.
Management recommendations include:
- Control feral animals, mainly foxes, in areas of known nesting. Electric fences and nest caging have proved to be successful methods in controlling predators.
- Protect nesting sites from access of stock to prevent trampling.
- Monitor the impact of grazing on water quality and adjust grazing management to reduce adverse impacts.
- Strictly adhere to watercourse protection zone guidelines, as outlined in the Code of Practice - Native Forest Timber Production.
- Control public access at known Mary River turle nesting sites on State forests and timber reserves.
Cann, J 1998. Australian Freshwater Turtles, Beaumont Publishing.
Cogger, HG 2000. Reptiles and Amphibians of Australia, Reed New Holland.
Cogger, HG, Cameron, E, Sadlier, R & Eggler, P 1993. The Action Plan for Australian Reptiles. Australian Nature Conservation Agency, Canberra.