University of QLD News Online

Published: 04 August 2006


The endangered Mary River Turtle has learned the perfect way to avoid being eaten — stay underwater.

UQ PhD student Natalie Mathie, who has been studying Mary River hatchlings for the last two years, has shown that the turtle can stay submerged for at least three days, possibly up to a week in the right conditions.

Ms Mathie said unlike most fresh water turtles, the Mary River Turtle could extract about half of its oxygen requirements from river water using special sacs in its bottom.

The endangered Mary River Turtle is unique to the Mary River and it’s believed only hundreds of eggs are laid each breeding season.

Ms Mathie, with UQ’s School of Integrative Biology, has been studying how changes in water temperature, oxygen levels and also the presence of predators affect the turtles’ respiration and diving behaviour.

She believes their diving is a survival strategy to lessen their chance of being eaten by birds on the surface or by fish and eels.

She also tested the turtles’ performance in cooler and hotter temperatures and found that they didn’t adapt well to any temperature changes.

Ms Mathie said the Mary River Turtle was under threat because turtle eggs were being eaten by cats, dogs and foxes or their nests were being trampled by cows along the river.

She is also worried about how the planned Traveston Dam will change the Mary River landscape and damage turtle habitat washing away undercut banks, nesting banks, fallen logs and well oxygenated streams.

She said the Mary River Turtles needed riffle zones, which were shallow rocky areas that ran into big pools keeping water oxygen levels high.

“The Dam will have a lot less oxygen and it will also be cooler because it’s deeper.”

Ms Mathie, who has been supported by the local Tiaro Landcare group, will soon fix depth recorders and transmitters to the shells of adult turtles.

She said this would allow her to exactly measure their diving rates and where and how far away they were living and nesting.

MEDIA: Ms Mathie (0416 106 363, 07 3365 2516) or Miguel Holland at UQ Communications (3365 2619) *Hi-res photos available

Mary River turtle

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).

Description: The shell of the adult Mary River turtle is massive, smooth, streamlined, dull and unpatterned. Its eyes are dull, dark and unpatterned. A pale eye ring is absent or vague in adults and the eyelid is slightly translucent. The neck has tubercles (small rounded bumps) in two longitudinal rows, in which five to seven transverse whorls are vaguely distinguishable. There are usually four chin barbels (slender feelers near the mouth) with one large median pair between two much smaller lateral barbels.

Habitat and distribution: 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.

This turtle lives in areas of clear, slow moving water in the Mary River and its tributary Tinana Creek. This turtle has been found in areas where the riparian communities are heavily grazed and disturbed.

Behaviour and life history: Mature males are aggressive and cannot be kept in the same aquaria with other males of the same species. Individuals of Elusor are easy to handle and seldom attempt to bite, unlike most other shortnecked turtles. This species likes to bask in sunny locations.

This species is a cloacal ventilator (meaning it takes in oxygen through its bottom) and historically these types of freshwater turtle do not do well in large standing water bodies. This feature allows the species to stay under water for days at a time.

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.

Threatening processes: Its apparently restricted distribution and low population size renders it susceptible to any threatening processes. 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 vulnerable to 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.

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. The few known nesting sites have been illegally raided for eggs to raise hatchlings for the pet trade. Nest sites are subject to predation by foxes, trampling by stock and people, and to flooding.

Recovery actions:

    * Control feral animals, mainly foxes, in areas of known nesting.
    * Protect nesting sites from access of stock to prevent trampling.
    * Undertake further surveys to more accurately determine the distribution, habitat requirements and conservation requirement for this species.
    * 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 E. macrurus known nesting sites on State forests and timber reserves.

Last updated: 01 September 2006

UQ NEWS ONLINE

Vulnerable turtle focus of research
Published: 12 January 1999

Samantha Flakus admits she’s “hooked on turtles” - and turtles of the freshwater kind are her special interest.

The postgraduate zoology student at the University of Queensland is studying the Mary River turtle for her masters thesis.

She stalks them on the sandbars and in the waterholes of the lower Mary River, catches, measures, weighs and tags them, even tracks them and takes their temperature using radio signals from implanted transmitters.

Samantha, 23, originally from Sydney, did a degree in applied science, specialising in coastal management, at Southern Cross University, Lismore, in 1994-96 and began her postgraduate study at the University of Queensland in mid-1997.

The Mary River turtle is found only in the Mary River which rises in the mountains near Kenilworth in south-east Queensland and runs through Gympie and Maryborough. It is described as “vulnerable” under Queensland legislation, a status due possibly to its restricted distribution.

The turtle numbers also possibly were affected by commercial collecting of eggs at an estimated 10,000 a year in the 1960s and 1970s for hatching for the petshop trade before the turtle, along with all Queensland reptiles, became a protected species in 1974.

The turtle (Elusor macrurus - meaning elusive with big tail) was identified as a new species only in 1994. Before that it was believed to be, and called, a sawshell turtle. It is one of the largest of Australia’s 25 species and five sub-species of freshwater turtles. Adult males’ shells can measure up to 400mm in length.

Samantha’s research has found few juveniles of the slow-growing species. Most of the turtles she finds are of an ageing generation.

“We don’t know why,” she said. “Perhaps the breeding population has declined. I’ve been monitoring sites for two years and have found very few nests.”

She said she had found as few as 100 eggs at sites where it was known that thousands of eggs were collected in the past for the petshop trade.

Samantha’s study area is from Kenilworth to the Gunalda-Tiaro area. Her work is partly financed by the Queensland Department of Environment and Heritage. It is part of a major DEH study looking at the effects of weirs and dams on turtle populations in the Mary, Burnett and Fitzroy river systems.

DEH senior principal research scientist Col Limpus, who is also an adjunct associate professor with the University of Queensland’s Centre for Conservation Biology, is overseeing the research.

Dr Limpus said Samatha’s project was the first detailed study of the Mary River turtle. “It is a different species, in a genus by itself,” he said. “It is also one of the largest of Australia’s freshwater turtles.”

For further information, contact Samantha Flakus at the Zoology Department, the University of Queensland, telephone 07 3365 1391.