Fitzroy River turtle
|Fitzroy River turtle|
Legler & Cann, 1980
The Fitzroy River turtle (Rheodytes leukops) is a species of turtle in the Chelidae family. It is the only surviving member of the genus Rheodytes, the other member being the extinct form Rheodytes devisi. The species is endemic to south eastern Queensland, Australia.
This recently described freshwater turtle is restricted to the Fitzroy River drainage system of Queensland, Australia. Their habitat comprises a total area of less than 10,000 km² and includes the Fitzroy, Mackenzie and Dawson rivers. Its limited distribution and being the sole survivor of a once more widespread genus give it a high priority for conservation. The Fitzroy River turtle is known as the “bum breathing turtle” by locals. This nickname is derived from their unusual ability of being able to absorb oxygen whilst submerged, through highly vascularised bursae located in the cloaca.
The Fitzroy River turtle is light to dark brown in colour and can grow to around 26 cm carapace lengths. The shell of hatchlings is highly serrated while adults have a rounded, smooth shell. Adults have a pitted, grooved carapace that resembles the rough texture of water-logged drift wood. The upper surface of their necks are scattered with blunt to pointed conical skin tubercles which may have a sensory function similar to that of cat’s whiskers. Although a short necked species, their shell is reduced giving them the appearance of having a longer neck than other short-necked genera. Compared to other Australian freshwater turtles, they have relatively long legs and very long claws which makes them perfectly suited for life in fast flowing, turbulent water.
This turtle is an adept bottom feeder, preying on terrestrial and aquatic insects, macroinvertebrates, crustaceans, algae, aquatic snails, worms, freshwater sponges and aquatic plants such as ribbon weed (Vallisneria sp.).
Natural history and observations in the wild
This species shows preference at certain times of the year for slow to fast flowing water (near sand banks for egg laying) and has been found at depths as shallow as 15 cm. In most encounters, they have been found lying still, hidden by overhanging plant foliage along the shallow banks of fast flowing riffles (fast flowing streams or rapids) and under logs. In all encounters their preferred substrate was noted as coarse river sand and gravel.
One personal observation that we have made is that the Fitzroy River turtle has an acute sense of smell comparable to that of the Pig-nosed turtle (Carettochelys insculpta). When dropping insects into their enclosure it is only a matter of seconds before they begin to sniff out their favourite food. On many occasions we have remarked that the hatchlings are “dog-like” because of their keen sense of smell and distinguishable black nose.
We have never observed this species to come to the water surface to breathe air in the wild or in our collection of adults and hatchlings. This is not to say that they won’t surface for air if required. Another interesting observation is that we have never witnessed them actively swimming as they prefer to scurry along the bottom and climb obstacles to get to where they are going. On many occasions we have watched hatchling Fitzroy River turtles cling on to each other in small groups, some with their cloacae pointed upright. With closer observation we noted that these hatchlings pump water through their cloacae at a rate of up to 60 times per minute and with enough force to break the water surface immediately above. It was not uncommon when removing them from their aquarium to pick one up and find that it was clinging onto others, lifting them too from the water. In some instances the chain of turtles numbered up to six and had to be separated one by one.
There is limited sexual dimorphism with the tail of the female being marginally shorter than that of the male. The most accurate way to differentiate between sexes is to compare the distance between the anal scutes of the plastron and the cloacae. In males, the cloacae is located further away from the plastron than in females. Most other short-necked turtles in Australia show obvious differences in tail length and thickness. Females lay between three and five clutches of comparatively small eggs each breeding season (between September and January). Twelve to twenty one eggs are deposited in nesting chambers up to 170mm deep. Eggs artificially incubated at 28°Celsius hatched after fifty-five days.
The Fitzroy River turtle is currently listed as vulnerable in the Environment Protection and Biodiversity Conservation Act (EPBC Act 1999). Agriculture (particularly cotton and cattle farming), mining and salinity are three major areas of concern that impact on this species. Their once crystal clear, clean water has largely disappeared and been replaced by turbid, chemical and pesticide polluted water. In one area on the Dawson River where we have taken water samples, the pH was found to be as high at 9.1. In captivity, we have determined that a pH outside the range of 7.0–7.4 has drastic effects on the health of hatchlings, leading to life threatening skin problems. We have never encountered any hatchlings or juveniles in the wild. This could be one reason why there appears to be zero or very low recruitment i.e. no hatchlings reaching maturity to replace those that die of old age or other causes. This species is also unable to tolerate high levels of salinity, which is one of the after effects of land clearing. Along some of the roads that follow the Dawson River we were alarmed by the damage to patches of native forest caused by high soil salinity. Trampled banks were also a constant reminder of the damage that cattle can cause when allowed to drink from and graze beside river systems. We have travelled thousands of kilometers along the Fitzroy and Dawson drainages over the past five years and the entire area is extremely drought affected. Many of the smaller tributaries had either completely dried up or had become isolated, stagnant pools unsuitable as habitat for Fitzroy River turtles. Around these pools were rotting carcasses and sun bleached shells of Rheodytes, Emydura and Elseya species. The clear, clean water that they prefer was nowhere to be found.
There is an even more serious threat on the horizon. The Nathan Dam is proposed for the Dawson River, which will have significant environmental impacts. This 880,000 mega-liter dam will be Queensland's fourth largest dam. Its main purpose will be to irrigate 30,000 hectares of cropping land, most of which will be cotton. By far, cotton farming is the most threatening agricultural activity undertaken in the Dawson River area. Cotton crops require large amounts of fertilisers, pesticides and water for irrigation. The runoff from the crops can make its way back into the river system carrying with it high levels of pollutants and sediment. This will have detrimental effects on the whole river ecosystem, particularly the turtles, fish and migratory birds. The proposed dam may even impact on the Great Barrier Reef. One condition for the dam to proceed is the completion of a two-part Environmental Impact Study. These studies will target areas downstream from the dam as well as the impact of irrigated agriculture facilitated by the dam. In the past we have seen many environmental impact studies that completely lacked any consideration for freshwater turtles inhabiting the area of concern. Several years ago, we were involved in a turtle rescue and relocation where almost one thousand turtles were not included in the impact study and over four hundred were subsequently squashed on nearby roads the day the dam walls were broken. The site was to be developed into residential housing.
- Australasian Reptile & Amphibian Specialist Group 1996. Rheodytes leukops. 2006 IUCN Red List of Threatened Species. Downloaded on 29 July 2007.
- Legler, J.M. & Cann, J. 1980. A new species of chelid turtle from Queensland, Australia. Contributions to Science (Natural History Museum of Los Angeles County) 324:1-18.
- Fritz Uwe; Peter Havaš (2007). "Checklist of Chelonians of the World". Vertebrate Zoology 57 (2): 343. ISSN 18640-5755. Archived from the original (PDF) on 2010-12-17. Retrieved 29 May 2012.
- Thomson S. (2000). A Revision of the Fossil Chelid Turtles (Pleurodira) Described by C.W. De Vis, 1897. Memoires of the Queensland Museum 45(2):593-598.
- http://www.jstor.org/discover/10.2307/1565924?searchUrl=%2Faction%2FdoBasicSearch%3Ffilter%3Diid%253A10.2307%252Fi270521%26Query%3Drespiration%26Search.x%3D0%26Search.y%3D0%26wc%3Don&Search=yes&uid=3739600&uid=2134&uid=2&uid=70&uid=4&uid=3739256&sid=21101254679557 "Rheodytes leukops is a bimodally respiring turtle that extracts oxygen from the water chiefly via two enlarged cloacal bursae that are lined with multi-branching papillae."