Australian fitzroy river turtle

The Fitzroy River turtle (Rheodytes leukops) belongs to the freshwater turtle family Chelidae and is notable for being the sole surviving species of the genus Rheodytes, with its counterpart, the extinct form Rheodytes devisi. This aquatic reptile is endemic to the south eastern region of Queensland, Australia and can only be seen in tributaries connected to the Fitzroy River.

Description of the Fitzroy River turtle

The Fitzroy River turtle is characterized by its light to dark brown color and can grow up to 260 mm in carapace length. Hatchlings typically have highly serrated shells while adults have rounded, smooth-edged shells. The plastron of this species is lighter in color and tapers both anteriorly and posteriorly.

The carapace appears highly reticulated to the naked eye, however, it is actually a series of parallel ridges with occasional cross ridging that becomes visible under low magnification. Conversely, the plastron is smooth and the scutes are thin. The underlying sutures in both the carapace and plastron are visible through the scutes, particularly in lighter individuals.

Australian fitzroy river turtle

Sub-adults of this species, such as the Rheodytes leukops, have very visible sutures still in place. A significant diagnostic characteristic of the Fitzroy River Turtle is its thin carapace bones, a feature shared with the related fossil species Rheodytes devisi. The upper surfaces of their necks are adorned with blunt to pointed conical skin tubercles that lack specialized follicular centers, while a single pair of barbels adorns the turtle’s lower jaw.

The Fitzroy River Turtle has a unique ability to use cloacal respiration, capable of acquiring up to 70% of its oxygen needs from the water through its cloaca. This remarkable ability enables the species to submerge itself underwater for up to three weeks.

Biology Fitzroy River turtle

Diet – Australian fitzroy river turtle

The aforementioned turtle species is proficient at bottom feeding and has been observed to consume a variety of prey, including both terrestrial and aquatic insects, crustaceans, macroinvertebrates, algae, aquatic snails, worms, freshwater sponges, and aquatic plants such as ribbon weed (Vallisneria sp.). Upon conducting stomach flushing experiments, it was discovered that the majority of the turtle’s diet consisted of macroinvertebrates, with some freshwater sponges also present.

Diet – Australian fitzroy river turtle

Natural history and observations in the wild

The species under consideration exhibits a discernible inclination towards swift-moving water, especially in the proximity of sand banks, where they prefer to lay their eggs. It has been observed that they can be found in depths as shallow as 15 cm. Typically, they remain motionless and concealed under the cover of foliage from overhanging plants that grow along the shallow banks of fast flowing riffles, such as fast flowing streams or rapids, or under logs. During all observed encounters, it was noted that their preferred ground material was coarse river sand and gravel.

Natural history and observations in the wild

Breeding biology – Fitzroy River turtle

Limited sexual dimorphism is observed in this species, with the female’s tail being noticeably shorter than the male’s. When distinguishing between the sexes, the most reliable method is to measure the distance between the anal scutes of the plastron and the cloacae; in males, the cloacae is situated further from the plastron. Unlike other short-necked turtles endemic to Australia, this species does not exhibit conspicuous differences in tail length or thickness.

Breeding biology – Fitzroy River turtle

According to the original study conducted by Legler and Cann (1980), this species is capable of multi-clutching, as evidenced by the presence of corpora lutea, current eggs, and enlarged follicles in the females. Subsequent anecdotal records suggest that up to five clutches may be laid by females.

Conservation status

This turtle species, known as the Fitzroy River turtle or “bum-breathing turtle,” inhabits a total area of less than 10,000 km2, which includes the Fitzroy, Mackenzie, and Dawson rivers. Due to its limited distribution and status as the last surviving member of a once more widespread genus, conserving this species has become a high priority. Since 1994, the Fitzroy River turtle has been classified as vulnerable on the IUCN checklist.

Conservation status – Fitzroy River turtle

The species is considered bimodally respiring, extracting oxygen from the water primarily through two enlarged cloacal bursae lined with multi-branching papillae. Reductions in aquatic oxygen levels caused by factors such as agriculture and dams, significantly impact the turtle’s survivorship, particularly among juvenile classes.

Three significant threats identified for this species are the reduction in invertebrate prey, conversion of fluvial to lacustrine habitat, and the increase of sedimentation impacting the cloacal breathing mode. As a result, authorities have listed the Fitzroy River turtle as vulnerable under both the Environment Protection and Biodiversity Conservation Act (EPBC Act 1999) and the Queensland Nature Conservation Act, 1992, with the IUCN currently identifying it as in need of review.