Common snake-necked turtle
The oval, dark-brown to black carapace (to 27.5 cm) is broadest behind the center, has a smooth posterior rim, depressed vertebrals, and a pronounced medial groove on the 2nd to 4th vertebrals. Adult vertebrals are broader than long; the 1st is largest and flared anteriorly, the 4th is smallest, and the 5th is flared posteriorly. Neurals are not usually present. Marginals lying immediately over the tail are raised, and lateral marginals are often upturned. The plastron is large, almost covering the entire carapacial opening, and has a deep posterior notch. Its forelobe is as broad as or broader than the hindlobe. A slight lateral indentation may occur at the level of the abdominal-femoral seam, and the anal scutes taper toward the midline. The plastral formula usually is: intergul > abd > an > fem >< pect > hum > gul. The intergular is more than twice as long as the interpectoral seam. Plastron, bridge, and undersides of the marginals are cream to yellow with dark-brown or black pigment bordering the seams. The head becomes broader with age. Its snout is slightly upturned and protruding, and the upper jaw is unnotched. The thin neck is long (60% of the carapace length) and covered with pointed tubercles. Skin of the head and neck is brown to dark gray dorsally and laterally, but yellow ventrally. Jaws are cream to yellow. Exposed skin of the limbs is gray to brown, the undersides are cream colored. Each foreleg has four or five large transverse scales on the anterior surface.
Bull and Legler (1980) found the diploid karyotype to be 54.
Males have longer, thicker tails and concave plastra.
This species is found in eastern Australia from northern Queensland southward to southern South Australia, and on Fraser and Moreton Islands.
No subspecies are currently recognized, although the carapacial shape does vary between populations in different drainage systems. The rough-scuted Chelodina sulcifera Gray, 1856 is now known to be only a growth form of C. longicollis (Goode, 1967).
Chelodina longicollis lives in slow-flowing rivers, streams, ephemeral swamps, and lagoons. As its ephemeral waterbodies dry up during periods of low rain fall, which may span several years, C. longicollis retreats to more permanent waterbodies (Kennett and Georges, 1990). It may hibernate in the southern portions of its range, sometimes communally (Green, 1994, 1995).
According to Parmenter (1985) males mature at a carapace length of 14-15 cm, females at 17 cm. Mating occurs in September and October. The male pursues the female from the rear with his snout near her vent. He then touches his chin to her carapace and, by swimming faster, follows her vertebral groove with his chin until he reaches the anterior rim of her shell, where he grabs the rim of her carapace with his toes and mounts, bending his tail beneath hers (Murphy and Lamoreaux, 1978).
Ovulation occurs in late October and November (Parmenter, 1985). Most nesting occurs in November and December, but some may oviposit in January. The nests are dug in grassy or sandy areas at night during or after rains. While searching for a nesting site, a female explores the bank, walking back and forth or in circles, pausing on occasion until a suitable place for excavation is found (Green, 1997). Once found, the turtle rests its plastron on the ground with its neck and head stretched forward, and begins to push ground cover away from the body with its hind legs. After the debris is cleared, excavation of the nest cavity begins by digging with and alternating the hind feet. Two holes are thus created, one on each side of the plastron, which allow the plastron to slot in and allow the hindlimbs to dig deeper at a later period. The digging eventually changes to the excavation of one hole by swinging the anterior part of the body to the side, allowing the nearest foot to scratch in the newly formed hole before swinging the anterior body back to use the other leg. As the hole becomes deeper, the forelimbs are raised, tilting the posterior portion of the body downward and allowing the alternate hindlimbs to dig a deeper egg chamber. Soil is lifted out of the hole with by the hindfeet. Once a depth of about 10 cm is reached, the sides and front of the hole near the base are scraped to form the flask-shaped egg chamber measuring about 6 cm in diameter at the opening and 8 cm in diameter at the base. Nest excavation may take as long as five hours. Once oviposition occurs, the hind feet are used to position the eggs in the chamber. When the full compliment of eggs has been laid, the hindlegs are used to scrape in and fill the nest cavity. Once filled, the female raises her shell and drops it on the nest plug, and then returns to the water. Twelve nests measured by Vestjens (1969) were 82-127 mm in depth (X = 113) and flask shaped.
One to possibly as many as three clutches of 6 to 24, brittle-shelled, oval (21.0-33.8 x 12.5-21.3 mm) eggs are laid each year (Parmenter, 1985). Natural incubation periods range from 110 to 168 days and the young emerge from January to late April. Hatchlings have carapace lengths of 25-30 mm. They are black to dark gray with an orange spot at the rim of each marginal and on each plastral scute. A yellow to orange horseshoe-shaped mark occurs on the chin, and a broad yellow or orange longitudinal stripe runs from each corner of the mouth backward onto the ventral surface of the neck.
Chelodina longicollis is an opportunistic carnivore that taps a wide variety of sources—plankton, nekton, benthic macroorganisms carrion, and terrestrial organisms that fall into the water: oligochaetes, platyhelminths, snails, crustaceans, insects, fish, anurans (including eggs and larvae), and some algae (Georges et al., 1986). Turtles from permanent waterways grow faster and reproduce better than those from more ephemeral habitats (Kennett and Georges, 1990).
Wild C. longicollis often emit strong-smelling volatile fluids from their musk glands when first caught, but long-term captives seldom do this. Woolley (1957) reported that this species has the ability to match the color of its background by expanding or contracting the melanophores of its skin.
IUCN Red List Status (1996)