Giant snake-necked turtle
This is the largest of Australia's chelid turtles, reaching a carapace length of 48 cm. Its carapace is oval, slightly broader behind the center, has a smooth posterior rim, and lacks both a medial keel or groove. The carapace becomes deeper with age. Its posterior marginals may be slightly flared over the tail, but the lateral marginals are not upturned as in C. longicollis. Vertebrals are variable in shape and dimension. The 1st is the largest and is anteriorly flared, the 2nd and 3rd are elongated and may be longer than broad in adults, the 4th is the smallest and is broader than long, and the 5th is broader than long and posteriorly flared. No neural bones occur in the olive to brown carapace. The plastron is quite narrow (about twice as long as wide), and does not nearly cover the carapacial opening. Its forelobe is rounded in front and slightly broader than the hindlobe, which tapers toward the rear and contains a deep anal notch. The bridge is also narrow. The plastral formula is: intergul > pect >< abd > fem > an > hum > gul. The intergular never divides the gular scutes and is about 1.5 times as long as the length of the interpectoral seam. Both plastron and bridge are gray to cream or yellow. The broad head is large and flattened with a slightly upturned, protruding snout and an unnotched upper jaw. Two to four small chin barbels are present. The neck is very long (over 65% of the carapace length) and thick; it is covered with wrinkled skin but lacks tubercles. Skin of the head and neck is dark gray to olive dorsally and laterally, but yellow ventrally. The jaws and chin are cream to yellow. Exposed skin of the limbs is gray to olive or brown, that beneath cream to yellow. The forelegs have seven or eight large transverse scales on the anterior surface.
The karyotype is 2n = 54 (Bull and Legler, 1980).
Males have long, thick tails and concave plastra.
Chelodina expansa occurs in the Murray-Darling River system of South Australia, New South Wales and Queensland, the coastal basins of southeastern Queensland, and on Fraser Island.
Unstudied, but Cogger (1975) stated there are distinctive populations in central and eastern Queensland. Chelodina expansa (Fraser) from Fraser Island is smaller, more gracile, and its head, neck and limbs are black (John Cann, pers. comm.).
Chelodina expansa lives in permanent bodies of fresh water such as waterholes and rivers. Legler (1978) found them in medium to large, very turbid rivers.
Courtship has not been described; however, Legler (1978) reported frequent head bobbing in this species, and some of this may be associated with courtship.
Nesting occurs in the fall and winter (March-April, June, August, November) during or shortly after moderate to heavy rain, and several clutches are laid each year (Georges, 1984). The nest site is usually the top of a ridge or where the slope of the land levels off for a distance before rising again.
The white, hard-shelled, ellipsoidal eggs average 33.5-41.9 x 22.2-30.1 mm and a clutch may contain 5 to 25 eggs (X = 15.4) (Goode and Russell, 1968; Ewert, 1979; Georges, 1986). The incubation period is exceptionally long; often over a year, and as long as 664 days (Cann, 1978), so some hatchlings probably hatch and then overwinter in the nest. Hatchlings have 35-40 mm carapaces that are olive to dark gray with a yellow border. Their skin is also dark, but the jaws, chin, and throat are yellow.
Chelodina expansa is strictly carnivorous, consuming insects, shrimp, small fishes, and frogs. Legler (1978) observed that feeding is by a gape and suck method and always involves a forceful strike.
When handled, this turtle seldom bites, but may scratch with its feet and flail its neck and limbs. It does not omit an offensive odor, as do some other species of Chelodina.
IUCN Red List Status (1996)