Gray, 1841
Narrow-breasted snake-necked turtle
Recognition
This species has a narrow, oval carapace (to 40 cm), broadest behind the center, with a smooth posterior rim. The vertebrals are depressed with a pronounced medial groove on the 2nd to 4th; a low medial keel may also occur. Vertebrals 1, 4, and 5 are broader than long; 2 and 3 may be longer than broad. Vertebral 1 is largest and anteriorly flared, 4 is the smallest, and 5 is posteriorly flared. Five to eight neural bones are present. Surfaces of the carapacial scutes of juveniles and young adults may be rugose with radiating striations, but very old, large individuals are often smooth. Lateral marginals may be slightly upturned. The carapace ranges in color from light brown to black, and some dark flecking may be present. The long, narrow plastron is smaller than the carapacial opening. Its forelobe is rounded anteriorly; the hindlobe tapers to the rear and bears a large anal notch. The forelobe is broader than the hindlobe. The plastral formula is: intergul > fem > pect > abd > an > hum > gul. The intergular is about 1.2-1.5 times as long as the length of the interpectoral seam. Both plastron and narrow bridge are cream to yellow. The head is large and flat with a protruding snout and an unnotched upper jaw. Several chin barbels may be present. Head and jaws are olive to gray with numerous dark mottlings. The olive to gray neck is thick, with blunt rounded tubercles, and so long (over 75% of the carapace length) that it cannot be tucked entirely under the carapace. Limbs are olive to gray and the forelegs have seven large transverse scales on their anterior surfaces.
The karyotype consists of 54 chromosomes (Bull and Legler, 1980).
Males have slightly longer, thicker tails than do females, and the male plastron is concave.
Distribution
Chelodina oblonga is confined to the southwestern corner of Western Australia (Cann, 1978).
Habitat
Swamps and streams with permanent water seem to be the primary habitat. Under natural conditions it apparently does not aestivate.
Natural History
Males become sexually mature at about a carapace length of 14 cm (Kuchling, 1988). The germinal epithelium of the testes is quiescent during the winter, spermatogonia start to multiply in the spring, followed by spermatocytogenesis in late spring and summer (Kuchling, 1988). Spermiogenesis peaks in April, and spermiation starts in summer and continues until winter. Females of 21 cm or greater are mature (Kuchling, 1988). Follicular enlargement begins during the summer and continues until spring, with oviducal eggs occurring in October and November.
Nests examined by Clay (1981) were 20-105 m from water; distances traveled were longer during September-November (X = 86.56 m), shorter during December-January (X = 25.38 m). Nest sites were usually open and free from thick vegetation, and once the maximum daily air temperature remained above 17.5°C the females came ashore to nest. Clay (1981) also found a strong relationship between nesting and the approach of a rain-bearing atmospheric depression.
Up to three clutches may be laid between September and January, and females have a reproductive capacity of 25-40 eggs per year (clutches ranging from 3-16 eggs; Clay, 1981; Kuchling, 1988). The white eggs are elongated (30.8-35.7 x 18.1-24.0 mm; Clay, 1981; Kuchling, 1988). The natural incubation period ranges from 183 to 222 days, depending on weather conditions. Hatchlings are approximately 31 mm in carapace length (Ewert, 1979).
Cann (1978) reported that his captives ate fish and tadpoles which they stalked. The neck and head were retracted toward the carapace and held there until the prey moved within range, then the head was struck forward with amazing speed, seizing the victim.
IUCN Red List Status (1996)
Lower risk: near threatened.