Pseudemydura umbrina

Siebenrock, 1901
Western swamp turtle

This small side-neck (to 14 cm) has a flat, rectangular carapace with smooth posterior marginals and a medial depression on the 2nd to 4th vertebrals. All vertebrals are broader than long in adults. The 1st is the longest, and the 5th is the shortest and usually flared posteriorly. No neurals are present. The posterior marginals are elevated over the tail, and the surface of the scutes is wrinkled and leathery. The carapace varies from light brown to black. The plastron is very large, covering almost all of the carapacial opening. It has a posterior notch. The intergular scute is very large, separating both the gulars and humerals and also partially separating the pectoral scutes. The plastral formula is: intergul > an > pect > abd > fem > gul > hum. The bridge is broad, about one-third the length of the plastron. Plastron, bridge, and undersides of the marginals are yellow with dark seams. The head is broad and flat with a short, slightly projecting snout and an unnotched upper jaw. Gaffney (1977) lists the following skull characters as unique to Pseudemydura: contact between the quadrate and parietal bones, lateral expansion of the supraoccipital and parietal bones, ventrolateral expansion of the postorbital bone, anterior extension of the squamosal, separation of the coronoid and splenial bones by the prearticular, and separation or near separation of the premaxillae into anterior and posterior parts by the medial approximation of the maxilla. The head is covered with rough tuberculate skin and there are two small chin barbels. Dorsally, the neck is covered with numerous large conical tubercles. The forelimbs are covered with large scales, but lack transverse scales on the anterior surface. All toes are webbed. The head, neck, and limbs are brown, and the jaw surfaces are yellowish.
Bull and Legler (1980) found the karyotype of Pseudemydura to be distinct from those of other chelid turtles with a diploid number of 50 (22 macrochromosomes, 28 microchromosomes) in that macrochromosomes 6 and 10 are acrocentric and pair 10 has a secondary constriction adjacent to the centromere.
Males have longer tails than do females.

Pseudemydura umbrina is restricted to southwestern Australia where it ranges southward from Bullsbrook about 25 km to the marshy areas in the suburbs of Perth. Two reserves, Ellen Brook (53 ha) and Twin Swamps (142 ha) have been established within this area to protect the species.

This species lives in ephemeral swamps and marshes.

Natural History
Females mature at carapace lengths of 11-12 cm (Burbidge, 1981; Kuchling and Bradshaw, 1993); the youngest mature female reported by Kuchling and Bradshaw (1993) was 10.5 years old. Yolking of the ovarian follicles begins in and growth of the ovarian follicles continues through the period of aestivation. Ovulation occurs between late September and early November and is preceded by a feeding bout when the turtle emerges from aestivation (Kuchling and Bradshaw, 1993). Ovulation and egg production of captives has been easily suppressed when the animals are stressed or have low food intake (Kuchling and Bradshaw, 1993).
Nesting usually takes place in November and December (Kuchling and Bradshaw, 1993), but Cann (1978) also reported nesting in October. One to five (usually 3-5) eggs are laid in a clutch (Kuchling and Bradshaw, 1993); eggs are white, brittle-shelled, and elongated (35-44 x 19-22 mm) (Cann, 1978; Legler, 1985).
Pseudemydura umbrina is carnivorous, eating aquatic insects, crustaceans, and tadpoles. The western swamp turtle is active during the Australian winter and spring when the ephemeral swamps it inhabits contain water; it aestivates during the summer and autumn (November to early June) when these habitats are dry (Kuchling and Bradshaw, 1993). It does not dig terrestrial burrows to aestivate, but uses existing, natural holes in clay or sandy soil or digs into leaf litter at the base of bushes or trees (Gerald Kuchling, pers. comm.).

IUCN Red List Status (1996)
Critically endangered (A1c, B1+2c, C1+2b, D1). In 1991, it was estimated that only about 30 animals remained in the Ellen Brook Nature Reserve, while the only other known population, at Twin Swamps, had been virtually extinct since 1985 (Stephens, 1995). A highly manipulative recovery program was started in 1988 that includes predator-proof fencing of habitat in two small nature reserves, water supplementation into swamps during dry years, acquisition and rehabilitation of former habitat, intensive population monitoring with radio-tracking, ultra-sound scanning of reproductive females and nest monitoring, captive breeding and head starting, genetic management, reintroduction, public education, and enforcement of Australian endangered species laws and regulations regarding habitat protection (Kuchling, 1996a). A very serious present and future problem is the continuous sprawl of Perth which is destroying the shallow ephemeral swamps needed for survival of existing turtles and for reintroduction of the species. In the period 1988-1997, 228 P. umbrina hatched in captivity, 72 of which have so far been released into Twin Swamps Nature Reserve (Gerald Kuchling, pers. comm.).