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Western Swamp Tortoise

Class Order Family Genus Species Status

Reptilia Testudines Chelidae Pseudemydura umbrina Endangered

Description

The Western Swamp Tortoise is the smallest of Australia's tortoises. It is semi-aquatic. A mature adult is approximately l2.5cm. It has a short neck and a dark yellow and brown to black shell.

Reproduction

Sexual maturity occurs at 10-15 years, sometimes later. Mating in captive animals takes place in winter and spring and they nest around November. A single clutch of 3-5 hard shelled eggs is laid in a chamber 75-100 mm below the surface. Eggs incubate for 6 months.

To ensure the survival of the Zoo's young tortoises, small quantities of food are provided in the summer months. In the wild, desiccation (drying out) of the young tortoises during summer aestivation is a great threat to their survival.

Life Span

The Western Swamp Tortoise is thought to have a life span of approximately 40-50 years or more.

Habitat

The Western Swamp Tortoise is confined to a very marginal habitat. When the swamps are filled with water during the seasons of winter/spring, the tortoises live an aquatic life. As the swamp dries out in summer and autumn, they aestivate (go into a period of dormancy) under leaf litter and in holes. By mid-November all have taken to their refuges.

Social Organisation

There is little or no social interaction between Western Swamp Tortoises. They basically live a solitary life but aren't territorial, with individuals mixing freely whilst not really interacting. Males and females come together for a brief mating before the female lays her eggs in the swamp bank. There is no further parental care.

Predators

Even prior to the European settlement at Guildford, it is likely that the Western Swamp Tortoise was confined to a fairly limited range. Once settlement did occur, the region was developed for agriculture which further reduced the tortoise's habitat. The problems of a very small isolated environment, along with predation by foxes, feral cats and dogs, have contributed to their ever decreasing numbers.

Diet In the Wild

The Western Swamp Tortoise is carnivorous. When the water level in the swamp is high it feeds on insects, larvae, tadpoles, small crustaceans and aquatic earthworms. During its period of aestivation it does not eat. Growth and maturity rates vary and appear to be closely related to temperature, rainfall and food availability.

Diet at the Zoo

At the Zoo, Western Swamp Tortoises are fed a mixture of beef heart, blended prawns, squid, fish, carrots, algae powder, protein, vitamin supplement, and calcium carbonate in gelatine. Hatchings are fed on a live diet of brine shrimp, backswimmers and mosquito larvae for the first year of development.

Distribution

The Western Swamp Tortoise is a critically endangered species. It is restricted to two very small swamp reserves at Allen Brook and Twin Swamps on the outer metropolitan area of Perth, Western Australia.

Conservation Measures

Thc Western Swamp Tortoises were first discovered by European settlers in 1839. There were then no further reports for more than 100 years. In 1953 a child found a live specimen in Upper Swan. After much searching, more tortoises were found at Twin Swamps and Ellen Brook. These two areas were purchased by the Government and set aside as nature reserves for the Western Swamp Tortoises.

At Perth Zoo

In 1960, a colony of Western Swamp Tortoises was established at Perth Zoo. Breeding was sporadic with very few individuals surviving to maturity. In 1988, the number of tortoises in the wild was at crisis level. Five organisations, the Western Australian Department of Conservation and Land Management (CALM), Australian National Parks and Wildlife, World Wide Fund for Nature, Perth Zoo and the University of Western Australia (UWA) decided to mount a research and rescue program.

Research commenced by Perth Zoo and CALM has been continued by Dr Gerald Kuchling (UWA).

The breeding program has had increasing successes since it began. The results are as follows.

Year 1989 1990 1991 1992 1993 1994 1995 (up to May)

Number Hatched 11 11 16 12 (plus 6 hatchlings brought in from the wild) 28 (plus 2 hatchlings brought in from the wild) 32 38

Number still surviving 4 11 16 15 25 30 36

Some captive bred tortoises have already been released into protected habitats with more releases planned for the future.