The Western Swamp Tortoise (Pseudemydura umbrina), or Short-necked Freshwater Tortoise, is Australia’s most critically endangered reptile. This tortoise was thought to be extinct for over 100 years until rediscovered in 1953. In the 1980s, there were estimated to be less than 30 left in the wild. Habitat loss and introduced predators (foxes, cats, dogs and pigs) are major threats to this species.
The Western Swamp Tortoise has only ever been recorded in scattered localities in a narrow 3–5 km strip of the Swan Coastal Plain in Western Australia. It is believed that their original habitat was in the clay soil areas of the Swan Valley to the north of Perth. This area was one of the first to be developed for agriculture after the arrival of European settlers in 1829.
The Western Swamp Tortoise lifecycle requires shallow winter and spring ephemeral swamps with clay or clay overlay and sand substrates. The small remaining areas of this specialised habitat are all close to urbanisation.
Between 1963 and 2001, the numbers of these tortoises known to be alive in the wild fluctuated between 40 and 120. The breeding program at Perth Zoo began in 1989 and a Western Swamp Tortoise Recovery Team was established in 1990.
Diet – including a specially developed “pudding” comprising marron, rats, fish, beef heart and vitamin and mineral supplements in gelatine – has been an important factor in the breeding success at Perth Zoo.
Over the years, other research has been undertaken to improve the breeding, husbandry and genetic management of the Western Swamp Tortoise population at Perth Zoo.
One of the key factors in breeding Western Swamp Tortoises is to allow them to aestivate (sleep/be dormant during summer and autumn). This happens naturally in the wild from November to June each year (the exact timeframe varies with the amount of rain and when the region receives rain).
After the tortoises mate and lay their eggs at the Zoo, keepers carefully dig up the eggs and place them in incubators to increase the hatching success rate. The eggs incubate for about four to six months. After hatching, the young tortoises are weighed and their shells marked with dots of nail polish to aid identification (the dots wash off over time).
When the tortoises reach 100g in weight (about three years of age), they are released into managed wild habitats by the Western Australian Department of Environment and Conservation (DEC). The release sites include Twin Swamps Nature Reserve, Ellenbrook Nature Reserve, Mogumber Nature Reserve and Moore River Nature Reserve.
Since 1989, Perth Zoo has bred more than 800 Western Swamp Tortoises of which 600 have been released to boost their numbers in the wild (figures as at August 2012). Perth Zoo’s on-site breeding facility is also home to an insurance population of around 150–200 Western Swamp Tortoises. Without the recovery program and the significant efforts to restock the population, the Western Swamp Tortoise would most likely have become extinct.
Partners and Supporters
The Western Swamp Tortoise breed for release program is run by Perth Zoo in partnership with the Western Swamp Tortoise Recovery Team members, with input from Dr Gerald Kuchling (DEC) who initiated the breeding program in 1988, the World Wildlife Fund and Friends of the Western Swamp Tortoise. Work has begun on a second insurance population at Adelaide Zoo to ensure that all the Western Swamp Tortoise ‘eggs’ are not in one basket.
Boral Midland Brick has been a valued project sponsor, supporting the project by supplying many of the bricks used in the construction of the new western swamp tortoise facility. The facility is due for completion in November 2014.