The Western Swamp Tortoise (Pseudemydura umbrina) is only found in tiny pockets along a 3–5 km strip of the Swan Coastal Plain (Western Australia). Their original habitat was believed to be the clay-soil areas of Perth’s Swan Valley. This area was one of the earliest and heaviest to be developed for agriculture after the arrival of European settlers (1829).
Between 1963 and 2001, the known population in the wild fluctuated between 30 and 120. The breeding program at Perth Zoo began in 1989 and a Western Swamp Tortoise Recovery Team was established in 1990.
Since 1989, Perth Zoo has bred more than 900 Western Swamp Tortoises, of which over 741 have been released to boost their numbers in the wild (figures as at April 2018). Perth Zoo’s on-site breeding facility is home to an ‘insurance population’ of around 150–200 Western Swamp Tortoises. A second insurance population at Adelaide Zoo exists to ensure that all the Western Swamp Tortoise eggs are not in one ‘basket’.
Without the recovery program and the significant efforts to restock the population, the Western Swamp Tortoise would most likely have become extinct.
Breeding for Release
Over the years, research has been undertaken to improve the breeding, husbandry and genetic management of Perth Zoo’s Western Swamp Tortoise population.
These tortoises require shallow, ephemeral swamps that have clay or clay/sand substrates. The few remaining areas of this specialised habitat are all close to urbanisation. One of the key factors in successfully breeding Western Swamp Tortoises is to allow them to ‘aestivate’ (sleep or go dormant) during summer and autumn. This happens naturally in the wild from November to June each year (depending on the amount and lateness of rain).
In their Zoo setting, adult Western Swamp Tortoises eat a specially developed ‘pudding’ comprising marron, rats, fish, beef heart and supplements in gelatine. This scientifically designed custom diet has been an important factor in the Zoo’s breeding success.
After the tortoises at Perth Zoo mate and lay their eggs, keepers carefully dig the clutches up and place the eggs in incubators to maximise hatching success. The closely monitored eggs incubate for four to six months. After hatching, the young are weighed and their shells marked with a unique dot pattern to aid identification.
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 Parks and Wildlife. The release sites include Twin Swamps, Ellenbrook, Mogumber and Moore River Nature Reserves. We are currently also trialing release sites in Western Australia’s south-west, outside of the tortoise’s historic range where it is cooler and wetter to counteract the effects of a warming climate on the species.
Partners and Supporters
The Western Swamp Tortoise breed-for-release program is run in partnership with the Parks & Wildlife, Western Swamp Tortoise Recovery Team and Friends of the Western Swamp Tortoise. 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 opened in 2014.