What is the Western Swamp Tortoise and why is it endangered?
The Western Swamp Tortoise, Pseudemydura umbrina, is the most endangered reptile in Australia. It is listed as Critically Endangered and there are estimated to be only ~300 individuals remaining in the whole world and only ~100 in the wild (less than 50 of which are adults), mainly at two places in the Swan Valley near Perth, Western Australia. These two sites are Twin Swamps and Ellen Brook Nature Reserves, which are both surrounded by an electric vermin proof fence to protect the tortoises. They require a special type of swamp with clay or clay-and-sand bottoms that only fill with water for a short period every year. When Europeans settled the Swan Coastal Plain they cleared most of the Swan Valley for agricultural purposes, thus destroying most of their natural habitat. The introduction of foxes and feral cats, which eat the tortoise, have caused a major decline in numbers. There are also native animals which eat the tortoise, including crows, goannas and birds of prey. And now a drying climate is adding to pressure on their population.
What does the Western Swamp Tortoise look like?
The Western Swamp Tortoise’s colour varies with age and the type of swamp it lives in. It can be yellow-brown or black on top (Carapace) and black, yellow or cream underneath (Plastron). The animals grow to around 15cm in length. Their legs are short and covered in scutes (similar to fish scales) and their feet are webbed, with large, well developed claws. They have a short neck covered in small bumps, called tubercles, and there is one big scale protecting the top of the head. They also have small growths under their chin called barbells. The only other tortoise that occurs in the Perth region is the Long Necked or Oblong Tortoise. It can easily be distinguished from the Western Swamp Tortoise by its very long neck, which is almost the same length as the shell.
What does the Western Swamp Tortoise get up to?
The Western Swamp Tortoise is carnivorous; feeding on things such as crustaceans, insects and their larvae. They only feed when the water temperature is between 14 and 28 degrees Celsius. There are records of the Western Swamp Tortoise living for over 60 years and still reproducing. The tortoise goes underground during summer and autumn to escape the intense summer heat and dehydration from the dry conditions in a process called aestivation. It comes out of aestivation and becomes active in winter when the swamps fill with water and remains active through to spring until it becomes too hot and dry again.
In November to early December it lays from 3 to 5 hard shelled eggs in a shallow under ground nest and they hatch the following winter.
What is being done to help the Western Swamp Tortoise?
There is a Recovery Plan and Program for the Western Swamp Tortoise coordinated by the WA Department of Environment and Conservation. A recovery team comprising representatives of the Department of Environment and Conservation, the University of WA, Perth Zoo, the Friends of the Western Swamp Tortoise and the World Wide Fund for Nature works to implement the recovery program. Perth Zoo has developed a highly successful captive breeding program. Juvenile tortoises bred at Perth Zoo have been reintroduced back to their natural habitat at Twin Swamps Nature Reserve over the past decade. More recently two new sites at Mogumber Nature Reserve and Moore River National Park have been trialed with some releases. The Mogumber site is thought to have suitable habitat for the Western Swamp Tortoise but the animal has never been known to naturally occur there. The Friends of Western Swamp Tortoise Group are helping with recovery of the tortoise, helping with rehabilitation of habitat and on ground works, and providing educational and promotional material and activities on the tortoise and recovery program. Anyone can join to learn more and help save this special reptile from extinction.
Further Reading: Not megafauna, but charismatic, by Alex Stone