Project Leaders: Nicola Mitchell
Why is the research needed?
The western swamp turtle is a Critically Endangered reptile endemic to Western Australia, and is facing mounting pressure from climate change.
Only an estimated 50 mature individuals remain in two small isolated wetland reserves about 30km north of Perth. Surrounding land use and climate change have marginalised the habitat – by a 17% reduction in winter rainfall since the 1970s and hotter summer conditions.
Western swamp turtles are habitat specialists and rely on the presence of winter-wet ephemeral swamps that are wet for 5-7 months to allow the turtle to feed, grow and reproduce before aestivating over summer while the swamps are dry. Recent consecutive years with wet periods as short as three months limit the turtles’ capacity for reproduction and survival over summer dormancy.
Some of the species’ current habitat is intensively managed by improving water retention in swamps through bunding, lining refuge ponds with plastic and pumping groundwater to ensure adequate water during years of low rainfall. In addition, scientists from the WA Department of Biodiversity, Conservation and Attractions (DBCA) have been trans- locating individuals bred at the Perth Zoo to nearby nature reserves to try to establish new wild populations close to the natural populations.
With the current habitat likely to be altered under future climate change, assisted colonisation is an additional strategy that can be used to help conserve this species in the wild: first, due to the clearance of surrounding wetlands, turtles cannot disperse naturally to more suitable habitat; second, low rates of reproduction and long generation times (15–30+ years) minimise the potential for the western swamp turtle to rapidly adapt to a drier and warmer climate.
A western swamp turtle after release. Photo: Nicolas Rakotopare
How will the research help?
What happens when your efforts to save one threatened species creates a new problem involving another species of conservation concern. Suddenly you’re faced with some difficult choices. Helena Bowler at the University of Western Australia explains here the unexpected complication that arose when fencing was put up to save endangered turtles from foxes.
The western swamp tortoise has all the ingredients of a fairy tale. It’s the Goldilocks of tortoises needing water that isn’t too hot but isn’t too cold to survive. It’s the Rip Van Winkle of reptiles in that it seemed to vanish from sight for over 100 years during which time it was thought extinct – but then it was rediscovered. And it’s the Houdini of endangered wildlife in that it came close to oblivion in the 1980s with numbers fewer than 50 but, thanks to concerted efforts at recovery, it escaped extinction and there are over ten times that number now.
Twenty-four western swamp tortoises hit the headlines last month as they settled in to new homes in swamps south of Perth. The tortoises were moved to a new range in an attempt to protect the species from the effects of climate change and their story featured in several news outlets including the ABC, Science magazine, the Guardian and Australian Geographic
Western swamp tortoises have been translocated to a reserve south of their historic range in an attempt to negate the likely impact of climate change. It is the first time in Australia that a vertebrate species has been translocated in anticipation of climate change..