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50 Years Monitoring Tortoise

A large group of friends and supporters of the Western Swamp Tortoise gathered at the Ellen Brook Nature Reserve – home to one of the last wild populations of the critically endangered reptile – to celebrate 50 years of scientific monitoring of this species. On the 2nd of October 1963, then Bachelor of Science Honours student Andrew Burbidge, marked and released female Number 4, an adult estimated to be 15 years old. Fifty years to the day, radio-tracked by current Western Swamp Tortoise scientist Gerald Kuchling and accompanied by the Minister for the Environment, Albert Jacobs, Dr Burbidge once again held Number 4, now 65 years old.

The occasion was a fitting tribute to the work done by many people who were there to support the Western Swamp Tortoise. Introduced by the Head of the Western Swamp Tortoise Recovery Team, Craig Olejnik, Minister Albert Jacobs categorised the rediscovery of the supposedly extinct animal as ‘a fairy tale’. Dr Andrew Burbidge then spoke, detailing the difficulty of finding the tortoises in the wetlands during his doctoral research, and the work needed to try to adapt the 1960s radio transmitters, all of which had been designed for larger animals. He quickly identified the need to build very small transmitters which would transmit for at least 6 months, would not drown a tortoise with their weight and that worked both underwater and on land. Luckily, silicon transistors, which would work underwater, were just coming onto the market to replace germanium transistors—which would not.

By the late 1970s it became apparent that the tortoises were declining rapidly in the wild, in part because of predation by foxes. To make matters worse, the small captive colony at Perth Zoo was not breeding. Andrew attempted to breed some tortoises and discovered the incubated eggs needed cooling to trigger hatching. This mimics the situation in the wild, where hatching coincides with the first rains of winter running into the places underground where the tortoises have nested and then aestivated over summer.

When Austrian scientist Gerald Kuchling arrived in Perth in 1987, with a wealth of knowledge on threatened freshwater turtles and captive breeding, the recovery of the Western Swamp Tortoise moved forward another step.

Gerald’s work has focussed on getting the diet and conditions right for breeding in captivity, as well as monitoring the species in the wild. Due to his exemplary work, the Perth Zoo has been able to produce 20 – 30 hatchlings each year for eventual release to the wild. In his pioneering work, Gerald has also studied optimal conditions for tortoises in the wild and is currently advising a new crop of scientists studying the physiology of the animals and the hydrology of the swamps with a view to translocating our precious animals to areas less affected by climate change.

Another key person in the recovery of the Western Swamp Tortoise was also present for the anniversary: Mr WR Martyn, who generously donated the land on which stands the crucial nature reserves containing the last wild tortoises.

With the dedicated band of scientists and conservationists currently involved with the Western Swamp Tortoise, its future looks increasingly brighter.

50th anniversary of monitoring the tortoise

On October 2, 2013 a large group of supporters of the Western Swamp Tortoise gathered at Ellen Brook Nature Reserve to celebrate 50 years of scientific monitoring of the species. It was on October 2, 1963 that a BSc Honours student, Andrew Burbidge, marked and released female Number 4, then an adult estimated to be around 15 years old.

The WA Environment Minister, Albert Jacobs was in attendance, along with media representatives. Coverage of the event was aired on Channel 10 News that night - see the following link to the item.

http://tenplay.com.au/news/perth/2013/10/2/tortoise-trackers

There will be more posted on this event very soon, including pictures in the Photo Gallery.

Winter 2013 planting at Ellen Brook NR

The Friends (and friends of Friends!) recently planted around 1300 tube-stock of various species on bare land previously infested with weeds, near the western gate of Ellen Brook Nature Reserve. Check out the photo galleries for pictures! The campaign happened in two stages in June and July 2013 and also included removing plastic guards from maturing plants from previous years’ plantings. The melaleuca shrubs and other vegetation will provide cover for the tortoises, protecting them from the attention of birds like ibis, ravens and raptors. It will also encourage invertebrates that will ultimately result in more aquatic food for the tortoises.

Water levels are depressingly low in the reserve due to less-than-average rainfall this winter, so everything we can do to enhance the site will make a difference to the resident tortoises’ survival rate.

On the final day’s planting, the workers enjoyed a barbeque lunch on site, courtesy of Dept of Parks & Wildlife - and a feeling of a job well done!

Talk at WA Naturalists' Club

UWA PhD candidate Sophie Arnall came to speak about her research on assisted colonisation of the Western Swamp Tortoise, at the Darling Range Branch of the WA Naturalists' Club in April 2013. Below is a summary of her excellent and informative presentation. See 'Links' page for more information on her project.

Assisted colonisation of the western swamp tortoise

What should we do when a critically endangered animal faces the likelihood that its only habitat will soon be made untenable by climate change? Do we move it to a new location, where it hasn’t previously been found? Is such an action practical or ethical? It is to help answer these questions that UWA PhD candidate Sophie Arnall has been engaged on some groundbreaking research, with the Western Swamp Tortoise as her subject.

The most endangered reptile in Australia and one of the most endangered chelonians in the world, the Western Swamp Tortoise has been around since the Miocene, when most of Australia was under rainforest. This tiny freshwater tortoise (only 15 cm long) is sometimes called ‘the smiling tortoise’ because of its cheery upturned mouth. Discovered in 1839, it was only described in 1901 and was then presumed extinct until 1953. This all changed when keen schoolboy naturalist Robert Boyd presented two of them—which his cousin had found crossing a road in Bullsbrook—for inspection at the annual Wildlife Show held in Perth Town Hall. WA Naturalists’ Club (Darling Range Branch) member Eric McCrum remembers it well and tells us that Harry Butler was also present.

Since that fateful day, the tortoise has been studied by various scientists, including Gerald Kuchling and Andrew Burbidge. Andrew’s thesis established that the tortoise’s biorhythms are closely linked to our climate, with the wet winter-spring period spent feeding in shallow ephemeral swamps (the hydro-period) and the hot, dry summer-autumn in a semi-torpid state (aestivation) nestled in cracks in the dried wetland clay or under deep leaf litter. They await the rains before emerging; the eggs laid in late spring only hatch at this time, too. Then it’s time to feed up – the adults for breeding and the hatchlings to reach the crucial weight of 18g, below which they will not survive their first summer. Strangely, captive animals offered year-round water and food will not breed well, so these tortoises really do depend on the right wet-dry cycle to survive and thrive!

Now that the changes in the climate of south-western Australia threaten the life-cycle of this small yet charismatic animal, more innovative research and ideas are needed to prevent it from slipping into extinction. There are only 150-200 animals in the wild in a few locations near Perth and less than 50 of those are breeding adults. Perth Zoo holds a colony and has bred more than 700; juveniles are released to monitored reserves most years. However in years like 2010, released animals had to be returned to the zoo because climatic conditions were so poor.

What makes this animal a good candidate for assisted colonisation (the human movement of at-risk species into areas that are predicted to be climatically suitable long term)? The answer lies in its restricted range, special habitat requirements, inability to migrate unassisted, low fecundity and low current population, as well as a source of captive animals. We also have 30 years of data on the animal in the wild and in captivity—including data that shows it survives well at new sites.

How do we select sites for colonisation? With such a restricted range, one can’t use empirical modelling to infer its requirements. Mechanistic models appear to be the only way to proceed, since they can predict a species’ response to an environment, via its physiology and behaviour. Sophie’s research has therefore focussed on the tortoise’s gut, thermal and metabolic physiology and has led to a ‘thermal response curve’ for this animal. The data was then applied to the question: where could we put the tortoise?

Now other researchers came into the picture and ‘Project SWAMPI’ —a collaboration between universities, zoos and government departments around the country and internationally—really geared up. A preliminary hydrology model was developed that made predictions which fell close to actual data. A model called NicheMapper™ was used to run a behavioural routine that Sophie developed based on her physiological data and this predicted in general terms where the tortoise might live in the south-west. An approach called Dynamic Energy Budgeting (DEB) was used to predict the tortoise’s survival and reproduction, with a 96% fit to actual data. Much useful information has been gained from the model. For instance it predicts a tortoise at normal weight could fast in aestivation for 588 days and that the average lifespan of a Western Swamp Tortoise is 90 years. The latter was obviously not known because no one has been studying them for that long! Although the models are only in a preliminary stage, another, more frightening, prediction is that if the hydro-period in their habitat is shortened by any more than one month, small hatchling tortoises will not survive and that particular population may eventually die out.

This is the first time that anyone has explicitly modelled for assisted colonisation—an idea which was considered purely theoretical as recently as the late 80s. It is hoped that this work will not only help save the Western Swamp Tortoise but be a template for other species, particularly those in wetlands, such as the Sunset Frog (Spicospina flammocaerulea). Meantime the project is about 6 months from pinpointing possible colonisation sites, though areas around Donnybrook, Busselton and Augusta are being considered.

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