|
Four threatened mammal species have been successfully re-introduced to the reserve to date. Re-introductions began in 1998 with the Greater Stick-nest Rat followed by the Burrowing Bettong in 1999, Greater Bilby in 2000 and the Western Barred Bandicoot in 2001. The first trial release of the Numbat was undertaken in November 2005 and the Woma Python in September 2007.
Greater Stick-nest Rat (Leporillus conditor)
The Greater Stick-nest Rat is a native rodent that was once widespread throughout arid and semi-arid Australia, before becoming extinct on the mainland in the 1930s. Its natural distribution is now limited to just two offshore islands in South Australia, but it has been successfully reintroduced to three other islands. The Greater Stick-nest Rat is now listed nationally as Vulnerable.
True to its name, the Greater Stick-nest Rat builds large nests out of sticks, usually in bushes or under rocky overhangs. Its diet consists of the leaves, seeds and stems of a variety of plants including saltbush and bullock bush, and it is known for its gentle and placid nature.
After a trial release in 1998, 100 Greater Stick-nest Rats were obtained from Reevesby Island, South Australia, in 1999 and reintroduced into the Main Exclosure of the Arid Recovery Reserve. Their characteristic stick nests quickly became prominent throughout the reserve, and they bred soon after release. This represents the first mainland population of this species in over half a century.
Long term population monitoring in the reserve has shown that rat densities are highest over winter, with a summer die-off attributable to high temperatures. However, the summer death rate has begun to decrease in recent years as the rat nests have become larger and more developed, and rats have begun to utilise bettong and bilby burrows which provide increased shelter from the summer heat.
Burrowing Bettong (Bettongia lesueur)
The Burrowing Bettong is the only member of the kangaroo family that lives in burrows. Like rabbits, bettongs dig extensive warren systems. The species is about the size of a rabbit and eats a variety of foods including insects, roots, tubers, green vegetation, fungi and seed.
Burrowing Bettongs, also known as Boodies, once occurred in most of arid southern Australia and on several offshore islands. Old warrens which are thought to have belonged to Burrowing Bettongs have been found inside the Arid Recovery Reserve. The species became extinct in mainland Australia in the 1940s and Burrowing Bettongs are now present naturally on only 3 off-shore islands in Western Australia. It is classified as a vulnerable species by both Australian and world standards.
In October 1999, ten Burrowing Bettongs were obtained with the assistance of the CSIRO from a reintroduced population at Herrisson Prong in Shark Bay, Western Australia. They were then released into the main exclosure of the Arid Recovery Reserve.
The success of this trial release led to the release of a further 20 animals in September 2000. These bettongs came from Bernier Island in Western Australia, and were transported by plane to Roxby Downs using funding provided by the Threatened Species Network.
The bettong population in the reserve has increased significantly in the reserve over recent years and is estimated to be more than 1000 individuals.
Greater Bilby (Macrotis lagotis)
The Greater Bilby is a large, burrowing, nocturnal bandicoot. It digs extensively for the seeds, bulbs and invertebrates that constitute its diet.
The Greater Bilby has declined since European settlement, and although still found in the arid interior of the Northern Territory, Western Australia and Queensland, the species has undergone a more than 80% reduction in its range, again due to a combination of increased predation by cats and foxes and degraded habitat caused by rabbits and stock.
In April 2000, nine Greater Bilbies were obtained from the South Australian Bilby Recovery Team Captive Breeding Facility at Monarto. Carefully selected to maximize genetic diversity, they were then released into the Main Exclosure of the Arid Recovery Reserve.
This reintroduction represents the first time bilbies have been present in the South Australian arid zone since their local extinction in the 1930s.
Greater Bilby abundance continues to fluctuate within the reserve in reponse to seasonal and local conditions. During droughts, bilby numbers decline significantly but they are able to breed quickly after rainfall events and recolonise areas within the Reserve.
Arid Recovery hopes to establish a viable population of bilbies on the outside of the reserve. So far two releases have been conducted. With ongoing predator control and predator avoidance training we hope to establish the first wild unconfined population of bilbies in SA since their extinction last century.
Western Barred Bandicoot (Perameles bougainville)
The Western Barred Bandicoot is the smallest of the bandicoots. Western Barred Bandicoot remains were found within the sub-fossil deposit near Roxby Downs, suggesting that they formerly occurred in the region.
The species is listed as endangered with less than 3000 remaining in the wild. Once widespread across arid southern Australia, it is now extinct in mainland Australia, found naturally only on Bernier and Dorre Islands in Western Australia.
In September 2000, eleven Western Barred Bandicoots were obtained from Bernier Island with the assistance of The Department of Environment and Conservation (DEC) in Western Australia. Funds for this project came from the Australian Geographic Society, and a huge fundraising campaign by Arid Recovery's local Friends Group.
This trial release represented the first reintroduction of Western Barred Bandicoots outside of Western Australia.
The bandicoots were held within the reserve for one month. During this time the bandicoots were radio-tracked regularly, and were found to use 48 nest sites. Nest sites were all located on dunes under leaf litter; and were found under a variety of plants including Umbrella Wattle, Hopbush, Bullock Bush, a grass clump (Paractenium sp.) and a tumble weed (Salsola kali). Nests were comprised of a 10 -15cm depression in the sand and were covered with a layer of up to 10cm of leaf litter.
Bandicoots now occur throughout the Main Exclosure and more recently in the Northern Expansion and First Expansion. The current population estimate is between 70-100 individuals.
Numbat (Myrmecobius fasciatus)
South Australian records reveal the numbat previously inhabited the Flinders Ranges and Everard Ranges and was recorded anecdotally from the western shores of Lake Torrens. The species has apparently been extinct in South Australia since the 1940’s. Numbats were trial released into Arid Recovery in 2005 making it the first arid reintroduction site in Australia. Following the trial release of five numbats, animals were monitored using radio-tracking technology. Although both females were carrying pouch young a few months later, native birds of prey preyed on three individuals within 5 months of release. Both of the surviving males were still alive after 18 months and one has survived for 3 years since its release.
The small sample size and mortality of female numbats means it is unclear whether numbats can survive at Arid Recovery. Another trial release of a larger sample size is required to determine the suitability of the reserve for a viable population of numbats.
Woma Python (Aspidites ramsayi)
Womas used to be a key native predator throughout much of outback Australia, but have now declined within much of their former range. Although the massive two and a half metre adults are a fair match for cats and foxes, it is believed that predation of juveniles and habitat degradation are responsible for their demise. Womas are a natural predator of reintroduced bilbies and possibly burrowing bettongs and their introduction to Arid Recovery is aimed at both assisting woma conservation and helping balance these bourgeoning mammal populations to enable ecosystem restoration.
Nine woma pythons were captive-bred by Zoos SA at Adelaide Zoo from parents sourced as close as possible to Roxby Downs. Radio transmitters were inserted into the abdomen of the snakes under anaesthetic which enabled the snakes to be monitored after release.
The reintroduction of 9 captive-bred sub-adult snakes in September 2007 was the first time a native predator had been reintroduced into the reserve. Unfortunately all of the woma pythons were killed and/or eaten by local native mulga snakes within a few months of release. This result was surprising and suggests that native faunal patterns and interactions prior to European settlement may have been more complicated that previously thought. Arid Recovery would like to trial a release of wild adult woma pythons in the future to determine if this trial failed due to the use of captive-bred naive snakes.
|
