Threatened Species - Tammar Wallaby
Introduction
Prior to the turn of the century there were two distinct sub-species of Tammar Wallabies inhabiting South Australia. Today, there is only one. Extensive habitat clearance for agricultural production and predation by Foxes has lead to the extinction of the "mainland" Tammar subspecies over its entire former range. The only remnants of this extinct population in Australia are two preserved specimens held at the South Australian Museum. A similar related subspecies of Tammar Wallaby has survived on Kangaroo Island, due to the large areas of suitable habitat and the absence of Foxes from the Island. These two subspecies have been separated for more than 10,000 years and have developed quite distinct forms. The Mainland South Australian Tammar Wallaby is currently listed as 'extinct in the wild' under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. Tammars are the smallest of the wallaby family, weighing in at only 5 kg to 7 kg. They have a dark grey-brown coat above, a pale buff grey coat beneath, with reddish arms, feet and flanks. Most individuals also display a faint white cheek stripe. Tammar Wallabies share a mode of lifestyle common to many of the smaller wallaby species. During the day they shelter among dense shrubby vegetation, to hide from predators (eg Wedge-tailed Eagles), and venture out into open grassy areas at night to feed. Across most of their current and former range, the wallabies inhabited dense coastal heaths and mallee thickets. Although each wallaby has a defined home range, these ranges overlap with those of other wallabies and aggressive encounters are few. Tammar Wallabies can live to 14 years of age, though this is a rare occurrence in the wild. The wallabies have an unusual breeding pattern with most young being born on virtually the same day. Their fertilized eggs lay dormant, inside the mother (embryonic diapause), until the summer solstice, when foetal development resumes and all young are born approximately 40 days later, in late January or early February. Tammar Wallabies are an important part of Aboriginal culture and feature in local Narungga stories. Rugs were made from wallaby skins and worn as cloaks. The Unique History of the Mainland Tammar WallabyBy the 1920s, Tammar Wallabies had become extinct from the South Australian mainland. The loss of Tammar Wallabies from the mainland can be attributed to a severe reduction in available habitat, to make way for agricultural production, and to Fox predation. However, a somewhat convoluted chain of events has given this "extinct" species a second chance at life.
Following a diverse career as Governor for the Colony of South Australia (1841), Governor of New Zealand (1845) and Governor of Cape Colony and High Commissioner for South Africa (1854), Sir George Grey was appointed for a second term as Governor of New Zealand in 1862. Upon his return to New Zealand, Grey purchased Kawau Island, near Auckland, for his personal residence. To remind him of his travels, Grey planted a vast array of exotic trees and shrubs and introduced many bird and animal species to the island from all over the world. Amongst his menagerie of species were Zebras, antelopes, kookaburras, Brush-tailed Rock-wallabies, Parma Wallabies, Swamp Wallabies and Tammar Wallabies. Many of the Australian species found on Kawau Island have adapted well to their new environment and have increased substantially in number, due to a lack of predation. These species are now considered pests and the New Zealand Department of Conservation has recommended the removal and eradication of all introduced wildlife from the Island, to favour animals that naturally occur in New Zealand. There are no records of where Governor Grey obtained his original stock of Tammar Wallabies. However, Dr Andrea Taylor and Dr Des Cooper (CRC for Marsupial Conservation and Management) were inspired by the morphometric studies of Dr Bill Poole (CSIRO) to undertake some ecological detective work to uncover the source of the wallabies. By comparing genetic material from the Kawau Island and Kangaroo Island populations they discovered that the Kawau wallabies were indeed from the South Australian mainland. This rediscovery of a species once considered to be extinct provided a unique opportunity to bring the wallabies back home. Reintroducing the Mainland Tammar WallabyThe recent re-discovery of the mainland Tammar Wallaby, prompted the Australian and South Australian Governments to develop a cooperative program to repatriate this unique Australian. Eighty-five Tammar Wallabies were successfully repatriated from New Zealand in 2003-2004 and were held in quarantine for twelve months at the Monarto Zoological Gardens, pending a full assessment of their state of health. Prior to the removal of any wallabies from Kawau Island, a comprehensive site selection process was undertaken to decide where the wallabies could be reintroduced. The factors included in this decision were: (i) habitat suitability (historic range, habitat quality,
size of habitat, presence of historic threats, ability to undertake threat management)
Out of all the sites in the state, Innes National Park was clearly the most suitable location. A detailed reintroduction proposal was developed. See Tammar Wallaby reintroduction proposal (1.8Mb PDF). Tammar Wallabies are considered by many to be an agricultural pest on Kangaroo Island. This perception arises because the wallabies are often seen at the edge of crops, because they are known to eat crops and because the wallabies exist in relatively high numbers on the island. However, the high densities of Tammars on Kangaroo Island are due to an absence of Foxes, so it is very unlikely that the wallabies released on Yorke Peninsula will ever reach densities to approximate those on Kangaroo Island, particularly outside of Innes National Park. Further, studies on Kangaroo Island indicate that adult wallabies consume as little as one tenth the quantity of food that sheep do (0.1 DSE), so they are unlikely to have any significant impact on farm income. Nevertheless, as part of the risk assessment process a population modelling exercise was undertaken to gauge the rate at which the tammar population could be expected to increase, once they had been reintroduced to Innes National Park. This study was based on demographic data collected from the Kangaroo Island population of wallabies, during a period of average environmental conditions. The results indicated that the reintroduced population would remain stable or undergo a slight decline over a 50-year period. The model predicted that to achieve any measurable degree of growth, the population would require active management to establish itself, eg predator control, the provision of supplemental feed. Because the Innes wallaby population is unlikely to undergo rapid growth to high densities and because Fox predation will limit the range of the population, it is unlikely that the wallabies will have any significant effect on agricultural production on southern Yorke Peninsula. Despite this, there is a considerable amount of long-term monitoring and follow-up activities associated with the reintroduction program. All released wallabies will be fitted with radio collars, so that their movements can be tracked. This research is being undertaken by the University of Adelaide and the Royal Zoological Society of South Australia. A population monitoring program is currently being developed, to enable the future size of the population to be estimated. If any unforeseen problems do arise from the reintroduction program, then Department for Environment and Heritage DEH will develop a specific management plan for the wallaby population. The disappearance of Tammar Wallabies from the Yorke Peninsula occurred shortly after the migration of Foxes into the area. Although adult Tammar Wallabies are at the upper limit of the Fox's preferred prey weight, Foxes have been documented to prey on mature wallabies. Young Tammar Wallabies will be particularly prone to predation. A critical component of the Recovery Program is to create a Fox-controlled (ie low Fox density) environment within the Innes National Park release site. An extensive Fox control program began on the park in November 2003, building on previous programs. See Tammar Wallaby reintroduction proposal (1.8Mb PDF).
Early Results of Release to Innes National ParkA trial release of ten radio-collared Tammar Wallabies (two male, eight female) took place at Innes National Park in November 2004. All ten wallabies survived for the first three months and remained less than 1 km from their release locations. Research being undertaken by University of Adelaide PhD student, Leah Kemp, will provide valuable information on the animal's movements and social behaviour.
In February 2005, four of the Tammar Wallabies were found dead (their fitted radio-collars had switched to mortality mode). Post mortems performed at Monarto Zoo confirmed that the deaths were the result of Fox predation. The already considerable Fox control efforts were temporarily intensified and no further predation events occurred. The remaining Tammar Wallabies were trapped for a health assessment in late February 2005. All animals were in good condition, and one of the three females trapped had a small pouch young. In April 2005, one female tammar (with pouch young) was killed when it was hit by a car on the main road. Further road signage has been placed on the park, to reinforce the 40 km/hr speed limit. In May 2005, one male wallaby died from unknown causes. To date, four wallabies remain alive from the first release attempt. Three of the four animals have successfully bred at Innes and these young are now independent. Trapping in March 2006 revealed more tiny young in pouches. In June 2005, a further 36 radio-collared Tammar Wallabies were released at Innes National Park (six adult males, six juvenile males, 24 adult females). By the end of August 2005, 18 of the wallabies had died (seven juveniles, eleven adults). The results of the autopsies indicated that the wallabies were emaciated, probably due to the stress of being released into unfamiliar surroundings, with unfamiliar food. Because the autopsied wallabies had no fat reserves, it is probable that they were unable to cope with the sudden onset of cold and wet weather that occurred at Innes during the period immediately prior to the deaths. Given these unforseen losses, supplementary feed was provided as a temporary measure, to boost the condition of the remaining wallabies and help them better survive until the warmer weather arrived. The remaining wallabies were trapped for a health assessment in December 2005 and March 2006. All animals were in excellent condition and two animals had pouch young. By the end of April 2006, five of the 36 wallabies from the 2nd release remain (three male, two female). The inability to find 15 of the wallaby carcasses, plus the results of the autopsies, indicates that Fox predation/scavenging had occurred on 72% of wallabies.The Tammar Wallabies will continue to be monitored closely. Future releases will be undertaken in spring, when sufficient food is still present, but when the weather is milder.
A third release is planned for spring 2006. The current population (excluding pouch young) represents 26% of the number released. While this statistic does not represent an increasing population size, it is significant in that these animals have now clearly developed survival skills for the Innes National Park environment and form the nucleus from which the local population can now expand. All animals remain very close to their release locations. A report was prepared in March 2006 to document the progress of the tammars at Innes National Park, some 16 and nine months after their release. See Tammar Wallaby Progress Report March 2006 (2.8Mb PDF). The Tammar Wallaby reintroduction proposal was reviewed in May and November 2005, after a planned six and twelve month period following the release of animals to Innes National Park. The review highlighted minor deviations from the original Tammar Wallaby reintroduction proposal. See Translocation Proposal Review Report (50Kb PDF). Captive Breeding Program
The Tammar Wallaby Reintroduction Program proposes to release wallabies at, a minimum of two sites on mainland South Australia, with Innes National Park being the first. To successfully achieve this goal, a substantially larger number of wallabies are required for release in the wild than can be realistically trapped and removed from Kawau Island. A captive breeding program has been established at Monarto Zoological Gardens to increase the number of wallabies that will be available for future releases. Overseen by Monarto's Curator Peter Clark, this program utilises a variety of husbandry techniques to increase wallaby numbers, while monitoring and maintaining the genetic diversity of the population. One of these techniques is cross-fostering. This technique has been used on a variety of endangered macropod species and utilises the unique ability of macropods to initiate the development of a second foetus, if their first pouch young is lost. In the case of Tammar Wallabies, this procedure entails the careful removal of small pouch young from the captive bred mainland Tammar mothers and the placement of these young into the pouches of Kangaroo Island Tammars. The removal of the pouch young from the mainland Tammar Wallabies initiates the development a second embryo, which the birth mothers would continue to raise. In essence, the Kangaroo Island Tammars are raising the young of the mainland Tammars, at the same time that the mainland Tammars are raising their second batch of young. This process will halve the amount of time needed to increase the captive population of mainland Tammars and ensure that sufficient numbers exist to maintain a viable population. Interesting FactsTammar Wallabies were the first macropod species to be sighted by European explorers. In 1629, Francisco Pelsaert, captain of the Batavia, was shipwrecked on Abrolhos Island (WA) where he observed the wallabies and noted that they resembled "hopping cats". Tammar Wallabies take their name from the tamma (sheoak) thickets that they often inhabit in Western Australia. In arid areas, where fresh water is often scarce, Tammar Wallabies have been observed to survive on seawater. Frequently Asked QuestionsIf Tammar Wallabies are pests on Kangaroo Island, will they also become a pest on the Yorke Peninsula?
The Kangaroo Island Tammar Wallabies exist at high densities because of agricultural development on the island. The clearing of bushland for farming has increased the amount of the wallaby's preferred habitat, ie the "edge" habitat between dense woodland and open grasslands (crops). As a result, the wallaby population has increased substantially. However, this increase in wallaby abundance has only been possible because predators are absent from Kangaroo Island. Tammar Wallabies are particularly susceptible to predators and it is highly likely that the Kangaroo Island wallabies would also be extinct today, if Foxes had established themselves on Kangaroo Island. The presence of Foxes and feral cats across the entire Yorke Peninsula means that Tammar Wallabies are unlikely to establish themselves in large numbers outside the reintroduction site on Innes National Park. How will you know where the wallabies are after they have been released?All of the wallabies released between 2004-2006 will be fitted with radio-collars. These radio-collars allow the position of the wallabies to be determined at any time. This is made possible through a system of tracking stations established at Innes National Park. What will happen if the Tammar Wallabies do move into agricultural lands and become a pest?The presence of Foxes across the Yorke Peninsula is likely to keep wallaby abundance at very low levels outside of the Innes reintroduction site. However, the Department for Environment and Heritage (DEH) is implementing a monitoring program to keep track of wallaby abundance both on and off Innes National Park. If the wallabies do establish themselves outside the park, then DEH will conduct an evaluation of the losses to agricultural production and, if these losses are substantial, then DEH will support the active management of the wallaby population. See Tammar Wallaby reintroduction proposal (1.8Mb PDF) Apart from restoring an integral component of the Yorke Peninsula's ecology, what other benefits will arise from the reintroduction of Tammar Wallabies?Today, the ecotourism sector is one of the fastest growing components of the Australian economy. Many tourists travel to Australia to experience our landscape's natural beauty and to view our unique native wildlife. Many rural communities, suffering from falling commodity prices and slowing dwindling populations, have turned to ecotourism to booster their local economies. With its beautiful coast line and large areas of undisturbed bushland within easy travel from Adelaide, the Yorke Peninsula has the potential to tap into the tourism market. The reintroduction of the Tammar Wallaby represents both the return of one of the Yorke Peninsula's significant biodiversity assets and an additional attraction for tourists. An increase in the tourist market will result in an increased level of investment in the local area and the development of new jobs within the community. Opportunities for InvolvementThe Department for Environment and Heritage runs a number of monitoring programs associated with the tammar re-introduction. There are limited opportunities for volunteers with relevant experience to assist with Tammar trapping surveys, Kangaroo spotlight surveys and vegetation surveys. To register your interest or for further information, please contact DEH Project Officer, Julia Bignall on (61 8) 8854 3204 or email: bignall.julia@saugov.sa.gov.au Leah Kemp, a PhD student from the University of Adelaide is researching the establishment of the re-introduced Tammar Wallaby at Innes National Park. Leah is radio-tracking the wallabies every month until June 2006. Opportunities exist for volunteers to assist with the tracking of wallaby movements from fixed radio tower locations. The majority of field work is conducted at night time (from before dusk until dawn). To register your interest, please contact Leah Kemp from the University of Adelaide on mobile telephone 0418 551 440 or email: leah.kemp@adelaide.edu.au See Tammar Wallaby Radio-tracking Volunteer Information Sheet (100Kb PDF). Project ContributorsThe Tammar Wallaby Recovery Program is a collaborative effort being undertaken by the Australian Government Department of Environment and Heritage, the South Australian Department for Environment and Heritage, the University of Adelaide, Royal Zoological Society of South Australia and the Conservation Volunteers Australia (CVA). |
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