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Keeping yellow-footed rock wallabies on the rocks: integrating in- and ex-situ conservation in Australia and North America. (Conservation Spotlight).


The most successful species recovery programs incorporate many components; the work being done with yellow-footed rock wallabies (Petrogale xanthopus xanthopus) involves three of the most important ones: collaboration, conservation, and community involvement. Active captive conservation work is occurring with both the North American and Australian populations. The American Zoo and Aquarium Association is collaborating with the Australian Regional Association of Zoological Parks Aquaria and Environment Australia to import new founder stock needed to genetically revitalize the North American population. In-situ conservation work has involved habitat reclamation and reintroduction projects. In an additional collaborative venture, some of the same methodology used in the reintroduction project is being applied to work with tree kangaroos in Papua New Guinea. The value of community involvement was shown to be essential in the success of these projects.


In the late 1840s, the yellow-footed rock wallaby (YFRW) (Petrogale xanthopus xanthopus) was first noted by European naturalist Frederick Strange in the Flinders Ranges of South Australia, near what is now Aroona Dam (Copley 1983). The YFRW was an important resource for the Australian Aborigines. The meat was eaten, pelts were used for clothing, and sinew was used for sewing or making nets. Although all tribe members could hunt them, only initiated men could butcher and distribute the meat. After tribal initiations ceased in the 1940s, it is doubtful that YFRWs continued to be used by the Aborigines (Sharp 1994).

Native only to Australia, YFRWs inhabit rocky outcroppings in semiarid and add landscapes, using the deep caves and fissures as shelter from climate extremes and predators. It is believed their ancestors formed a continuous population from central South Australia into Queensland and on into the Great Dividing Range (Strahan 1995). The current population, although locally common in some areas of its range, is severely fragmented due to the initial over-hunting by Europeans, habitat destruction, predation by introduced foxes and cats, and resource competition from domestic sheep and goats. This fragmentation prohibits the natural dispersal of animals that helped maintain genetic diversity in their colonies.

Current population estimates range from a minimum of 5,000 (S. Lapidge personal communication) to a maximum of 10,000. However, this maximum count includes the closely-related Queensland subspecies, Petrogale xanthopus celerius (Sharp 1994) (#6 on Figure 1). The largest populations of Petrogale x. xanthopus are in the Flinders Ranges, South Australia (SA) with smaller colonies found in the Gawler Ranges, Olary Hills and Carriewerloo of SA (Figure 1). The two extant colonies in New South Wales (NSW) have less than 150 individuals (P. Christie personal communication).

The World Conservation Union (IUCN) (Baillie and Groombridge, 1996) lists the YFRW as Vulnerable; the U. S. Fish and Wildlife Service (USFWS), the only country to list nonnative species, lists it as Endangered; and the NSW population is listed as Endangered under the NSW Threatened Species Conservation Act of 1995. Recently, the Australasian Regional Association of Zoological Parks and Aquaria's (ARAZPA's) Australian Species Management Plan (ASMP) raised the species from a Category 3 (a medium level of regional management) to a Category 1 (a high level of regional management with the captive population managed as part of a wildlife agency species recovery program). At the same time, the American Zoo and Aquarium Association's Marsupial and Monotreme Taxon Advisory Group (AZA M & M TAG) recommended in its Regional Collection Plan (RCP) that the YFRW become a Species Survival Plan (SSP) species (AZA M & M TAG 2000). These separate actions indicate the importance of captive YFRW populations both in its native land and in North America.


In addition to conservation efforts in the wild, one of the goals of YFRW captive management in Australia has been to export surplus captive animals to North America to help establish and maintain a genetically stable population. The current captive North American population has less than twenty animals, with only one male capable of reproduction. One of Environment Australia's (EA) requirements prior to export was that a North American stud-book and a species management program be in place. The first edition of this studbook has been published by the author, and the species has been given SSP stares, with Jeff Holland from the Los Angeles Zoo recently being approved by the AZA M & M TAG as the SSP coordinator.

At the March 2001 Species Summit meeting of the ARAZPA, EA and AZA, one of the priority species was the YFRW. Much time was spent on discussions of cooperative exports/imports and the Australian requirements for institution approval. Currently, the Los Angeles Zoo is coordinating with ARAZPA and EA to complete the first step toward a self-sustaining North American population- the import of new genetic stock. It is estimated that importation of two breeding pairs (four founders, or animals unrelated to the current population) at six-year intervals could result in 90% gene diversity in the North American population (Lynch 2001).

Challenges of captive breeding

The same problems plague both the Australian and the North American captive breeding programs. The first is accurate determination of sires. Often several males are kept in captive colonies and, although the dominant male might indeed sire most of the offspring, it is not a certainty. Institutions that keep one male per female group often cannot determine sires when males are exchanged due to the reproductive adaptation of embryonic diapause. Since the cost of DNA analysis is prohibitive for many zoos, accurate record keeping has become a top priority for institutions wishing to house YFRWs. To enable genetic management, both the Australian and the North American studbook keepers have created analytic studbooks where hypothetical parents are created for the unknowns.

Second, the primary management challenge with YFRWs is surplus males. As male-male aggression is common, even if females are not present, the solution to create bachelor groups is generally unsuccessful. Therefore, pouch management, in the form of euthanasia of excess males, might become a husbandry requirement for a properly managed population. This is a controversial subject that may not be supported by all interested institutions.

Although one of the purposes of the Australian captive population is breeding for possible reintroductions, this is not the case with the North American captive population. Concerns over conspecific quarantine and possible introduction of disease make entry into Australia from captive North American collections highly unlikely. Thus, reintroduction is not a top priority for inclusion of the species in the TAG Regional Collection Plan. Instead, it is a flagship rock wallaby species, selected for its educational value in teaching habitat fragmentation, introduced species and adaptations, and for its collaborative in-situ conservation and ex-situ research possibilities.

In-situ conservation

Adrienne Miller, North American Studbook Keeper for the YFRW, participated in two in-situ projects as a volunteer field assistant. The first was a recovery program that focused on the impact of introduced species and involved the endangered population of New South Wales (Figure 1). Phase I of this project took place from 1980 to 1995 and involved the removal of over 42,000 goats from the Gap and Coturaundee Ranges to decrease the level of resource competition between the two species (Sharp 1999). Phase 2 began in 1995, testing the hypothesis that fox predation was the major factor negatively impacting YFRW population growth. The Coturaundee Range was baited with 1080 (sodium fluoro-acetate) to eliminate the predatory fox while the Gap Range was not (Sharp 1998). Fecal pellet counts were used as a means to monitor the rock wallaby population at both sites. The results of this project strongly indicated a negative impact of foxes on the wallaby population. Both sites are now baited and the YFRW population appears to be growing on both (P. Christie personal communication).

The second was a reintroduction project at Aroona Dam, Leigh Creek, in the Flinders Ranges of South Australia, the site where it is believed the first European sightings occurred, but where YFRWs have not been seen in over ten years. During the 1994 National Rock Wallaby Symposium, the Adelaide Zoo received unanimous support for a trial release of YFRW. The Aroona Dam site was selected because land use was stable as it had been dedicated as a sanctuary in 1995. Elimination of introduced animals (i.e. fox, cat, and goat) had already begun. A buffer zone of ten kilometers was created around the sanctuary with the assistance of local pastoralists.

The release of 2.7 captive animals from Monarto Zoological Park occurred on September 16, 1996. Steven Lapidge (1997) began a dietary study on the adaptation of the captive animals to their wild diet. The results indicated a smooth change to eating a wider variety of natural foods, which is valuable for future marsupial reintroductions.

In January 1998, Steven Lapidge also began monitoring of the reintroduced colony. The goals were to (1) identify the most successful methods of reintroducing captive-bred rock wallabies; (2) determine how individuals and the colony as a whole adjust once released; and (3) examine the effect of environmental variables and sympatric species on the establishment, ecology, and physiology of the YFRW. Quarterly trapping trips assessed the general health of the reintroduced population and their reproductive status. There are now second-generation wild YFRWs thriving at Aroona Dam. This reintroduction can serve as a model for other rock wallaby reintroductions.

The success of this venture was based not only on the health and reproduction of the wallabies, but also on community support as well. Leigh Creek took the wallaby reintroduction on as its own. Students were involved with radio-tracking, compiling issues of Rock Wallaby News, producing a model of the sanctuary, and inventing the "Wallaby Hop" for a school dance. The landowners around the sanctuary baited for fox and feral cats, and area residents baited the wallaby traps throughout the year, resulting in significantly higher success rates during trapping trips.



Due to the success of the YFRW reintroduction, the same methodology is being applied to tree kangaroos in Papua New Guinea where Steven Lapidge is collaborating with Dr. Lisa Dabek, Director of the Tree Kangaroo Conservation Program operating through the AZA Tree Kangaroo SSP.

The future looks bright for the yellow-footed rock wallaby. The captive population is sustained by collaborations between Australian and North American species managers, and the wild population is sustained by feral animal control, possible future reintroductions, and other in situ conservation efforts. On the rocks? Only if they want to be.


I would like to thank Andy Sharp, University of Queensland/NSW NPWS; Suzy Barlow, Western Plains Zoo; and Steven Lapidge, University of Sydney, for their guidance, encouragement, and willingness to share their knowledge and experience with a rock wallaby enthusiast from across the ocean.

Literature cited

AZA M & M TAG. 2000. Marsupial and Monotreme Regional Collection Plan 2000-2003. Silver Spring, MD.

Baillie, J. and B. Groombridge, eds. 1996. IUCN red list of threatened animals. IUCN, Gland, Switzerland.

Copley, P.B. 1983. Studies on the yellow-footed rock wallaby distribution in South Australia. Australian Wildlife Research 10:47-61.

Lapidge, S. 1997. A dietary study on reintroduced yellow-footed rock wallabies in the northern Flinders Ranges, South Australia (Honors Thesis). Flinders University of South Australia, School of Biological Sciences.

Lim, L., N. Sheppard, P. Smith, and J. Smith. 1992. The biology and management of the yellow-footed rock wallaby (Petrogale xanthopus) in NSW. NSW National Parks and Wildlife Service, Hurstville, NSW, Australia.

Lynch, C. 2001. Management recommendations for the Marsupial & Monotreme Taxon Advisory Group. AZA Population Management Center, Lincoln Park Zoo, Chicago.

Sharp, A. 1994. Yellow-footed rock weasels? Wildlife Australia Spring: 4-7.

Sharp, A. 1998. Yellow-footed rock wallaby recovery program: briefing notes for Adrienne Miller, Roger Williams Park Zoo, Providence, RI, USA. NPWS District Office, Broken Hill, NSW, Australia.

Sharp, A. 1999. The NSW yellow-footed rock wallaby recovery program: I. Background and history of the project. Unpublished report to the New South Wales National Parks and Wildlife Service, Sydney, Australia.

Strahan, R. 1995. Mammals of Australia. Reed Books, Chatswood, New South Wales.

Adrienne Miller North American Yellow-footed Rock Wallaby Studbook Keeper, M & M TAG Studbook Advisor, Collection Manager, Roger Williams Park Zoo, 1000 Elmwood Avenue, Providence, RI 02907; (401) 785-3510 x310;(401) 941-3988 (fax);
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Author:Miller, Adrienne
Publication:Endangered Species Update
Date:Sep 1, 2001
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