National Recovery Plan for the Brush-tailed Rock-wallaby

Appendix 1. Detail of Recovery Actions

An assessment of threats acting on sub-populations across the Central and Northern ESUs, and current management responses to those threats, will be undertaken to allow prioritisation of management needs, including outlying populations on the inland side of the species range. This information will be used to select sub-populations with the greatest potential to respond to management and to provide the greatest benefit to the conservation of the species.

Although several likely threatening processes have been documented in management plans for the Brush-tailed Rock-wallaby, they are mostly based on conjecture, and evidence of their actual impact on populations is scant. If management actions can be designed to include hypothesis testing, via comparisons between different treatments and careful monitoring of outcomes, the relative importance of different threatening processes could be clarified. This information can then inform future recovery plans and priorities. An adaptive experimental management approach to management of Brush-tailed Rock-wallaby populations and their habitat will be used, so that the relative significance of different threats can be elucidated.

Although there is some predation on the Brush-tailed Rock-wallaby from native predators, the added predation pressure imposed by introduced predators is recognised as a key threatening process (Hill 1991; ACT 1999; Waldegrave-Knight & Henry 2003; DECC 2008). Feral predator control has been used as a tool for many years to conserve threatened species and populations across several states, and there is a considerable body of experience from a range of control programs. There is a need to review the range of predator control strategies used by state agencies, especially broad-scale versus intensive localised baiting, to determine the most efficient and effective methods for sustained control of feral predators. The range of control strategies, such as broad-scale baiting used in East Gippsland (Waldegrave-Knight & Stevens 2003) will be reviewed, and a recommended program aimed specifically at assisting the recovery of the Brush-tailed Rock-wallaby will be developed.

Using the results of Action 2.1, and adopting an adaptive experimental management approach, feral predator control programs aimed at reducing Red Fox, wild Dog and feral Cat numbers will be implemented at key sites across the range of the Brush-tailed Rock-wallaby. The aim of these programs will be to reduce predation to levels that do not significantly constrain population growth or dispersal between colonies, and that will allow colonies to expand to include refuge habitat that was unsuitable in the presence of introduced predators. Care will be necessary to ensure that predator baiting programs do not adversely affect populations of non-target species, particularly the Spotted-tailed Quoll. A potentially detrimental affect of wild Dog/Dingo control is the possible subsequent increase in numbers of Red Fox and Cat (through reduction of Dog/Dingo numbers), and this will require close monitoring of the results, and an adaptive approach by the land managers.

The effectiveness of control programs in reducing fox and wild Dog numbers will be monitored. There is also evidence from Western Australia that the numbers of feral Cats can increase following fox control programs and that Cat predation can constrain population growth rates of the Brush-tailed Rock-wallaby (Short et al. 1992). Therefore, there is a need to monitor changes in Cat populations in areas where fox and Dog baiting is occurring, with a view to undertaking Cat control if required. Monitoring of rock-wallaby numbers will occur under Objective 3.

Competitor control programs at key sites will be maintained or initiated where competition is deemed to be a threat.

Building on Action 2.2, appropriate community groups and individuals will be engaged to provide a broader, more robust, community-wide support base for predator control programs on freehold land around key rock-wallaby sites.

Determining the presence of the Brush-tailed Rock-wallaby at a given site can be difficult, so there is a need for guidelines that define survey methods and effort required to be reasonably confident that the search outcomes reflect reality. Standardised survey techniques will be developed for application across the species’ range, and guidelines will also be set for defining the process of reporting and curating survey results.

Using the guidelines developed under Action 2.1, comprehensive surveys of Brush-tailed Rock-wallaby distribution in each ESU will be planned and undertaken, with the highest priority being the Northern ESU as that is where information is most lacking.

A predictive model of the distribution of colonies in each ESU will be developed, using GIS topographic and vegetation layers, combined with known Brush-tailed Rock-wallaby sites and habitat characteristics. This information will be especially useful for detecting isolated populations that may warrant extra conservation attention and for identifying priority areas for conservation management.

Several different methods for estimating the size of Brush-tailed Rock-wallaby colonies have been trialled, including trapping grids, scat counts and spotlight transects and faecal DNA analyses. Faecal DNA analysis can complement information gained from other monitoring methods for rare species, by providing data on sex ratios, the reproductive success of individuals and information on movement. While it is likely that the most effective technique will vary according to site conditions and resources available, monitoring guidelines and standards will be developed to ensure the accuracy and value of data, and that the information is comparable across sites and over time.

Monitoring of Brush-tailed Rock-wallaby populations, especially following predator control/habitat management activities is necessary to understand the response of the species to management intervention and determine ongoing requirements to manage the species. A strategic subset of colonies will be selected for monitoring of population trends. These will include colonies subjected to active management, as well as colonies not receiving active management, to help assess the effectiveness of that management. Monitoring will be undertaken at least annually at all key sites for the species and expanded where possible to cover the full distribution of the species, to determine overall population and species trends. The results of population monitoring will be reviewed on a regular basis and management activities adapted where necessary.

When adequate information is available from the other recovery actions, population modelling and viability analysis will be utilised to assess extinction risk, compare management scenarios and to assess factors likely to affect the probability of persistence of key/vulnerable populations. This will enable refinement of management guidelines and determination of appropriate management.

The locations of the boundaries between the three ESUs are not known with any precision. The boundary between the Northern and Central ESUs passes somewhere between Broke and Woko National Park, and between Warrumbungle National Park and Armidale (Eldridge & Browning 2004). Populations that lie between these locations cannot currently be assigned to an ESU for management purposes. The location of the boundary between the Central and Southern ESUs is of somewhat academic interest because all intervening populations are thought to be extinct. However, an improved understanding of the location of the boundary will assist the selection of the most appropriate founder stock for reintroductions to sites south of Kangaroo Valley, NSW, including the ACT. Colonies and museum specimens will be selected and samples collected for the genetic analyses, to determine if a clear disjunction in haplotypes can be identified. Boundaries will be defined and mapped, and the results will be used to better target conservation management of the species.

While some populations of the species have been identified, there has been no comprehensive identification of important populations across the entire range. As information from monitoring, surveys, predictive distributional studies and molecular analysis becomes available, populations important to the survival of the species can be comprehensively determined.

Captive populations originating from Southern and Central ESU animals are already established, and will be managed separately. A captive management plan will be developed for each ESU, stating targets for that population and the strategies and protocols required to achieve them. Central ESU captive animals will be managed to maintain gene diversity above 90% of that currently in the wild population. The Southern ESU captive population will be managed to at least 95%, because this population is so small and is the only source of animals for reintroductions.

Captive management plans will include the need to:

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  Determine the proportion of wild gene diversity present in the captive population using sampling theory and pedigree analysis
  
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  Maximise gene diversity over time using breeding strategies aimed at equalising founder representation and controlling the rate of inbreeding
  
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  Calculate required breeding rates using life-table analyses
  
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  Maintain a studbook to support the required analyses
  

There is now considerable experience in the captive management of the Brush-tailed Rock-wallaby, including assisted reproductive techniques such as cross-fostering of pouch young. All of the captive management institutions contributing to this recovery program will need to be aware of the best available techniques, and the standards and management protocols required for the conservation management of the captive populations, especially the management of animals suitable for reintroduction. The current husbandry manual (Muranyi 2000) will be updated to reflect these recent advances.

The captive populations of Southern and Central ESUs will be managed to their respective captive management plans. While few options are available for the Southern ESU population, the Central ESU captive population will be expanded to ensure that there are at least 20 founders, at least 16 of which need to be wild-caught animals from across the Central ESU. A small number of Kawau Island animals could be included but their genetic line will need to be carefully controlled to avoid over-representation.

One factor that strongly influences the probability of inbreeding depression in small populations is the number of generations spent at that small size. An effective means of minimising the genetic impact of a population bottleneck is to rapidly increase the population. Rapid increases in the population also serve to buffer against extinction through some catastrophic event. Extensive trials have shown that reproductive output of the species can be enhanced by the removal of pouch young from their mother’s pouch and their placement in the pouch of a captive foster mother for rearing (Taggart et al. 2002). Upon losing her pouch young, the biological mother can quickly become pregnant again, thus maximising reproductive output for both captive and wild populations. This will be the primary technique for quickly increasing captive population numbers to meet genetic management and reintroduction targets for the S-ESU populations. The successful trials of this technique will be upgraded into a routine species management protocol, based on specially-managed captive populations of Brush-tailed Rock-wallaby and/or Tammar Wallabies housed at appropriate collaborating ZAA-accredited institutions. This process is especially important for the Southern ESU, where so few animals remain. Given the tiny size of this captive and wild population, it is essential to conserve as much of the remaining genetic diversity as possible. Therefore, it is highly desirable to obtain pouch young from each remaining wild female.

The need for a captive population of Northern ESU animals to be established as insurance against continuing any decline in the wild will be assessed.

There are fewer than 10 individuals left in the remaining two colonies of the Southern ESU, and as such there are several difficult management issues that require further consideration and decision-making guidelines. A management plan for the Southern ESU population will be developed, including assessing the relative merits and costs of translocations to re-enforce remaining colonies or establishing new colonies in East Gippsland and/or the Grampians. The plan will also address trigger points for deciding when to take remaining wild animals into captivity.

There is strong genetic partitioning between many sub-populations, even when they are separated by less than one kilometre. As sub-populations become increasingly isolated and their size declines, the risk of inbreeding depression rises. Under these circumstances artificial supplementation of some colonies will be required to mimic successful dispersal events and maintain or improve genetic and demographic robustness of sub-populations. This may be very important for the long-term conservation of outlying sub-populations that are now well separated from other sub-populations. A strategy to achieve this will be developed, taking into account ESU boundaries, critical sub-populations and outlying populations.

Translocations include reintroductions to establish new colonies, and reinforcement to supplement existing colonies. Translocation of captive-bred animals to the wild is essential for the survival of the Southern ESU in the wild, and is likely to be an important component of the management strategy for the Central and Northern ESUs. The best strategy to achieve a successful outcome will vary between ESUs according to the varying needs of each ESU and the other factors such as the availability of animals for release. Previous macropod translocations will be reviewed to design and then test options covering the range of situations. The Victorian translocation strategy (Delaney et al. 2004) is an important start to this process. The aims of translocation will vary between ESUs and need to be clearly understood and supported by all participants. Strategies will include an agreed set of criteria against which to evaluate success. The Central ESU strategy will include investigation of the feasibility of reintroduction to former sites in the ACT.

Predation by the Red Fox is thought to be a major threat to the species. Understanding the impact of predation, especially on dispersing individuals, and changes in predation levels before and after habitat disturbance (e.g. clearing, road construction), is essential for effective conservation management of the species. The response of Brush-tailed Rock-wallaby populations to predation and predator control will also lead to a better understanding of the level of predator control required (for each location) for the short- and long-term management of the species.

Since the Brush-tailed Rock-wallaby is associated with a variety of vegetation types and climatic regions, there is no single fire regime that can be specified for all habitat types. Specific fire regimes would ideally be determined for each key population and account for factors such as food availability, cover, predation levels and disturbance. The role of fire in promoting the growth of key plants in the diet, and the interactions between fire and total grazing/browsing pressure need to be better understood, and will be investigated. Where managed fire is thought to be beneficial for the Brush-tailed Rock-wallaby, trial ecological burns will be undertaken at selected sites to determine their effectiveness as a conservation management tool.

While there is a considerable amount of information on aspects of habitat utilised by the Brush-tailed Rock-wallaby, there are still key aspects of habitat use that are not known, especially how habitat varies across the distribution of the species, and habitat used in the absence of predation pressure from feral mammals. Obtaining this information is important for conservation management of the species, and a project will be established to determine these factors and determine habitat that is critical to survival of the species across its total range.

Studies of dietary ecology of Brush-tailed Rock-wallaby and other herbivores at key sites in each ESU will be undertaken to determine the potential for dietary competition and the need for competitor control programs. The available information suggests that the Brush-tailed Rock-wallaby is a generalist grazer and browser, with grass an important component of the diet. However, key dietary components will vary between sites, as will the species of terrestrial mammalian herbivores sharing each site. Investigations of dietary ecology, including overlap and the potential for competition with other herbivores, native and introduced, will provide a sound basis for management. Scat analysis techniques will be used to determine seasonal variation in dietary preferences, and degree of dietary overlap with other terrestrial mammal herbivores, at key sites in each ESU.

It is thought that there is generally limited dispersal of Brush-tailed Rock-wallabies away from their natal site (especially of females), but the factors influencing dispersal remain largely unknown. In a study on population structure of four colonies in south-east Queensland, female dispersal among colonies was low, despite some colonies being separated by only 1 to 2 km of suitable habitat. There was evidence of multiple, spatially distinct female groups within colonies, which represent discrete breeding groups (Hazlitt et al. 2010). In contrast, males tended to disperse among breeding groups, coupled with infrequent among-colony dispersal (Hazlitt et al. 2010). Habitat familiarity was thought to be an important element for the survival of individuals. A study of dispersing Brush-tailed Rock-wallabies is required to investigate factors such as the success of dispersal, distance travelled, use of corridors and exposure to predators. This will provide important information in planning and undertaking recovery actions such as assisted dispersal to minimise loss of genetic variability amongst colonies of rock-wallabies.

Any threatened species recovery program relies heavily upon close collaboration between all groups with an interest in the outcome, or with an interest in the surrounding land. In cases where threatening processes such as introduced predators are dispersed widely through the surrounding landscape, the cooperation of neighbouring landholders is essential to a successful outcome. The Friends of the Brush-tailed Rock-wallaby group already assists recovery actions in southern NSW. Where feasible, additional regional, community-based rock wallaby support groups will be established in each ESU to support recovery efforts.

Community volunteers and landholders supporting rock-wallaby conservation will be trained and involved in methods for finding and estimating the size of Brush-tailed Rock-wallaby colonies, and avenues for reporting this information to appropriate wildlife authorities.

An information package outlining key elements of Brush-tailed Rock-wallaby biology, habitat requirements and management guidelines will be developed and provided to landholders in key locations for Brush-tailed Rock-wallaby conservation.

A regular newsletter that will report on recovery program news and progress will be developed and circulated to local communities and other interested stakeholders.

Appendix 2 - Extralimital Populations

Populations of the Brush-tailed Rock-wallaby have become established in New Zealand and Hawaii. In New Zealand, animals were deliberately released on Motutapu Island and Kawau Island in Hauraki Gulf by the Governor of New Zealand, Sir George Grey, in about 1863. Wallabies from Motutapu Island naturally colonised the adjoining Rangitoto Island (Warburton & Sadlier 1995). There is some uncertainty about whether the Kawau Island animals were obtained independently from Australia or whether they came from Motutapu Island. However, genetic analyses confirm that the Kawau Island population originates from central NSW (i.e. the Central ESU) (Eldridge et al. 2001). The New Zealand populations have long been regarded as pests. The populations on Motutapu and Rangitoto Islands were eradicated during the 1990s and the Kawau Island population is currently being reduced with the goal of eradication. Past control programs included capture for export to captive institutions, and an unknown number of animals were exported to overseas zoos. As a result, animals derived from the New Zealand island populations are now strongly over-represented in captive populations worldwide (C. Lees pers. comm.). Brush-tailed Rock-wallabies are also found on the island of Oahu, Hawaii, where a wild population became established in 1916 after animals escaped from captivity (Lazell et al. 1984). Genetic analyses clearly show that the founders of this population came from the northern ESU, most probably from south-east Queensland (Eldridge & Browning 2002). Some animals of New Zealand provenance have been used in the recovery program. However, the role that animals from these extralimital populations can play in the recovery of the Brush-tailed Rock-wallaby requires careful management, given their limited provenance and genetic history.