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Petrogale penicillata 

Scope: Global
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Diprotodontia Macropodidae

Scientific Name: Petrogale penicillata
Species Authority: (Gray, 1827)
Common Name(s):
English Brush-tailed Rock Wallaby, Brush-tailed Rock-wallaby

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2bce+3bce+4bce ver 3.1
Year Published: 2016
Date Assessed: 2014-05-28
Assessor(s): Woinarski, J. & Burbidge, A.A.
Reviewer(s): Johnson, C.N.
Contributor(s): Menkhorst, P., Lunney, D., Bluff, L., Eldridge, M. & Soderquist, T.
Justification:
The Brush-tailed Rock-wallaby has experienced a very substantial historical decline, and decline is continuing at many or most subpopulations. The rate of decline is not well resolved, but suspected to be >30% over a 21 year (=three generation) period. Hence it qualifies for listing as Vulnerable.
Previously published Red List assessments:

Geographic Range [top]

Range Description:

The Brush-tailed Rock-wallaby has a disjunct range in south-eastern Australia, mostly associated with the Great Dividing Range, from the Grampians in western Victoria to south-eastern Queensland (Yarramam, north of Toowoomba). The isolated Grampians subpopulation was extirpated in about 1999 (Corrigan et al. 2012), but is the subject of a current reintroduction program using animals from East Gippsland and hybrids between the two ESUs (Corrigan et al. 2012; Malam et al. 2012; P. Menkhorst pers. comm. 2014).

Historically, the Brush-tailed Rock-wallaby has been reported at nearly 1000 sites (DECC 2008): of these, 77% were still occupied in 2004, 15% were unoccupied and persistence at the remainder was uncertain (DECC 2008). Many (‘dozens of’) subpopulations (including at Taralga and several sites in the Warrambungles) have been extirpated since 2004 (M. Eldridge pers. comm. 2014).

The species'  distribution has declined considerably since European settlement, with losses particularly from isolated subpopulations in inland and southern New South Wales (Menkhorst and Hynes 2011), and from Victoria (Menkhorst 1995). It has not been recorded in the Australian Capital Territory since 1959 (ACT Government 1999).

There is an extralimital population in Hawaii (Menkhorst and Hynes 2011) and formerly another in New Zealand (now exterminated: M. Eldridge pers. comm. 2014), both derived from introductions.

Countries occurrence:
Native:
Australia (New South Wales, Queensland, Victoria)
Additional data:
Estimated area of occupancy (AOO) - km2:100000Continuing decline in area of occupancy (AOO):Yes
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:390000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:15Continuing decline in number of locations:Yes
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:

In 2008, the population size was estimated to be between 15 000 and 30 000 individuals (DECC 2008), with most (80%) in north-eastern New South Wales, and far smaller proportions in central and south-eastern New South Wales (2%), south-eastern Queensland (17%) and Victoria (<1%) (DECC 2008).

The population is declining, however the rate of decline is poorly resolved: Taggart et al. (2008) considered that the decline was ‘significant’ but <30% over a 10-year period. Decline (and extirpation) is probably now inexorable at many to most of the smaller colonies unless these are intensively managed (by threat reduction and manipulation of genetic stocks). Mahon et al. (2011) reported on trends in 12 colonies in the Hunter-Central Rivers region of New South Wales from 2003 to 2011, with six of the colonies subject to intensive fox control, three colonies as unmanaged controls, and three colonies in more productive habitat and subject to wild dog control. There was no difference in population trends between treatments and a fitted regression model predicted decline in an abundance index (rock-wallaby pellets) of 58% over 10 years.

There have been many intensive monitoring programs for individual colonies (or groups of colonies) of Brush-tailed Rock-wallabies, and more broadly-based ongoing assessments of the persistence of larger groups of colonies (Dovey et al. 1997; DECC 2008). Eldridge et al. (2004) described the decline of a colony at Jenolan Caves from about 90 individuals in 1985 to seven individuals in 1992, probably due to predation. Monitoring at the two regional populations of Brush-tailed Rock-wallabies in Victoria demonstrated incremental loss of subpopulations and total population size, culminating in the extirpation of the Grampians population in 1999 (with subsequent trial reintroduction in 2008: Molyneux et al. 2011), and the persistence of only one subpopulation in eastern Victoria at Little River Gorge (Bluff et al. 2011)

Current Population Trend:Decreasing
Additional data:
Number of mature individuals:20000Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:Yes
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:

The Brush-tailed Rock-wallaby is closely associated with rugged rocky areas, including rock faces and outcrops with boulders, ledges and caves (Short 1992; Menkhorst and Hynes 2011); however this association may be an artefact reflecting retreat from a far broader habitat distribution since European settlement (Menkhorst and Hynes 2011). The rocky sites now occupied may occur in a range of vegetation types including rainforests, eucalypt forests and woodlands (Eldridge and Close 2008). At night, Brush-tailed Rock-wallabies move from their daytime shelter sites to a foraging area, typically using a habitual route. Home range size varies from 6-30 hectares (Short 1992), although more recent radio-tracking data demonstrate that movements of c. 500 m distance per night are relatively common, suggesting home range sizes may be larger than previously published values (T. Soderquist pers. comm. 2014). Foraging areas may include forests, woodlands and pastures. The Brush-tailed Rock-wallaby has a mixed diet: grass is the main item, but flowers, forbs, leaves, fruit, bark and fungi are also eaten (Short 1989; Menkhorst and Hynes 2011).

The Brush-tailed Rock-wallaby lives in colonies, usually comprising fewer than 30 individuals (Piggott et al. 2006; Hazlitt et al. 2006a), with many colonies now comprising just a few individuals (Menkhorst and Hynes 2011). Habitat clearance and predation away from shelter sites lead to a decreased rate of successful dispersal between colonies, and increased risks of inbreeding impacts (Hazlitt et al. 2006b).

The Brush-tailed Rock-wallaby can breed throughout the year, although births peak from February to May (Eldridge and Close 2008), and at least in some colonies breeding may be highly synchronized (Wynd et al. 2006). Sexual maturity is reached at about 1.5-2 years (longer for males: Lee and Ward 1989). Longevity may reach at least 14 years (reported for the Jenolan subpopulation: T. Soderquist pers. comm.) (Jones et al. 2009); although the maximum recorded in the wild in studies of Victorian subpopulations is 8 years (L. Clausen pers. comm. 2014). Generation length is taken here as 7-8 years.

Systems:Terrestrial
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):7
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: This species was formerly hunted intensively for pelts and because it was perceived as a pest (Short and Milkovits 1990; Menkhorst 1995; Lunney et al. 1997). This hunting pressure may have been a primary factor in the historical decline (Taggart et al. 2008) and thence to the species’ vulnerability to other threats. At least 500 000 individuals were killed between 1894 and 1914, and almost 100,000 skins were marketed by a single company in one year (1908) (Lunney et al. 1997). This activity no longer occurs.

Threats [top]

Major Threat(s): There is a lack of data about the threats to the Brush-tailed Rock Wallaby (Eldridge and Close 2008). Predation by introduced foxes and competition with introduced goats are likely to be the greatest threats. Foxes prey on young rock wallabies and probably limit dispersal as well as recruitment. Introduced dogs and cats are also probably threats, but the habitat in which this species lives is not well suited to these predators. Habitat fragmentation and land clearance between colonies is also thought to limit dispersal and reduce numbers of individuals by exposing rock wallabies to higher rates of predation. As colony isolation increases so does the risk of inbreeding (Hazlitt et al. 2006a,b).

Hunting was perhaps the main historical factor in reducing the population and range of this species. A sustained commercially-driven period of hunting led to the decline of many populations and local extinctions, and may have been the primary cause of the initial decline, at least in central and southern New South Wales. Bounties were paid on over half a million rock-wallabies between 1894 and 1914 (Short and Milkovits 1990) and there was an extensive fur trade from pre-1890 to 1927 (Lunney et al. 1997). The species was also hunted extensively in the Grampians area of Victoria. The magnitude of hunting is apparent when one considers that the current population of the species is estimated at between 15,000 and 30,000 individuals, and in 1908 alone 92,590 skins were marketed by a single company (Lunney et al. 1997).

Conservation Actions [top]

Conservation Actions:

A recovery plan (Menkhorst and Hynes 2011) includes the objectives:

  • determine and manage threats to the Brush-tailed Rock-wallaby and its habitat;
  • determine distribution, abundance, population trends and viability;
  • establish and maintain separate, viable captive populations derived from the Southern and Central Evolutionarily Significant Units (‘ESUs’);
  • undertake translocations to improve the genetic and demographic robustness of populations and to establish new colonies;
  • investigate key aspects of biology and ecology for conservation management;
  • increase community awareness and support.

Most of these activities are being undertaken (and have been previously, through other management planning), with some local-scale success. However, captive populations have not necessarily been maintained as separate ESUs.

In additional to this national recovery plan, there is a recovery plan for New South Wales (DECC 2008), a recovery plan for the Queensland subpopulations (Hinsch and Clancy 1995), an action plan for the Australian Capital Territory (ACT Government 1999), and an Action Statement for Victoria (Hill and Baker-Gabb 2003, with 2010 draft review). Roache (2011) provides a series of costed management and research actions aimed at recovering the species to Least Concern status.

There has been a substantial management effort devoted to the conservation of this species (Menkhorst and Hynes 2011). This includes the establishment of several captive breeding populations; survey and monitoring; research into ecology, genetics and threats; habitat protection; re-introductions; supplementation of small colonies for genetic or demographic concerns; and intensive management of some threats at some colonies. Management has achieved some local success (increased population size or stabilization of some populations), however the overall population trend remains declining.

The recovery of this species is particularly complex and requires a consideration of threats and management interventions at a variety of spatial scales, from local to regional (Murray et al. 2008; DECC 2008). Threats also vary across the range of the species so that, for example, fox predation is considered less of a threat in the northern portion of the range than in the south (DECC 2008).


Citation: Woinarski, J. & Burbidge, A.A. 2016. Petrogale penicillata. The IUCN Red List of Threatened Species 2016: e.T16746A21955754. . Downloaded on 01 October 2016.
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