Brush-tailed Rock-wallaby

(Petrogale penicillata)

This beautifully marked medium-sized wallaby is distinguished by its long, dark tail ending in a brush of coarse hair, a white to buff cheek-stripe and a black dorsal stripe along the head. The upper body is brown, tending to rufous on the rump and grey on the shoulders. The chest and belly are paler and the feet and paws are black. Males are larger than females and may weigh up to 11 kg.

Brush-tailed Rock Wallabies are adapted to steep and precipitous habitats as their main form of defence against predators. Like all rock wallabies this species has skin ridges on its foot pads (like finger prints) allowing it to grip to almost vertical slopes. The claw of the fourth toe is reduced in size compared to other wallaby species and the tail is characteristically longer than the body measuring approximately 600mm, compared to the head-body length of around 550cm. The long tail provides balance as it makes great leaps from rock to rock. With these adaptations it shows amazing agility, occupying places its main competitors and predators cannot use.

Brush-tailed Rock Wallabies favour precipitous habitat which offers protection from predation, adjacent to feeding areas with favourable shrub and browse. Their current range is in “refuge” areas that commonly feature heaped boulders with caves, ledges and sheer cliffs for protection. They are largely night time feeders, and although generally shy, may be seen sunning themselves during the day especially in the morning and early evening. This species’ major predators are thought to be Wedge Tailed Eagles and introduced carnivores such as foxes and cats. These predators are likely to have the greatest impact on juveniles (joeys) preventing or reducing the recruitment of young animals.

wallaby Brush-tailed Rock Wallabies form small territorial groups comprising one dominant male and around 5-7 females. The dominant male will fight and expel rival males thereby excluding them from the group. These males generally occupy less favourable habitat outside the territory where there is reduced protection from predation.

Breeding occurs year-round in warm climates. Females reach maturity at 18 months of age and males at 20 months. There is a gestation period of 31 days after which the embryo is born and transfers to the pouch. Joeys remain about 29 weeks in the pouch. The joey gradually leaves the pouch but will continue to suckle for up to three months. The mother may hold another fertilized embryo and this will develop as sucking from the previous joey decreases.

Three genetic population zones are recognized —

Northern Nth NSW and Southern Qld- classed as Endangered in NSW and Vulnerable in Qld (where they are still moderately abundant)
Central and Southern NSW – classed as Vulnerable with a few isolated and declining populations including the Warrumbungles, Pokolbin, Wattagans, Jenolan Caves and Kangaroo Valley. Virtually extinct in all other parts of its previous southern NSW range.
Victoria-classed as Criticially Endangered in this state with estimates of only about 20 animals left in the wild and 20 in captivity.

The Decline

At the time of European settlement the Brush-tailed Rock-wallaby was the most abundant species of rock wallaby and one of the most common of all wallaby species. It was recorded as being present in the thousands in some areas during the late 19th century. Its range extended from southern Victoria (Grampians) to central Queensland from the coast to as far west as Bourke. At this time it appears to have occupied less precipitous and marginal habitat than it does today and was even recorded from Middle Head and Pittwater around Sydney.

A number of factors have contributed to the decline in distribution and abundance of Brush-tailed Rock Wallabies including hunting, competition with sheep and rabbits for food and predation by foxes and cats. The earliest impacts were probably from hunting and sheep grazing. Rock Wallabies were an easy target for shooters due to their occupying treeless areas and their habit of hopping away and then “freezing” in the open. This species was shot for their skins and for sport for many decades. The destruction reached record levels of possibly up to 100,000 animals a year in the 1890s and 1910s. So many animals were shot that Brush-tailed Rock Wallaby skins were sold “by the bale” to the London markets according to records kept by Goldsbrough Mort.

The impact of sheep grazing was also detrimental to brush-tailed Rock Wallabies and would have contributed to its retreat to less favoured areas as prime habitat was “eaten out”. There are also some clear associations of rock wallaby decline with an increase in goat numbers at Mount Kaputa and the Warrumbungles. Clearly this species was regarded as agricultural pest as a bounty was paid on its skin by the pastures protection board up to 1914 when the last bounty was paid at Tenterfield NSW. In 1918 the Brush-tailed Rock Wallaby was finally protected under the Native Animal Protection Act but shooting still occurred during declared “open seasons” and illegal hunting continued.

The explosion of the fox population, first from the south and heading steadily northward, was another factor contributing to the decline of Brush-tailed Rock Wallabies. Whole areas such as the Kosiusko region suffered massive rock wallaby declines which do not appear to be due solely to hunting pressure. It is likely that the fox and also the cat have caused severe predation on the young preventing recruitment of new adults. A change in fire regimes from small frequent fires lit by aborigines to infrequent catastrophic bushfire may has also contributed to its decline.

The demise of Brush-tailed Rock Wallabies was worst in the southern-most closely settled districts. Populations in many areas became fragmented with areas of suitable habitat becoming separated by great areas of cleared farming land. Where reasonable populations remain today these are usually in the steepest and most rugged “refuges” such as the New England and the Border Ranges where the extreme ruggedness of their habitat allows them to hold their own against foxes and cats.
The isolated small populations of the Warrumbungles, Wattagans, Goulburn River, Pokolbin and Jenolan Caves areas face additional problems including genetic isolation and severe predation pressure. In one case at Goulburn River the decline in numbers has led to an isolated group of females ( i.e a harem) without a male.

Some introduced populations outside Australia such as Kawau Island off New Zealand and in Hawaii potentially preserve genetic material from the southern populations.

The Future

It has now evident that captive breeding programs and intensive management are vital to enhance the survival prospects of small isolated populations of Australian Mammals. A NSW and Victorian Brush-tailed Rock Wallaby recovery program concentrating on the viable populations is now in full swing. It includes trapping programs, captive breeding program and release targets.
Using informed well directed assistance it is possible to build up viable populations of this species in favoured locations. These populations must be large enough and genetically robust enough to resist further decline.