Kangaroos are marsupials and belong to the Family Macropodidae (i.e. big feet) that is grouped with the Potoroidae (potoroos, bettongs, rat-kangaroos) and Hypsiprymnodontidae (musky rat-kangaroo) in the Super-Family, Macropodoidea. This comprises around 50 species in
The Rock-wallabies (Petrogale spp.) is the most diverse genus amongst the living macropods with 16 species ranging from 1 to 12 kg in size. They are found across mainland Australia and on some recently separated offshore islands but not on the Bass Strait Islands, Tasmania or New Guinea. The species diversified from a common ancestor about 4 million years ago and their closest affinity to other macropods is with the Tree-kangaroos. Diversification of species occurred in two waves. The first gave rise to the Short-eared Rock-wallaby, the Monjon, the Narbelek, the Yellow-footed Rock-Wallaby and the Proserpine Rock-wallaby. The second was about a million years ago and lead to species that are not all morphologically distinctive like those along the Queensland seaboard. All Rock-wallabies favour habitat with rocky outcrops and slopes, cliffs and gorges or are found on boulder piles and escarpments especially in the wet-dry tropics. Their ability to scale precipitous rock faces in leaps that appear to defy gravity comes from adaptations to the feet and tail. The feet are short relative to the majority of macropods that inhabit flat ground. The pads are thick, spongy and highly granulated so that they compress on the rock surface and maximise grip. The tail is long and cylindrical with little taper and great flexibility. The tail acts as a counterbalance and rudder in rapid hopping across uneven surfaces and allows changes of direction in mid-air.
Petrogale inornata ('Unadorned rock-weasel')
Cape Upstart National Park, Queensland
Cape Upstart National Park is on the coast between Ayr and Bowen. It is a location for the more adventurous as it is not accessible by vehicle and requires a boat trip from a boat ramps south of Gumlu at Molongle Bay or the Elliot River near Guthalungra. The park has no facilities but allows camping at Coconut Beach or a bush camp on the north side of the Elliot River. The Cape is formed from a large granite headland covered in a range of vegetation types from vine thicket to heath. The headland is flanked by sandy beaches. The Park includes Eastern Grey Kangaroos, Swamp Wallabies and Common Wallaroos in its macropod fauna.
An alternative and easier place to see Unadorned Rock-wallabies is at the Eungella Dam, 120 km west of Mackay. The species has colonised the dam walls and may use your stationary vehicle roof as a temporary 'boulder'. The Unadorned Rock-wallaby is also listed for the Eungella National Park, 80 km from Mackay. This Park is a good place to see platypus and includes Eastern Grey Kangaroos, Red-legged Pademelons, Swamp Wallabies and Common Wallaroos in its macropod fauna.
Males to 5.6 kg (average 5.0 kg) and females to 5.0 kg (average 4.2 kg). In spite of its unassuming common name, the colouration of the Unadorned Rock-wallaby is variable and tends to follow to the colour of the rock and soil where it lives. Individuals that have in freshly moulted in autumn have a grey back that become progressively browner as the year advances. The colour of the back is a medium brown in varying shades of grey, highlighted with white. Individual hairs have dark brown to black bases, a broad white mid-band, and a short brown to black tip. The upper part of face and head is coloured rather like the back. Some individuals have a thin dark dorsal stripe on the head down to almost the centre of the back. In others the stripe is indistinct. The nose is black and naked. A dark facial stripe beginning near the nose passes through the eyes and almost reaches the ear. The dark stripe is highlighted below by a white stripe that begins at the nose and almost reaches the ear. In some individuals the facial stripes are indistinct. The outside of the ears is grey at the base with a black terminal patch and white band around the margin. The inside the ears is white or cream. The shoulders are defined by a brown or black patch with a white stripe behind but like other markings the patch may be indistinct in some individuals. The fur at the base of tail is variable in colour from faint to distinctly yellow. The distal quarter to one half is dark brown to black. There is usually no distinct brush, but the hairs near the tail tip are much longer. The fore legs are pale brown-grey and the hair of the fingers dark brown to black. The hind legs are similar in colour to the sides, and the feet are a medium brown-grey. The toes are dark brown to black. The chin is almost white, and the overall colour of the undersides is pale yellow to pale brown. Individual hairs have dark grey bases with white or pale brown tips.
The head and body ornamentation is usually more marked in animals close to the range of Herbert's Rock-wallaby.
In common with other Rock-wallabies, the Unadorned Rock-wallaby inhabits boulder fields and rock-strewn slopes and outcrops within a variety of habitats that includes coastal scrub as well as the more typical woodland, open forest and vine forest. It has colonised artificial structures like dam walls (e.g. Eungella Dam and Peter Faust Dam).
The diet of the Unadorned Rock-wallaby has not been studied. In general Rock-wallabies are opportunistic and generalist feeders eating mainly forbs and browse from shrubs and trees, some grass, and seasonal items like fruit, seeds, flowers and insect larvae in the tropics.
Reproduction has been studied in a sample of Unadorned Rock-wallabies held in captivity. The characteristics are an oestrus cycle of 30-32 d, post-partum oestrus, embryonic diapause, a pouch life of 6-7 months, with weaning at 11 months. Sexual maturity is reached at about 18 months in both sexes. Breeding is continuous and aseasonal.
Rock-wallabies are typically social and live in colonies varying from a few individuals to over 100. Some low density colonies of the Unadorned Rock-wallaby have been studied to examine how individuals allocate time between foraging, vigilance and locomotion and whether the time budget varies with group size and distance to cover. In these small populations, a relatively short time was spent foraging (23%) and individuals remained close (average 2.1 m) to the rock outcrops. Comparative studies with Allied and Mareeba Rock-wallabies in high density populations habituated to people showed that the Unadorned Rock-wallabies were more vigilant. Aggregation in larger groups did not accrue an individual benefit of less vigilance and more time for foraging or other activities in any of the three species. Rock-wallabies compete amongst themselves for rock shelters and this may limit sociality since the contravening benefit of many eyes to watch out for potential predators seems weak.
Blumstein DT, Daniel JC (2003) Developing predictive models of behaviour: do rock-wallabies receive an antipredator benefit from aggregation. Australian Mammalogy 25, 147–154.
Clancy TF, Close RL (1997) The Queensland rock-wallabies - an overview of their conservation status, threats and management. Australian Mammalogy 19, 169-174.
Eldridge MDB, Close RL (1992) Taxonomy of rock wallabies, Petrogale (Marsupialia: Macropodidae). I. A revision of the eastern Petrogale with the description of three new species. Australian Journal Of Zoology 40, 605-625.
Eldridge MDB, Close RL (1997) Chromosomes and evolution in rock-wallabies, Petrogale (Marsupialia: Macropodidae). Australian Mammalogy 19, 123-135.
Johnson PM (1979) Reproduction in the plain rock-wallaby, Petrogale penicillata inornata Gould, in captivity, with age estimation of the pouch young. Australian Wildlife Research 6, 1-4.