General information

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 Australia and a dozen or more in New Guinea.  Some of the smaller species, such as Yellow-footed Rock-Wallabies, Burrowing Bettongs, accompanied Pig-footed and Golden Bandicoots, Bilbies and possibly Hairy-nosed Wombats into extinction with the advent of pastoralism. However, the largest species remain in much of their original range with the grey kangaroos expanding inland as grazing habitat increased and coastal habitat was lost in clearance for agriculture. The defining feature of the kangaroo family is that they are the largest vertebrates to hop (both currently and from what we know from palaeontology).

 

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.

Species

Rothschild's Rock-wallaby

Petrogale rothschildi ('Rothschild's brush rock-weasel')

Best place to see

Karijini National Park, Western Australia

Karijini National Park (formerly Hamersley Range National Park) is in the Pilbara region of Western Australia, 310 km from Roebourne and 1400 km from Perth. The Park is in the tropics and receives predominantly summer rainfall. Temperatures are high in summer but some respite can be found in rock pools. The Park is noted for its spectacular chasms and gorges which provide ideal Rock-wallaby habitat. In the north, small creeks cut into the rolling hillsides and plunge into sheer-sided chasms up to 100 metres deep. These gorges widen further downstream,  and their sides change from sheer cliffs to steep slopes of loose rock. The rocks originated as fine-grained sediment (rich in iron and silica) which accumulated on an ancient sea floor 2,500 million years ago. The gorges were eroded out of the sediment when a sharp drop in sea level caused the rivers to down cut and the climate became more arid depleting the protective vegetation cover on the valley sides. To explore the gorges you must be physically fit and prepared to submerge in very cold water, follow narrow paths and cling to rock ledges.

Karijini Visitor Centre has camping with toilets, water, an information shelter, picnic tables, gas barbecues. Karijini Eco Retreat, located in the Savannah Campground 35 km from the Visitor Centre and 10 km south of Weano, provides more salubrious accommodation.

In addition to Rothschild's Rock-wallaby, you can see Red Kangaroos and Common Wallaroos (Euros).

Identification

Males  to 6.6 kg (average 6.1 kg) and females to 5.3 kg (average 4.1 kg). The back of Rothschild’s Rock-wallaby is grey-brown from behind the shoulders to the rump. There is some variation between individuals with a pale colouration in some and more grey after the winter moult.  The upper part of face to the back of the head is a rich dark brown with a dark brown cap between ears.  Unlike most other Rock-wallabies there is no central stripe on the head.  The fur is pale grey from the back of the head to the shoulders.  The outside of the short ears is dark brown and this colouration is carried into the sparsely furred inside of the ears.  The nose is naked and black.  Some individuals have an indistinct brown patch behind the shoulder.  There is no pale side stripe unlike the Black-footed Rock-wallaby.  The base of the tail is pale yellow-brown.  The first half of the long tail is coloured like the back but the distal half of is black, and the hairs lengthen towards the tip, forming a brush.  The underparts are pale grey or pale grey-brown.   The back of the hands and fingers is dark brown in the toes are dark brown to black.  At certain times, a purple pigmentation develops over the fur, particularly round the neck and shoulders.  The pigment decays rapidly from museum specimens and its origin, composition and adaptive significance have not been studied.   

Habitat

In common with other Rock-wallabies, Rothschild's Rock-wallaby inhabits rock outcrops, boulder piles, cliffs and gorges. The scree slopes extending out from cliffs are typically covered with spinifex (mainly Triodia basedowii and T, wiseana) with scattered eucalypts. Other rock outcrops are surrounded by sandplains with hummock grassland. Rothschild's Rock-wallaby is also found on islands in the Dampier Archipelago. There the scree slopes have a patchy hummock grassland interspersed with soft grasses and fig trees. This Rock-wallaby is highly susceptible to predation by the introduced Fox and remnant populations are often protected by Fox baiting.

Foraging behaviour

Rothschild's Rock-wallaby inhabits hot, dry regions with brief periods of intense rain from tropical depressions and cyclones. Thus it is active only at night in hot weather and spends the day in much cooler and more humid caves and crevices. Eco-physiological studies have shown that this behaviour reduces water use and enables this Rock-wallaby to cope with extended dry periods.

 

It forages for soft grasses, forbs and fruit (especially figs from native Ficus spp.) amongst the hummock grassland that typically surrounds its rocky shelters.

Reproductive behaviour

Reproduction has not been studied in Rothschild's Rock-wallaby. It likely follows that of the Black-footed Rock-wallaby. The  characteristics are an oestrus cycle of 30 d, post-partum oestrus, embryonic diapause, a pouch life of 6-7 months, with weaning at 11 months. Breeding may be seasonal and cued to the monsoonal rains of the summer Wet season.

Social organisation

Rock-wallabies are typically social and live in colonies varying from a few individuals to over 100. The social organisation of Rothschild's Rock-wallaby has not been studied.

Further readings

Bradshaw SD, Morris KD, Bradshaw FJ (2001) Water and electrolyte homeostasis and kidney function of desert-dwelling marsupial wallabies in Western Australia. Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology 171, 23-32.

Campeau-Peloquin A, Kirsch JAW, Eldridge MDB, Lapointe FJ (2001) Phylogeny of the rock-wallabies, Petrogale (Marsupialia: Macropodidae) based on DNA/DNA hybridisation. Australian Journal Of Zoology 49, 463-486.

Pearson DJ, Kinnear JE (1997) A review of the distribution, status and conservation of rock-wallabies in Western Australia. Australian Mammalogy 19, 137-152.