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

Sharman's Rock-wallaby

Petrogale sharmani ('Sharman's rock-weasel')

Best place to see

Mt Fox, Girringun National Park, Queensland

Sharman's Rock-wallaby is confined to a small area west of Ingham with scattered colonies in the Seaview and Coane Ranges. It was originally discovered at Mt Claro in 1976 but has recently been reported in the region of Mt Fox in the Girringun National Park, 75 km south-west of Ingham. Mt Fox is an ancient volcano with a large crater and this geological feature is the main attraction for visitors. The landscape is riddled with boulders but amongst these are vine-thicket rainforest. These gullies around the crater are habitat for Sharman's Rock-wallaby. Walking to the summit and return takes about 2 hours, climbing 160 m along a difficult grade. There is no camping in the Mt Fox section of the Park. A campground is found in the nearby Wallaman Falls section.

Identification

Males average 4.4 kg and females average 4.1 kg. Sharman's Rock-wallaby is part of a complex of species that includes the Allied Rock-wallaby, the Unadorned Rock-wallaby and the Mareeba Rock-wallaby. These species are not easily distinguished except by the shape and number of chromosomes. The genera tourist does not have a cytologist's kit to make such distinctions and so locality is the best guide to determine which species you are seeing.   Freshly moulted individuals are typically greyish on the back but as the year advances the colour changes to pale through to dark brown.  The underside of the the body and limbs is lighter and typically a sandy brown. There is a pale cheek stripe, with indistinct and patchy  markings behind the shoulders and a dark dorsal stripe along the crest of the head. The paws and feet are dark and the tail darkens to almost black towards the tip which has an indistinct brush.

Habitat

Sharman's Rock-wallaby inhabits rocky slopes, rocky outcrops, boulder piles, cliffs and gorges, usually associated with tropical woodland with a grassy understorey or vine-thicket rainforest.

Foraging behaviour

The diet of the Sharman's Rock-wallaby has not been studied but presumably includes grasses, forbs, fruits and some browse. In summer it is basically nocturnal but may emerge around twilight in cooler months and sun-bake in the early mornings. It shelters in caves, deep crevices and fissures in rock, under boulders or in dense vegetation during the heat of the day. It forages out from this shelter into the surrounding woodland.

Reproductive behaviour

Reproduction has not been studied in Sharman's Rock-Wallaby but is presumably typical of the North Queensland species. 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 is continuous.

Social organisation

Rock-wallabies are typically social and live in colonies varying from a few individuals to over 100. Sharman's Rock-wallaby is no exception and colonies of 40 or more individuals are known. The lack of sexual dimorphism with a similar size in males and females suggests intra-male competition for mates is not intense. However, whether they are highly promiscuous or pair-bonded is not known.

Further readings

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.

Clancy TF, Close RL (1997) The Queensland rock-wallabies. An overview of their conservation status, threats and management. Australian Mammalogy 19, 169-174.