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

Allied Rock-wallaby

Petrogale assimilis ('similar rock-weasel')

Best place to see

Bowling Green Bay National Park, Queensland

The Allied Rock-wallaby is widespread in north-eastern Queensland and is found offshore on Palm and Magnetic Islands. Bowling Green Bay National Park is 28 km south of Townsville and is formed by rugged mountains (including Mt Elliot at 1342 m) running down to a coastal plain of wetlands, saltpans and mangroves. A central feature is Alligator Creek with a large formal campground with toilets. There are three other remote bush camping sites and one main walking track of 17 km return to Alligator Falls. The Allied Rock-wallabies can be viewed around the campsites along with Agile Wallabies and occasional Rufous Bettongs.

Identification

The Allied Rock-wallaby is part of a complex of species that includes the Sharman's 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. As is typical of Rock-wallabies, males (4.7 kg) are larger than females (4.3 kg). 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. In some individuals there may be 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 towards the tip which has an indistinct brush. Some individuals, particularly in the northern part of their range, have a whitish to greyish tail tip.