Queensland's Rock Wallabies from Airlie Beach to Cairns
Mareeba, Allied and Sharman's Rock Wallabies
The area of north-east Queensland, Australia, between Airlie Beach and Cairns is home to three species of rock-wallaby. Rock wallabies belong to the most diverse genus of the family Macropodidae. Although it would seem that the kangaroo would be closest relation to the rock wallaby, it is actually the tree kangaroos.
The three species of the north-east Queensland area are the Mareeba Rock-Wallaby, the Allied Rock-Wallaby and Sharman's Rock-Wallaby. These are sometimes grouped under the general term 'allied rock-wallaby'.
The differences between these three species are very subtle – with one being invisible altogether - and that is the number and/or shape of their chromosomes. The species are described as parapatric (meaning they keep to their own areas with normally little or no overlapping of home ranges). The area in which the animal is seen is often the only way to guess at its species. The species are also described as cryptic (meaning it is difficult to distinguish one species from another). The Mareeba was only recognised as a genetically distinct species in 1992.
Rock-wallabies are marsupials (giving birth to underdeveloped young) and macropods (meaning 'big foot'). They are adapted for life in a rocky environment. Although they are macropods (meaning 'big foot'), the feet are actually somewhat shorter and broader than those that live in more open country. The pads are thick, spongy and heavily granulated giving much better grip on rocks. When landing on a rock surface the pads compress, maximising grip. These animals have no trouble leaping up steep rock faces.
The cylindrical tail is long in comparison to open country species and tapers very little. It has great flexibility and is used as a counterbalance and rudder. It may be held upright when travelling at speed up rock faces. The rock-wallaby can change direction in mid-air if it so desires. Although agile and fast in its native habitat it is rather more clumsy in open country.
Rock wallabies gain most of their moisture from their food. They cannot afford to be fussy eaters and will take advantage of whatever is available. Rock wallabies eat native grasses (called 'wallaby grass'), flowers, seeds, leaves, roots, bark and even fruit. In tourist areas, they will try whatever is offered to them and quickly become tame enough to eat from the hand. In fact, they almost line up to do so.
The rock-wallaby lives in colonies. They live in groups in the safety and shelter of rocks, cliffs or escarpments. Its predators are not as 'at home' in such rocky, steep terrains and foxes, eagles and feral cats find it difficult to prey on these animals when they are among the rocks.
Habitat may typically consist of granite boulders in tropical open woodland. The habitat of Sharman's rock-wallaby is usually associated with tropical woodland with a grassy understorey. They generally shelter among the rocks during the day, coming out in the mornings and evenings to feed and sunbake. In drought times, they may travel long distances from their home range.
Breeding takes place throughout the year. Males and females form pair bonds although this is not proven in the case of Sharman's rock-wallaby. The joey is the size of a bean when it is born. It instinctively claws its way from the birth canal up the mother's belly to the pouch and, once inside, fastens itself to a teat. It is furless, blind and helpless at birth. Further development takes place in the pouch. Once out of the pouch, the young are left in the shelter of the rocks until they have the ability (and agility) to keep up with their mother. They have a pouch life of six to seven months and are weaned at around eleven months.
Rock wallabies can halt the development of an embryo until conditions are conducive to having a joey or until the joey from the previous season has vacated the pouch. This ability is called 'embryonic diapause' and is common in macropods.
The colour of the fur tends to reflect the type of country in which the animal finds itself. Thus animals living in granite type terrain will be more brown than those living in sandstone or basalt areas. Moulting occurs each autumn. Typically the fresh fur is grey on the back and changes through the year to some variation of brown. The chest and belly are lighter, typically a sandy brown and the paws and feet are dark. There is a dark mark from the centre of the forehead to the back of the head and a pale stripe running from below the eye to the mouth. The paws and feet are dark. The tail darkens towards the tip.
Mareeba and Allied males weigh about 4.7kg and the females a little less. Sharman's males are slightly lighter at about 4.4kg and females 4.1kg.
The Mareeba Rock-Wallaby is found only in the Mareeba area, inhabiting the highlands west of Cairns (around Mount Garnet) to the Herbert and Mitchell Rivers inland to Mungana. In this area there are several very popular tourist destinations and the Mareeba rock-wallaby has become very used to human contact and will line up for handouts. It is probably easiest to see these cute creatures at one of the picnic sites.
The 'assimilis' in the Allied Rock-Wallaby's scientific name means 'similar to a rock-weasel'. It is found south of Townsville northwards to Croydon and west out to Hughenden. It is also found on Magnetic and Palm Islands.
Sharman's Rock-Wallaby has one of the smallest ranges. It is only found in scattered colonies in the Seaview and Coane range west of Ingham. Mt Claro is also in this region, which is no larger than 200,000ha. Its tiny distribution means it is at risk should there be any habitat loss or disturbance. It is basically nocturnal but in cooler months it sometimes emerges around twilight and again in the early morning to sunbake. Colonies of 40 or more individuals are not unusual.