Tropical Topics A n i n t e r p r e t i v e n e w s l e t t e r f o r t h e t o u r i s m i n d u s t r y Macropods of the wet tropics No. 42 September 1997 Tree roos — evolutionary U-turners Notes from the Along with possums, the three types of rainforest macropods — musky rat- kangaroos, pademelons and tree-kangaroos — represent different chapters in Editor the story of macropod evolution in the rainforest. Yes it’s green! All macropods are thought to have Over time, as climates changed, Thanks largely to lobbying by evolved from possum-like animals. In Australian rainforests shrank and Daintree tour operators, funds have the days when most of the Australian grasslands spread. Ground-dwelling been made available from the continent was clothed in rainforest, life macropods continued to adapt to the Daintree Rescue Program to also must have been easy for these tree- new lifestyle and diet, changing in rescue the wet tropics issues of dwelling, leaf-munching marsupials. shape accordingly. Their hindlegs got Tropical Topics. As a result, you However, some of them, at some stage, longer, tails became less flexible and will again receive eight issues per seem to have descended to the teeth and stomachs adapted to grazing year, alternating, as before, between ground, perhaps in search of rather than browsing. Some kangaroos blue issues with marine themes and fallen fruit and fungi. Finding it and wallabies left the forests far green ones with wet tropics themes. to their liking, some stayed behind them as they ranged into arid If, however, you are interested in there. regions. reading only the marine issues, please let me know (address at the While many of these Meanwhile, some kangaroos made back) and I will endeavour to adjust venturesome animals an unpredictable choice. They the mailing list accordingly. changed shape quite looked back up at the trees and Green radically when adapting recognised a food source or, This issue looks at macropods in possum to life on the ground, one perhaps, a refuge from predators. the wet tropics. The Macropod, or species found in today’s Having evolved quite ‘big feet’, superfamily is divided rainforests, has retained thoroughly from tree- into two families. The Potoroidae several possum characteristics. dwelling possums to ground- family includes rat-kangaroos, The musky rat-kangaroo is the dwelling kangaroos, having potoroos and bettongs and the only macropod to have a ‘thumb lost their opposable toes and Macropodidae is made up of the toe’ — an opposable toe on prehensile tails, they headed various kangaroos, wallabies and each hind foot. Possums use this back up into the trees. pademelons. Both of these are for climbing, but the musky rat- Tree-kangaroo represented in the wet tropics by kangaroo is essentially a forest floor Tree-kangaroos have since particularly interesting species. animal, doing little more than readapted to an arboreal life (see clambering through fallen tree page 4) but are still, essentially, branches. Musky rat-kangaroos have kangaroos in trees. However, the also retained the ability to clutch with bizarre decision of their ancestors Please note their tails; possums make good use of to return to the canopy seems to that you are welcome to their prehensile tails when climbing have paid off. Tree-kangaroos photocopy Tropical Topics. whereas kangaroos and wallabies have have managed to survive However, if the text is reproduced heavy straight tails which they use for successfully for millions of years side separately it must not be altered balance and support. by side with their possum ancestors. and must acknowledge the Environmental Protection Agency as the source. Illustrations must not be reused without permission. Please Musky rat-kangaroo contact the editor (details on the Wallaby back page) if in doubt. Outside the rainforests In addition to rainforests, the wet tropics includes other habitat types which appeal to various macropods. Agile wallaby Rock-wallabies The agile wallaby is the most There are at least 15 species of rock-wallabies in Australia, common wallaby in tropical living in rocky habitats where they can easily find shelter coastal Australia — it from predators and from the sun. With granulated soles, ranges all across the top which have been compared with off-road tyres, they hop end from Broome in WA easily through this inhospitable environment, arching their to Rockhampton in tails over their backs to aid their balance. They become Queensland — and is active in the late afternoon, feeding throughout the night on probably the most a wide variety of plants. commonly seen wallaby in the wet tropics. Mobs of agile wallabies can Mareeba rock-wallaby be seen grazing when they emerge from resting A number of rock-wallaby species which lack any distinct places in dense vegetation in the late afternoon — or even markings were regarded as the same species until the 1970s earlier on gloomy days. Unfortunately, they are also likely to when scientists discovered that their chromosome numbers be seen dead at the side of the road. and shapes differed. Swamp wallaby In 1992 three distinct species — the allied, Sharman’s and, in the wet tropics, the Mareeba rock-wallaby — were The swamp wallaby is a peculiar creature. Although it looks formally described, distinguished only by their chromosome like a typical wallaby, its teeth are different, it has a different make-up. (They also look similar to the unadorned rock- reproduction strategy and it behaves in a different way. wallaby, with which they were once all grouped.) Just to Also, while other ‘typical’ wallabies* have 16 chromosomes, confuse the issue further, the Mareeba rock-wallaby the male swamp wallaby has only 11 and the female 10. It is interbreeds with Godman’s rock-wallaby and a hybrid race, thought to be the only surviving member of the genus with mixed characteristics, exists where the ranges of the Wallabia. two species meet. The swamp wallaby can be found all along the east coast. It The Mareeba rock-wallaby is found hides in thick undergrowth in forests and woodlands during from the Mitchell River, near Mount the day, coming out at night to eat. A browsing rather than Carbine, in the north to south of grazing animal, it prefers coarser shrubs and bushes to Mount Garnet, and inland to grass. It also eats agricultural crops close to shelter as well Mungana. (Godman’s is found as plants such as hemlock which are highly poisonous to north from Mount Carbine to cattle and people. Despite its name, the swamp wallaby is Bathurst. Although once more likely to be found in hills than swamps. common on Black Mountain, near Cooktown, it is now rare In the wet tropics, the swamp wallaby is less common than there.) the agile wallaby and although similar in size can be distinguished from it by its very dark colour. It has a yellow Like the two similar species, to rufous front and Queensland animals tend to have a the colour of the Mareeba white tip to the tail. It is also more solitary than the agile rock-wallaby varies, from wallaby. almost black to light brown, according to the colour of the *In the genus macropus. rock on which it lives. Northern bettong Belonging to the same family (potoroid) as the musky rat- composed of a soft nutritious core and an outer coating kangaroo, bettongs also retain some ‘primitive’ which contains reproductive spores. characteristics from their possum-like ancestors. Their tails are prehensile and, although not as strong as a possum’s, Numbers of these truffles seem to increase dramatically after are used to carry nesting material. Their stomachs, teeth and fire. The reason for this may be connected to the limb proportions are also different from those of more relationship between the parent fungi and the forest. Known typical macropods. as mycorrhizae, these fungi form associations with trees. Wrapping themselves around the tree roots they extract Only three populations of the northern bettong are known sugars produced by the plants but also feed back water, to exist — small ones on the Mt Windsor and the Carbine nitrogen and phosphorus. It is a close relationship without Tablelands and the other on the Lamb Range, in the vicinity which either party could die. of Davies Creek National Park. This animal’s preferred habitat is wet sclerophyll forest which generally occupies a When the forest is burnt, the stress experienced by the trees fairly narrow strip between rainforest and dry sclerophyll. may be transmitted to the fungi which, faced with possible With the decrease in burning by Aboriginal people and death, reproduce. The resulting abundance of truffles may graziers, rainforest is advancing into wet sclerophyll and come at the best time for the bettongs, when this little animal’s habitat is in danger of shrinking. conditions are dry and other food scarce. In return, the bettongs, by The northern bettong is strictly nocturnal, sleeping in a consuming the truffles, disperse grassy nest under the skirt of a grass tree or in a hollow log the fungal spores. Bettongs are during the day. Using its well-clawed forefeet and elongated therefore a vital part of these third toes, it digs up grass roots, tubers and the fruiting forest ecosystems. bodies of underground fungi. Known as truffles, these are a very important part of the bettong’s diet. They are 2 Out and about Report stranded marine wildlife Note: Items past their 'use-by The Department of Environment and date' have been removed from this the Great Barrier Reef Marine Park page for website.