Tropical rainforest ramblers – why they deserve your votes

Rainforests covered most of Australia until about 20 million years ago. These vast forests supported a huge diversity of mammals, evident in the Riversleigh fossil deposits. As the continent became more arid, the characteristic Australian mammal fauna – such as kangaroos and koalas – diversified into the expanding woodlands and grasslands. Nevertheless, a contingent of mammals persisted in the ever-contracting areas of rainforests. By the last ice-age, rainforests had retreated to a few refugial areas in wet locations along the east coast of Australia.

The largest refuge, in the Wet Tropics of north Queensland, has conserved the most diverse suite of specialist fauna, like a moist Noah’s Ark sailing through an arid sea (?!). Here, over 20 species of rainforest specialist mammals have persisted – possums and tree-kangaroos, dasyurids and rodents, mega- and micro-bats. Some are closely related to the ancient rainforest fauna – the bones of ancestral musky rat-kangaroos, green possums and striped possums have been found at Riversleigh.

Another suite of species persisted in the rainforests of Cape York, or at least recolonised those forests from New Guinea, including Australia’s two species of cuscus, the spiny bandicoot, and endemic species of Antechinus, Melomys and Rattus.

Almost everywhere else across northern Australia, rainforest contracted into patches so small that, at best, only specialist rodents (Zyzomys) could eke out a living. Most other mammals across northern Australia can only utilise rainforests as part of their ecology; microbats are the stand-out example, with 27 of the 30 species in northern rainforests also utilising other habitats. The three rainforest specialist microbats – flute-nosed, golden-tipped and eastern forest bats – are restricted to the east coast.

Rainforest specialists have strong associations with the characteristic features of the ecosystem – for example, most of the nine species of possums that are rainforest specialists in northern Australia, along with both species of tree-kangaroo, feed on foliage, an abundant resource in rainforest. Rodents are the second-most diverse group of rainforest specialists, with the giant and pygmy white-tailed rats, tree mouse, and fawn-footed melomys being capable climbers, exploiting resouces in the rainforest canopy. Megabats consume rainforest fruits and flowers, although most extend their foraging into adjacent sclerophyll forests, which blossum seasonally. The rainforest dasyurids – the spotted-tailed quoll, several species of Antechinus and a dunnart – predate the invertebrates and small animals that abound in the forest. One particularly specialised mammal is the striped possum, which uses its elongated fourth finger to extract beetle lavae from rotting wood – an anatomical adaptation it shares (convergently) with the rainforest-adapted aye aye of Madagascar.

At the other end of the spectrum, a few habitat generalists occur in rainforest including the echidna (a termite specialist), the platypus and water rat (both requiring streams, rather than rainforest per se), and the dingo, which lives wherever it can get a meal (and hasn’t been persecuted to local extinction). These examples show it’s not essential to be a specialist to live in rainforest.

However, being a specialist helps when it comes to dealing with ecosystem-specific problems. One of the challenges of living in rainforest is coping with lots of rain. While many mammals shelter in burrows or hollow trees, a few – such as tree-kangaroos – spend their life exposed to the elements. Tree-kangaroos meet this challenge by having a ‘whorl’ in their fur behind their shoulders, which sheds water when animals sit hunched over in the rain. In fact, tree-kangaroos have a number of adaptations that have ‘reverse-engineered’ the arboreal lifestyle abandoned by their ancestors millions of years ago: they have strong forearms; a wide foot with a soft, flexible pad; big curved claws; a long tufted tail for balance; and legs that can move independently. Their bones are strong, too, permitting leaps from high in the canopy if an animal feels under threat.

Worldwide, rainforests are under threat from wholesale destruction and conversion to agriculture. In Australia, fortunately, most rainforest clearing has ceased, and our mammals aren’t hunted for food by people desperate for protein. The main threat to Australian rainforest mammals is climate change, which is reducing the extent of cool habitats to which many species are adapted. To conserve our precious cargo of mammals living in the ‘Noah’s Ark’ of Australia rainforests, we need to address this pressing global issue.

Meet the nominees:

Atherton antechinus (Antechinus godmani), north-east Queensland

They are the largest and most aggressive of the three species of antechinuses found in the Wet Tropics.

Australian spotted cuscus (Spilocuscus maculatus), Far North Queensland

Also known as the common spotted cuscus. The upper part of their curled, prehensile tail (closest to the body) is covered in fur, while the lower half is covered in rough scales to grip branches.

Bare-backed fruit-bat (Dobsonia magna), north-eastern coast of Queensland

They are the only Australian megabats that roost in caves, where groups of around 100 bats roost together.

Bennett’s tree-kangaroo (Dendrolagus bennettianus), northeastern coast of Queensland

They can only be found at high and low altitudes north of the Daintree River in an area only about 70km by 50km in size.

Christmas Island flying-fox (Pteropus natalis), Christmas Island

They are active during the day and can sometimes be seen flying and foraging in the mid-afternoon.

Christmas Island shrew (Crocidura trichura), Christmas Island

One of Australia’s most enigmatic animals, they have re-appeared after two periods of being considered extinct. Though as of today, they haven’t been spotted since 1985.

Lumholtz’s tree-kangaroo (Dendrolagus lumholtzi), north-east Queensland

They gracefully traverse branches using their muscular legs and powerful arms, and can even manage a suspended arm crawl under a branch, Tarzan style.

Musky rat-kangaroo (Hypsiprymnodon moschatus), north-east Queensland

Aptly named, they emit a distinct musky odour used for communication and territory marking.

Prehensile-tailed rat (Pogonomys mollipilosus), Queensland

They live in burrows in the ground, but spend their nights in understorey and trees, climbing with the help of its tail and feeding on leaves and fruits.

Red-legged pademelon (Thylogale stigmatica), eastern Queensland, north-east New South Wales

They are mostly silent, except when males make a harsh rasping noise during courtship and mothers coo softly to their young.

Spectacled flying-fox (Pteropus conspicillatus), north-east Queensland

They can fly 112 km and spread 60,000 seeds in a single night while foraging for food.

Torresian striped possum (Dactylopsila trivirgata), north-east Queensland

They have an elongated fourth finger that they use to extract juicy grubs out of rotting timber – very handy!