By Damon Ramsey of www.ecosystem-guides.com
While most people (visitors and residents alike) think of kangaroos and wallabies being open woodland and grassland “outback” animals, there is a high diversity of these animals in the Australian tropical rainforest.
The tropical rainforest and its edge supports a range of very types of “roos” including primitive rat kangaroos, rainforest floor pademelons, and tree kangaroos in the canopy.
The superfamily that comprises all of the kangaroos, wallabies and their various relatives is a diverse but recognizable group.
In total, there are at least 65 species, with most being found in Australia and also New Guinea.
Despite the varied range of forms, there is a common body plan to all members of this group.
They are often referred to as the “macropods” from the scientific name of the superfamily, which translates from the Greek to mean “big-footed”.
This term describes one of their most defining and distinctive characteristics: long toes on big feet, and on the end of strong hind legs.
In contrast, the arms and hands are generally much shorter and weaker.
Kangaroos probably evolved from a possum-like ancestor.
The tropical rainforest is home to what is usually considered the most primitive of the kangaroos, the Musky Rat Kangroo (see below).
All of the extant species belong to two families:
the smaller, more primitive potoroids (rat kangaroos, potoroos, bettongs),
and the generally larger and more recently evolved macropodids (kangaroos and various wallabies).
All living macropods are more or less herbivorous, the smaller ones being a little more omnivorous, and the larger ones being more standard grazers.
Of the 2 families of kangaroos, the potoroids are considered the more primitive.
As kangaroos are thought to have evolved from a possum-like ancestor, the potoroids retain more “primitive” arboreal possum-like conditions than their larger wallaby and kangaroo relatives, such as less developed hind legs and shorter feet than their “big-foot” cousins, and slightly prehensile (climbing) tails.
Potoroids are much more omnivorous in their diet, and they cannot generally digest grass like their larger stomach relatives, but eat “easier” food such as fruit, tubers, fungi, insects, and may even scavenge dead animals.
There are also behavioural differences: unlike the bigger kangaroos, which essentially plonk down on the ground or rest up against a tree to snooze, the smaller, more vulnerable potoroids make nests, constructed out of plant materials such as grasses and fallen branches.
They use their grasping “possum-like” tail to carry material for their nest making; the glimpse of a small kangaroo bounding through the undergrowth with a curled tail full of sticks is quite an odd sight.
Apart from reproduction and raising young, potoroids are not considered gregarious, and are usually seen scampering alone along the ground.
Currently, there are about 10 species of potoroids in Australia.
The main species in the tropical rainforest of Australia is the "Musky Rat Kangaroo".
The unusual common name of “Pademelon” is probably corrupted from a word used for this wallaby by Aboriginals in the Sydney region.
They can be considered a rainforest wallaby, for the 4 species are found in the denser, wetter forests of eastern Australia and New Guinea, as well as in nearby sclerophyll forest and grasslands.
Pademelons are rather small, squat wallabies with soft, thick fur and relatively short tails.
They usually sleep and rest deeper in the forest through the middle part of the day.
In the afternoon, night and mornings they may come out onto the edge of the forest and into clearings to feed, often wearing out little trackways in the denser foliage.
They feed on fruits, grasses and leaves and some have even been blamed for crop losses.
Pademelons are usually thought as solitary animals, with feeding in groups only due to sharing of the resource, and are reported to scatter when alarmed rather than bunching together as the more gregarious macropods do.
However, this is countered by observations by John Chambers of the Red-Legged Pademelon in North Queensland that seem to operate in groups, complete with dominant individuals and guards that sound perimeter alarms by thumping the ground with their big feet much like rabbits.
Breeding occurs all year, with males that are not usually much taller than the females, but may weigh almost twice as much due to more muscle.
There are 8 species of Tree-kangaroo, including some that have only recently been discovered.
They occur mainly in New Guinea, but there are 2 species found in Australia.
Kangaroos may have evolved from possum-like marsupials that once lived in trees; but the tree kangaroos represent a group of kangaroos that have gone back and re-colonized the canopy.
While some species are noted on the ground in New Guinea, the Australian species are tree-dwelling (arboreal) kangaroos and thus the largest animals to be found in the rainforest canopy.
They are the only kangaroos that regularly move the legs independently, obviously useful in walking along branches and climbing up trunks.
They also have large and sharp claws, and much heavier, thicker forearms than other kangaroos.
They browse on a variety of different leaves of rainforest trees.
However, they are not perfectly adapted to their habitat: their long tails hang down and are not prehensile (although they are useful for balance), and they often climb down backwards and rather awkwardly out of trees, or if alarmed, they may simply jump out and hop away, creating a crashing sound as they do.
The 2 species found in Australia are restricted to the rainforests of north-eastern Queensland:
Bennett’s Tree-kangaroo, and