Goodfellow’s tree kangaroo
Tree kangaroo might sound like an oxymoron to someone not familiar with the wildlife of New Guinea, but these arboreal macropods really do exist and inhabit the tropical rainforests of the island and the far northeastern territory of Queensland, Australia. In fact, the evolutionary history of tree kangaroos is a beautiful example of how life will always adapt to a new habitat to fully exploit its environmental carrying capacity.
Looking at the map one would naturally assume that the wildlife of New Guinea is similar or closely related to the fauna and flora of the other islands of the Indonesian archipelago. This supposition proves to be rather untrue: though New Guinea’s flora is a mixture of tropical rainforest species with Asian origin and typically Australasian plants, the second largest island of the Earth is inhabited overwhelmingly – and surprisingly – by animals of Australian origin.
New Guinea’s endangered Goodfellow’s tree kangaroo
©Copyright Zweer de Bruin /
The explanation lies in the geological history of the region: unlike the rest of the archipelago, New Guinea with the surrounding smaller islands is part of the Australian continental plate called Sahul and not the Sunda Shelf (extension of the Southeast Asian continental shelf). Sahul had separated from Antarctica and South America by the beginning of the Miocene; and kept slowly drifting northwards, colliding with the Sunda Shelf about 15 million years ago.
For long periods from the Miocene until the Holocene, today’s Australian mainland and New Guinea were linked by a land bridge during the repeated episodes of glacial advance when sea levels fell more than 100 meters and Sahul was exposed as dry land. Similarly, from time to time the Sunda Shelf used to be a continuous land mass connecting southeastern Asia and the Indonesian islands – Borneo, Sumatra, Java, Bali. In these periods the migration and distribution of species on the mainland and the respective future islands was unrestricted, but a barrier of a wide deep-water sea-channel along/above the colliding edges of the two continental shelves kept most species from crossing, and thus Asian and Australian wildlife – especially fauna – mostly separated.
However, many plant species have managed to spread through the channel; and as Sahul kept slowly drifting north to the tropical zone and the climate has gradually changed, the lush vegetation of the Asian tropical forests started to invade and replace the original flora on the northern territories of the shelf, developing into an entirely new habitat. This vegetation was quite different from the native flora, providing superior quality food in comparison with the plants of that age that were adapted to the more arid climate of the Australian landmass.
Only few animals – mainly bats and birds – have been able to cross the stretches of open water between the shelves; and the absence of leaf monkeys or any leaf-eating mammals occupying the canopy of the average Asian tropical forest left this niche of the new forests empty, presenting an evolutionary opportunity.
Tree kangaroos inhabit montane and lowland tropical forests of New Guinea and northeastern Australia
©Copyright Stu Rapley /
Around that time, rock-wallabies were abundant in northern Australia. Rock-wallabies are terrestrial kangaroos, but some of their species have a propensity to climb trees to feed on the flowers, fruits and leaves. Molecular evidence – genetic studies show that the Proserpine rock-wallaby is the closest living relative of tree kangaroos – strongly suggests a rock-wallaby ancestor around 5-7 million years ago that moved in into the new habitat and has slowly adapted to the arboreal lifestyle, evolving over time into a dozen of new species today known as tree kangaroos.
At the end of the last glacial period about 12 000 years ago the rising sea level separated New Guinea from the Australian mainland: most species of tree-kangaroos live now in the tropical forests of the islands, only two species are native in Queensland. Most tree-kangaroos are endangered, with decreasing populations threatened by hunting for food and by habitat loss: one of the endangered species is the Goodfellow’s tree kangaroo, also known as ornate tree kangaroo.
Range: The Goodfellow’s tree kangaroo is endemic to the island of New Guinea; the current range of the species covers the mid-montane regions of the Central Cordillera from the Indonesian border to Milne Bay province. Historically it used to occur in lowland areas too but now it’s locally extinct: rapid deforestation of these regions has destroyed most of its habitat.
Habitat: Goodfellow’s tree kangaroos inhabit montane and lowland tropical forests, they adapted to a canopy-dwelling lifestyle.
Goodfellow’s tree kangaroos have two golden stripes on their back and every individual has a unique pattern of rings and blotches on their tail
Description: The anatomy of the Goodfellow’s tree kangaroo (Dendrolagus goodfellowi) is a great example of a living transitional form of evolution. Tree kangaroos have several features clearly showing the adaptation to arboreal lifestyle; but their general anatomy is still close to the ground-dwelling ancestor and is rather unsuited to a life in the canopy of trees. They have shorter and broader hind limbs with ankle joints that are modified from the highly specialized ankles of terrestrial hopping kangaroos to allow the foot to be rotated to grip branches; their arms are proportionally larger and stronger; they have rubbery pads on the soles of their feet and their paws and large, curved claws; their tail is lighter built and they use it well to balance while moving; and – unlike hopping kangaroos – they can move their hind limbs independently. But compared with perfectly adapted tree-dwelling animals like monkeys, possums or squirrels they are still clumsy climbers.
Goodfellow’s tree kangaroos have a body length of around 55-80 cm with a tail length of 70-85 cm. They have maybe the nicest coloration among tree kangaroos: their short, wholly fur has a soft reddish-brown shade; they have a greyish-brown face and light golden underbelly, throat and limbs. Two longitudinal golden stripes run on their back where they have a characteristic vortex of hair. Every individual has a unique pattern of brown and golden rings and blotches on their tail.
Goodfellow’s tree kangaroos eat large quantities of leaves
©Copyright Nathan Rupert /
Goodfellow’s tree kangaroos feed mainly on leaves of the forest trees; but occasionally they consume flowers, fruits, cereals and even insects. They have a sacculated stomach with fermenting bacteria to digest the large quantities of fibrous foliage. They are active in the morning and afternoon, except near human settlements where they are mostly nocturnal.
Goodfellow’s tree kangaroos are solitary and territorial animals. Being marsupials, females have a well-developed pouch opening forward. They have one young per birth after a 21-38 days gestation period, and the joey grows for almost a year in the pouch before first leaving.
Endangered Goodfellow’s tree kangaroos in the Melbourne Zoo
©Copyright Tim Williams /
Threats: Except humans there are virtually no predators or competitors for Goodfellow’s tree kangaroos in their habitat; the species – as all tree kangaroo species – is primarily threatened by uncontrolled hunting for meat and extensive habitat destruction. The lowland tropical forests of the island had been almost completely eliminated and replaced by plantations – coffee, rice, palm oil and wheat – and farm gardens of locals; and logging continues in the montane areas for timber, mining and more agricultural land.
The Goodfellow’s tree kangaroo poster at the top of this post is available in my store on Redbubble, with design variations more suitable for apparel and other products. My whole profit goes to the Sea Shepherd to support their fight to protect our oceans and marine wildlife.
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