The endangered tree-kangaroos of Australia and New Guinea
Tree-kangaroos are marsupials and give birth to very underdeveloped young. Tree-kangaroos belong to the marsupial order Diprotodontia. Di- (two) proto- (protruding) dontia (teeth ). The family is Macropodidae meaning 'big foot', and the genus Dendrolagus (Latin for tree-hare).
Tree-kangaroos are agile and confident in the forest canopy but slow and clumsy on the ground. They may hop or walk when on the ground. All limbs can be moved independently and it can move backwards in contrast to its terrestrial kangaroo cousin.
They lean well forward when hopping to balance the heavy tail which they curl over the back. In the trees, it leaps for up to 9 metres or more but always in a downwards direction. When going to the ground it will descend backwards down a trunk, gripping with the forefeet and letting the hind feet slide. At some distance from the ground (even ten metres or so) it will launch itself from the tree, turn in mid-air and land on its feet much like a cat does. The tail is used for balance and is not prehensile ie it cannot wind itself round a branch. The tail is longer than the body and head put together.
The paws have spongy, rough pads and sharp, curved claws. The ground-dwelling kangaroo has very short forearms and very long hind legs but the tree-kangaroo is more 'balanced' with the forearms being more muscular and longer. The hind feet are broader and shorter than a terrestrial kangaroo.
The baby (joey) is born blind and naked and about the size of a jellybean. The mother usually sits back on her rump with the tail pointing forward between the hind legs. She licks a path through her fur to the pouch but that is all the help she gives the tiny creature. Once out of the birth canal, he must pull himself, with the forearms, through the fur until he reaches the pouch.
The hind legs are very undeveloped at this stage. He instinctively searches for the pouch and, once inside, he attaches himself to a teat. He will spend some months on the teat while he develops further. His fur will grow, his eyes open and soon he will begin to poke his head out of the pouch. Once out of the pouch he will continue to suckle from outside for some time and may spend more time in the company of the mother before going off to find his own home range. Usually only one joey is born at yearly intervals.
Like many marsupials of the kangaroo family, the females can delay the development of an embryo if conditions are not conducive to giving birth (embryonic diapause).
Tree-kangaroos are classed as ruminant herbivores although they will also eat birds' eggs and insects, especially in captivity. They have a large stomach similar to a cow's. One section of the stomach contains bacteria which break down cellulose (fibre) from the vegetation.
Australia is home to two species of tree-kangaroo. Another eight or so species of tree-kangaroo are found in New Guinea. The two Australian species, along with the grizzled tree-kangaroo, have longer feet than the rest of the group. DNA research has shown these three species to be more primitive than the others.
The Australian species are Lumholtz's (Dendrolagus lumholtzi) and Bennett's (Dendrolagus bennettianus) tree-kangaroos.
Lumholtz's tree-kangaroo is named for Dr Carl Lumholtz, a Norwegian naturalist-explorer, who obtained a number of animals from the Herbert River area in 1882. The males of the species 52 to 59 cm with the tail being another 70 cm. Females are quite a bit smaller. They have a small, round head, a large snout and rounded, small ears. The lower back is speckled with lighter coloured fur and they have a 'sweat-band' of yellow-grey across the forehead, down the cheeks and on the throat. The ventral surfaces are also a yellow-grey. The tail is a light brown near the body and a dark blackish-brown to the tip. The rest of the animal is a blackish-brown. The hair behind the shoulders parts in such a way as to channel water off the back when it rains. There may be a bare patch at the base of the tail where the animal sits. Immature animals have a pronounced tuft on the tail.
Leaves form the main diet with some fruit or flowers. This species is cathemeral ie active on and off throughout the day. To sleep the head will simply rest on the chest or even droop down between the feet.
Bennett's tree-kangaroo is slightly larger than the Lumholtz. It is found in both mountain and lowland tropical rainforests in the far north-east of Australia but has a very small geographic range. The coat is dark brown but the top of the head and the shoulders are reddish-brown. It has a grey snout and forehead, and small, rounded ears. Very dark ventral surfaces camouflage the animal well from below. Weight varies from 8 to 14 kg. Males are larger than females. This species is nocturnal. Leaves from the umbrella tree form the major part of its diet along with vines, ferns and wild fruit.
Goodfellow's Tree Kangaroo (Dendrolagus goodfellowi) (also known as the Ornate Tree Kangaroo) has short chestnut to crimson fur and a pale belly. The red-brown coat has double golden stripes running from half way down the back to the top of the tail. The tail is ringed red and gold. It is commonly believed that every animal has an individual arrangement of the colours on the tail rather like zebras having an individual pattern of stripes. The face is a grey-brown. Cheeks, neck and feet are yellow. It weighs around 7 to 9.5 kg with males being slightly larger than females. This species is nocturnal. Its main diet is the leaves of the silkwood tree. It also eats flowers, grasses, fruit and ferns. In captivity they have a life span of over 14 years.
This species is widespread throughout the mountainous rainforests and tropical deciduous forests of New Guinea. It is listed as endangered.
The Grizzled Tree-kangaroo (Dendrolagus inustus) has two sub-species. It was first discovered in 1828 and was the second tree-kangaroo to be given a scientific name. However, there is still relatively little known about it. It is widely distributed in the tropical rainforest and foothills of New Guinea. When fleeing from danger, these animals always move downwards. As they are slow and unwieldy on the ground they are then easily captured by hunters, who will often just grab them by the tail.
It is hunted as a food source and for the pet trade. It can reach a very large size with males weighing almost twice as much as females. The males appear to continue to increase in size throughout their life. Generally weight seems to range from 8 to 15 kg (one zoo specimen reached 23 kgs) and length from 80 to 90 cm with the tail adding almost as much again.
Compared to the other New Guinea tree-kangaroos, the Grizzled is rather rangy with a small head, flat muzzle and long limbs. Males have particularly strong forearms. It is slate grey to chocolate brown in colour with medium length fur. It has a grey head and black ears. The inside of the .ears is hairless. The fur on the shoulders grows in the reverse direction to the rest of the fur.
The grey tail is often bushy and may be banded with light and dark stripes. It has much larger ears than the other species and the ears point sideways from the head rather than upwards. It is most active at dusk and dawn.
Unique among tree-kangaroos is a calloused 'pad' at the base of the tail but on the upper side. The characteristic resting position of the Grizzled Tree-kangaroo is sitting on this pad with the tail projecting forward between the legs. This is also the typical position for female macropods when giving birth. The pad is present in young still in the pouch. The lifespan is believed to be around ten years. Its natural foods are leaves, soft bark and fruit. In captivity, they will eat eggs and mealworms.
Tenkile's Tree Kangaroo (Dendrolagus scottae) is restricted to a small area on the summit of the Torricelli Mountain Range in the north western Papua New Guinea. Following the arrival and influence of missionaries in the area, once taboo places are now regarded as safe areas for hunting and the Tenkile has been hunted almost to extinction. The large, dark brown Tenkile has a musky odour which stays on the hands and/or clothes of anyone handling a Tenkile. Males weigh about 11.5kg with the female slightly smaller. Tenkile's Tree Kangaroo is one of the most endangered mammals in the world.