Tree-Kangaroos of Australia
The tree-kangaroo is a marsupial. Marsupials give birth to very underdeveloped young. Lumholtz's tree-kangaroo belongs to the marsupial order Diprotodontia. This means they have two (di-), protruding (-proto-) teeth (-dontia) (incisors) at the front of the lower jaw. The next division down the scientific classification of animal is the family which in this case is Macropodidae meaning 'big foot', and finally the genus is Dendrolagus (Latin for tree-hare). This species is one of the smallest of the tree-kangaroos.
Lumholtz's and Bennett's tree-kangaroos (seen below) are endemic to Australia. 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 live in the North Queensland rainforests. Lumholtz's tree-kangaroo once frequented coastal lowlands but is now seldom seen below 300 metres from sea level.
Although having 'kangaroo' as part of its name, there are marked differences between it and its ground-dwelling relations. The tail of the tree-kangaroo is very long and pendulous. It is not prehensile and thus not used for gripping branches but it does help the animal to balance. Whereas ground-dwelling kangaroos have very short forelimbs and very long hind limbs, the forelimbs of the tree-kangaroo are stronger and longer. They are also more muscular and of more use when climbing. The hind feet are broader and shorter. Spongy, rough surfaces on the paws are an adaptation to assist with gripping and climbing.
Unlike the kangaroo, the tree-kangaroo can move the hind feet independently of each other. It can move backwards too unlike its terrestrial cousins. When descending a trunk, it grips with the forepaws and travels down tail first, allowing the hind feet to slide down bit by bit. Before reaching the ground it will kick off from the trunk and, cat-like, twist in the air and land on its feet. It may let go the trunk at perhaps ten metres from the ground. Once on the ground, it will hop or walk. The home range is marked by scent but not defended against others. The range of the female seems to be within the resident male's range. Female ranges do not normally overlap. There are loose social structures in place with a male, several females plus young keeping a vague connection but in the main the animals remain solitary. Every three or four days the male will visit each female's home range but unless courting or mating, it will keep some distance away.
Baby marsupials are born blind and hairless. They instinctively make their way from the birth canal to the pouch. The Lumholtz baby weighs just a few grams at birth and uses its forearms to claw a path to the pouch. The hind legs are so underdeveloped as to be useless yet the task takes less than five minutes. The pouch is forward opening and has four teats.
In the pouch, the baby attaches itself to a teat and continues its development. The fur starts to grow at three months, the eyes open at four months and they emerge from the pouch at five months. From that time on they spend more and more time out of the pouch foraging for food. Captive Lumholtz babies were eight to nine months old before they permanently leave the pouch. They suckle from outside the pouch until weaned at around 13 months of age. In the wild, they probably stay with the mother for another twelve months before going off to find their own home range. It is believed that only one baby is born each year.
Males measure 52 to 59cm in length and the tail is another 70cm. The females are quite a bit smaller weighing about 48cm. The head is small and rounded. The snout is large and the ears small and round. They are blackish-brown in colour with yellow-grey ventral surfaces. The half of the tail near the body is light brown and the rest a dark blackish-brown. The lower back is speckled with lighter coloured fur and there is yellow-grey down the cheeks and on the throat. There is also a yellow-grey 'sweat-band' across the forehead. Behind the shoulders, the hair parts to channel water off the back when it rains. The base of the tail is often nude where the animal sits. Immature animals have a distinct tuft on the tail.
This species feeds mainly on leaves with some fruit and flowers. The Lumholtz is cathemeral meaning that it is active on and off throughout the day. When it sleeps it just rests the head on the chest or will even droop forward till the head is between the feet. The exact position depends on the position and vegetation of its position at the time. It does not build a nest nor does it sleep in hollow trees.
The main threats to the Lumholtz are habitat destruction, accidents with traffic and predators such as dogs and dingoes. It is most prevalent on the Atherton Tablelands (mostly on private land). Cars and dogs account for most casualties here. Young males crossing open grounds or roads while looking for a new range are the most common victims. National parks and reserves are home to small populations but the genetic base is very small and a constant concern.
When frightened they may freeze. If in the trees, they may leap down and attempt to outrun their predator. While they can outrun natural enemies such as owls and eagles, dogs and dingoes find them an easy meal.
An incorporated community group based on the Atherton Tablelands in Far North Queensland, Australia, has been functional since 1997. It has a particular interest in the tree-kangaroo and endeavors to conserve these animals plus other Far North Queensland mammals by promoting awareness and knowledge of the local species. Its other aims are to undertake and assist with research and to liaise with other organizations and groups that have similar aims.