Marsupials of Australia
The kangaroo is symbolic of Australia and is widely used as an Australian icon. In a scientific sense, kangaroos range from tiny potoroos and bettongs to the large red kangaroo. The smallest species weighs 0.5 kgs and the largest around 90 kgs. All belong to the super family Macropodoidea (macropod meaning 'great-footed'). This super family is further divided into Marcorpodidae and Potoroidae families. In all there are over 60 different species of kangaroo and their close relatives.
The different species are found in all types of habitat throughout Australia from alpine snowfields to arid deserts and tropical rainforests. Some species including tree-kangaroos are also found in New Guinea.
Kangaroos are herbivorous and mostly nocturnal although some are crepuscular ie active mostly in twilight hours (early morning and late afternoon). Their meagre diet of grass and leaves is converted into energy-giving glucose. They have a complex forestomach which breaks down plant fibre by fermentation.
Kangaroos have powerful back legs and long feet. When moving at speed they hop on the back legs using the tail to balance. When moving slowly, the kangaroo balances on the forelegs and the tail, swinging the hind legs forward in a pendulum movement. In this way the tail is used as a fifth limb. The hind legs are moved virtually together when hopping or 'walking' but when swimming (and roos are quite good swimmers) they may move the hind legs independently of each other.
Tree-kangaroos move each hind limb separately when climbing. While some of the smaller species can wrap their tail round nesting material to carry it to their nest, the tree-kangaroos cannot use their tails to grasp branches.
The most comfortable speed for the largest species, the red kangaroo, is 20 to 25 km per hour. To increase the speed at around 40 km per hour, the length of the hop increases although the rate does not. Short distances can be covered at 65 to 70 km per hour at which the rate and the length increases.
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Kangaroos are marsupials meaning they give birth to an underdeveloped baby. The females (called does) have pouches which open to the front. There may be four teats in the pouch each producing milk of a different constitution. She may have a blind, hairless, jelly-bean sized 'joey' attached to one teat and the previous season's offspring who is still suckling but feeds from outside the pouch. When conditions are good, the does will breed all year round. The does of some species are able to practise embryonic diapause, that is, they can delay the continued development of an embryo in the uterus if conditions are not suitable. Thus, while the normal gestation period is less than 35 days, a full twelve months can elapse between a successful mating and the birth of that offspring.
Some species when giving birth lean back against a support with the tail forward between the hind legs. Others don't use a back support and still others don't bring the tail forward. When born the embryo is less than 25mm long. It claws itself from the birth canal through the fur on the mother's belly to the pouch. Once in the pouch it attaches itself to a teat. The teat swells to firmly hold the joey for a period of time. Once the fur begins to grow, the joey is able to release the teat and reattach itself. Soon it will be peeping out of the pouch.
The muscles controlling the pouch can be contracted or relaxed to either tip the joey out or to prevent his entry or egress depending on circumstances. Joeys enter the pouch head first then completely somersault to end up facing the pouch opening. They do not always lay in the pouch with the head poking out. Sometimes a tail and two spindly hind legs will emerge or a head and tail or some other combination.
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the life within one mob of wild Eastern
Grey Kangaroos over a two year period.
Learn more about kangaroos and other
marsupials with this informative DVD.
The Red Kangaroo
The largest of the species is Macropus rufus or the red kangaroo. The red kangaroo often lives in mobs and can cover a distance of five metres each leap. The male red kangaroo or buck, when seated on its haunches, can measure 1.8m in height. When preparing to fight, males raise themselves onto their toes using their tails to balance. They will grapple with each other, keeping their heads well back while attempting to claw the eyes of their opponent. Balancing on the tail, they will bring the hind legs up and strike violently downwards. In this way they try to disembowel the other animal. The hind feet have strong, hard toes which can inflict great damage on an adversary.
Four species of kangaroo are commercially harvested. These species are not endangered or threatened. The meat is increasing in popularity and is considered a fine game meat. It contains minimal amounts of saturated fat and is high in protein, zinc and iron.
The skin and fur is also used. Kangaroo skin is lightweight but very strong. It produces high quality leather goods including shoes. Because of its high tensile strength, kangaroo leather is also used in the manufacture of sporting footwear.
Albino kangaroos are not uncommon, particularly in zoos and wildlife parks. The baby above is very young and has yet to grow his fur.
The more common species of kangaroo are often hit by cars and can do a considerable amount of damage to a vehicle. If a doe is hit, always check to see if she has a joey in her pouch. Joeys have the greatest chance of survival if taken to a wildlife centre but you may need to look after it overnight. Looking after an orphan joey needs a big commitment in time and energy.
In our area of south-western Australia, there are many western grey kangaroos. We often have kangaroos in the garden of our small property and we now try to grow mostly those plants that they don't like. We enjoy watching them, especially when the joeys begin poking out of the pouches.