Kangaroo

Macropus rufus
Macropus giganteus
Macropus fuliginosus

</table> A kangaroo is any of several large macropods (the marsupial family that also includes the wallabies, tree kangaroos, wallaroos, pademelons and the quokka: 45 species in all). The term kangaroo is sometimes used in a broader sense to refer to all members of the macropod family. The kangaroo is native to the continent of Australia. There are three species of kangaroo:

• The Red Kangaroo (Macropus rufus) is the largest surviving marsupial anywhere in the world. Red Kangaroos occupy the arid and semi-arid centre of the continent. A large male can be 1.5 m tall and weigh 85 kg.
• The Eastern Grey Kangaroo (Macropus giganteus) is less well-known than the red, but the most often seen, as its range covers the fertile eastern part of the continent.
• The Western Grey Kangaroo (Macropus fuliginosus) is slightly smaller again at about 54 kg for a large male. It is found in the southern part of Western Australia , South Australia near the coast, and the Darling River basin.

In addition, there are over 40 smaller macropods that are closely allied to the kangaroos:

• Tree kangaroos are arboreal relatives of the true kangaroo which are found in the dense rainforests of north-east Australia and New Guinea. Several tree kangaroos are endangered, largely because of habitat destruction.
• Wallabies are smaller, usually more thick-set, macropods.
• A wallaroo is a very large wallaby or a small kangaroo.
• Pademelons are small, forest living macropods of around 4 to 6 kg.
• The Quokka is a small wallaby-like macropod of Western Australia.
• Rat kangaroo is a term loosely applied to any of several very small kangaroo-like marsupials, some from the family Macropodidae, some not.
• Kangaroo rats, in contrast, are rodents.

Kangaroos have large powerful hind legs, large feet designed for leaping, a long muscular tail for balance, and a small head. They are the only large animal that uses hopping as a means of locomotion. The comfortable hopping speed for a red kangaroo is about 20-25 km/h, but they can hop as fact as 70 km/h on short distances. Kangaroos are herbivores, feeding on grass and roots, and they chew cud. All species are nocturnal and crepuscular, usually spending the days idling quietly and the cool evenings, nights and mornings moving about and feeding, typically in groups called mobs. The life expectancy of a kangaroo is about 18 years. Unlike many of the smaller macropod species, the large red and grey kangaroos have fared well since European settlement reduced dingo numbers, created vast grasslands intended for sheep and cattle, and added stock watering points in arid areas. In some areas, kangaroos are culled by professional hunters, and the meat (which is tasty, tender, and low in fat) and hides are sold. Some conservationists argue that selective hunting practices (targeting young adult males) has put the population at risk, but there is no evidence of a decline in numbers. Some activists have undertaken campaigns to prevent the culling or farming of kangaroos, presumably misunderstanding the differences between kangaroos (which are not at all threatened) and other macropods, several of which are in considerable danger of extinction. The word kangaroo is said to derive from the Guugu Yimidhirr (an Australian Aboriginal language) word gangurru, referring to a particular species of kangaroo. The belief that it means "I don't understand" is a popular myth that is also applied to any number of other Aboriginal-sounding Australian words. Male kangaroos are called bucks, boomers or jacks; females are does, flyers, or jills and the young are joeys. The collective noun for kangaroos is a mob. Kangaroos are popularly known as, along with koalas, the signature animals of Australia. As such they are common subject of toys and souvenirs of the continent. The animal is included in the Australian coat of arms and is also part of the logo of Qantas, the largest Australian airline, sometimes nicknamed the flying kangaroo. The Australian national rugby league team are nicknamed the Kangaroos.

Biological specificities

The kangaroo has many peculiar biological specificities. As with all marsupials, babies are born at a very early stage of development after a gestation of 31-36 days. At this stage, only the forelimbs are somewhat developed, to allow the newborn to climb to the pouch and attach to a teat. In comparison, a human embryo at a similar stage of development would be about 7 weeks old, and premature babies born at less than 23 weeks are usually not mature enough to survive. The baby kangaroo will usually stay in the pouch for about 9 months (for the Western Grey kangaroo), before starting to leave the pouch for small periods of time. He will usually be fed by its mother until he is 18 months, at which age he will reach sexual maturity.

A female kangaroo is usually pregnant in permanence, except on the day she gives birth; however, she has the ability to freeze the development of an embryo until the previous joey is able to leave the pouch.

The composition of the milk produced by the mother vary according to the needs of the baby. In addition, she is able to simultaneously produce two different kind of milk for the newborn and the older joey who still lives in the pouch.

A sequencing project of the Kangaroo genome was started in 2004 as a collaboration between Australia (mainly funded by the State of Victoria) and the NIH in the USA. The genome of a marsupial such as the kangaroo is of great interest to scientists studying comparative genomics because marsupials are at the right "distance" from humans: mice are too close and haven't developed many different functions, while birds are already too far away. The dairy industry has also expressed some interest in this project.

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