? Kangaroos | ||||||||||||||||
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| [image] Eastern Grey Kangaroo | ||||||||||||||||
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| Species | ||||||||||||||||
| Macropus rufus Macropus giganteus Macropus fuliginosus |
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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. Kangaroos are native to the Continent of Australia, while a number of tree kangaroos are found in New Guinea.
The word kangaroo is said to derive from the Guugu Yimidhirr (an Australian Aboriginal Language) word gangurru, referring to the Grey Kangaroo (see photo to the right). The name was first recorded as kangaru by Joseph Banks on James Cook's first voyage of exploration, when they were beached at the mouth of the Endeavour River in the harbour of modern Cooktown for almost 7 weeks repairing their ship which had been damaged on the Great Barrier Reef.
Kangaroo soon became adopted into standard English where it has come to mean any member of the family of kangaroos and wallabies. 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.
In addition, there are over 40 smaller macropods that are closely related to the kangaroos:
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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 animals to use hopping as a means of Locomotion. The comfortable hopping speed for Red Kangaroos is about 20-25 km/h (13-16 mph), but they can hop as fast as 70 km/h (43 mph) over short distances.
Kangaroos are large herbivores, feeding on grass and roots, and they chew Cud. Their heads in fact look much like those of llamas. 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.
Kangaroos have few natural predators. One of the major natural predators, the Thylacine, is now extinct. However, humans arrived in Australia at least 50,000 years ago and introduced the Dingo about 5,000 years ago. The use of dingoes, and later hunting dogs by Europeans, to hunt kangaroos has resulted in most kangaroos having an enmity for dogs. The mere barking of a dog can set a full-grown male boomer into a wild frenzy. In extreme circumstances, one or more wedge-tailed eagles will attack and sometimes kill a kangaroo (even an adult Red), but only when no more suitably-sized food is available. Goannas and other carnivorous reptiles also pose a danger to the smaller kangaroo species when other food sources are lacking.
Along with dingoes and other canids, introduced species like foxes and feral cats also pose a threat to kangaroo populations, as they do most native populations. Kangaroos and wallabies are apt swimmers, and often flee into waterways if presented with the option. If pursued into the water, a large kangaroo may use its forepaws to hold the predator underwater to drown it.
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 varies according to the needs of the joey. In addition, she is able to simultaneously produce two different kinds of milk for the newborn and the older joey who still lives in the pouch.
Kangaroos and wallabies have a unique ability to store elastic strain energy in the tendons of their large hind legs. As a consequence, most of the energy required for each hop is provided by the spring action of the tendons rather than by muscular effort. There is also a linkage between the hopping action and breathing: as the feet leave the ground, air is expelled from the lungs; bringing the feet forward ready for landing fills the lungs again, providing further energy efficiency. Studies of kangaroos and wallabies have demonstrated that, beyond the minimum energy expenditure required to hop at all, increased speed requires very little extra effort (much less than the same speed increase in, say, a horse, a dog, or a human), and also that little extra energy is required to carry extra weight. For kangaroos, the key benefit of hopping is not speed to escape predators - the top speed of a kangaroo is no higher than that of a similarly-sized quadruped, and the Australian native predators are in any case less fearsome than those of other continents - the benefit is economy: in an infertile continent with very variable weather patterns, the ability of a kangaroo to travel long distances at moderately high speed in search of fresh pastures is crucial.
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.
Along with the Koala, the kangaroo is regarded as the signature animal of Australia. The kangaroo and the Emu appear on the Australian Coat of arms. Kangaroos are often represented in toys and souvenirs. The kangaroo is part of the logo of Qantas, the largest Australian Airline. The Australian national rugby league team is nicknamed the Kangaroos.
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Some animal rights activists and Conservationists argue that the selective hunting of kangaroos for meat (targeting young adult males) has put the population at risk, but there is no evidence of a decline. Some activists have undertaken campaigns to prevent the culling or farming of kangaroos, sometimes using the slogan "Tourist drawcard - Not dead meat". Arguments center on the cruelty of shooting a National emblem. Major conservation organisations, on the other hand, point out that none of the three species of kangaroo is remotely threatened, and focus on the plight of smaller macropods, many of which are threatened or endangered. These campaigns have had some success in the United States, where few people know the real status of the kangaroo population, in preventing the establishment of an export market for kangaroo meat. Many people outside Australia mistakenly believe kangaroos to be an endangered animal, when in fact there are probably around 50 million kangaroos in Australia .
In 2002 the number of kangaroos allowed to be shot by commercial hunters was increased from 5.5 million to 7 million per year. While animal rights activists protested the move, Australian farmers said that there was a "plague" of kangaroos after a huge increase in their numbers. In July 2003 animal activists protested a planned cull of 6,500 kangaroos near the Puckapunyal army base. In July 2004 the ACT government began a program of shooting kangaroos around the Googong Dam near Canberra while animal activists, many who had come from overseas, protested against it. It was ordered because of fears of the dam becoming contaminated after a large downpour of rain if the kangaroos ate away all the grass.
Kangaroo meat has been quite successful on the European market, particularly in Germany. It is also processed into Dog food. Culling is closely monitored by the RSPCA and state authorities. Kangaroo farming is a substantially more environmentally friendly meat industry than present sheep or cattle farming: kangaroos require less feed than placental stock, are well-adapted to drought, do not destroy the root systems of native grasses in the way that sheep do, and have much less impact on Australia's fragile topsoils. However as of 2004, the traditional regulatory restrictions on the sale of kangaroo meat in the Australian domestic market make kangaroo farming economically unattractive. Nevertheless, the industry is worth around AUD $200 million annually.
Kangaroos are shy and retiring by nature, and in normal circumstances present no threat to humans. Male kangaroos often "box" amongst each other, playfully, for dominance, or in competition for mates. The dexterity of their forepaws is utilized in both punching and grappling with the foe, but the real danger lies in a serious kick with the hindleg. The sharpened toenails can disembowel an opponent, and this is the fate of many dogs that wrestle with a boomer. Boxing Kangaroos have been portrayed in Popular culture, especially Bugs Bunny cartoons.
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There are very few records of kangaroos attacking humans without provocation, however several such unprovoked attacks in 2004 spurred fears of a Rabies-like disease possibly affecting the marsupials. The only reliably documented case of a fatality from a kangaroo attack was New South Wales, in 1936. A hunter was killed when he tried to rescue his two dogs from a heated fray. Other suggested causes for erratic and dangerous kangaroo behaviour have been extreme thirst and hunger.
Arguably, the greatest threat kangaroos pose to humans is the danger of car accidents on Outback roads. Kangaroos blinded by headlights or startled by engine noise have been known to leap in front of cars. Since a kangaroo in mid-bound can reach speeds of ~50 km/h(31 mph) and are relatively heavy, the damage to vehicles can be severe. Small vehicles may be destroyed, while larger vehicles may potentially suffer engine damage. If thrown through the windscreen, the risk of harm to vehicle occupants is greatly increased. For this reason, vehicles that frequent isolated highways where roadside assistance may be scarce are often fitted with "roo bars" to protect from the damage caused by such accidents. (See also Roadkill)