Kangaroo
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| Eastern Grey Kangaroo | |
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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: 65 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 tree-kangaroos are also found in New Guinea.
Terminology
The word kangaroo derives from the Guugu Yimidhirr (an Australian Aboriginal language) word gangurru, referring to a grey kangaroo. The name was first recorded on 4 August,1770, by Lieutenant (later Captain) James Cook on the banks of the Endeavour River at the site of modern Cooktown, when HM Bark Endeavour was beached for almost 7 weeks to repair damage sustained 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" or "I don't know" is a popular myth that is also applied to many 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, troop, or court. Kangaroos are sometimes coloquially referred to as 'roos.
Zoology
Overview
There are three species:
- The Red Kangaroo (Macropus rufus) is the largest surviving marsupial anywhere in the world. Fewer in numbers, the Red Kangaroos occupy the arid and semi-arid centre of the continent. A large male can be 2 metres (6 ft 6 in) tall and weigh 90 kg (200 lb).
- The Eastern Grey Kangaroo (Macropus giganteus) is less well-known than the red (outside of Australia), 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 (119 lb) 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 60 smaller macropods that are closely related 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 (9 to 13 lb).
- 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.
Pre-historic kangaroos
- Procoptodon
- SthenurusStrong Tail[1]
- Propleopus, carnivorous kangaroo during the pliocene and pleistocene periods (e.g. giant rat kangaroo)
- Simosthenurus, leaf-eating (browsing) kangaroos
Physical description
Kangaroos have large powerful hind legs, large feet designed for leaping, a long muscular tail for balance, and a small head.
Unlike that of many other mammals, kangaroos' scrotum is located far ahead of the penis, almost in the middle of the belly. In hot weather it can be seen lowered by the relaxed animal to keep the testes cool, and raised when moving about. (This body part can be found in souvenir shops as "lucky pouch"...)
Kangaroos 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.
This fast and energy-efficient method of travel has evolved less in response to the danger of predators, but more because of the need to regularly cover large distances in search of food and water.
The average life expectancy of a kangaroo is about 9-18 years, with some living until they are about 28.
Diet
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 mobs.
Predators
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.[citation needed] The mere barking of a dog can set a full-grown male boomer into a wild frenzy.[citation needed] 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. Another defensive tactics described by witnesses is catching the attacking dog with the forepaws and disemboweling it with the hind legs.
Social life and courtship
A mob may have ten or more males and females. The dominant male (called a boomer) is based on his size and age. A boomer has temporary exclusive access to females in a mob for mating. A boomer may find himself wandering in and out of a mob - checking out the females and intimidating the other males who try to mate with the females within the mob.
Courtship behavior in most species of kangaroos includes the male "checking" the female's cloaca. The males are often rejected by the females for their smaller size, but in the case of a larger kangaroo, the female may instead simply move away. Often, when the female is being checked, it urinates. The male kangaroo will then make a practice of sniffing the urine multiple times until it is satisfied, then proceed to the mating cycle. Studies of Kangaroo reproduction conclude that this ritual is typical for a male kangaroo to check if the female kangaroo is receptive to the male.
The sexually aroused male follows the responsive female (she raises her tail). Tail scratching (a form of foreplay) can occur between the male and female. The arched tail is indicative that either one or both kangaroos are ready to mate. The male kangaroo may sometimes be found giving the female kangaroo a back rub before mating.
Adaptations
Kangaroos have developed a number of adaptations to a dry, infertile continent and a highly variable climate. As with all marsupials, the young 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 joey will usually stay in the pouch for about 9 months or (for the Western Grey) 180 to 320 days, before starting to leave the pouch for small periods of time. It is usually fed by its mother until the age of 18 months.
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.
Kangaroo blindness
The eye disease is rare but not new among kangaroos. The first official report of kangaroo blindness took place in central New South Wales in 1994. The following year, reports of blind kangaroos appeared in the southern states of Victoria (Australia) and south Australia. By 1996, the disease had spread "across the desert to western Australia". Australians were concerned that the disease could spread to other livestock and to humans. Researchers at the Australian Animal Health Laboratories or (AAHL) in Geelong, Australia, detected a virus called the Wallal virus in two species of midges or sand flies, which they believe were the carriers. Veterinarians also discovered by screening the kangaroo population, that less than three percent of kangaroos exposed to the virus developed blindness.[2]
Kangaroos and humans
Unlike many of the smaller macropod species, kangaroos have fared well since European settlement. European settlers cut down forests to create vast grasslands for sheep and cattle grazing, added stock watering points in arid areas, and have substantially reduced the number of dingos. There are more, probably many more, kangaroos in Australia now than were present in 1788.
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, as is the North Melbourne Football Club in Australian Rules Football.
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.
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.
- Kangaroos have been culled, and they have also been used for their meat, fur and leather. For details, see Kangaroo culling and produce.
Kangaroo traffic sign
The "Kangaroo crossing" sign is to warn motorists to drive carefully and to watch out for kangaroos, because of the possibility of the presence of kangaroos in the area. The signs are placed based on the frequency of reported collisions. A collision between a car and kangaroo is capable of killing the kangaroo and damaging the car.
Kangaroos blinded by headlights or startled by engine noise have been known to leap in front of cars.
Since kangaroos in mid-bound can reach speeds of ~50 km/h(31 mph) and are relatively heavy, the damage to vehicles can be severe. It will also kill the kangaroo. 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. Hood-mounted devices, designed to scare the wildlife off the road with ultrasound and other effects, are being devised and marketed.
Another horrifying responsibility of a motorist is to finish off the wounded animal. A broken hind leg, for example, spells prolonged and painful death for the creature. Shooting or a swift smashing of the head by a hammer or a rock is required by the humane custom.
A dead animal should never be left on the road, otherwise a scavenging carrion-eater (such as Tasmanian Devil or a bird) eating it may be killed by another car. It is advocated that the corpse be moved as far away from the road as practical.[citation needed]
If a female marsupial is a victim of a collision, animal welfare groups ask that her pouch be checked for an infant joey, which may often survive the accident. In this case the joey should be taken to a wildlife sanctuary or veterinary surgeon so that the joey can be cared for and hopefully saved.
Some people would nurse the little joey themselves. The rule-of-thumb says that if the joey is already covered with fur at the time of the accident, it stands a good chance of growing up properly. Lactose-free milk is required, otherwise the animal may develop blindness. They hop readily into a cloth bag when it is lowered in front of them approximately to the height where the mother's pouch would be. The joey's instinct is to "cuddle up", which endears them to their keepers, but after around six months the grown animal should be released into the wild after several preparatory visits there.
Famous Kangaroos
- Skippy the Bush Kangaroo - the kangaroo star of an Australian television series
- Lulu, a pet Kangaroo who saved a farmer's life. Lulu was the winner of the
RSPCA National Animal Valor Award on May 19, 2004. [3] , [4] , [5]
- Matilta, the mascot at the 1982 Commonwealth Games held in Brisbane, Queensland, Australia, was represented by a cartoon kangaroo (shown at right), and also a 13-metre (42 feet 8 inches) high mechanical winking kangaroo (which winked at spectators during the opening and closing ceremonies).
- The 'medal', which was worn by both the cartoon and mechanical versions of Matilda, features the 1982 Commonwealth Games logo, a stylized representation of a kangaroo in "flight" – similar to the pose of the kangaroo featured on the Australian pre-decimal half penny coin (shown at right).
- The Kangaroo was also featured on the Australian pre-decimal penny coin.
- The five Kangaroos are featured on the Australian One Dollar coin.
- The Kangaroo and Emu are standard bearers on the Australian Coat-of-Arms
- The Kangaroo is the logo of Australia's national airliner Qantas.
- The Boxing Kangaroo, mascot for the Australia II team in the 1983 America's Cup. There is also a green and gold "Sporting Kangaroo", which is Cricket version of the Boxing Kangaroo flag, featuring a Kangaroo batsman, with cricket bat and batting gloves.
- Kidding Kangaroo in the Sweet Pickles book series by Ruth Lerner Perle,
Jacquelyn Reinach, and Richard Hefter
- Kasey Kangaroo is the mascot for the University of Missouri - Kansas City
- Zippy the kangaroo is the mascot for The University of Akron
- Lizzie (a purple and white kangaroo) is the mascot of Lake Washington High School in Kirkland, Washington
- Kangaroo Jack - the title of an American film
See also
- Embryonic diapause
- Kangaroo culling and produce
- Kangaroo court (mock justice)
References
- Dawson, Terence J. 1995. Kangaroos: Biology of the Largest Marsupials. Cornell University Press, Ithica, New York. Second printing: 1998. ISBN 0-8014-8262-3.
- Flannery, Timothy Fridtjof, et al. 1996. Tree Kangaroos: A Curious Natural History. Reed Books, Melbourne. ISBN 0-7301-0492-3
- Underhill D (1993) Australia's Dangerous Creatures, Reader's Digest, Sydney, New South Wales, ISBN 0-86438-018-6
- Weldon, Kevin. 1985. The Kangaroo. Weldons Pty. Ltd., Sydney. ISBN 0-949708-22-4