第4个回答 2006-11-12
A kangaroo is any of several large macropods (the marsupial family that also includes the wallabies, tree-kangaroos, wallaroos, pademelons and the Quokka: 63 species in all). The term kangaroo is sometimes used in a broader sense to refer to all members of the macropod family. Kangaroos are endemic to the continent of Australia, while tree-kangaroos are found on both Australia and New Guinea.
The word kangaroo derives from the Guugu Yimidhirr (an Australian Aboriginal language) word gangurru, referring to a grey kangaroo. The name was first recorded (as "Kangooroo or Kanguru") 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 seven weeks to repair damage sustained on the Great Barrier Reef.[1]
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[citation needed] 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 ones are joeys. The collective noun for kangaroos is a mob, troop, or court. Kangaroos are sometimes colloquially referred to as roos. [2]
[edit] Overview
A Tasmanian Forester (Eastern Grey) Kangaroo in motion.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 7 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 in the family Macropodidae.
[edit] Pre-historic kangaroo genera
Procoptodon
Sthenurus "Strong Tail" [3]
Propleopus, carnivorous kangaroo during the pliocene and pleistocene periods (e.g. giant rat kangaroo)
Simosthenurus, leaf-eating (browsing) kangaroos
[edit] Physical description
Red Kangaroo (Macropus rufus)Kangaroos have long been regarded as strange animals. Early explorers described them as creatures that had heads like deer (without antlers), stood upright like men, and hopped like frogs. Combined with the two-headed appearance of a mother kangaroo, this lead many back home to dismiss them as travelers tales for quite some time.[citation needed]
Kangaroos have large, powerful hind legs, large feet adapted for leaping, a long muscular tail for balance, and a small head. Like all marsupials, kangaroos have a pouch called a marsupium in which their young complete their development after birth.
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.
Unlike that of many other mammals, a kangaroo's scrotum (which the males have in place of a pouch [citation needed]) 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.
The average life expectancy of a kangaroo is about 9-18 years [citation needed], with some living until they are about 28.
[edit] Diet
Kangaroos are large 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 mobs.
[edit] Predators
Kangaroos have few natural predators. The Thylacine, considered by palaeontologists to have once been a major natural predator of the kangaroo, is now extinct. However, with the arrival of humans in Australia at least 50,000 years ago and introduction of the dingo about 5,000 years ago, kangaroos have had to adapt to introduced predators. The mere barking of a dog can set a full-grown male boomer into a wild frenzy.[citation needed] Wedge-tailed Eagles are opportunistic predators who may prey upon juvenile kangaroos and will attack and sometimes kill a kangaroo (even an adult Red), but only when no more suitably-sized food is available. Wedge-tailed Eagles and other raptors usually eat already deceased kangaroos and can be found feeding on road-kill. 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 populations of native animals. 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 tactic described by witnesses is catching the attacking dog with the forepaws and disemboweling it with the hind legs.
[edit] Social life and courtship
A mob of Forester (Eastern Grey) Kangaroos grazing.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 sniff 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.
[edit] Adaptations
Newborn joey sucking on a teat in the pouchKangaroos 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. This is known as diapause and will occur in times of drought and poor food sources. The composition of the milk produced by the mother varies according to the needs of the joey. In addition, the mother is able to produce two different kinds of milk simultaneously for the newborn and the older joey who still lives in the pouch.
Kangaroos and wallabies have large, stretchy tendons in their hind legs which have evolved for leaping. They store elastic strain energy in the tendons of their large hind legs, providing most of the energy required for each hop by the spring action of the tendons rather than by muscular effort. This is true in all animal species which have muscles connected to their skeleton through elastic elements, like tendons, but the effect is more pronounced in kangaroos.
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 highly 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.
[edit] 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.[4]
[edit] Kangaroos and humans
Before white settlement, the kangaroo was a very important animal for Australian Aborigines, both for its meat, its hide, its bones and its sinews. In addition, there were important Dreaming stories and ceremonies involving the kangaroo. Aherrenge is a current kangaroo dreaming site in the Northern Territory. The game of Marn grook was played using a ball made from kangaroo by the Kurnai people.
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.
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.
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.
For details on Kangaroo culling, and their use for meat, fur and leather, see Kangaroo culling and produce.
[edit] Kangaroo traffic sign
A kangaroo-crossing sign in mainland Australia.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, and, as already mentioned, 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.
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. Likewise, when an adult kangaroo is injured in a collision, a Veterinary Surgeon, or the RSPCA, or the National Parks and Wildlife Service should be consulted for instructions about what to do for the kangaroo. An injured kangaroo should never be left to suffer. Also, injured kangaroos can sometimes be rehabilitated.
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 (as opposed to still being in its embryonic stage), 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 hand-rearing a joey, it cannot usually be released into the wild and expected to provide for itself effectively. Usually wildlife sanctuaries are willing to adopt kangaroos which are no longer practical, or have grown too large to contain, needing at least 1 acre and 7ft boundary fences for a fully grown kangaroo
袋鼠是任一种属于袋鼠目的有袋动物(袋鼠目的其他成员：小袋鼠、树袋鼠、大袋鼠、小型沙袋鼠和短尾矮袋鼠:共计45种)。袋鼠 这个词有时候指所有的有袋动物。大多数袋鼠都是澳大利亚的特产，但是有些树袋鼠则生活在新几内亚。
袋鼠这个词源自Guugu Yimidhirr(一种澳洲原住民语言) 。后来袋鼠这个词被约瑟夫·班克斯在 詹姆斯·库克的第一次航海旅行中命名，何时他们靠岸了在努力河的嘴在现代库克镇 港口几乎7 个星期修理被损坏了的船?。
袋鼠"很快成为了采取成它来意味任一名袋鼠和鼠家庭的成员的标准英语。信仰,“它意味”我不了解 普遍神话向任一个其它原史听起来澳大利亚词的数字并且被申请。马律袋鼠叫做大型装配架的,boomers 的' 或起重器的'； 女性是' ， 飞行物的', 或jills 的' 和年轻人是joeys。集体 名词为袋鼠是'暴民' 。
袋鼠属有3种:
红大袋鼠 (Macropus rufus)是现存最大的有袋动物。红大袋鼠生活在澳洲中部的半沙漠地带。成年雄性袋鼠的体长可达两米(6英尺)，体重可达90千克(200磅).
东部灰大袋鼠 (Macropus giganteus)虽然没有红大袋鼠著名，但是东部灰大袋鼠是最常见的。生活在较为肥沃的地区。
西部灰大袋鼠 (Macropus fuliginosus)是三种袋鼠中最小的一种：成年雄性的体重为54千克 (119磅)。生活于澳洲西南海岸和达令河盆地。
另外，有与袋鼠相关紧密地的40 更小的macropods：
树袋鼠是找到在东北部澳洲"密集的雨林并且纽几内亚真实的袋鼠的树木亲戚。几只树袋鼠被危及，主要由於栖所破坏。
鼠的更小，通常更加繁茂，macropods 。