|A kangaroo is a marsupial from the family Macropodidae (macropods, meaning 'large foot'). In common use the term is used to describe the largest species from this family, the Red Kangaroo, the Antilopine Kangaroo, and the Eastern and Western Grey Kangaroo of the Macropus genus. The family also includes many smaller species which include the wallabies, tree-kangaroos, wallaroos, pademelons and the Quokka, some 63 living species in all. Kangaroos are endemic to the continent of Australia, while the smaller macropods are found in Australia and New Guinea.
In general, larger kangaroos have adapted much better to changes wrought to the Australian landscape by humans and though many of their smaller cousins are endangered, they are plentiful. They are not farmed to any extent, but wild kangaroos are shot for meat, over which there is controversy.
The kangaroo is an Australian icon: it is featured on the Australian coat of arms, on some of its currency, and is used by many Australian organizations, including Qantas.
A common legend about the kangaroo's English name is that it came from the Aboriginal words for "I don't understand you." According to this legend, Captain James Cook and naturalist Sir Joseph Banks were exploring Australia when they happened upon the animal. They asked a nearby local what the creatures were called. The local responded "Kangaroo", meaning "I don't understand you", which Cook took to be the name of the creature.
Kangaroo soon became adopted into standard English where it has come to mean any member of the family of kangaroos and wallabies. Male kangaroos are called bucks, boomers, jacks, or old men; 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.
In addition, there are about 50 smaller macropods closely related to the kangaroo in the family Macropodidae.
Kangaroos have large, powerful hind legs, large feet adapted for leaping, a long muscular tail for balance, and a small head. Like all marsupials, female kangaroos have a pouch called a marsupium in which joeys complete postnatal development.
Because of its long feet, it cannot walk normally. To move at slow speeds, it uses its tail to form a tripod with its two forelimbs. It then raises its hind feet forward, in a form of locomotion called "crawl-walking.
The average life expectancy of a kangaroo is about 4-6 years, with some living until they are about 23.
Because of its grazing, kangaroos have developed specialized teeth. Its incisors are able to crop grass close to the ground, and its molars chop and grind the grass. Since the two sides of the lower jaw are not joined together, the lower incisors are farther apart, giving the kangaroo a wider bite. The silica in grass is abrasive, so kangaroo molars move forward as they are ground down, and eventually fall out, replaced by new teeth that grow in the back.
Absence of digestive methane release
Along with dingoes and other canids, introduced species like foxes and feral cats also pose a threat to kangaroo populations. Kangaroos and wallabies are adept 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 so as to drown it. Another defensive tactic described by witnesses is catching the attacking dog with the forepaws and disemboweling it with the hind legs.
The 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 in areas with 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 still in the pouch.
Unusually, during a dry period, males will not produce sperm, and females will only conceive if there has been enough rain to produce a large quantity of green vegetation.
Kangaroos and wallabies have large, stretchy tendons in their hind legs. 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 any muscular effort. This is true in all animal species which have muscles connected to their skeleton through elastic elements such as tendons, but the effect is more pronounced in kangaroos.
There is also a link 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 refills the lungs, 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, dog or human), and that the 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, but 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 food sources is crucial to survival.
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 National Institutes of Health in the US. The genome of a marsupial such as the kangaroo is of great interest to scientists studying comparative genomics because marsupials are at an ideal degree of evolutionary divergence from humans: mice are too close and haven't developed many different functions, while birds are genetically too remote. The dairy industry has also expressed some interest in this project.
Interaction with humans
Unlike many of the smaller macropods, 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 dingoes.
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 hind leg. The sharpened toenails can disembowel an opponent.
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 occurred in 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 behavior include extreme thirst and hunger.
In 2003, Lulu, an Eastern Grey, saved a farmer's life. She received the RSPCA National Animal Valor Award on May 19 of the next year.
Conflict with vehicles
Vehicles that frequent isolated roads, where roadside assistance may be scarce, are often fitted with "roo bars" to minimize damage caused by collision. Bonnet-mounted devices, designed to scare wildlife off the road with ultrasound and other methods, have been devised and marketed.
If a female is the victim of a collision, animal welfare groups ask that her pouch be checked for any surviving Joey, in which case it may be removed to a wildlife sanctuary or veterinary surgeon for rehabilitation. Likewise, when an adult kangaroo is injured in a collision, a vet, the RSPCA or the National Parks and Wildlife Service can be consulted for instructions on proper care. In New South Wales, rehabilitation of kangaroos is carried out by volunteers from WIRES.
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