Kangaroo facts for kids
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| Female Eastern Grey Kangaroo with joey | |
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Macropus rufus |
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The 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, especially the red kangaroo, antilopine kangaroo, eastern grey kangaroo, and western grey kangaroo. Kangaroos are indigenous to Australia. The Australian government estimates that 34.3 million kangaroos lived within the commercial harvest areas of Australia in 2011, up from 25.1 million one year earlier.
The largest species in the family are called "kangaroos" and the smallest are generally called "wallabies". The term "wallaroos" refers to species of an intermediate size. There is also the tree-kangaroo which inhabits the tropical rainforests of New Guinea, far northeastern Queensland and some of the islands in the region.
The kangaroo is a symbol of Australia and appears on the Australian coat of arms and on some of its currency and is used by some of Australia's well known organisations, including Qantas and the Royal Australian Air Force. The kangaroo is important to both Australian culture and the national image, and consequently there are numerous popular culture references.
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Terminology
The word "kangaroo" derives from the Guugu Yimithirr word gangurru, referring to grey kangaroos. The name was first recorded as "kanguru" on 12 July 1770 in an entry in the diary of Sir Joseph Banks; this occurred at the site of modern Cooktown, on the banks of the Endeavour River, where HMS Endeavour under the command of Lieutenant James Cook was beached for almost seven weeks to repair damage sustained on the Great Barrier Reef. Cook first referred to kangaroos in his diary entry of 4 August.
Guugu Yimithirr is the language of the people of the area.
Europeans have long regarded kangaroos 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 led many back home to dismiss them as travellers' tales for quite some time.
The first kangaroo to be exhibited in the western world was an example shot by John Gore, an officer on Captain Cook's Endeavour in 1770. The animal was shot and its skin and skull transported back to England whereupon it was stuffed (by taxidermists who had never seen the animal before) and displayed to the general public as a curiosity. The first glimpse of a kangaroo for many 18th-century Britons was a painting by George Stubbs.
Kangaroos are often referred to as "roos". 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.
Background
The kangaroo is a herbivore, eating mainly grass, but some species also eat shrubs. Because of its grazing habits, the kangaroo has developed specialised teeth that are rare amongst mammals.
Kangaroos are the only large animals to use hopping as a means of locomotion. They can hop or jump as far as about three times their own height. The comfortable hopping speed for a red kangaroo is about 20–25 km/h (12–16 mph), but speeds of up to 70 km/h (43 mph) can be attained over short distances, while it can sustain a speed of 40 km/h (25 mph) for nearly 2 km (1.2 mi).
This fast and energy-efficient method of travel has evolved because of the need to regularly cover large distances in search of food and water, rather than the need to escape predators. At slow speeds, it uses its tail to form a tripod with its two forelimbs while bringing its hind feet forward. Kangaroos are adept swimmers, and often flee into waterways if threatened by a predator.
Kangaroos are marsupials because they carry their young in a special pouch on their bodies. Baby kangaroos are called joeys. Kangaroos can be dangerous because of their powerful legs. They can lean back on their tails to deliver powerful kicks.
Kinds of kangaroos
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There are four living species of kangaroos:
- The Red Kangaroo (Macropus rufus) is the largest marsupial anywhere in the world. The Red Kangaroo lives in the arid and semi-arid centre of Australia. A large male can be two 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 south part of Western Australia, South Australia near the coast, and the Darling River basin.
- The Antilopine Kangaroo (Macropus antilopinus) is similar to the Eastern and Western Greys. Like them, it lives on the grassy plains and woodlands. It lives in large groups.
There are also about 50 other smaller macropods in the macropodidae family.
Biology and behaviour
Kangaroos are the only large mammals to use hopping on two legs as their primary means of locomotion. The comfortable hopping speed for a red kangaroo is about 20–25 km/h (12–16 mph), but speeds of up to 70 km/h (43 mph) can be attained over short distances, while it can sustain a speed of 40 km/h (25 mph) for nearly 2 km (1.2 mi). During a hop, the powerful gastrocnemius muscles lift the body off the ground while the smaller plantaris muscle, which attaches near the large fourth toe, is used for push-off. Seventy percent of potential energy is stored in the elastic tendons. At slow speeds, it employs pentapedal locomotion, using its tail to form a tripod with its two forelimbs while bringing its hind feet forward. Both pentapedal walking and fast hopping are energetically costly. Hopping at moderate speeds is the most energy efficient, and a kangaroo moving above 15 km/h (9.3 mph) maintains energy consistency more than similarly sized animals running at the same speed.
Adaptations
Kangaroos have developed a number of adaptations to a dry, infertile country and highly variable climate. The young are born at a very early stage of development—after 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. When the joey is born, it is about the size of a lima bean. The joey will usually stay in the pouch for about 9 months (180–320 days for the Western Grey) before starting to leave the pouch for small periods of time. It is usually fed by its mother until reaching 18 months.
Kangaroos and wallabies have large, elastic 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 skeletons 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, 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 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 countries—but economy: in an infertile country 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.
New research has revealed that a kangaroo's tail acts as a third leg rather than just a balancing strut. Kangaroos have a unique three-stage walk where they plant their front legs and tail first, then push off their tail, followed lastly by the back legs. The propulsive force of the tail is equal to that of both the front and hind legs combined and performs as much work as what a human leg walking can at the same speed.
Diet
Kangaroos have single-chambered stomachs quite unlike those of cattle and sheep, which have four compartments. They sometimes regurgitate the vegetation they have eaten, chew it as cud, and then swallow it again for final digestion. However, this is a different, more strenuous, activity than it is in ruminants, and does not take place as frequently.
Different species of kangaroos have different diets, although all are strict herbivores. The eastern grey kangaroo is predominantly a grazer, and eats a wide variety of grasses, whereas some other species such as the red kangaroo include significant amounts of shrubs in their diets. Smaller species of kangaroos also consume hypogeal fungi. Many species are nocturnal, and crepuscular, usually spending the hot days resting in shade, and the cool evenings, nights and mornings moving about and feeding.
Predators
Kangaroos have a few natural predators. The thylacine, considered by palaeontologists to have once been a major natural predator of the kangaroo, is now extinct. Other extinct predators included the marsupial lion, Megalania and Wonambi. However, with the arrival of humans in Australia at least 50,000 years ago and the introduction of the dingo about 5,000 years ago, kangaroos have had to adapt.
Along with dingoes, introduced species such as foxes, feral cats, and both domestic and feral dogs, pose a threat to kangaroo populations. Kangaroos and wallabies are adept swimmers, and often flee into waterways if presented with the option.
Extinct family
There was a now-extinct family of giant kangaroos, the Sthenurinae. They were adapted for browsing in woodland areas, rather than open grassland. The largest (Procoptodon goliah) had an estimated body mass of 240 kg., which is almost three times the weight of the largest living kangaroos. They probably moved at slower speeds, since hopping was not possible. They would have moved by striding (walking). The family went extinct about 30,000 years ago.
Interaction with humans
The kangaroo has always been a very important animal for Australian Aborigines, for its meat, hide, bone, and tendon. In addition, there were important Dreaming stories and ceremonies involving the kangaroo. Aherrenge is a current kangaroo dreaming site in the Northern Territory.
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. In 2003, Lulu, an eastern grey which had been hand-reared, saved a farmer's life by alerting family members to his location when he was injured by a falling tree branch. She received the RSPCA Australia National Animal Valour Award on 19 May 2004.
There are very few records of kangaroos attacking humans without provocation.
Emblems and popular culture
The kangaroo is a recognisable symbol of Australia. The kangaroo and emu feature on the Australian Coat of Arms. Kangaroos have also been featured on coins, most notably the five kangaroos on the Australian one dollar coin. The Australian Made logo consists of a golden kangaroo in a green triangle to show that a product is grown or made in Australia. The kangaroo and wallaby feature predominantly in Australian sports teams names and mascots.
Kangaroos are well represented in films, television, books, toys, souvenirs and several Christmas carols. Skippy the Bush Kangaroo was the star of the popular 1960s Australian children's television series of the same name.
Meat
Historically, the kangaroo has been a source of food for indigenous Australians. Kangaroo meat is high in protein and low in fat (about 2%). Kangaroo meat is a rich source of vitamins and minerals.
Most kangaroo meat is currently sourced from wild animals as a byproduct of population control programs. Kangaroos are hunted by licensed shooters in accordance with a strict code of practice and are protected by state and federal legislation.
Kangaroo meat is exported to many countries around the world.
Images for kids
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A male red kangaroo
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A male red kangaroo grazing
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A baby kangaroo (joey)
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A newborn joey sucking on a teat in the pouch
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Aboriginal Australians hunting kangaroos
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A kangaroo in a domestic setting, Queensland, Australia, circa 1900–1910
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A "kangaroo crossing" sign on an Australian highway
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Kangaroo meat on sale in Melbourne
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See also
In Spanish: Canguro para niños
