The kangaroo is a marsupial of the species Macropodidae (macropods, which means “big foot”). In everyday use, the term represents the largest species of this family, the red kangaroo, the eastern grey kangaroo, the Antelopine kangaroo and the western grey kangaroo.
Kangaroos are an Australian Native Animal and also native to New Guinea. The Australian government estimates 34.3 million kangaroos lived in Australia’s economic harvest areas in 2011, compared with 25.1 million a year earlier.
As with the titles “wallaroo” and “wallaby,” “kangaroo” refers to one (a group of organisms) descended from a common evolutionary ancestor or ancestor group, but does not include all descendant groups.
All three refer to segments of the same family, Macropodidae, and are separated according to size. The family’s largest species are called “kangaroos”, and the tiniest are commonly titled “wallabies“.
The term “wallaroos” refers to species of an in-between size. There are also tree kangaroos, another type of macropod, which inhabits the tropical rainforests of New Guinea, far northeast of Queensland and the nearby islands. A general idea of the relative size of these common terms could be:
- Wallabies: Head and body length 45-105 cm and tail length 33-75 cm; Miniature wallabies (the smallest of all known macropod types) are 46 cm long and weigh 1,6 kg;
- Tree kangaroos: varies from Lumholtz “tree kangaroo: body and a head length of 48-65 cm, the tail of 60-74 cm, weight of 7,2 kg with males and 5,9 kg with females; to the grilled tree-kangaroos: length of 75-90 cm and weight of 8-15 kg;
- Wallaroos: the black wallaroo (the smallest of the two species) with a tail size of 60-70 cm and a weight of 19-22 kg in males and 13 kg in females;
- Kangaroos: An adult male can grow to 2 m tall and weigh 90 kg.
Kangaroos have enormous, powerful hind legs, large feet modified to jump, a long, muscular tail for stabilisation, and a tiny head. Like most marsupials, female kangaroos have a pouch in which they achieve postnatal development.
The large kangaroos have adapted much better than the smaller macropods to land clearing for grazing and human-induced habitat changes in the Australian landscape. Many of the smaller species are limited and threatened with extinction, while kangaroos are relatively abundant.
The kangaroo is a symbol of Australia. It appears on the Australian coat of arms and part of its currency.
It is used as a logo for some of Australia’s most famous groups, including the Qantas Royal Australian Air Force Roundel. The kangaroo is essential to both Australian culture and national image and therefore has many references in popular culture.
Wild kangaroos are killed for meat, leather skins and to protect grassland. Although provocative, kangaroo meat has been shown to have health benefits for human consumption compared to conventional meat due to the low-fat content of kangaroos.
What does the Word Kangaroo Mean?
The word kangaroo comes from the Guugu Yimithirr word gangurru and refers to eastern grey kangaroos. The title was first written as “kanguru” on July 12, 1770, in a diary entry by Sir Joseph Banks, at the site of today’s Cooktown, on the banks of the Endeavour River, where the HMS Endeavour, led by Lieutenant James Cook, stranded for almost seven weeks to repair the damage suffered on the Great Barrier Reef.
Captain Cook first spoke of kangaroos in his diary entry of August 4. Guugu Yimithirr is the language of the inhabitants of the region.
It was the Endeavour voyage under James Cook that gave the first written European contact with a kangaroo species, which was sighted while fixing the ship at what is now Cooktown in June and July 1770. Cook wrote in his journal “it bears no sort of resemblance to any European animal I ever saw”, but it had the colour of a mouse, was the size of a greyhound, looked like a jerboa, and moved like a hare.
Transcript available at http://southseas.nla.gov.au/journals/cook/17700714.html
A common myth about the kangaroo’s English name is that it was a Guugu yimithirr expression for “I don’t know” or “I don’t understand.” Cook and Banks were investigating the area when they came across the animal, asking a local what the animals were called, and the local replied “kangaroo,” which Cook then assumed to be the name of the animal.
Anthropologist Walter Roth tried to correct this legend as early as 1898, but few took notes until 1972 when translator John B. Haviland confirmed the correct etymology in his research with the Guugu yimithirr. There are similar, more credible stories about the name confusion, like with the Yucatan Peninsula.
The first kangaroo to be exhibited in the Western world was an example killed in 1770 by John Gore, an officer on Captain Cook’s ship, HMS Endeavour. The animal was shot and its skin and skull shipped back to England, after which it was stuffed (by taxidermists who had never seen the creature before) and displayed to the public as a curiosity.
Kangaroos are often colloquially regarded to as “roos”. Male kangaroos are called bucks, jacks, boomers, or old men; females are does, flyers, or jills; and the youthful ones are joeys. The collective noun for a crowd of kangaroos is a mob, court, or troupe.
Species of Kangaroo
Four existing species are commonly referred to as kangaroos:
- The Red Kangaroo (Osphranter Rufus) is the largest surviving marsupial on the planet. It occurs in the dry and semi-arid centre of Australia. The highest population masses of the Red Kangaroo occur in the fringes of western New South Wales. Red kangaroos are usually considered the most common kangaroo species, but eastern greys have a larger population. A large male can grow to 2 metres tall and weigh 90 kg.
- The Eastern Grey Kangaroo (Macropus giganteus) is less well known than the red kangaroo (outside Australia), but is most commonly observed as it covers the fertile eastern part of the country. The eastern grey kangaroo range extends from the summit of the Cape York Peninsula in northern Queensland to Victoria and into areas in southeastern Australia and Tasmania. Populations of the eastern grey kangaroo usually reach close to 100 per km2 in suitable open forest habitats. Populations are more restricted in clearing areas, including farmland, where forest and forest habitats are limited in size or abundance.
- The Western Grey Kangaroo (Macropus fuliginosus) is slightly smaller and weighs approximately 54 kg for a large male. It is found in the southern part of Western Australia, in South Australia near the coast and in the Murray Darling Basin. Populations are highest in the western Riverina District of New South Wales and in the western regions of the Nullarbor Plains in Western Australia. Populations may have declined, especially in agricultural areas. The species has a high tolerance to the plant poison sodium fluoroacetate, indicating a possible origin from the southwestern region of Australia.
- The Antilopine Kangaroo (Osphranter antilopinus) is basically the far-northern equivalent of the eastern grey and western grey kangaroos. Sometimes it is also called the antelope wallaroo. It is even more compared to the red, eastern grey and western grey kangaroos in behaviour and environment. Like them, it is a creature of grassy plains and forests and lives in groups or loosely organised communities. Its name comes from its fur, which resembles the gazelle in colour and structure. Characteristically, the noses of the males bulge behind the nostrils. This enlarges the nasal passages and allows them to release more heat in hot and humid climates.
What’s the Difference Between Kangaroos and Wallabies?
Kangaroos and wallabies belong to the same taxonomic family (Macropodidae) and often to the same genera. However, kangaroos are explicitly classified into the four largest species of the family. Wallaby is an informal classification commonly used for all macropods smaller than a kangaroo or wallaroo that have not been otherwise classified.
Kangaroo Biology and Behaviour
How Do Kangaroos Jump?
Kangaroos are the only large animals that use jumping as a means of transportation, and the comfortable jumping speed for a red kangaroo is about 20 to 25 km / h. However, accelerations of up to 70 km / h can be achieved over short distances, while it can maintain a speed of 40 km / h over almost 2 km.
During a bounce, the strong gastrokemus muscles lift the kangaroo’s frame off the ground. However, the tiny plantar muscle, which attaches itself to the big fourth toe, is used for repulsion.
Seventy per cent of the possible energy is stored in the elastic tendons. It uses the five-legged movement at slow speeds by using its tail to form a tripod with its two front legs while bringing its hind legs forward.
What Do Kangaroos Eat?
Kangaroos have one-chamber stomachs that are completely different from those of cattle and sheep, which have four chambers. Sometimes, they regenerate the plants they have eaten, chew them as cheese and then consume them again for final digestion. However, this is a different, more demanding activity than in ruminants and is not common.
Ruminants are herbivorous mammals that can obtain nutrients from plant foods by fermenting them in a special stomach before digestion, mainly through microbial measures.
Different species of kangaroos eat a different diet, although they are all strict herbivores. Eastern grey kangaroos grazing animals and feed on a wide variety of grasses, while some other species such as red kangaroos include important shrubs in their diet. Smaller species of kangaroos also eat hypogonous mushrooms.
Many species are nocturnal and crawling (animals that appear at dusk) and usually spend the hot days in the shade. In the cool evenings, nights and mornings they go for walks and feed.
With its grazing habits, the kangaroo has acquired specialised teeth that are rare among mammals, its incisors can harvest grass near the ground, and its molars chop and grate the grass.
As the two sides of the lower jaw are not connected or fused together, the lower incisors are further apart, giving the kangaroo a wider bite. Silica in the grass is abrasive, so the kangaroo’s molars are rubbed off.
In fact, they move forward in the mouth before eventually falling out, and are replaced by new teeth growing in the back. This method is known as polyphyodontics and is found among other mammals only in elephants and manatees.
Kangaroos Don’t Release Methane
Although herbivorous mammals (mammals that only eat plants), such as cattle, release large amounts of digestive methane by exhaling and belching (burping), kangaroos release next to nothing. Rather, the hydrogen byproduct of fermentation is converted into acetate, which is then used to produce more energy.
Scientists are looking at the possibility of transferring the bacteria responsible for this process from kangaroos to cattle because the greenhouse gas effect of methane is 23 times higher than carbon dioxide per molecule.
Social and Sexual Behaviour
Groups of kangaroos are referred to as mobs, courts or groups where ten or more kangaroos regularly live. Crowd life can provide protection for the weaker members of the group.
Size and stability of the mobs vary by geographical region, with eastern Australia having more extensive and stable associations than in arid areas further west. Larger gatherings have a high number of interactions and complicated social structures, similar to ungulate animals.
Typical behaviour is touching and sniffing the nose, which usually happens when an individual enters a group. The kangaroo sniffing gains much information from traces of smell.
This behaviour strengthens social cohesion without causing aggression. If a kangaroo is smaller, it keeps its body closer to the ground. Its head will tremble, causing it to become susceptible.
The sexual activity of kangaroos consists of pairs of partners. The females are usually in Estrus (The estrogen cycle is a series of recurring physiological changes caused by reproductive hormones in most female mammals.)
The females stray around and direct the attention of the males with conspicuous signals. A male observes a female and follows her every movement. He sniffs at her urine to see if she is in estrogen, a method that shows the reaction of the females (lip rolls).
The male then approaches her slowly so as not to frighten her. If the female does not move away, the male will continue by licking, mating, scratching and mating.
Fights between kangaroos can be short or long and ritualised, but in highly competitive situations, including males fighting for access to oestrogen females or insufficient drinking sites, the fights are short.
Both sexes fight for drinking sites, but extensive ritualised fights or “boxes” are often fought by males. Smaller males more often fight near females in estrus, while stocky males do not seem to interfere with companions.
Ritualised fights can occur suddenly when males feed together. However, most fights after two males scratching and grooming each other. One or both of them choose a high posture, with one male engaging in a provocation by grabbing the other male’s neck with the front paw. Sometimes, the challenge is rejected.
Short fights are similar, but there is no locking of the forearm. The defeated fighter seems to kick more frequently, perhaps to parry the last trick of the victor. A winner is determined when a kangaroo breaks off the fight and retreats.
Winners can push their participants backwards or to the ground. They also seem to grab their opponents when they break off contact and push them away. Initiators of the fights are regularly the winners.
These fights can serve to establish hierarchies of dominance between the males, as winners of competitions are known to remove their opponents from resting places later in the day. Aggressive males can also pull grass to scare inferior males.
Kangaroos have some natural predators, and thylacine, once considered by palaeontologists to be one of the kangaroos “largest natural predators, is now extinct, but other extinct predators have joined the marsupial lions, Megalania and Wonambi.
However, with the arrival of humans in Australia at least 50,000 years ago and the introduction of dingo around 5,000 years ago, kangaroos have had to adapt. Wedge-tailed eagles and other predators regularly eat kangaroo remains.
Goanen and other carnivorous reptiles also pose a threat to smaller kangaroos when other food sources are scarce.
In addition to dingoes, introduced species such as foxes, feral cats, and domestic and wild dogs pose a threat to kangaroo populations. Kangaroos and wallabies are skilled swimmers and often escape into waters when they have the opportunity.
If stalked into the water, a large kangaroo may use its forepaws to hold the predator under to drown it. Another defensive tactic reported by witnesses is grabbing the attacking dog with the forepaws and disembowelling it with the hind legs.
Kangaroos have adapted several times to dry, barren land and a very changeable climate. As with all marsupials, the young are born at a very early growth stage—after a gestation of 31–36 days.
At this stage, only the forelimbs are slightly developed, to allow the newborn to climb to the pouch and connect to a teat. However, a human embryo at a similar stage of development would be around seven weeks old, and premature babies born below 23 weeks are regularly not mature enough to survive. When the joey is born, it is around the size of a lima bean.
The joey will normally stay in the pouch for about nine months (180–320 days for the Western Grey) before beginning to leave the pouch for a short time. It is usually fed by its mother until approaching 18 months.
Normally, the female kangaroo is constantly pregnant, except on the day of birth; but she can freeze the growth of an embryo until the previous kangaroo can leave the pouch. This is recognised as embryonic diapause and will happen in drought times and in regions with low food sources.
The combination of milk produced by the mother varies according to the requirements of the joey. The mother can produce two distinct kinds of milk together for the newborn and the older joey still in the pouch.
Strangely, males do not create sperm during a dry period. Females will conceive only if sufficient rain has fallen to create a significant amount of green vegetation.
The Hind Leg of a Kangaroo
Kangaroos and wallabies have elongated elastic tendons in their hind legs. They store elastic strain energy in the tendons of their enlarged hind legs, giving most of the energy needed for each hop by the tendons’ spring action rather than by any muscular force.
This applies to all animal species whose muscles are attached to their skeletons by elastic elements such as tendons. Still, the effect is more noticeable in kangaroos.
There is also a link between jumping and breathing: when the feet leave the ground, the air is drained from the lungs; moving the feet to land fills the lungs, which leads to further energy efficiency.
Studies of kangaroos and wallabies have shown, beyond the minimum energy expenditure needed to hop at all, increased speed needs little extra effort (much less than the same speed increase in, say, a horse, human or dog), and the extra energy is needed to carry extra weight.
For kangaroos, the key advantage of hopping is not that they are faster at escaping predators – a kangaroo’s top speed is no higher than that of a four-legged friend of the same size, and Indigenous Australians are certainly less fearsome than those in other countries, but economically: in a barren country with highly changeable weather conditions, a kangaroo’s ability to travel at moderately high speeds for long intervals in search of food sources is vital.
A new study has found that a kangaroo’s tail acts as a third leg rather than a mere balancing act. Kangaroos make an unusual three-step walk, where they first shed their front legs and tail, then push off their tail and are eventually accompanied by the hind legs.
The tail’s propulsive force is equivalent to both the front and hind legs combined and does as much work as what a human leg walking can at the same pace.
Kangaroo Reproduction and Life Cycle
The reproduction of kangaroos is comparable with that of opossums. The egg (still contained in the shell layer, a few micrometres thick, and only a little quantity of yolk inside it) descends from the ovary toward the uterus.
There it is fertilised and soon develops into a newborn mammal. Even in the largest kangaroo kind (the red kangaroo), the newborn appears after only 33 days. Ordinarily, only one young is born at a time.
It is blind, hairless & only a few centimetres long; its hind legs are bare stumps; it climbs alternately with its more strongly developed front-legs through the thick fur at the stomach of its mother into the bag, what lasts approximately three to five minutes. Once inside the pouch, it fastens onto one of the four teats and begins to feed.
Almost immediately, the mother’s sexual cycle begins all over again. Another egg falls into the uterus, and she becomes sexually responsive. Then, if she mates & a second egg is fertilised, its growth is temporarily halted.
The kangaroo has the ability to halt the development of its baby embryos.
This is known as embryonic diapause & will take place in droughts and areas with reduced food sources. Meanwhile, the baby kangaroo in the pouch grows quickly. After about 190 days, the baby kangaroo (joey) is adequately large and developed to reach its full emergence out of the pouch, after holding its head out for a few weeks until it eventually feels secure enough to fully emerge.
From then on, he spends more and more time in the outside world, and finally leaves the bag for the last time after about 235 days. The lifespan of kangaroos averages six years in the wild to more than twenty years in captivity, differing by the species. Most individuals, though, do not reach maturity in the wild.
Interaction With Humans
Aboriginal Australians Hunting Kangaroos
The kangaroo has always been an important animal for Australian Aborigines because of its meat, bone, skin and tendon. Kangaroo skins were sometimes used for recreation; in particular, some tribes (kurnai) used a stuffed kangaroo scrotum as a kicking ball for the traditional football marngrook.
In addition, there were significant Dreaming stories and ceremonies concerning the kangaroo. Arrange is a current kangaroo dreaming locality in the Northern Territory.
Unlike many of the smaller macropods, the kangaroo has thrived since European colonisation. European settlers cut down forests to build vast grasslands for sheep and cattle grazing, added stock watering points in arid regions, and heavily reduced dingoes.
Kangaroos are naturally shy and retreat and do not pose a threat to humans under normal conditions.
In 2003, Lulu, a grey-haired hand-reared farmer, saved the life of a farmer by notifying family members of his location when a falling branch injured him.
Lulu won the RSPCA Australia National Animal Valour Award on May 19, in the year 2004.
There are few reports of kangaroos attacking people without provocation, yet many of these unprovoked attacks in 2004 stoked fears of a rabies-like disease that could potentially affect marsupials.
The only reliably documented case of a death from a kangaroo attack happened in New South Wales in 1936. A hunter was killed trying to save his two dogs from a heated scuffle. Other implied causes for erratic and dangerous kangaroo behaviour involve extreme thirst and hunger.
In July 2011, a male red kangaroo struck a 94-year-old woman in her own backyard, prompting her son and two police officers to respond.
The kangaroo was capsicum sprayed (pepper sprayed) & was euthenised following the attack.
Kangaroos – even those that are not domesticated – can communicate with humans, according to a study.
Kangaroo Emblems and Popular Culture
A kangaroo and an emu on the Australian coat of arms.
The kangaroo is an iconic symbol of Australia. Kangaroo and emu are on the Australian coat of arms. Kangaroos have also been highlighted on coins, most prominently the five kangaroos on the Australian one-dollar coin. The Australian Made logo is made up of a golden kangaroo in a green triangle to confirm that a product is grown or produced in Australia.
The registered trademarks of the early Australian companies that used the kangaroo included Yung, Schollenberger & Co. Walla Walla Brand Leather & skins (1890); Arnold V. Henn (1892), whose emblem represented a family of kangaroos frolicking with a skipping rope; Robert Lascelles & Co. linked the animal’s speed to its velocipedes (1896); while some foreign corporations, such as the “kangaroo” safety games (made in Japan) of the early 1900s, also used the symbol. Today, Australia’s national airline, Qantas, uses a bouncing kangaroo for its logo.
The kangaroo and wallaby feature prominently in the names and mascots of Australian sports teams. Cases include the Australian national rugby league team (the Kangaroos) and the Australian national rugby union team (the Wallabies).
In a national competition held in 1978 for the XVII Commonwealth Games by the Games Australia Foundation Limited, Hugh Edwards’ design was accepted; a simplified form of six thick stripes arranged in pairs and emanating from the edges of a triangular centre represents both the kangaroo in full flight and a stylised “A” for Australia.
Kangaroos are well represented in movies, television, toys, books and souvenirs throughout the world. Skippy, the Bush Kangaroo, was a favourite 1960s Australian children’s television series regarding a fictional pet kangaroo.
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