Kangaroo Australian Kangaroo Facts
What is a Kangaroo?
Let's Start with Macropods
The Kangaroo is macropod. It is a member of the scientific animal family classification Macropodidae. The word is derived from the Greek language and means 'big foot' (macro=big + pod=foot). And we all know a kangaroo seems to have big feet. The key characteristic of macropods is that they are marsupial herbivores with elongated hind legs that they use for hoping and jumping. There are over 54 different species of animals in this family. These range in size from those as small as a rat to ones as tall as a man. Macropods are found mostly in Australia. A few species can also be found in New Guinea.
So is it a Kangaroo?
So how do we know if a particular macropod is a kangaroo? The classification is fairly arbitrary. The four largest macropods are referred to as kangaroos. These are the Red Kangaroo, Eastern Grey Kangaroo, Western Grey Kangaroo and Antilopine Kangaroo. Just to make absolutely sure we don't get it wrong - they are also need to be terrestrial. That is; they move on land. (This is not to confuse them with tree-kangaroos). So the proper definition of a kangaroo is; a terrestrial marsupial herbivore that is one of the top four largest animals in the family group; Macropodidae.
A Simple Definition of a Kangaroo
A simple definition of a kangaroo is a plant eating, ground dwelling, mammal that rears its young in a pouch in its abdomen, has elongated hind legs with big feet, and hops.
Kangaroos can vary in size from the Red Kangaroo which can grow to 2.5 meters and weigh up to 90kilos to the Antilopine Kangaroo which is about 1.3 meters tall and weighs about 43 kilos. Kangaroos have short fur which varies in colour from orange-brown, to grey to dark brown. Males are larger than females. Being marsupials, the females have pouches on their abdomen in which they carry and rear their young. The most defining characteristic of kangaroos is their upright posture supported by two disproportionately large hind limbs and feet, small forelimbs and a large thick tail. Kangaroos can live 6 to 27 years. Surprisingly, for an animals which spends most of its life in dry arid areas, kangaroos are also good swimmers. Kangaroos live and move around in small social groups called 'mobs' or 'troops'.
A kangaroo's eyes are located high on its skull and provide it with a 324° field of vision with a 25° overlap (humans have a 180° vision with 120° overlap). Its eyesight has a sensitivity comparable with that of rabbits, cattle or horses.
Kangaroos have large pointed ears which can swivel independently of each other through 180°.
The kangaroo has large outward projecting front incisor teeth which it uses to slice through grass and leaves on which it feeds. Large molars at the back of its mouth chop and grinds its food. The kangaroo replaces its teeth throughout its life. New teeth grow and slowly move forward replacing those in front which have been worn down or damaged. Four sets of replacement teeth are produced during the animal's lifetime, after which lost teeth are no longer replaced. If the animal hasn't died of old age by then, it will eventually die of starvation because it has no teeth left.
Kangaroos have very small almost non-existence vocal chords. For this reason they have a very limited range of vocal sounds. A mother communicates with her offspring with clicking sounds. An alarmed kangaroo may hiss and growl. A kangaroo may display aggression by making a "ha" sound. A male kangaroo may also make a chuckling sound during courtship.
The kangaroo has short small forelimbs with hands on which there are five clawed fingers. These hands are used primarily for grasping and pulling down branches, fighting and grooming. They are also used for pentalpedaling (crawl-walking). The kangaroo has an unusual way of keeping cool. It licks its forelimbs covering them with saliva, and as the saliva evaporates its helps to cool its body.
Beings a marsupial mammal, the female kangaroo rears its offspring in a pouch and feeds it milk. The pouch is located on its abdomen. A young kangaroo, which is born very immature, crawls up from the mother's birth canal to the pouch where it attaches itself to a nipple and remains for over four months before it ventures out. Even adolescent kangaroos will hop back into their mothers pouch when frightened. Male kangaroos don't have pouches.
The kangaroo uses its powerful hind legs for hopping, its primary means of locomotion. It has extraordinarily large and long Achilles tendons that store elastic energy used to assist it in hopping. (in the photograph below you will notice the huge tendon behind its shin-bone). The kangaroo has long narrow feet with four toes each. Its feet have soft pads, like that of a cat or dog. The first toe no longer plays any important role. The second toe is large and strong with a massive claw. It is used to provide traction when it is hopping. The third and fourth toes are fused, covered by skin, but still have two small claws. The kangaroo used these two smaller toes for grooming. While highly efficient at higher speeds the kangaroo's hind legs are ineffective at low speeds and hardly used. It uses pentapedaling locomotion at slow speeds. The kangaroo also uses is feet as an alarm. It does so by 'foot thumping' one or both of its feet. It is not certain if this behaviour is to alert other kangaroos of danger or as a warning to a predator to stay away, or both.
The kangaroo's large thick tail serves a number of useful purposes. Without it a kangaroo wouldn't be able to stand up, hop or move at slow speeds. It is also where a kangaroo stores its excess fat for use in times of hardship. When a kangaroo stands its tail acts as the third point of a tripod and prevents it from toppling over backwards. The tail also serves a similar purpose when a kangaroo springs up from a standstill position. While hopping, the tail acts are a counterbalance to its body, preventing the kangaroo from tipping forward. At slow speeds the tail is a vital part of its pentapedaling movement. The kangaroo also stands up on its tail, carrying its full weight on it, when it is fighting.
Folklore About the Name 'Kangaroo'
Popular legend has it that the first European explorers asked a local Australian aboriginal what the name of the hopping animal was. He replied 'kangaru'. The explorers thought this was the name of the animal, but in actual fact what the aborigine was merely saying "hey I don't understand your question". This interpretation of how the name originated is not correct.
The first description of the strange hopping animals of Australia was in 1629 by the Dutch navigator Francois Pelsaert while sailing off the western coast of Australia. He didn't give these animals a name.
The first detailed accounts of this hopping animal came from members of the crew of Captain James Cook's voyage to Australia in 1770. Cook's ship, the Endeavour, was badly damaged while trying to cross the Great Barrier Reef and beached itself near modern-day Cooktown on the Queensland coast for urgent repairs. While there the crew came across many weird animals. They even shot a few kangaroos, noting that the animal's meat was quite delicious.
It was Joseph Banks, a naturalist on the Endeavour, who wrote the following note in August 1770 "Quadrupeds we saw but few and were able to catch few of them that we did see. The largest was called by the natives kangooro".
This was his interpretation of the word "gaNurru" used by the Guugu Yimidhirr aboriginal people who lived in the area where the Endeavour was beached. This is the word these Aboriginals used to describe the grey kangaroo.
The scientific name for the kangaroo species is macropod which in Latin means 'large foot'.
A male kangaroo is called a boomer
A female kangaroo is called a flyer
A baby kangaroo is called a joey
Locomotion by Hopping
As with all macropods, kangaroos have very strong hind legs and large feet specially designed for hopping. It has perfected this mode of locomotion to make it one of the fastest and most efficient methods of traveling over the vast distances the animal travels in search of food.
A kangaroo's legs have muscles just like all other animals. The difference is that it has evolved a very efficient and different means of moving around. It hops instead of walking. It is the only large animal that uses this method of locomotion. The kangaroo's legs are specially designed for this purpose. Because of the unusual shape of these legs and its bulky tail, a kangaroo can't walk.
Using this method of locomotion a Red Kangaroo, for example, usually hops at a speed of about 20-25 km/h. It can also speed away at over 70km/h and leap over 3 meter obstacles when required. These kangaroos have been recorded travelling up to 20 kilometres at speeds of 40km/h without a stopping for a rest. A single hop from a kangaroo can cover up to 8 meters! A human stride is only about 1 meter. Even an elephant can only manage about 2.5 meters.
How Does it Work?
A Kangaroo's legs look like powerful compression springs at work. When it hops its legs compress, bringing its toes towards its body. This looks like a spring being compressed. Then its toes move away from its body and its bounces up like a spring being released. The concept is similar to how a Pogo Stick works.
The actual mechanics are not what it seems. In fact the kangaroo gets its bounce from its Achilles tendons and ligaments in the back of its legs which store and return energy with each hop. These act like giant stretching and shrinking rubber bands. When its legs compress, its tendons get stretched. Then the energy stored in the stretched tendon, referred to as elastic potential energy, together with contracting muscles start pulling the bottom part of the leg downwards giving the animal a springing bounce back into the air. In this way a Kangaroo uses very little energy to move itself about.
Kangaroo Hopping is Super Efficient
Scientist suggest that the red kangaroo has the most efficient method of locomotion of any ground animal in the world. As it travels faster and faster it actually uses less and less energy. At speeds above 18kph, a kangaroo hoping uses less energy than any other animal of equal weight. If a foxhound were to chase a kangaroo, it would consume twice as much energy as the kangaroo and would tire out in less than 2 kilometres. The kangaroo, on the other hand, could go another 20 kilometres and still seems as fresh as when it started.
Kangaroo Hopping is Silent
Kangaroos move extremely quietly compared to other animals. You would hardly notice a mob of kangaroos whooshing silently past you at top speed. An equivalent number or deer, which are similar in body sizes, would create quite a loud racket. The reason for this is the kangaroo's soft padded feet, relatively small footprint and the fact the only two feet touch the ground.
Did You Know
The biggest non-marsupial animal to hop is the rabbit, which hops using all four legs.
Kangaroos increase their speed by increasing the length of their hops, not the frequency of hops. When its wants to go slow it takes small hops. When it wants to go fast it takes giant hops. All other animals increase the speed of each step, with only a very small increase in their stride.
Hopping Doesn't Work Well at Slow Speeds
At low speeds, however, a kangaroo is far less agile. Its super-efficient hopping legs let it down. (See next section to learn how a kangaroo moves at slow speeds).
Despite the kangaroo's reputation for gracefully hopping through the landscape, it actually spends more time moving at more leisurely pace of about 6 kilometres an hour as it feeds and socialises with other kangaroos. At this speed its movements are ungainly indeed. While highly efficient at higher speeds, a kangaroo's hind legs are cumbersome and almost useless at lower speeds. The kangaroo has adapted to this shortcoming by developing a fifth leg! Where is it, your wonder? It's the kangaroo's tail.
A kangaroo moves at low speeds by leaning forward on to its short front limbs, hoisting itself up with its tail and then shifting its hind legs forward. This method of movement is called
'pentapedal' (four limbs + tail) locomotion. Only the kangaroo does this. Recent research has shown that the kangaroo's tail with its 20 vertebrae acts like a fifth limb fulfilling the role of a
normal leg. In this role it is capable of generating more forward force than all of the kangaroo's other limbs combined.
Kangaroos are categorised and being nocturnal animals. That is they are active mainly at night. Strictly speaking, however, this is not entirely correct. A more correct definition of kangaroo activity is that they are mainly crepuscular. That is that they are most active around dawn and dusk and this activity can continue into the night. Kangaroos usually rest during the day but it is not uncommon the see a mob of kangaroos moving through the countryside during the daytime.
A Kangaroo Can't Move its Legs Independently
False - A kangaroo can. While hopping kangaroos usually move both hind legs together. They can move them independently of each other when required. The independent movement of its legs occur when the animal is turning while it is hopping, when it places one leg slightly in front of the other to execute a turn. When it uses its feet in 'foot thumping' to warn other kangaroos of danger.
True - Given that a kangaroo usually lives in dry areas, it is unusual that a kangaroo is quite comfortable in water. There are many recorded sightings of kangaroos swimming in the sea and also fleeing into watering holes and rivers when threatened. The kangaroo swims by 'dog-paddling' with its hind legs. It can swim at a reasonable speed.
True - Because the kangaroo uses bi-pedal (two legs like humans) locomotion it can easily pivot on one foot and rapidly change direction. It is claimed that it can make a 180 degree turn in a single hop. Four-legged animals with their relatively long bodies cannot turn as rapidly.
A Kangaroo Can't Walk Backwards
False - A Kangaroo can make very limited hops backwards when fighting. It cannot however actually do so as a means of locomotion.
A Kangaroo Can't Walk
True - A Kangaroo cannot walk forward or backwards by moving its legs independently. The kangaroo can, however actually move its legs independently it just can't do so for walking.
The Kangaroo Uses its Tail as a Rudder
False - The tail is used for balance, storing fat and for pentapedaling.
A Kangaroo Doesn't Need Water
True - A Kangaroo is well adapted to the harsh dry Australian environment. It can go for months without drinking water, provided it it is eating its usual diet of grasses and shrubs. The kangaroo needs only 13% of the water required by a sheep.
Kangaroos do Environmentally Friendly Farts
A kangaroo produces almost no methane (Ch4) gas which is produced in large quantities by cattle and sheep through exhaling, burping and to a lesser extent by farting. The kangaroo's digestive system has evolved to convert the hydrogen by-products of digestion to acetate which is then absorbed and used to provide energy. The kangaroo releases carbon dioxide (CO2) instead, which is 23 times less harmful to the environment than methane.
Kangaroos are herbivores. They eat mostly grass. Some like the Red Kangaroo also eat the leaves and shrubs.
Kangaroos prefer to feed at night but also graze early in the morning and late evening when its cool. They rest in the shade during the day.
The Kangaroo has a chambered stomach. Its U-shaped fore-stomach helps it digest fibrous plant material too tough for even goats to handle. Its stomach is more similar to that of a horse than cattle. The kangaroo regurgitates its food, chews it again and swallows it. This extra munching breaks down the rough fibres of their diet and greatly improves its digestion.
The Kangaroo is well adapted to the dry hot Australian climate. It needs very little water extracting moisture it needs from its food. A kangaroo requires only 13% of the water required by a sheep. It can survive for months without drinking.
Kangaroos also have an excellent sense of the weather and have been known to detect rainfall as far as 20 kilometers away and head towards it.
The kangaroo reaches sexual maturity at around the ages of 16 months for females and 24 months for males. They have no fixed breeding period, but mate more often during times of plenty than during periods of hardship.
Female Kangaroo Reproductive Anatomy
As with all marsupials, the female kangaroo has three vaginas and two uteruses (uteri). The two outermost vaginas are used for sperm transportation to the two uteruses. Babies are born through the middle one. (See photo). By contrast, female placental mammals have only one uterus and one vagina.
With this unusual reproductive system a female kangaroo can be in a continuous state of pregnancy, with a fertilised egg in one uterus waiting to be released, a baby growing in the second uterus, one in her pouch and another hopping outside but coming to its mother for milk. Another unique feature of these animals is that during times of extreme drought and starvation the female kangaroo can can practice birth control by putting the babies growing in her uteruses "on hold", stopping their future development until conditions improve. This is called embryonic diapause. When the mother's pouch becomes free the next baby will be born and the fertilised egg will start developing into a new foetus.
Because of this multiple-offspring strategy and other adaptabilities unique to the kangaroo, populations can increase rapidly when food is plentiful.
Male Kangaroo Reproductive Anatomy
The male kangaroo has a penis located behind its scrotum. (Most animals have the penis located in front). When flaccid, the penis is withdrawn into the animal's body. Another adaptation for Australia's harsh environment is that the male kangaroo's body shuts down sperm production during period of severe drought in order to conserve energy.
The kangaroo egg, which is about 0.12 mm in diameter, descends from the female's ovary into an uterus where it is fertilized. Once fertilised the eggs is encased in a very thin shell similar to that of birds and reptiles. This shell is just a few microns thick and disintegrates when the egg reaches the third phase of gestation. A remnant from the evolutionary past this unusual characteristic is common amongst marsupial mammals. The gestation period for a kangaroo is approximately 30 days and varies amongst the different types of kangaroos.
As the time approaches for the young kangaroo to be born the female kangaroo cleans out its pouch by sticking her head into her pouch licking the inside of it clean. It then takes up a "birthing position" by sitting on its back with its tail between its legs and the hind legs extended straight forward. It also leans the trunk of its body forward. It then licks its birth canal opening possibly to stimulate the birth.
The young kangaroo, no larger than a jelly-bean (2 cm) and weighing less than one gram soon emerges from the birth canal. It is born blind, hairless, with stumpy forelimb and hardly any trace of its hind legs. Even though it is still so underdeveloped the young newborn has an excellent sense of direction, knowing which way is up and down, and also an acute sense of smell. Using its little forelimbs in a swimming motion, the young joey crawls laborious up its mother's fur to the pouch. This journey takes it about three minutes. The joey's journey is made entirely by itself. The mothers does not assist it in any way. Once inside its mother's pouch the joey quickly attaches itself firmly to one of four nipples in the pouch.
Once it has attached itself to its mother's nipple the young joey will stay hidden for up to six and a half months. Then it will start to tentatively pop its head out of its mother's pouch and observe the world around it. About two weeks later it will have gained enough confidence to venture out of the pouch and hop about close to its mother. However if frightened it will immediately jump back into the safety of the pouch. By the time it is about 8 months old the joey no longer uses its mother's pouch.
Unusual Weaning (Milk Production)
The female kangaroo can produce two types of milk depending on the joey it is feeding. The milk produced in the nipple on which an embryonic joey is attached will be different from the milk produced to feed a joey which has already left the pouch and only comes back to be weaned.
Did Young Kangaroos Bud from their Mother's Nipples?
Because the young joey attaches itself so firmly onto its mother's nipple and is very difficult to pull away from it, early European explorers thought that baby kangaroos just miraculously grew off the nipple in the mother's pouch. This is because they could see no apparent opening inside the pouch the from which the joey could have emerged. They didn't know of the little joey's perilous journey from the birthing canal to the pouch.
Kangaroos fight less than most other types of herbivores. A male kangaroo fights by kicking its opponent with its powerful hind legs and hitting with its front paws (which have sharp claws). These fights usually occur over mating rights and are more ritualistic than aggressive. Very rarely do kangaroos hurt each other during fights.
Contrary to popular folklore a Kangaroo doesn't box like humans do.
The Red Kangaroo (Macropus rufus) is the largest kangaroo in the world. It is also the world's largest marsupial. An adult red kangaroo can measure up to 2 meters in height and weight as much as 90 kilos. It can hop at a top speed of over 60km/h, each leap covering a distance of up to 8 meters. It can also leap over obstacles 3 meters high. Red kangaroos have a more squared-off snout than other kangaroos. The male is usually reddish brown in colour. The female is blue-grey in colour and about half the size of the male. (See the photo on top of this web-page for an image of male and female kangaroos at a waterhole). They live in groups of between 2 to 4 members. A red kangaroo lives for about 22 years. The red kangaroo is mainly nocturnal, feeding at night and resting during the day.
The red kangaroo lives in the arid and semi-arid interior of Australia. They prefer open plains, grasslands and desert with at least some trees for shelter from the hot sun. There are estimated to be about 15 million red kangaroos living in the wild.
The main diet of the red kangaroo is grasses and forbs.
Eastern Grey Kangaroo (Macropus giganteus) is not as well knows as the red kangaroo but is the one most often seen by people. It is smaller than the red kangaroo, measuring about 1.5 meters in height and weighing about 60kgs. It is the second largest of kangaroo species. It has greyish fur. The eastern kangaroo can reach speeds of up to 50km/p and has a stride of nine meters. This kangaroo lives for up to 12years. The eastern grey kangaroo is mainly diurnal, that is it is actively predominately during day light.
It lives in the more moist scrub-lands of eastern, southern and south western Australia. The population is estimated at about 13 million animals. The eastern grey kangaroo is nocturnal and mainly active at night, resting in the shade during the heat of the day.
The diet consists of grasses, herbs, leaves and other low, shrubby vegetation.
Western Grey Kangaroo (Macropus fuliginosus) is found in the south-western parts of Western Australia and South Australia. I is about 1.3 meters tall and weighs up to 54kgs. It has pale grey to brown fur. The male western grey kangaroo is much larger than the female. The adult male has a strong, pungent odour, thus earning it the nickname of 'stinker'. It lives for about 10 years. The western grey kangaroo is mainly diurnal, that is it is actively predominately during day light.
It lives in grasslands, open woodlands.
The western grey kangaroo is most active from late afternoon to early morning, resting during the day in the shelter of trees and shrubs.
The diet of the western kangaroo consists mainly of grasses supplemented with leaves and tree bark.
Antilopine (Macropus antilopinus) has a slender face and doe-like eyes hence its name which translates to 'antelope-like long-foot'. It is about 1.2 meters tall and the can weigh up to 37kgs. Males which are larger than females are usually reddish-tan in colour. The females are grey. antilopine kangaroo is relatively common and not threatened. Its exactly numbers is not known.
The antilopine kangaroo lives in topical woodlands in the northern parts of Australia where there is grass beneath the forest canopy.
It feeds during the cooler parts of the day and at night.
The most noticeable difference between a kangaroo and wallaby is size. In general a kangaroo is larger than a wallaby but sizes can overlap. Another visual difference is that because a kangaroo is built for speed on open terrain and its hind legs are longer between the ankles and knees compared to a wallaby which usually prefers forested areas where it needs to be more agile to navigate through a forest.
A scientific way to differentiate the two is to examine their teeth. The wallaby which lives in forests and feeds on leaves has flat grinding molars (back teeth) with flat crowns and smaller front cutting teeth. The kangaroo on the other hand which feeds mostly on grasses has more pronounced front cutting teeth and its back teeth have curved crowns with ridges better suited for cutting and shearing grass.
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