The Kangaroo

Australia - Scott #992a (1986
Australia – Scott #992a (1986)

I had a 36-year-old Kate Bush song* stuck in my head for half of the night so my topic was chosen long before I actually woke up. Far from being the “random stamp” I usually select when confronted with days for which I cannot make a date match with a stamp, I simply had to take a look at all of the kangaroo-themed stamps in my collection and pick the one I liked the best. I only had to examine stamps from a single country, the one “in a land down under” (another song from the early 1980’s that is inexplicably stuck in my head). The “winning” stamp was released in 1986 and specifically portrays a red kangaroo (Macropus rufus) — the largest of all kangaroos, the largest terrestrial mammal native to Australia, and the largest extant marsupial. It is found across mainland Australia, avoiding only the more fertile areas in the south, the east coast, and the northern rainforests.

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 those of the genus Macropus: 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.

Red kangaroo (Macropus rufus). Photo taken at Western Plains Zoo, Dubbo, Australia, on June 3, 2006.
Red kangaroo (Macropus rufus). Photo taken at Western Plains Zoo, Dubbo, Australia, on June 3, 2006.

As with the terms “wallaroo” and “wallaby”, “kangaroo” refers to a paraphyletic grouping of species. All three refer to members of the same taxonomic family, Macropodidae, and are distinguished according to size. 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, another genus of macropod, which inhabits the tropical rainforests of New Guinea, far northeastern Queensland and some of the islands in the region. A general idea of the relative size of these informal terms could be:

  • wallabies: head and body length of 45–105 cm and tail length of 33–75 cm; The dwarf wallaby (the smallest member) is 46 cm long and weighs 1.6 kg;
  • tree-kangaroos: from Lumholtz’s tree-kangaroo body and head length of 48–65 cm, tail of 60–74 cm, weight of 7.2 kg (16 lb) for males and 5.9 kg (13 lb) for females; to the grizzled tree-kangaroo length of 75–90 cm (30 to 35 in) and weight of 8–15 kg (18–33 lb);
  • wallaroos: the black wallaroo, the smallest by far, with a tail length of 60–70 cm and weight of 19–22 kg for males and 13 kg for females;
  • kangaroos: a large male can be 2 m (6 ft 7 in) tall and weighs 90 kg (200 lb).
Female Eastern grey kangaroo with joey in pouch. Photo taken on October 15, 2006.
Female Eastern grey kangaroo with joey in pouch. Photo taken on October 15, 2006.

Kangaroos have large, powerful hind legs, large feet adapted for leaping, a long muscular tail for balance, and a small head. Like most marsupials, female kangaroos have a pouch called a marsupium in which joeys complete postnatal development.

The large kangaroos have adapted much better than the smaller macropods to land clearing for pastoral agriculture and habitat changes brought to the Australian landscape by humans. Many of the smaller species are rare and endangered, while kangaroos are relatively plentiful.

The kangaroo is a symbol of Australia and appears on the Australian coat of arms and on some of its currency. It is used by some of Australia’s well known organizations, 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.

Wild kangaroos are shot for meat, leather hides, and to protect grazing land. Although controversial, kangaroo meat has perceived health benefits for human consumption compared with traditional meats due to the low level of fat on kangaroos.

Female red kangaroo at the Nashville, Tennessee, Zoo. Photo taken on June 16, 2004.
Female red kangaroo at the Nashville, Tennessee, Zoo. Photo taken on June 16, 2004.

The word “kangaroo” derives from the Guugu Yimithirr word gangurru, referring to grey kangaroos. The name was first recorded as “kanguru” on July 12, 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 August 4. Guugu Yimithirr is the language of the people of the area.

A common myth about the kangaroo’s English name is that “kangaroo” was a Guugu Yimithirr phrase for “I don’t understand you.” According to this legend, Cook and Banks were exploring the area 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. This myth was debunked in the 1970s by linguist John B. Haviland in his research with the Guugu Yimithirr people.

Kangaroos are often colloquially 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.

There are four species that are commonly referred to as kangaroos.

Red Kangaroo
Male red kangaroo (Macropus rufus) at the Melbourne Zoo. Photo taken on November 22, 2006.
Male red kangaroo (Macropus rufus) at the Melbourne Zoo. Photo taken on November 22, 2006.

The red kangaroo (Macropus rufus) is the largest surviving marsupial anywhere in the world. It occupies the arid and semi-arid center of the country. The highest population densities of the red kangaroo occur in the rangelands of western New South Wales. Red kangaroos are commonly mistaken as the most abundant species of kangaroo, but eastern greys actually have a larger population. A large male can be 2 meters (6 feet 7 inches) tall and weighs 90 kg (200 pounds).

This species is a very large kangaroo with long, pointed ears and a squared-off muzzle. They are sexually dimorphic as the males have short, red-brown fur, fading to pale buff below and on the limbs. Females are smaller than males and are blue-grey with a brown tinge, pale grey below, although arid zone females are colored more like males. It has two forelimbs with small claws, two muscular hind-limbs, which are used for jumping, and a strong tail which is often used to create a tripod when standing upright. The red kangaroo’s legs work much like a rubber band, with the Achilles tendon stretching as the animal comes down, then releasing its energy to propel the animal up and forward, enabling the characteristic bouncing locomotion. The males can cover 8–9 meters (26.2–29.5 feet) in one leap while reaching heights of 1.8–3 meters (5.9–9.8 feet), though the average is 1.2–1.9 meters (3.9–6.2 feet).

The red kangaroo maintains its internal temperature at a point of homeostasis about 36 °C (97 °F) using a variety of physical, physiological, and behavioral adaptations. These include having an insulating layer of fur, being less active and staying in the shade when temperatures are high, panting, sweating, and licking its forelimbs.  The red kangaroo’s range of vision is approximately 300° (324° with about 25° overlap), due to the position of its eyes.

Mob of male and female Red Kangaroos (Macropus rufus) at the Wagga Wagga Botanic Gardens. Photo taken on January 5, 2010.
Mob of male and female Red Kangaroos (Macropus rufus) at the Wagga Wagga Botanic Gardens. Photo taken on January 5, 2010.

The species ranges throughout western and central Australia which encompasses scrubland, grassland, and desert habitats. It typically inhabits open habitats with some trees for shade. Red kangaroos are capable of conserving enough water and selecting enough fresh vegetation to survive in an arid environment. The kangaroo’s kidneys efficiently concentrate urine, particularly during summer. Red kangaroo primarily eat green vegetation, particularly fresh grasses and forbs, and can get enough even when most plants look brown and dry. One study of kangaroos in Central Australia found that green grass makes up 75–95% of the diet, with Eragrostis setifolia dominating at 54%. This grass continues to be green into the dry season. Kangaroos also primarily consumed this species, along with Enneapogon avanaceus, in western New South Wales where they comprised much as 21–69% of its diet according to a study. During dry times, kangaroos search for green plants by staying on open grassland and near watercourses. While grasses and forbs are preferred, red kangaroos will also eat certain species of chenopods, like Bassia diacantha and Maireana pyramidata, and will even browse shrubs when its favored foods are scarce. However, some perennial chenopods, such as round-leaf chenopod Kochia are avoided even when abundant.

At times, red kangaroos congregate in large numbers; in areas with much forage, these groups can number as much as 1,500 individuals. Red kangaroos are mostly crepuscular and nocturnal, resting in the shade during the day. However, they sometimes move about during the day. Red kangaroos rely on small saltbushes or mulga bushes for shelter in extreme heat rather than rocky outcrops or caves. Grazing takes up most of their daily activities. Like most kangaroo species, they are mostly sedentary, staying within a relatively well-defined home range. However, great environmental changes can cause them to travel great distances.

Range of red kangaroos (Macropus rufus)
Range of red kangaroos (Macropus rufus)

Kangaroos in New South Wales have weekly home ranges of 258–560 ha, with the larger areas belonging to adult males. When forage is poor and rainfall patchy, kangaroos will travel 25–30 km to more favorable feeding grounds. Another study of kangaroos in central Australia found that most of them stay close to remaining vegetation but disperse to find fresh plants after it rains. The red kangaroo is too big to be subject to significant non-human predation. They can use their robust legs and clawed feet to defend themselves from attackers with kicks and blows. However, dingoes and eagles will kill and eat joeys. Joeys are thus protected in their mother’s pouch. The red kangaroo formerly did have major predators that are now extinct. Extinct predators included the marsupial lion, Megalania, and the wonambi. Kangaroos are adept swimmers, and often flee into waterways if threatened by a predator. If pursued into the water, a kangaroo may use its forepaws to hold the predator underwater so as to drown it.

Eastern Grey Kangaroo
Female and male Eastern Grey Kangaroos (Macropus giganteus) at the Wagga Wagga Botanic Gardens Zoo. Photo taken on January 5, 2010.
Female and male Eastern Grey Kangaroos (Macropus giganteus) at the Wagga Wagga Botanic Gardens Zoo. Photo taken on January 5, 2010.

The eastern grey kangaroo (Macropus giganteus) is less well-known than the red (outside Australia), but the most often seen, as its range covers the fertile eastern part of the country. The range of the eastern grey kangaroo extends from the top of the Cape York Peninsula in north Queensland down to Victoria, as well as areas of south-eastern Australia and Tasmania. Population densities of eastern grey kangaroos usually peak near 100 per km2 in suitable habitats of open woodlands. Populations are more limited in areas of land clearance, such as farmland, where forest and woodland habitats are limited in size or abundance. It is also known as the great grey kangaroo and the forester kangaroo. Although a big eastern grey male typically masses around 66 kilograms (145 pounds) and stands almost 2 meters (6.6 feet) tall, the scientific name, Macropus giganteus (gigantic large-foot), is misleading: the red kangaroo of the semi-arid inland is larger, weighing up to 90 kilograms.

The eastern grey is easy to recognize: its soft grey coat is distinctive, and it is usually found in moister, more fertile areas than the red. Red kangaroos, though sometimes grey-blue in color, have a totally different face than grey kangaroos. Red kangaroos have distinctive markings in black and white beside their muzzles and along the sides of their face. Grey kangaroos do not have these markings, and their eyes seem large and wide open. Where their ranges overlap, it is much more difficult to distinguish between eastern grey and western grey kangaroos, which are closely related. They have a very similar body and facial structure, and their noses/muzzles are fully covered with fine hair (though that is not obvious at a distance, their noses do look noticeably different from the noses of reds and wallaroos). The eastern grey’s coloration is a light-colored grey or brownish-grey, with a lighter silver or cream, sometimes nearly white, belly. The western grey is a dark dusty brown color, with more contrast especially around the head. Indigenous Australian names include iyirrbir (Uw Oykangand and Uw Olkola) and kucha (Pakanh). The highest ever recorded speed of any kangaroo was 64 kilometers per hour (40 miles per hour) set by a large female eastern grey kangaroo.

Range of the eastern grey kangaroo
Range of the eastern grey kangaroo

Although the red is better known, the eastern grey is the kangaroo most often encountered in Australia, due to its adaptability. Few Australians visit the arid interior of the continent, while many live in and around the major cities of the south and east coast, from where it is usually only a short drive to the remaining pockets of near-city bushland where kangaroos can be found without much difficulty. The eastern grey prefers open grassland with areas of bush for daytime shelter and mainly inhabits the wetter parts of Australia. It also inhabits coastal areas, woodlands, sub-tropical forests, mountain forests, and inland scrubs.

Western Grey Kangaroo
Wild western grey kangaroo (Macropus fuliginosus) at sunset. Photo taken at Donnelly Mills, Western Australia, on January 2, 2006.
Wild western grey kangaroo (Macropus fuliginosus) at sunset. Photo taken at Donnelly Mills, Western Australia, on January 2, 2006.

The western grey kangaroo (Macropus fuliginosus) is slightly smaller again at about 54 kg (119 pounds) for a large male. It is found in the southern part of Western Australia, South Australia near the coast, and the Darling River basin. The highest population densities occur in the western Riverina district of New South Wales and in western areas of the Nullarbor Plain in Western Australia. Populations may have declined, particularly in agricultural areas. The species has a high tolerance to the plant toxin sodium fluoroacetate, which indicates a possible origin from the south-west region of Australia.  It has thick, coarse fur with color ranging from pale grey to brown; its throat, chest and belly have a paler color. This species is difficult to distinguish from its sibling species, the eastern grey kangaroo (Macropus giganteus). However, the western grey kangaroo has darker grey-brown fur, darker coloration around the head, and sometimes has a blackish patch around the elbow.

Long known to the Aboriginal Australians, for Europeans, the western grey kangaroo was the center of a great deal of sometimes comical taxonomic confusion for almost 200 years. It was first noted by European explorers when Matthew Flinders landed on Kangaroo Island in 1802. Flinders shot several for food but assumed that they were eastern grey kangaroos. In 1803, French explorers captured several Kangaroo Island western grey kangaroos and shipped them to Paris, where they lived in the Ménagerie du Jardin des Plantes for some years. Eventually, researchers at the Paris Museum of Natural History recognized that these animals were indeed distinct from the eastern grey kangaroo and formally described the species as Macropus fuliginosus in 1817. For reasons that remain unclear, the species was incorrectly described as native to Tasmania.

Family of Kangaroo Island kangaroos (Macropus fuliginosus fuliginosus) in springtime. Photo taken at Flinders Chase National Park, Kangaroo Island, South Australia on November 7, 2013.
Family of Kangaroo Island kangaroos (Macropus fuliginosus fuliginosus) in springtime. Photo taken at Flinders Chase National Park, Kangaroo Island, South Australia on November 7, 2013.

There the matter rested for over 100 years, and it was not until 1917 that researchers realized that the “forester kangaroo” of Tasmania was in fact Macropus giganteus, the same eastern grey kangaroo that was, and still is, widespread in the southeastern part of the mainland. By 1971, it was understood that the Kangaroo Island kangaroo belonged to the same species as the kangaroos of southern and Western Australia, and that this population extended through much of the eastern part of the continent as well. For a time, three subspecies were described, two on the mainland and one on Kangaroo Island. The current classification scheme emerged in the 1990s with two subspecies of the western grey kangaroo:

  • Macropus fuliginosus fuliginosus (commonly known as the Kangaroo Island kangaroo), which is endemic to Kangaroo Island, South Australia
  • Macropus fuliginosus melanops, which has a range of different forms that intergrade clinally from west to east.
Range of the western grey kangaroo (Macropus fuliginosus)
Range of the western grey kangaroo (Macropus fuliginosus)

The western grey kangaroo is not found in the north or the southeast of Australia, and the eastern grey does not extend beyond the New South Wales–South Australia border, but the two species are both common in the Murray–Darling basin area. They never interbreed in the wild, although it has proved possible to produce hybrids between eastern grey females and western grey males in captivity.

Antilopine Kangaroo
Female antilopine kangaroo (Macropus antilopinus). Exhibit in the Museo Civico di Storia Naturale di Genova, Via Brigata Liguria, 9, 16121, Genoa, Italy. Photo taken on September 26, 2013.
Female antilopine kangaroo (Macropus antilopinus). Exhibit in the Museo Civico di Storia Naturale di Genova, Via Brigata Liguria, 9, 16121, Genoa, Italy. Photo taken on September 26, 2013.

The antilopine kangaroo (Macropus antilopinus) is, essentially, the far-northern equivalent of the eastern and western grey kangaroos. It is one of a few macropods to display sexual dimorphism, with the male being mostly a reddish color above, and females being considerably greyer. It is one of the largest macropods, being only slightly smaller than the red kangaroo (Macropus rufus) and the eastern grey kangaroo (Macropus giganteus).

It is sometimes referred to as the antilopine wallaroo, but in behavior and habitat it is more similar to red and grey kangaroos. Like them, it is a creature of the grassy plains and woodlands, and gregarious. The name antilopine means antelope-like, given because its fur is similar in color and texture to that of antelopes. Characteristically, the noses of males swell behind the nostrils. This enlarges nasal passages and allows them to release more heat in hot and humid climates.

Range of the Antilopine kangaroo
Range of the Antilopine kangaroo

In addition, there are about 50 smaller macropods closely related to the kangaroo in the family Macropodidae. Kangaroos and other macropods share a common ancestor with Phalangeridae from the mid-Miocene. This ancestor was likely arboreal and lived in the canopies of the extensive forests that covered most of Australia at that time, when the climate was much wetter, and fed on leaves and stems. From the late Miocene though the Pliocene and into the Pleistocene the climate got drier which led to a decline of forests and expansion of grasslands. At this time there was a radiation of macropodids characterized by enlarged body size and adaptation to the low quality grass diet with the development of foregut fermentation. The most numerous early macropods, the Balbaridae and Bulungmayinae, became extinct in the late Miocene around 5–10 million years ago. There is dispute over the relationships of the two groups to modern kangaroos and rat kangaroos. Some argue that the balbarines were the ancestors of rat kangaroos and the bulungmayines were the ancestors of kangaroos. while others hold the contrary view.

The middle to late bulungmayines, Gungaroo and Wanburoo lacked digit 1 of the hind foot and digits 2 and 3 were reduced and partly under the large digit 4, much like the modern kangaroo foot. This would indicate that they were bipedal. In addition their ankle bones had an articulation that would have prohibited much lateral movements, an adaptation for bipedal hopping. Species related to the modern grey kangaroos and wallaroos begin to appear in the Pliocene. The red kangaroo appears to be the most recently evolved kangaroo with its fossil record not going back beyond the Pleistocene period, 1–2 million years ago.

The Kongouro from New Holland (Kangaroo) 1772 by George Stubbs. National Maritime Museum object reference ZBA5754
The Kongouro from New Holland (Kangaroo) 1772 by George Stubbs. National Maritime Museum object reference ZBA5754

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 travelers’ 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 and wallabies belong to the same taxonomic family (Macropodidae) and often the same genera, but kangaroos are specifically categorized into the six largest species of the family. The term wallaby is an informal designation generally used for any macropod that is smaller than a kangaroo or wallaroo that has not been designated otherwise.

Locomotion
A Forester (Eastern Grey Kangaroo)
A Forester (Eastern Grey Kangaroo) “in flight”. Picture taken in en:Narawntapu National Park, en:Tasmania in December 2005.

Kangaroos are the only large animals to use hopping as a 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 miles). 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 employs pentapedal locomotion, using 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. If pursued into the water, a kangaroo may use its forepaws to hold the predator underwater so as to drown it.

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.

Red kangaroo (Macropus rufus),skull. In the collection of Museum Wiesbaden, Germany. Photo taken on March 10, 2011.
Red kangaroo (Macropus rufus),skull. In the collection of Museum Wiesbaden, Germany. Photo taken on March 10, 2011.

Because of its grazing habits, the kangaroo has developed specialized teeth that are rare amongst mammals. 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 or fused together, the lower incisors are farther apart, giving the kangaroo a wider bite. The silica in grass is abrasive, so kangaroo molars are ground down and they actually move forward in the mouth before they eventually fall out, and are replaced by new teeth that grow in the back. This process is known as polyphyodonty and, amongst other mammals, only occurs in elephants and manatees.

Despite having herbivorous diets similar to ruminants such as cattle, which release large quantities of digestive methane through exhaling and eructation (burping), kangaroos release virtually none. The hydrogen byproduct of fermentation is instead converted into acetate, which is then used to provide further energy. Scientists are interested in the possibility of transferring the bacteria responsible for this process from kangaroos to cattle, since the greenhouse gas effect of methane is 23 times greater than carbon dioxide per molecule.

Social and Sexual Behavior
Western grey kangaroos (Macropus fuliginosus) feeding, Darling Range, western Australia. Photo taken on May 10, 2010.
Western grey kangaroos (Macropus fuliginosus) feeding, Darling Range, western Australia. Photo taken on May 10, 2010.

Groups of kangaroos are called mobs, which usually have 10 or more kangaroos in them. Living in mobs can provide protection for some of the weaker members of the group. The size and stability of the mobs vary between geographic regions, with eastern Australia having larger and more stable aggregations than in arid areas farther west. Larger aggregations display high amounts of interactions and complex social structures, comparable to that of ungulates. One common behavior is nose touching and sniffing, which mostly occurs when an individual joins a group. The kangaroo performing the sniffing gains much information from smell cues. This behavior enforces social cohesion without consequent aggression. During mutual sniffing, if one kangaroo is smaller, it will hold its body closer to the ground and its head will quiver, which serves as a possible form of submission. Greetings between males and females are common, with larger males being the most involved in meeting females. Most other non-antagonistic behavior occurs between mothers and their young. Mother and young reinforce their bond though grooming. A mother will groom her young during or after it is suckling. A joey will nuzzle its mother’s pouch if it wants access to it.

Sexual activity of kangaroos consists of consort pairs. Oestrous females roam widely and attract the attention of males with conspicuous signals. A male will monitor a female and follow her every movement. He sniffs her urine to see if she is in oestrus, a process exhibiting the flehmen response. The male will then proceed to approach her slowly to avoid alarming her. If the female does not run away, the male will continue by licking, pawing, and scratching her, and copulation will follow. After copulation is over, the male will move on to another female. Consort pairing may take several days and the copulation is also long. Thus, a consort pair is likely to attract the attention of a rival male. As larger males are tending bonds with females near oestrus, smaller males will tend to females that are farther from oestrus. Dominant males can avoid having to sort through females to determine their reproductive status by searching for tending bonds held by the largest male they can displace without a fight.

Fighting red kangaroos. Photo taken on May 23, 2010.
Fighting red kangaroos. Photo taken on May 23, 2010.

Fighting has been described in all species of kangaroos. Fights between kangaroos can be brief or long and ritualized. In highly competitive situations, such as males fighting for access to oestrous females or at limited drinking spots, the fights are brief. Both sexes will fight for drinking spots, but long, ritualized fighting or “boxing” is largely done by males. Smaller males fight more often near females in oestrus, while the large males in consorts do not seem to get involved. Ritualized fights can arise suddenly when males are grazing together. However, most fights are preceded by two males scratching and grooming each other. One or both of them will adopt a high standing posture, with one male issuing a challenge by grasping the other male’s neck with its forepaw. Sometimes, the challenge will be declined. Large males often reject challenges by smaller males. During fighting, the combatants adopt a high standing posture and paw at each other’s heads, shoulders and chests. They will also lock forearms and wrestle and push each other as well as balance on their tails to kick each other in the abdomens.

Brief fights are similar except there is no forearm locking. The losing combatant seems to use kicking more often, perhaps to parry the thrusts of the eventual winner. A winner is decided when a kangaroo breaks off the fight and retreats. Winners are able to push their opponents backwards or down to the ground. They also seem to grasp their opponents when they break contact and push them away. The initiators of the fights are usually the winners. These fights may serve to establish dominance hierarchies among males, as winners of fights have been seen to displace their opponent from resting sites later in the day. Dominant males may also pull grass to intimidate subordinates.

Female eastern grey kangaroo (Macropus giganteus) grazing.. Photo taken on September 7, 2008.
Female eastern grey kangaroo (Macropus giganteus) grazing.. Photo taken on September 7, 2008.
Predators

Kangaroos have few natural predators. The thylacine, considered by paleontologists to have once been a major natural predator of the kangaroo, is now extinct. Other extinct predators included the marsupial lion, Megalania and the 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. Wedge-tailed eagles and other raptors usually eat kangaroo carrion. Goannas and other carnivorous reptiles also pose a danger to smaller kangaroo species when other food sources are lacking.

Along with dingos, 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. 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 disembowelling it with the hind legs.

Adaptations
Joey (baby kangaroo) in its mother's pouch. Photograph by Geoff Shaw at the Department of Zoology, University of Melbourne, Australia, on June 29, 2005.
Joey (baby kangaroo) in its mother’s pouch. Photograph by Geoff Shaw at the Department of Zoology, University of Melbourne, Australia, on June 29, 2005.
A baby kangaroo. Photo taken on May 1, 2004.
A baby kangaroo. Photo taken on May 1, 2004.

Kangaroos have developed a number of adaptations to a dry, infertile country and 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 seven weeks old, and premature babies born at less than 23 weeks are usually not mature enough to survive. When the joey is born, it is about the size of a lima bean. The joey will usually stay in the pouch for about nine 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.

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 enough rain has fallen to produce a large quantity of green vegetation.

Hindleg of a kangaroo. From
Hindleg of a kangaroo. From “Mitteilungen aus dem Zool. Garten Halle”, 1910

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.

Female Red Kangaroo (Macropus rufus) in the Zoo at the Wagga Wagga Botanic Gardens. Photo taken on December 7, 2008.
Female Red Kangaroo (Macropus rufus) in the Zoo at the Wagga Wagga Botanic Gardens. Photo taken on December 7, 2008.

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.

A DNA sequencing project of the genome of a member of the kangaroo family, the tammar wallaby, was started in 2004. It was a collaboration between Australia (mainly funded by the state of Victoria) and the National Institutes of Health in the United States. The tammar’s genome was fully sequenced in 2011. 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 have not developed many different functions, while birds are genetically too remote. The dairy industry could also benefit from this project.

Interaction with Humans
Three girls and a kangaroo, circa 1900-1910. The girls pose in a garden in front of a shed covered in creepers. The girl on the right stands and holds the kangaroo aloft. The youngest girl sits in a small, wicker chair. Item is held by John Oxley Library, State Library of Queensland.
Three girls and a kangaroo, circa 1900-1910. The girls pose in a garden in front of a shed covered in creepers. The girl on the right stands and holds the kangaroo aloft. The youngest girl sits in a small, wicker chair. Item is held by John Oxley Library, State Library of Queensland.

The kangaroo has always been a very important animal for Australian Aborigines, for its meat, hide, bone, and tendon. Kangaroo hides were also sometimes used for recreation; in particular there are accounts of some tribes (Kurnai) using stuffed kangaroo scrotum as a ball for the traditional football game of marngrook. In addition, there were important Dreaming stories (Australian Aboriginal totemistic design or artwork which can be owned by a tribal group or individual.) 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 May 19, 2004.

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 July 2011, a male red kangaroo attacked a 94-year-old woman in her own backyard as well as her son and two police officers responding to the situation. The kangaroo was capsicum sprayed (pepper sprayed) and later put down after the attack.

Conflict with Vehicles
A
A “kangaroo crossing” sign on the Stuart Highway in Australia. Photo taken on April 13, 2001.

A collision with a vehicle is capable of killing a kangaroo. Kangaroos dazzled by headlights or startled by engine noise often leap in front of cars. Since kangaroos in mid-bound can reach speeds of around 50 km/h (31 mph) and are relatively heavy, the force of impact can be severe. Small vehicles may be destroyed, while larger vehicles may suffer engine damage. The risk of harm or death to vehicle occupants is greatly increased if the windscreen is the point of impact. As a result, “kangaroo crossing” signs are commonplace in Australia.

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 Australia 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. Council road signs often list phone numbers for callers to report injured animals.

Kangaroo meat
Kangaroo Meat for sale at the Queen Victoria Market, Melbourne, Victoria State, Australia. Photo taken on September 15, 2009.
Kangaroo Meat for sale at the Queen Victoria Market, Melbourne, Victoria State, Australia. Photo taken on September 15, 2009.

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 has a high concentration of conjugated linoleic acid (CLA) compared with other foods, and is a rich source of vitamins and minerals. Low fat diets rich in CLA have been studied for their potential in reducing obesity and atherosclerosis. 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.

Emblems and Popular Culture

The kangaroo is a recognizable symbol of Australia. The kangaroo and emu are bearers on the Australian Coat of Arms. It has been claimed these animals were chosen to signify a country moving ‘forward’ because of a common belief that neither can move backward. The coats of arms of several Australian states and the Northern Territory feature kangaroos including two red kangaroos serving as bearers to the Coat of Arms of Western Australia, a red kangaroo acting as the animal emblem of the Northern Territory, and the Victorian Coat of Arms including the upper portion of a kangaroo holding an Imperial Crown in its paws. It is also the official emblem of Northern Territory Police.

Warships of the Royal Australian Navy have red kangaroo symbols (based on the kangaroo on the reverse of the Australian penny) fixed to either side of their superstructure or funnel. This originated during the Korean War: as the destroyer HMAS Anzac was repeatedly mistaken for a British warship, her executive officer had a brass ‘weathervane’ in the shape of a kangaroo made and mounted to the ship’s mainmast.

Several of the logos, emblems and coats of arms that feature the kangaroo.

The Royal Australian Air Force roundel features a bounding red kangaroo while the kangaroo is part of the official emblem of the Royal Australian Regiment with a kangaroo in between two Lee–Enfield bolt-action rifles.

Australia’s national airline, Qantas, uses a bounding kangaroo for its logo. The kangaroo has always been part of the Qantas logo, and the airline has previously been known informally as “The Flying Kangaroo”. Tourism Australia makes use of the kangaroo in its logo to “help ensure instant recognition for Australia around the world”. The Australian Made and Australian Grown logos use a golden kangaroo in a green triangle to show that a product is originates in Australia.

British clothing and headwear company Kangol, known for its berets, features a kangaroo in its logo.

Pre-decimal Australian coins featuring the kangaroo on their reverses.
Pre-decimal Australian coins featuring the kangaroo on their reverses.

Kangaroos have also been featured on coins, most notably the five kangaroos on the Australian one dollar coin as well as half-penny and one penny pre-decimal coinage.

The kangaroo and wallaby feature predominantly in Australian sports teams names and mascots. Examples include the Australian national rugby league team (the Kangaroos) and the Australian national rugby union team (the Wallabies).

Kangaroos are well represented in films, television, books, toys and souvenirs around the world. Skippy the Bush Kangaroo was the star of the popular 1960s Australian children’s television series of the same name. Kangaroos are featured in the Rolf Harris song “Tie Me Kangaroo Down, Sport” and several Christmas carols.

Australia - Scott #992 (1986)
Australia – Scott #992 (1986)

Australia Post released a set of five stamps featuring indigenous animals on August 13, 1986. The Scott catalogue assigned a single number to the strip with minor letters representing each of the individual stamps (Scott #992 for the full set). The stamps all bear the denomination of 36 Australian cents and were printed using offset lithography, perforated 14¼ x 14. Left to right, the stamps portray a red kangaroo (Macropus rufus, Scott #992a); an emu (Dromaius novaehollandiae, Scott #992b); a koala (Phascolarctos cinereus, Scott #992c); a kookaburra (Dacelo novaeguineae, Scott #992d); and a duck-billed platypus (Ornithorhynchus anatinus, Scott #992e). The other major stamp catalogues number the stamps much more sensibly in which they can be found as Michel #988-992, Stanley Gibbons #1023-1027, and Yvert et Tellier #964-968.

For the record, the “losing” stamps in picking today’s kangaroo emission include the ‘Roos which formed Australia’s first definitive issue in 1913, considered classics but I always felt the iconic kangaroo on the map of Australia to look rather sickly. Close runners-up were Scott #166 issued in 1942 featuring a solo kangaroo in the bush and a pair of “in-flight” ‘roos on 1959’s Scott #322. As for tomorrow, I think we’ll stay in the region with something from New Zealand; ASAD featured a kiwifruit just over a month ago so perhaps I’ll “randomly pick” a kiwi-bird stamp or a Kiwi-person. We’ll see….

Kate Bush
Kate Bush “The Dreaming” single, EMI Ltd. (1982)

*The Dreaming”, the title track from her fourth studio LP, released on September 13, 1982, and termed by different critics as one of the “Top 50 Eccentric Albums of All Time” land and one of the “Great Underrated Albums of Our Time”. The single preceded the album, released in the UK, on July 26, 1982, the first “new” single I’d ever purchased from Bush. The song is about the destruction of Aboriginal homelands by white Australians in their quest for weapons-grade uranium. Musical guest Rolf Harris plays the didgeridoo on the recording. “The Dreaming” starts with the sound of screeching tires and the immortal line that inspired today’s topic:

Bang, goes another kanga
On the bonnet of the van…

Flag of Australia
Flag of Australia
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