Kangaroo Mob Producer Sally Ingleton discusses the genesis of the documentary and what urban kangaroos can teach us.

Trips to the city become less frequent when there’s an abundance of grass in the hills.

The four species commonly referred to as kangaroos are: the red kangaroo (Macropus rufus), the eastern gray kangaroo (Macropus giganteus), the western gray kangaroo (Macropus fuliginosus), and the antilopine kangaroo (Macropus antilopinus).

Size and weight: A kangaroo can reach heights from anywhere between 3- 8 feet (1 to 3 meters) and can weigh between 40 and 200 lbs (18-100kg). The eastern gray kangaroo is the heaviest marsupial in the world and the red kangaroo is the largest.

Physical Features: The kangaroo has powerful hind legs and large feet, and a large muscular tail to keep it balanced while in motion. It is the only large animal to use hopping as its primary means of locomotion. A male kangaroo can leap to lengths of close to 30 feet and at a height of up to 10 feet. Its can reach speeds of up to 40 mph (60kmh).

Diet: The kangaroo is an herbivore, though its diet varies according to species. The animal has a chambered stomach, similar to that of cows, to help with the digestion process. The species also has highly specialized teeth. Its incisors are able to cut grass and shrubs extremely close to the ground and its molars are designed to grind down the vegetation. Its molars fall out regularly due to the wear and tear that comes with its diet, and are replaced with new teeth. The species has an unusual eating practice. The kangaroo regurgitates grass and shrubs that it has already eaten and chews it once more before swallowing it for final digestion. A kangaroo can survive for long periods without drinking water—hydrated by the moisture in the vegetation it consumes.

Geography: The kangaroo is endemic to Australia. The species is also found in Tasmania and nearby islands. Other marsupials can be found in some parts of Asia and the Americas, though the continent of Australia has by far the most, both in terms of species and population numbers.

Habitat: Woods and bushland, as well as grassland, savannas, forests, and scrubland. The species is highly adaptable and can live successfully in a wide range of habitats.

Breeding and Social Structure: The species often live in large groups known as mobs. These mobs can range in numbers anywhere from small groups to more than hundred kangaroos. The kangaroo is a highly social species, and often engages in nose touching or sniffing to build cohesion within the group. Boxing between males in the group is used to establish dominance. The dominant male leads the mob and has exclusive access to the females for mating.

A baby kangaroo is born only after about a month-long gestation period. Like all marsupials, the female kangaroo has a pouch, called a marsupium. Immediately after birth, the newborn—which is born hairless, blind, and under an inch in length—crawls into the pouch where it nurses and continues to develop. The joey, or baby kangaroo, remains in the pouch from anywhere between 120 and 400 days, depending on species. Even after leaving the pouch, it continues to feed off the mother for approximately a year and a half. Females produce two different types of milk, one for newborns and another for more mature joeys. During periods of drought, a female kangaroo loses the ability to conceive. As necessary resources are again available to the population, a female regains the ability to have offspring. In good conditions, a female gives birth annually.

Risks: Primarily humans who hunt the species for its meat and hide.

Additional Facts:

• The family name Macropodidae derives from macropods, meaning “big or large footed.”
• The word kangaroo comes from the aboriginal Guugu Yimithirr people’s word for the gray kangaroo (gangurru). The word was first recorded as “Kangooroo or Kanguru” in 1770 by British explorer James Cook.
• A long-standing myth says that the kangaroo’s name actually derives from a miscommunication between Cook and the aboriginal peoples. When Cook asked the locals the name of the species, they responded with the word “kangaroo”—supposedly translating to “I don’t know.” This, however, was not the case.
• A male kangaroo is called a buck, boomer, or jack and a female is referred to as a doe, flyer, or jill. A group of kangaroos (usually ten or more roos) is known as a mob, troop, or court.
• A kangaroo has excellent hearing. Like a cat, a kangaroo swivels its ears to pick up sounds.
• A kangaroo is unable to walk backwards.
• The kangaroo is represented on the Australian Coat of Arms, alongside the emu.
• Kangaroos are good swimmers.

What anatomical characteristics distinguish marsupial mammals from placental?

Living marsupials and placentals can be distinguished by a number of anatomical features, including structural differences in their ear regions, teeth, postcranial skeletons, reproductive tracts, and brains. Most people think of pouches when they think about marsupials, but not all marsupials have pouches.

When did these two subclasses of mammals separate from their common ancestor? What do we know about that common ancestor?

The lineages that gave rise to living marsupials and placentals are recognizably distinct in the fossil record as far back as the Early Cretaceous (about 125 million years ago), so the most recent common ancestor of these groups must have lived even earlier. How much earlier is controversial, with some estimates suggesting a date of almost 150 million years (in the Late Jurassic). We don’t know anything about that ancestor for certain, but we assume that it was not unlike the earliest known marsupials and placentals: probably a small climbing (arboreal or semiarboreal) mammal, perhaps superficially resembling living opossums or tree shrews. Because the earliest known marsupial and placental fossils are from China, most paleontologists assume that their most recent common ancestor lived somewhere in eastern Asia.

What is convergent evolution and what are some examples of convergent evolution between marsupial and placental mammals?

Convergent evolution is the appearance of similar traits in distantly related lineages. Examples of convergent evolution between placentals and marsupials are the extinct Tasmanian “wolf” (a very wolflike marsupial), marsupial “moles” (living molelike marsupials that burrow in the sandy deserts of Australia), and kangaroo rats (North American rodents that hop on their hind legs like kangaroos).

Why are the majority of current-day marsupials found in Australia? Why are they not more successful elsewhere?

Good question. First, however, it’s important to point out that there are still over 100 species of marsupials alive today in the New World. Most live in South America, although many species also occur in Central America and one (the Virginia opossum) occurs as far north as southern Canada. Before the Panama land bridge connected North America and South America in the Pliocene (about 3 million years ago), South America was an island continent with an even more diverse marsupial fauna than it has today. In fact, the most recent common ancestor of living marsupials probably lived in South America, and its descendants crossed Antarctica (then ice-free) to invade Australia. One line of thinking is that marsupial diversity is greater in Australia than in South America because there were no terrestrial placental mammals to compete with marsupials in ancient Australia.

Kangaroos are the only large mammal to use hopping as their primary form of locomotion. Do we know when this adaptation occurred and why? How does the species benefit from this adaptation? And why are kangaroos the only large mammals to maneuver vast terrains by hopping?

Bipedal hopping, as seen in modern kangaroos, evolved gradually, over millions of years, and resulted from many anatomical adaptations that appear at different times in the fossil record. Some form of primitive hopping locomotion by kangaroo ancestors is probably quite old, perhaps dating back to the Eocene (based on inferences from molecular dates, not fossils). However, fast bipedal hopping is only an effective means of locomotion in deserts, grasslands and other open habitats (free of overhanging woody vegetation), which became widespread in Australia much later, in the last 15 million years or so. The advantages of hopping are still not clear: it’s only energetically efficient at high speeds. Hopping is similar to galloping in that energy is stored in elastic tendons between strides, so these gaits might be energetically equivalent solutions for fast or long-distance locomotion. I don’t know why only kangaroos are the only large mammals that hop, but many smaller mammals (especially rodents) have convergently evolved to do so.

How have marsupials, especially kangaroos and their predecessors, evolved over the years as Australia’s ecosystem changed?

Australian marsupials evolved in many ways to meet the challenges of drier habitats over the last 15 million years. Teeth, for example, reflect adaptive changes from browsing (on woody vegetation in moist climates) to grazing (on grasses in arid climates). Kangaroo ancestors were quadrupedal (walking on four legs most of the time) in forested habitats and became progressively more bipedal as habitats dried out and opened up.

Do you have a favorite marsupial (living or extinct)?

Well, I must confess a fondness for opossums (New World marsupials), so much less charismatic than kangaroos and koalas, but with their own unique adaptations. Several opossum species, for example, eat venomous snakes. Snake-venom resistance is a biochemical, not a morphological adaptation, and it is another example of convergent evolution: besides opossums, mongooses and hedgehogs are also snake-venom resistant.

Wildlife Protection Association of Australia, Inc.
A non-government community-based group dedicated and committed to the conservation and protection of the nation’s native wildlife.

The Australia Zoo
Kangaroo facts supplied by the Australia Zoo, a 100-acre zoo located in the Australian state of Queensland.

A summer day in the Outback can mean temperatures well over 100 degrees Fahrenheit. How does the kangaroo survive in such blistering heat?

Most mammals cope with excess body heat by sweating. Kangaroos are unique in that they sweat while they’re hopping, but once they come to a halt, they stop sweating and start panting — up to 300 breaths per minute, keeping a nearly constant flow of air over their windpipes — to keep from overheating.

Another cooling system unique to kangaroo anatomy: a network of hundreds of small blood vessels just under the surface if their forearms. To stay cool, the roos lick their arms; the moisture on their skin evaporates to cool their warm blood.

THREAT #2: Thirst
RESPONSE: Efficient energy burning

Hot and arid, the Outback is an easy place in which to die of thirst — but taking the time to stop at the water hole puts the roo at risk from predators like dingoes, who may ambush them while they drink. How does the roo stay alive between trips to the oasis?

While hopping may seem like an odd way to get around, it’s actually one of the most efficient ways to travel on the planet. The faster they hop, the less energy kangaroos burn (at least up to about 20 miles per hour, which is their average cruising speed).

Kangaroos have extra-strong calves, a giant bundle of tendons that reach from their tails to their hipbones, and hind feet that work like a pair of springs. Add to that the fact that the tail acts as a rudder, allowing the roo to bound up to 30 feet and change direction in midair, and you have the closest thing to a perpetual-motion machine in the animal kingdom. Given their uniquely efficient body design, kangaroos can conserve enough energy to keep drinks to a minimum, lessening their risk.

THREAT #3: Predators
RESPONSE: Marsupial pouch

While all roos have predators to worry about, roo babies, or joeys, are the most susceptible prey. From Wedgetail eagles in the sky to fierce dingoes prowling the landscape below, the young kangaroo has its fair share of enemies hoping to turn it into lunch — and threaten the next generation, which has only a 40 percent chance of making it out of childhood. How does a small roo survive?

For a joey, the marsupial pouch serves as an all-purpose tote bag, minivan, and emergency hiding place. When she’s born, the average joey is tiny — about the size of a peanut — blind, and completely helpless. Bu unlike some other mammals that stand and walk at birth, the newborn joey isn’t expected to do much: she’ll crawl into the pouch and stay there for weeks, suckling constantly. As she grows heavier, a bone at the base of her mother’s pouch helps support the joey’s weight.

Once the joey ventures into the outside world, the pouch is her first place of refuge. The Wedgetail eagle is a fast enough flier to overtake a kangaroo hopping at full speed — 40 miles per hour — and has talons strong enough to latch onto a joey and carry her off. That means that the safest place to be is in mom’s pouch, where she can contract a muscle to safely seal her baby in.

THREAT #4: Dying out
RESPONSE: Boxing

The kangaroo group, or mob, is full of males vying for the attention of its females. The males of a mob form a hierarchy based mainly on age and size. The dominant male, called a boomer, gets to mate and sire the next generation, while the loser sees his line die out. How does a male kangaroo ensure the continuation of his line?

Male kangaroos settle their disputes in a simple and fascinating way: they box. Using their forearms to punch and their hind legs to kick, they spar in the Outback, and the roo left standing wins the prize: the available female, and a new baby. Kangaroos are perfectly designed for hand-to-hand cobat. As males get older, they grow much larger in proportion to females — they can weigh 200 pounds at full growth, up to five times the weight of females — with long, thickly muscled arms that pack a powerful punch and broad, strong chests to withstand a punishing kick. Adult males constantly spar with one another to keep in shape, posturing to intimidate one another by looking tough to beat.

Web Sites
NPWS: Kangaroos and Wallabies

http://www.npws.nsw.gov.au/wildlife/
factsheets/kangaroo.html

Kangaroo facts from the New South Wales National Parks and Wildlife Service. The site also features pages on the kangaroo’s neighbors the dingo and emu.

NPWS: Sturt National Park
http://www.npws.nsw.gov.au/parks/outback/out006.html
Information on the Australian park that is the setting for BIG RED ROOS.

Kangaroos
http://www.australianwildlife.com.au/features/kangaroo.htm
Detailed biological information on kangaroos, including species classification and the relationships among different types of roos.

Everything You Always Wanted to Know About Kangaroos
http://www.nwf.org/internationalwildlife/
kangaroo.html
Roo facts and lore, from the National Wildlife Federation.

Rangeland Kangaroos
http://bioscience.babs.unsw.edu.au/
rootourism/guides.htm
Features downloadable PDF reports on the animals of Sturt National Park, including a detailed report on the red kangaroo.

Creature World: Red Kangaroo
http://www.pbs.org/kratts/world/index.html

Get more facts about red roos by clicking on the Australia link from this page of the PBS Kids site KRATT’S CREATURES.

Books

Bennet, Jane. WATCHING WILDLIFE: AUSTRALIA. Lonely Planet, 2000.

Corbett, Lawrence K. and Laurie Corbett. THE DINGO: IN AUSTRALIA AND ASIA. Cornell University Press, 1995.

Kanze, Edward. KANGAROO DREAMING: AN AUSTRALIAN WILDLIFE ODYSSEY. Random House, 2000.

McCullough, Dale R. and Yvette McCullough. KANGAROOS OF OUTBACK AUSTRALIA. Columbia University Press, 2000.

Menkhorst, Peter. A FIELD GUIDE TO THE MAMMALS OF AUSTRALIA. Oxford University Press, 2001.

Watts, Dave. KANGAROOS & WALLABIES OF AUSTRALIA. New Holland/Struik, 1999.

NATURE invites viewers to share the inspiring beauty and harsh realities of survival in the land of the Big Red Roos.

They box and wrestle, kick with authority, and cover large patches of ground with powerful leaps. In fact, the red kangaroos of Australia’s Outback are among the finest athletes of the animal world. And that’s just as well, since the Outback presents one of the most challenging environments on the planet.

Some of the hardships kangaroos must learn to endure are summer temperatures reaching more than 140 degrees Fahrenheit; persistent drought that’s occasionally interrupted by deadly floods; powerful eagles that swoop down from the skies; lethal parasites borne by mosquitoes; and the ever-present danger of hungry dingos. Moreover, the rising human demand for kangaroo meat does little to brighten life expectancy for members of future generations. Yet kangaroos thrive by the millions. Big Red Roos provides an incisive look at how they survive, by following the adventures of a small group, which includes a mother and the young joey she must do her best to protect.

To order a copy of Big Red Roos, please visit the NATURE Shop.

Producer
RONNIE GODEANU

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SABINA DALEY

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SARAH BIRNBAUM

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About the Writer
Sarah Birnbaum is an educational Web producer in New York.

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Television Credits

Narrated by
ANTHONY LA PAGLIA

Photography and Sound
OWEN NEWMAN

Editor
STUART NAPIER

Music
JOHN ALDER

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ROBERT LLEWELLYN

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DAVID STEWART

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AMANDA BILTON

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LUCY TILNEY
ANNA KINGTON

Unit Manager
CHRISTINA HAMILTON

The BBC Wishes to thank
NEW SOUTH WALES NATIONAL PARKS AND WILDLIFE SERVICE
LARS AND SALLY KOGGE
and
THE STAFF OF STURT NATIONAL PARK
and
THE PEOPLE OF TIBOOBURRA

Producers
OWEN NEWMAN
AMANDA BARRETT

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NEIL NIGHTINGALE

For NATURE:

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ED CAMPBELL

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WILLIAM GRANT

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FRED KAUFMAN

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