"Each day when I came home from school, Joey, my pet1 kangaroo2, would be sitting there waiting for me at the gate," John recalls. "As soon as I opened the gate, he would jump up and embrace me with his forelimbs3, and I would embrace him. We'd talk to each other in a language that said, 'It's great to see you!' Then Joey would bound up4 the driveway5 a few yards like an excited dog, hop6 back, and repeat the process until we got to the house."
People living in the Australian bush7 are legally permitted to have pet kangaroos, as John's family did. Generally, these kangaroos are orphans8, having been rescued9 as babies after their mothers were killed, perhaps when trying to cross a road. Even though it was the name John gave his pet, "joey" is, in fact, the common term for a baby kangaroo.
Naturally, the joey's adopted family want to make it feel at home quickly. So one of the first things they do is give it a pouch10. They choose a location away from the elements -- and at a comfortable distance from the fireplace11 -- and there they nail12 a large, tough13 cloth bag with a slot14 cut in it to resemble15 a mother kangaroo's pouch. Then they put the joey into it with a bottle of warm, specially prepared milk. In this way many joeys are helped to survive. They soon adapt to their new pouch, diving16 into it headfirst17, as if it were their mother's.
How Do You Describe a Kangaroo?
Animals that raise their young in a pouch, or marsupium, are called marsupials. Comprising some 260 species, marsupials include the kangaroo, koala, wombat18, bandicoot19, and opossum20, the only species native to North America. Understandably, early explorers found these unusual animals, especially the kangaroo, difficult to describe to people back home. The first to put the word "kangaroo" into written English was British explorer Captain James Cook. He likened21 the animal to 'a greyhound22 that jumps like a hare23 or a deer24.' When a live kangaroo was later exhibited25 in London, it caused a sensation.
Kangaroos have big ears that swivel26 about on a deerlike head. Their small but powerful forelimbs resemble human arms, especially when the kangaroo stands erect27. Kangaroos also have large, muscular hips28; a long, thick, sinuous tail; and, of course, huge feet -- a characteristic that has earned them the designation29 "Macropodidae," meaning "long feet."
Some 55 species of Macropodidae range in size from that of a man down to that of a rat30. All Macropodidae have short forelimbs and long hind31 limbs for hopping. Red kangaroos, gray kangaroos, and wallaroos32, or euros, are the largest. One male red kangaroo measured over seven feet [200 cm] from his nose to the tip33 of his tail and weighed 170 pounds [77 kg]. Smaller species of kangaroo are called wallabies34.
Have you ever seen or heard of a kangaroo that lives in trees? Well, believe it or not, kangaroos do have a "monkey" in the family -- the tree kangaroo. Found in the tropical rain forests of New Guinea and northeastern Australia, these shorter-legged, agile animals, so at home in trees, can leap35 some 30 feet [9 m] from one branch36 or tree to another. At night they descend to the forest floor, where they feed37 mainly on herbs and grubs38.
Fast, Graceful, Efficient
When moving slowly, kangaroos seem ungainly39 and awkward40. Their tail and short forelimbs become a tripod41 that supports their weight as they lift their hind legs forward. But they are graceful42 runners. When bounding along at up to 30 miles [50 km] an hour, they use their great tail to balance themselves. According to The World Book Encyclopedia, they "can reach a top speed of over 60 kilometers [38 miles] an hour." In the case of a large kangaroo, a single hop at high speed may span from 30 [9] to 44 feet [13.5 m] -- a leap that could almost pass43 for flying!
Kangaroos are not only fast but also efficient in their use of energy. Professor Uwe Proske, of Monash University in Melbourne, Australia, says that a kangaroo's oxygen consumption is actually more energy efficient at higher speeds than it is at lower speeds. Proske also calculated that "at 20 kilometres [12 miles] per hour or faster, the energy used by the hopping kangaroo was less than that of a four-legged placental mammal44 [a mammal that is born fully developed45, like a dog or a deer] of similar weight, running at the same speed." Because of the kangaroo's energy-efficient locomotion, it can travel long distances without tiring. But how does the kangaroo manage to run so economically?
The secret lies in its long Achilles tendons. "It is as though kangaroos are hopping on pairs of coiled springs46," says Proske. Like those attached to a human calf47 muscle, the kangaroo's Achilles tendons stretch48 on landing and compress during takeoff49. Kangaroos hop at the same number of hops per second (about two for a red kangaroo) over a wide range of speeds. To go faster, they simply lengthen50 each stride. An exception is when a kangaroo is startled. Then it may take off with a few small, rapid hops for better acceleration.
Kangaroos are also expert swimmers. Not only do they use their powerful legs but they get additional propulsion by swinging51 their tail from side to side. When chased52 by dogs, kangaroos have been known to use their aquatic skills by bounding into a water hole53 or a river. Any dog brave enough to go after the kangaroo promptly gets shoved54 under the water by the kangaroo's muscular forelimbs and five-fingered paws55, each armed with sharp56 claws57. John, mentioned at the outset58, had two dogs that were almost drowned59 by a wild60 buck61 kangaroo when it took them on in a small reservoir62 on his family's property.
The Marvel of Marsupial Birth
Although adults are tough and robust, kangaroos are extremely undeveloped and delicate at birth. Resembling little more than a pink worm measuring about an inch long and weighing a fraction of an ounce, they are born hairless, blind63, and deaf. Yet, thanks to its precociously64 developed forelimbs equipped with claws and its sense of smell, the tiny "worm" crawls65 instinctively through its mother's fur66 and up into her pouch. When inside the pouch, it latches67 onto one of four teats68. The end of the teat immediately swells69 into a bulb inside the infant's mouth, locking it firmly in place for several weeks. Considering its mother's mode of travel, a solid anchor is clearly an advantage! In fact, so good is this anchor that early observers assumed70 that the young grew from the teat!
Eventually71, of course, the joey will grow to the stage where it will leave the pouch, although only temporarily at first. However, after seven to ten months, when it is fully weaned72, it will leave the pouch permanently. But let's go back in time to when the joey first anchored itself to a teat and see another marvel of kangaroo reproduction.
A few days after the newborn latches onto its mother's teat, she again mates73. The embryo resulting from this mating develops for about a week, but then it goes dormant74 -- on hold, so to speak75 -- while its older sibling76 continues to grow in the pouch. When the older but still unweaned sibling leaves the pouch, the embryo in the womb77 resumes growth. After a 30-day gestation, it also attaches itself to a teat, but not the one suckled78 by the older sibling
Therein79 lies another marvel of kangaroo biology. The mother gives her youngest joey one kind of milk and the older one a different kind. Commenting on this, Scientific American says: "The two milks secreted by the separate mammary glands are quite different in volume and composition. How this can be achieved under the same hormonal conditions is an intriguing80 question."
Where to See Kangaroos
If you want to see kangaroos in their natural setting81, you must be prepared to leave the cities and go out into the Australian bush, or the outback82. Foraging for83 grass and small plants, kangaroos can be found individually as well as in small groups or in larger groups called mobs84, which are presided over by big buck kangaroos called boomers85. Because kangaroos feed mainly at night and rest in the shade (where they are well camouflaged) during the heat of the day, a good time to see them is early in the morning or at dusk86. But in cooler weather, they may be active throughout the day. Whatever the case, be sure to bring a telephoto lens87 and binoculars88 -- wild kangaroos are very shy animals.
Of course, you can also see kangaroos at most zoos, wildlife sanctuaries, and national parks throughout Australia and in some other countries as well. Regular exposure to humans has made these kangaroos less timid, and so you should be able to get some good close-ups89, perhaps even of a mother with a joey peeking90 out of her pouch. Larger joeys always win a smile when they dive into mother's pouch, only to have their lanky91 hind legs stick out awkwardly, making mother kangaroo resemble an overstuffed92 shopping bag. (Young kangaroos seem to be all legs93!) A handsome buck may even grant94 you an erect, stately95 pose96. Who knows? You may even see a couple of big boomers standing as tall as their long, sinuous legs permit and having a sparring match97 -- genuine98 boxing kangaroos!
But to many, the best sight is a big red or gray buck hopping at full speed. True, other animals may be able to run faster or jump higher, but with no other creature will you see such a remarkable combination of grace, power, and spring99 on just two mighty legs.