KANGAROO

any of about 47 species of Australasian marsupial mammals comprising the family Macropodidae. Kangaroo is also the particular name of all the larger species and some of the smallest, which are described in this article. (For other small forms, see rat kangaroo; for those of medium size, see wallaby; for wallaroo, see below.) Kangaroos are found in Australia, Tasmania, New Guinea, and the islands east to the Bismarcks; one species has been introduced into New Zealand. Most are terrestrial and all are herbivorous: natively, they occupy the place held elsewhere by grazing and browsing animals. Their principal enemies are humans, who kill kangaroos for meat, for their hides (used in shoes), and because they compete for forage with livestock. By the late 20th century, the number of kangaroos in Australia had increased to the point that the animals had to be systematically reduced by hunting. The animals are the best known and most distinctive representatives of the fauna of that continent. With the exception of Dendrolagus and Hypsiprymnodon, all kangaroo genera rely on long, powerful hind legs and feet for hopping and leaping, their predominant forms of locomotion. Their long tails, thickened at the base, are used for balancing. Each long, narrow hind foot has four toes, with the large fourth toe bearing most of the animal's weight; the second and third toes are united and merely vestigial. The short forelimbs, with five unequal digits apiece, are used almost like human arms, but all digits of the hand are sharp-clawed, and the thumb is not opposable. The head is relatively small; the ears are large and rounded; and the mouth is small, with prominent lips. The pelage is soft and wooly; in many species it is grizzled, and stripes may be present on the head, back, or upper limbs. All kangaroos have a chambered stomach that is functionally similar to those of such ruminants as cattle and sheep. They regurgitate the vegetation they have eaten, chew it as cud, and then swallow it again for final digestion. Kangaroos usually have one young annually. In all kangaroos the pouch is well developed, opens forward, and contains four teats. The young kangaroo, or joey, is born alive at a very immature stage, when it is only about 2 cm (1 inch) long and weighs less than a gram (0.03 ounce). Immediately after birth it uses its precociously developed forelimbs (equipped with claws) to crawl up the mother's body and enter the pouch. The baby attaches its mouth to a teat, which then enlarges and holds the young animal in place. After continuous attachment for several weeks, the joey becomes more active and gradually spends more and more time outside the pouch, which it leaves completely at 7 to 10 months of age. Female kangaroos enter into heat within a few days after giving birth; they mate and conceive, but after only one week's development the microscopic embryo enters a dormant state that lasts until the previous young leaves the pouch. The development of the second embryo then resumes and proceeds to birth after a gestation period of about 30 days. Gray kangaroo (Macropus canguru) Red kangaroo (Macropus rufus) The three largest species of kangaroos belong to the genus Macropus; they are the gray kangaroo, or forester, Macropus canguru (sometimes called M. giganteus or M. major; see photograph); the wallaroo, or euro, M. robustus; and the red kangaroo, or red flyer, M. rufus (see photograph). The best-known species, the gray kangaroo, is found mostly in open forests of eastern and southwestern Australia and Tasmania. It is long-haired and silvery gray in eastern coastal regions but short-haired and dark gray inland. The red kangaroo, which is found throughout Australia's interior grasslands, is the largest and most powerful species. A male may attain a head-body length of 1.5 m (5 feet); have a tail 1 m (3 feet) long; stand 2 m (6 feet) tall; and weigh 90 kg (200 pounds). A gray kangaroo can clear more than 9 m (30 feet) at a bound13.5 m (44 feet) has been recordedand attain a speed of 48 kilometres per hour (30 miles per hour). The wallaroo, a smaller and stockier animal, may be dark gray to pinkish brown; it lives in rocky country throughout Australia except Victoria. These large kangaroos travel in groups (mobs) under the leadership of the largest male (old man, or boomer), which dominates younger rivals by biting, kicking, and boxing. Tree kangaroos make up the genus Dendrolagus; three species inhabit New Guinea, and two others are found in Queensland rain forests. About 95 to 175 cm (37 to 69 inches) long, they are short-eared, short-legged, and long-tailed, with complex markings. They spend the day in trees; at night they descend to feed on herbs and grubs.