Rhinoceroses (rhinos), which are among the
world's largest land animals, belong to the
ungulate family Rhinocerotidae. There are three
Asian and two African species existing today; the
fossil record shows several dozen extinct species
as well. The name of the animal comes fromGreek
rhino + ceros, meaning "nose-horned."
Physical Characteristics of Rhinoceroses
Rhinos weigh up to four tons and have short, thick, supportive legs. Rhino skin is thick, gray to brown in color, hangs loosely on the body, and is almost hairless. In the Asian species, skin folds at the junctures of the neck and limbs make them look armored. The Asian species also have have incisors and canine teeth, which are missing in the African species. Rhinos have long, prehensile upper lips, for grasping branches and removing leaves, which they eat. Depending on the species, rhinos have one or two nose horns. In two-horned species, the horn closest to the end of the snout is longer. The horns are made of keratin, a fibrous substance that also composes hair. The horns are used for digging food, for defense, and in mating combats. Rhinos are ungulates with three toes per foot, each of which ends in hooflike nails. Each front foot has a vestigial fourth toe. Rhinos, which are ruminants related to horses, eat grass, bulbs, leafy twigs, and shrubs. Although they look clumsy, rhinos can run as fast as horses. They have sharp vision, very good smell, and excellent hearing. Their keen hearing is due in part to their funnelshaped ears, that swivel in different directions.
Rhino Life Cycles
Most rhinos are both diurnal and nocturnal, active in daylight hours as well as after dark. They eat during the cool mornings and evenings, staying in mud wallows during hot afternoons. Rhinos have few enemies because of their size and their dangerous horns-an angry rhino charges its attackers. Humans are rhinos' great enemies, killing them for their horns, which are used in jewelry or medicinally. Most rhinos, especially males, live alone except during mating. There are some exceptions to solitary living: mothers live with their offspring, and young males or females may form same-sex groups. Males have territories, which are marked and defended. They fight each other for mates. While rhinosmaynot live with others of theirown species, they almost always have symbiotic birds, called oxpeckers, living on and around them. The birds eat insects from the rhinos' skins. This gives the birdfood, and frees the rhino fromthe insects. Mating takes place year round, and gestation lasts up to fifteen months. The female gives birth to a baby that weighs between 100 and 150 pounds. The young rhino stays with mother for 2.5 years, though it can feed itself in 2.5 months. Rhinos mate at seven to ten years of age. Females wait for approximately three years between gestations, only becoming pregnant after the previous offspring has left them. Rhinos live for up to fortyfive years.
There are five rhino species: three in Asia and Malaya, and two in Africa. African rhinos are twohorned and classified as "black" or "white", though all are bluish-gray. Black rhinos live in habitats from mountain forests to scrub lands. Their maximum body length is 10 feet, their height is 5 feet at the shoulder, and they weigh 1.75 tons. Each has a front horn up to 3.5 feet long. The rear horn is shorter. Black rhinos are mostly nocturnal, eating in the cool morning and evening hours and wallowing in river mud during the hot daylight hours. They eat grass, leaves, herbs, fruit, branches, and twigs. In the wild, a male has a marked territory, which he defends. When the territories of several males overlap, they form groups that share resources and defend the combined territory from strangers. White rhinos, similar to black rhinos, are the largest land mammals except elephants. Their maximum length is 13 feet, shoulder height is 6.75 feet, and they weigh 4 tons. Females use their horns for digging, defense, and guiding their offspring. Nearly extinct, white rhinos exist only in preserves. Indian rhinos-the largest Asian rhino species- average 10 feet in length and 5.5 feet in shoulder height, and weigh 2.75 tons. They have one thick, foot-long horn; their skin is sprinkled with knobs, and folds at the limb joints make them look as though they have armor. Females, although 75 percent the weight of males, have similar body heights and lengths. These rhinos live in marshy jungles and eat reeds, grass, twigs, and plant shoots. There are 1,500 Indian rhinos, all living in preserves and protected by legislation. Javan rhinos are similar to the Indian species, but smaller. They occur only inWestern Java, though they once lived in forests of Bengal, Burma, Borneo, Java, and Sumatra. Sumatran rhinos, the smallest rhinos, have two horns. They are approximately 4 feet tall, and weigh about 1 ton. Unlike the smooth-skinned African rhinos, they are hairy, especially on the tail and ears. The few living Sumatran rhinos are in Sumatra's forested hills. Rhinoceroses are reputedly dangerous. However, they are usually peaceful and timid, except when threatened. Legally protected rhinos suffer from the market for rhino horn, reputed to be a medicine and aphrodisiac in traditional Asian medicinal practice. This market has been a major factor in driving four of the five rhino species into endangerment.
Family: Rhinocerotidae (rhinoceroses)
Genus and species: Ceratotherium simum (white rhino); Diceros bicornis (black rhino); Rhinoceros unicornis (Indian rhino), R. sondaicus (Javan rhino); Dicerorhinus sumatrensis (Sumatran rhino)
Geographical location: Africa and Asia
Habitat: Forests, grasslands, and scrub lands
Gestational period: Eight to seventeen months
Life span: Twenty to forty-five years
Special anatomy: Incisors and canine teeth in Asian species; very thick skin; one or two horns; three-toed feet
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