The rhinoceros are the world's second largest land animal after the elephant. The word rhinoceros is derived through Latin from the Ancient Greek rhino ("nose") and keras ("horn"). The plural in English is rhinoceros or rhinoceroses. A group of rhinos is called a "crash" or “herd.” [Sources: Richard Conniff, Smithsonian magazine, November 2011; Wikipedia; Edmond Bradley Martin, National Geographic, March, 1984; Heimanta Raj Mishra and Eric Dinerstein, Smithsonian, September 1987.]
Richard Conniff wrote in Smithsonian magazine, “The peculiar appeal of rhinos is that they seem to have lumbered straight out of the Age of Dinosaurs. They are massive creatures, second only to elephants among modern land animals, with folds of thick flesh that look like protective plating. A white rhino can stand six feet at the shoulders and weigh 6,000 pounds or more, with a horn up to six feet in length, and a slightly shorter one just behind. (“Rhinoceros” means “nose horn.”) Its eyes are dim little poppy seeds low on the sides of its great skull. But the big feathered ears are acutely sensitive, as are its vast snuffling nasal passages. The black rhino is smaller than the white, weighing up to about 3,000 pounds, but it’s more quarrelsome.”
Rhinoceros belong to the order Perissodactyla (odd-toed ungulates, or a mammal with hooves that feature an odd number of toes), the suborder Ceratomorpha; the superfamily Rhinocerotoidea; and the family Rhinocerotidae.
There are only about 25,000 rhinos in the world. Most live in carefully guarded and managed game parks and reserves in South Africa. According to Save the Rhino there are 20,165 white rhinoceros , 4,880 black rhinoceros , 2,850 Indian rhinoceros, 200 Sumatran rhinoceros and 50Javan rhinoceros. South Africa has the largest population with 18,563 white rhinoceros and 1,570 black rhinoceros. India has the second largest population with about 2,200 Indian rhinoceros. Kenya has the third largest population with 300 white rhinoceros and 600 black rhinoceros.
Members of the rhinoceros family are characterized by their large size (all species can reach a weight of one ton or more); their herbivorous diet; small brains; and large horn. There is some debate as to which are larger: hippopotami or rhinoceroses. Hippopotami can weigh as much as four tons (the size of a whale) but average around 3,000 pounds. White rhinoceros, the largest rhino species, weigh up to 4,500 pounds but on average are larger than hippos.
Rhinos are not closely related to any other animals. They belong to one of the oldest mammal families. In many ways they are more similar to the large extinct mammals that roamed the earth millions of years ago than they are to modern mammals. The five living species of rhinoceros fall into three categories. The two African species, the white rhinoceros and the black rhinoceros, belong to the Dicerotini group, which originated in the middle Miocene, about 14.2 million years ago. The species diverged during the early Pliocene (about 5 million years ago).
There are two living Rhinocerotini species, the Indian rhinoceros and the Javan rhinoceros, which diverged from one another about 10 million years ago. The Sumatran rhinoceros is the only surviving representative of the most primitive group, the Dicerorhinini, which emerged in the Miocene (about 20 million years ago). The extinct woolly rhinoceros of northern Europe and Asia was also a member of this tribe.
According to Wikipedia: Rhinocerotoids diverged from other perissodactyls by the early Eocene period (56 to 34 million years ago). Fossils of Hyrachyus eximus found in North America date to this period. This small hornless ancestor resembled a tapir or small horse more than a rhino. Three families, sometimes grouped together as the superfamily Rhinocerotoidea, evolved in the late Eocene: Hyracodontidae, Amynodontidae and Rhinocerotidae.
Hyracodontidae, also known as 'running rhinos', showed adaptations for speed, and would have looked more like horses than modern rhinos. The smallest hyracodontids were dog-sized; the largest was Indricotherium, believed to be one of the largest land mammals that ever existed. The hornless Indricotherium was almost seven metres high, ten metres long, and weighed as much as 15 tons. Like a giraffe, it ate leaves from trees. The hyracodontids spread across Eurasia from the mid-Eocene to early Miocene. The Amynodontidae, also known as "aquatic rhinos", dispersed across North America and Eurasia, from the late Eocene to early Oligocene. The amynodontids were hippopotamus-like in their ecology and appearance, inhabiting rivers and lakes, and sharing many of the same adaptations to aquatic life as hippos.
The family of all modern rhinoceros, the Rhinocerotidae, first appeared in the Late Eocene in Eurasia. The earliest members of Rhinocerotidae were small and numerous; at least 26 genera lived in Eurasia and North America until a wave of extinctions in the middle Oligocene wiped out most of the smaller species. However, several independent lineages survived. Menoceras, a pig-sized rhinoceros, had two horns side-by-side. The North American Teleoceras had short legs, a barrel chest and lived until about 5 million years ago. The last rhinos in the Americas became extinct during the Pliocene.
Modern rhinos are believed to have began dispersal from Asia during the Miocene. Two species survived the most recent period of glaciation and inhabited Europe as recently as 10,000 years ago: the woolly rhinoceros and Elasmotherium. The woolly rhinoceros appeared in China around 1 million years ago and first arrived in Europe around 600,000 years ago. It reappeared 200,000 years ago, alongside the woolly mammoth, and became numerous. Eventually it was hunted to extinction by early humans. Elasmotherium, also known as the giant rhinoceros, survived through the middle Pleistocene: it was two meters tall, five meters long and weighed around five tons, with a single enormous horn, hypsodont teeth and long legs for running.
Of the extant rhinoceros species, the Sumatran rhino is the most archaic, first emerging more than 15 million years ago. The Sumatran rhino was closely related to the woolly rhinoceros, but not to the other modern species. The Indian rhino and Javan rhino are closely related and form a more recent lineage of Asian rhino. The ancestors of early Indian and Javan rhino diverged 2 to 4 million years ago. The origin of the two living African rhinos can be traced back to the late Miocene species Ceratotherium neumayri. The lineages containing the living species diverged by the early Pliocene (1.5 million years ago), when Diceros praecox, the likely ancestor of the black rhinoceros, appears in the fossil record. The black and white rhinoceros remain so closely related that they can still mate and successfully produce offspring.
Rhinoceroses have a long life span. They generally live to of 30 to 35 years. It is not unusual for an animal to reach the age of 40. Rhinos have thick armourlike hid, a bright pink underside and relatively tiny three-toed hooves. Their thick protective skin, which is 1.5 to five centimeters cm thick, is formed from layers of collagen positioned in a lattice structure. Their brains are relatively small for mammals (400 to 600 grams).
Rhinos have poor eyesight and are extremely nearsighted. They have been known to charge tree trunks. A charging rhino can reach speeds of 35 miles per hour (compared to 70 mph for a cheetah and 9 mph for a chicken). Rhinos are odd-toed ungulates with three toes. In some species three toes in useful in securing oneself on slippery ground.
Rhinos have powerful lips, adapted for feeding on both long and short grasses. When rhinos are fed apples by hand their tender pink upper lip gently takes the fruit out of one's hands. They often suck the entire hand in their feeder inside their mouths, and it can take some to effort to get the hand back. Rhinos don't have incisors so if your hand get sucked in get it out before it reaches the molars. Their method of digestion of Asian rhinoceros is thought to be similar to tapirs (See Tapirs).
Both African species and the Sumatran rhinoceros have two horns, while the Indian and Javan rhinoceros have a single horn. A 19th century description of Indian rhinoceros explains that the horn "projects, not infrequently 30 inches upwards. So long as the animal is quiet, this appendage lies loose between the nostrils, but when excited, the muscular tension is so great that it becomes immovably fixed, and can be darted into a tree to the depth of several inches."
A rhinoceros’s horn is not made out of bone, rather it is composed matted hair and fibrous keratin, the same horny substance found in fingernails, human hair and lizard scales. It has been said that Asian people who take rhino horn for a folk medicine could obtain the same results from swallowing hair trimmings or chewing their fingernails. If a rhinoceros loses its horn, the horn grows back at a rate of about three inches a year.
On the purpose of rhinos horns, SOS Rhino says on its website: “The horns are very well developed in the two species in Africa (black and white rhinos), but much smaller in the three species in Asia (Sumatran with 2 very small horns, Indian and Javan with one horn). The Asian species certainly do not use the horns to fight or to defend themselves, they use their incisors (sharp front teeth for the purpose). The horns have come about in evolution and they had (have) a general function to impress members of the opposite sex. Horns are also used for digging in waterbeds to find water, or to uproot shrubs etc. Some rhinos use the horn to guide their offspring. This is generally the front horn, the second horn does not have a very specific purpose at the moment. We suppose that they had some purpose in the course of evolution.”
Rhinos are sedentary, largely solitary animals. If the have enough forage and water they do little but graze, drink and wallow in the mud. Rhinos require large territories. When a rhino marks its territory it can shoot a spray of urine five meters backwards.
Like elephants, hippos, water buffalo and other sparsely-hair, rhinoceros like to wallow in water holes or mud holes to moisturize their skin, cool off and remove parasites. During the monsoon season the rhino spend up to eight hours a day wallowing in the mud. They can sometimes be seen in pools of water covered with hyacinth, which the animals feed on.
Rhinos frequent the same mud pits, or wallows, over the course of their life, where they roll on the ground to smear their bodies with wet soil to keep ticks away. Sometimes rhinos look like they are covered in flour. This a result of taking a sod or dust bath.
Rhinos make a strange huffing sound when running away from danger. Baby rhinos cry "miya, miya" when they want their mothers. Sometimes near-sighted rhinos mistake elephants for their mothers. When alarmed rhinos charge. They have been known to charge trees and jeeps.
Aggressive Rhino Behavior
Rhinoceroses, particularly black rhinos, are known for their aggressiveness and grumpy disposition. A group of rhinos isn’t called a “crash” for nothing. While rhinos rarely fight with other animals they often fight with themselves. Males go after each other when they seek a female in estrus. During the mating season even females go after one another and bulls have on occasions charged calves.
Describing a charge by an Indian rhino, Geoffrey Ward wrote in National Geographic, "A cow concerned for her calf and agitated by the sound of the jeep...suddenly whirled, kicking up dust, and charged straight for us. Sharma...clapped his hands and shouted to warn her off, she kept coming, amazingly fast, her broad body seeming to float above the ground, the head high, ears straining to make out the sources of the annoying sound---Mrs. Magoo at full tilt...We pulled away. She lost track of us, slowed sniffed the air, and went back to grazing."
According to journalist Esmond Bradley Martin when a black charges its head sways “back and forth menacingly, making a thunderous noise each time its feet hit the ground and snorting loudly. Your only thought is how to escape. Usually that means climbing a tree, but many of us are around to tell about charges simply because a black rhino became distracted from the attack by something else at the last moment, or because it had intended only an intimidating mock charge in the first place.”
Black rhinos have a reputation for being very unpredictable. They have been known to charge trees and jeeps. Some animals have been observed walked into camp sites at night scattered smoldering logs of a fire, and then walked away peacefully. One explanation for their erratic behavior is that they have terrible eyesight and may perceive something as a threat when it actually isn't. Jed Bird, a 27-year-old rhino capture officer in South Africa in charge of watching over black rhinos there, told Smithsonian magazine, “The first time I saw one I was a 4-year-old in this park. We were in a boat, and it charged the boat. That’s how aggressive they can be.” Bird makes his living keeping tabs on the park’s black rhinos and sometimes works by helicopter to catch them for relocation to other protected areas. “They’ll charge helicopters,” he said. “They’ll be running and then after a while, they’ll say, “Bugger this,” and they’ll turn around and run toward you. You can see them actually lift off their front feet as they try to have a go at the helicopter.” [Source: Richard Conniff, Smithsonian magazine, November 2011]
Feeding Rhinos and Their Food
Rhinoceroses are browsers. They feed on aquatic plants, shrubs, grass, trees, twigs and branches of low bushes and when available crops from farmer's fields.. Rhinos in captivity love watermelon. Veterinarians often put medicine in watermelons.
Rhinos generally eat leafy material, although their ability to ferment food in their hindgut allows them to subsist on more fibrous plant matter, if necessary. Unlike other perissodactyls, the two African species of rhinoceros lack teeth at the front of their mouths, relying instead on their powerful premolar and molar teeth to grind up plant food.
Rhinos eat primarily at night, in the early mornings and in the late afternoons. They sleep during the heat of the afternoon. Rhinos are choosy about the kinds of grasses they eat. In some cases they eat grass and deposit seeds near the river banks where they wallow, thereby ensuring supplies of the grasses they like.
Rhinos in India and Nepal are very fond of eating the potato-like fruit of trewia trees. The seeds are deposited by rhinos on river banks, an ideal place of them to grow. B.D. Loutit noted the rhino feed on a plant with "formidable spines and highly irritating latex." It appears the rhino are "able to overcome some major chemical and physical defenses of plants without apparent harm.”
Rhinoceros are non-ruminant herbivores. According to Animal Digestion by S. Sydenham and R. Thomas, For non-ruminants the “fermentation takes place further down their digestive system. This means that by the time the tough walls of the plant cells are broken down, the food has already gone past the part of the gut that absorbs most nutrients. This means that they have to eat huge quantities in order to get enough nutrition. Non-ruminants pass quite a lot of undigested food out of their bodies. They have to spend about three quarters of the day feeding.
Mating Rhinos and Their Young
Females probably mature sexually after three years. Males take six years. Males will fight aggressively and make a frightful roaring sound during the rut which occurs non seasonly and sporadically.
Before mating a female rhino often charges her mates for several hours to size him up and make sure he is worthy enough to bear her children. She usually initiates sex. The penis of a one ton male rhino is only about two feet long. Sex often last for an hour and half or more, with the male sometimes ejaculating every 10 minutes.
The gestation period is 16 months. At birth a calf weighs around 75 pounds and can walk within a couple hours. A calf accompanies its mother for two years. Rhino milk has two thirds te calories of human milk and only 0.2 percent fat, one of the lowest of any species. Young rhinos and horses get their energy from sugars rather fat. In contrast hooded seal milk is 61 percent fat, with about 1,400 calories in an eight ounce glass. A mother may tend her calf for up to four years after birth.
Rhinos and Other Animals
No predator except man will go after an adult rhinoceros. In Africa hyenas, crocodiles, lions, wild dogs and leopards will sometimes dispatch baby rhinos. Rhinos usually back down before confronting an elephant. Trained elephants that have never seen a rhino before trumpet and run for the trees when faced with a charging rhino. Young male elephants at Pilanesberg National Park and Hluhluwee-Umfolozi Park in South Africa have been observed knocking over young rhinos and going after them with their tusks.
In South Africa’s Pilanesberg National Park, 18 white rhinos were gored to death by young bull elephants. Why? Some scientists believed it was because the bulls were removed from their group at an early age and had no mature males to discipline. They came into musth and took out their aggression on the rhinos. Naturalist Douglas Chadwick witnessed a female rhino with a calf challenge an elephant over rights to a drinking spot at a water hole. The rhino stamped , snorted and made a bluff rush, he said, adding: "The elephant — a young male — fortunately called her bluff by reaching his trunk into the water and proceeded to hose down the apoplectic mother rhino."
Egrets and myna birds often hang out on the backs of rhinos feeding on insects that make their home in the thick armourlike hide. Frogs like to sunbathe on the back of rhinos in Nepal.
Image Sources: Wikimedia Commons
Text Sources: National Geographic, Natural History magazine, Smithsonian magazine, Wikipedia, New York Times, Washington Post, Los Angeles Times, Times of London, The Guardian, Top Secret Animal Attack Files website, The New Yorker, Time, Newsweek, Reuters, AP, AFP, The Economist, BBC, and various books and other publications.
Last updated November 2012