The Rhinoceros, or Rhino for short, is one of the largest remaining megafauna, with all species known to weigh one ton or more. Grey or brown in color, these animals are unique in their appearance. Rhinoceroses belong to the family Rhinocerotidae and belong to the order Perissodactyla, (perissodactls) which means ‘odd toed ungulates’. ‘Odd toed ungulates’ are animals that have hoofs but have a reduced number of toes (usually 3 toes). Rhinoceroses carry their main weight on the middle toe of each foot. Horses and zebras are also members of this species, however, they are divided up again into sub-orders as you can see below:
Perissodactyls are divided into 2 suborders, 3 families and 15 species which include:
Sub-order Ceratomorpha: Family Tapiridae – tapirs, Family Rhinocerotidae – rhinoceroses
Sub-order Hippomorpha: Family Equildae – horses, zebra and asses
The word ‘perissodactyl’ comes from the Greek language and means ‘odd-number finger or toe’. Perissodactyl are herbivores which means they do not eat meat, they only eat vegetation, plants and grasses.
There are five remaining species of rhino, which are the White Rhinoceros, the Black Rhinoceros, the Greater One Horned Rhinoceros (also known as the Indian Rhinoceros), the Javan Rhinoceros and the Sumatran Rhinoceros. Two of these species live in Africa, and two live in Asia.
Unfortunately, the rhino is an endangered animal, with some species already extinct. Conservation efforts have prevented the surviving species from disappearing, but hunting by humans is their biggest threat. Keep reading on to find out more about these interesting animals and learn some cool rhino facts.
History and Taxonomy
The rhino is one of the oldest groups of mammals that once roamed throughout Asia and Africa, and their population was thought to be around half a million at the beginning of the 20th century.
There have been to close to 100 known species of rhino, but now only five species remain. However, within these species, there are further subspecies of rhino. There are two subspecies of the White Rhino (the Southern White and the Northern White), four subspecies of the Black Rhino (the South-Central Rhino, the South-Western Rhino, the East African Rhino and the West African Rhino), and three subspecies of the Sumatran Rhino (the Sumatran Rhinoceros Proper, the Bornean Rhinoceros and the possibly extinct Northern Sumatran Rhinoceros).
The white and black rhinos live in Africa, while the greater one horned rhino, the Javan rhino and the Sumatran rhino live in Asia. The word “rhinoceros” comes from the Greek “rhino” (nose) and “ceros” (horn).
Characteristics
Rhinos are very large animals and, while all species differ slightly, they share common characteristics such as one or two horns, a broad chest, thick skin, poor eyesight and excellent hearing. They have very thick legs, like tree trunks, and are mostly thought to move slowly — however, they can run at nearly 40 miles an hour when needed (64 kilometers per hour)! They also have a short tail.
Rhinos are the second largest land animal, behind only the elephant. The largest rhino is the white rhino, and can grow up to 12 to 13 feet (3.7 to 4 meters) long and up to 6 feet (1.8 m) from hoof to shoulder. They can weigh around 5,000 lbs (2,300 kilograms)! The smallest rhino is the Sumatran rhino and usually grows to about 8 to 10 feet (2.5 to 3 m) long and up to 4.8 feet (1.5 m) from hoof to shoulder. They weigh around 1,765 lbs (800 kg). Male rhinos are usually larger than female rhinos.
The Indian rhino has a gray-brown hide with skin folds that give it an armor-plated appearance, which looks similar to the Javan rhino, although the Javan rhino has a much smaller head, and has less apparent skin folds. The greater one horned rhino also has a small, prehensile lip, different from other rhino species. The Sumatran rhino, despite being the smallest rhino, is actually the hairiest of the species, and is reddish-brown in color.
Despite their names, the black and white rhinos are actually the same color — brownish grey! It is unclear how the white rhino came to be named. The biggest difference between the two species is their lip — as grazers, the white rhino has a wide lip, while the browser black rhino has a more narrow lip that is used to pull leaves into its mouth. White rhinos also have a hump of muscle on their neck and shoulders to hold up a head that can weigh 800 to 1,000 pounds (362 to 454 kilograms).
Rhinos do not have very good eyesight and are extremely near-sighted. This means that they often charge when they are startled, and have even been observed charging at boulders or trees! Despite their eyesight being poor, they do have very good hearing. A rhinos ears can move independently of each other, and one may be cocked forward while the other is directed backward.
Each species of rhino has a different type of skin. The Sumatran rhino has a lot of hair, probably due to the fact that it lives in higher elevation territory, while the greater one horned rhino has very little hair yet warts on its shoulders and upper legs. The Javan rhino is hairless, and the black and white rhinos both have hair on the tips of their ears and tail bristles.
Horns
Black rhinos, white rhinos and Sumatran rhinos have two horns, while Javan rhinos and Indian rhinos have one. Rhinos horns are made of keratin, which is the same material that makes up our fingernails and hair.
These horns do not have a bony core like other mammal horns have and CT scans have shown dense mineral deposits of calcium and melanin in the core of the horn. This means that they are pretty soft and can be worn down or sharpened after years of use. If a horn breaks off, it can gradually grow back.
Rhino horns tend to curve backwards towards the head because the keratin in front grows faster than the keratin in the back
Black and white rhinos grow the longest horns, with black rhinos typically grow longer horns than other rhino species. Their front horn can grow to 20 to 51 inches (51 to 130 cm), while the rear horn can grow to about 20 inches. Sumatran rhino horns grow to about 10 to 31 inches (25 to 79 cm) in the front and less than 3 inches (7 cm) in the rear. The greater one horned rhino’s horn is 8 to 24 inches (20 to 61 cm), and Javan rhinos have a horn that is about 10 inches (25 cm) long. Female Javan rhinos either do not have a horn or they have just a stubby knob in its place.
Lifespan
The rhino has a lifespan of between 35 and 50 years.
Diet
Rhinos are herbivores and spend the morning, late afternoon and nighttime eating, while the spend the hottest part of the day resting. The type of vegetation they eat varies by species, which is because their snouts are different shapes to accommodate different types of food.
Rhinos fall into one of two categories when it comes to dietary habits — grazers and browsers. Grazers primarily feed on grasses with a preference for shorter grasses, while browsers focus their attention on food that’s above eye level — with preferences including twigs, fruit, and leaves.
For example, the black rhino, a browser, eats trees or bushes because its long lips allow it to pick leaves and fruit from up high. The white rhino, a grazer, has a flat-shaped snout that lets it get closer to the ground for eating grass.
Black and white rhinos share Africa’s savanna habitats, as they don’t compete for food. Black rhinos can go for up to five days without drinking water, getting needed moisture from succulent plants. White rhinos crop grasses so short when they graze in their habitat that they create “grazing lawns” that benefit smaller herbivores and serve as firebreaks.
In captivity, rhinos are typically fed on a diet of alfalfa and soy. Unfortunately, it could be this diet that is responsible for infertility in female rhinos in captivity.
Behavior
Most rhinos are solitary animals. Black rhinos will aggressively defend their territory, and Sumatran rhinos are known to mark their trails with feces and urine. The Indian Rhinoceros (greater one horned rhino) and the Javan rhino have a more loosely defined territory, and their territories may overlap. Rhinos use their horns to defend their territory and fights amongst rhinos can lead to death. In fact, 50 percent of black rhino bulls and 30 percent of females die from wounds received during a fight, which is the highest rate for any mammal.
Male rhinos, known as bulls, occupy a small territory and they may allow one or two subordinate males to share the territory with him. Neighboring bulls show respect and will not enter this territory unless water is needed during the dry season.
The white rhino is the most social of all the rhino species, with groups of around a dozen rhinos forming. These groups will usually be made up of mothers and calves, as calves will be more protected in a larger group. A group of rhinos is called a “crash”.
While rhinos may look indestructible, their skin is actually quite sensitive, especially to sunburn and biting insects. Their blood vessels are close to the skin’s surface, which mean they can be easily scarred. This is why wallowing is so important to their everyday behavior — they cover themselves in mud to cool themselves down and to protect themselves from the sun’s rays. Rhinos may even share a wallowing spot without any fighting.
Because of their bad eyesight, rhinos rely on the alarm calls of a bird called the oxpecker. These birds hop onto a rhino’s back, plucking ticks and other parasites off the rhino’s skin, even entering the ears and nostrils to get rid of them. They also make a loud sound when there is potential danger for the rhino nearby.
Rhinos use sounds to communicate. Long and short snorts are used for anger, alarm, or when the rhino is startled, and high-pitched screams indicate fear. When rhinos are happy, they make a loud “mmwonk” sound with their mouths.
Reproduction
Females choose males to mate with by showing up to their territory when they are ready to mate. The bull approaches the female with a series of “hic-pants,” which is a breathy inhalation followed by a hiccup. He may rest his chin on her rump to test whether she will tolerate a mating, too.
Females reproduce every two and a half to five years. The gestation period for a rhino is 15 to 16 months, and they usually give birth to just one offspring. Twins are rare. Baby rhinos, called calves, will weigh around 88 to 140 lbs (40 to 64 kg).
A newborn calf is able to stand relatively soon after birth, although they will be wobbly on their feet. They begin to nurse two to three hours after birth and will continue until they are 12 to 18 months of age, although male claves will nurse for longer as they grow much larger as adults. They begin to eat solid food at 7 to 10 days of age. Rhinos will stay with their mother until they are around three years old, but may be pushed out earlier if their mother has another baby.
Habitat and Location
Rhinos live in Africa and Asia. The white and black rhinos live in the grasslands and floodplains of eastern and southern Africa, while the Indian rhino, the Sumatran rhino and the Javan rhino live in Asia. More specifically, the greater one horned rhino is found in India and Nepal, the Sumatran rhino is found on the islands of Sumatra and Borneo, and the Javan rhino is only found in one protected area on the island of Java, Indonesia.
The three Asian rhinos species can be found in the swamps and rainforests, which means all Asian rhinos are excellent swimmers.
The black rhino favors open woodlands, while the greater one horned rhino likes forests and the tall grasslands. The Javan rhino prefers dense rainforests, tall grasses and reed beds, while the Sumatran rhino lives at the highest elevation of all the rhino species.
Conservation Status
Rhinos of all species are in danger of becoming extinct. According to International Union for Conservation of Nature’s (IUCN’s) Red List of Threatened Species, black rhinos, Sumatran rhinos and Javan rhinos are “critically endangered”, greater one horned rhinos (also known as the Indian Rhino) are “vulnerable” and white rhinos are “near threatened”. In fact, there are now only two northern white rhinos left in the world, both living in captivity, according to the World Wildlife Fund.
The Sumatran rhinos and Javan rhinos are two of the most critically endangered large mammals in the world. The Javan rhino is the rarest of the rhinos, with none living in zoos. It is thought there are fewer than 50 Javan rhinos in the wild, although they have only been counted with a sensor camera and little is known about the species. The Sumatran rhino is also critically endangered, with less than 80 individuals left in the wild. Because there are so few of this species left, isolation is another threat — they are simply too scattered to find mates to breed. While Sumatran rhinos have been brought to zoos for breeding purposes, there has been little success in breeding them.
Importance
Rhinos are very important to the environment and ecosystem in which they live. For example, greater one horned rhinos maintain the health of grasslands and the waterholes in which they wallow, which allows other herbivores and small animals to live in optimal conditions. Rhinos also disperse the seeds of plants and fruit they’ve eaten through their dung, allowing their ecosystem to thrive.
Predators and Threats
Adult rhinos are at the top of the food chain and do not have any natural predators. Unfortunately, their biggest predator is humans. Rhino calves are a different story though; both African and Asian rhino calves are sometimes prey for large cats — lions and tigers respectively. In most instances, predators won’t actively hunt calves but won’t pass up on the opportunity to pick off a calf that strays from the herd. Calves are especially easy prey at night, as the poor eyesight of rhino mothers means it can be difficult for them to keep track of their offspring. Hyenas and Nile crocodiles also prey on rhino calves.
Humans are the biggest threat to rhinos. Rhinos are hunted for their horns, which are sold illegally. Rhino horns are often ground up and used in traditional Asian medicines. They are thought to treat a range of ailments from fevers to cancer, and are also uses as a status symbol to display success and wealth is also increasingly common. Although a ban was put on international trade in rhino horn in 1977 and the medical use of rhino horn has been illegal since 1993, between 1960 and 1995, 98% of black rhinos were killed by poachers purely for their horns. Habitat loss due to humans is another threat to rhinos.
In Captivity
Worldwide, 302 zoos hold 1037 rhinos. 174 of these hold 671 southern white rhinos; 61 zoos hold 184 black rhinos and 67 zoos hold 182 greater one-horned rhinos. While zoos used to be a place where you could go and look at exotic animals, they are now imperative in protecting and breeding endangered animals that are vulnerable in the wild.
In zoos, rhinos are protected from poaching. There have also been reproduction efforts made in order to save almost extinct species of rhino. That being said, breeding in captivity is difficult and some conservationists have turned to in vitro fertilization. However, IVF is challenging within rhinos and there is a struggle to get immature eggs to develop outside of the female’s body and also difficulty injecting sperm into these eggs.
Conservation Efforts
Fortunately, thanks to conservation efforts, there is hope for the rhino yet! The population of black rhinos has doubled this century and the population of the white rhino has gone from about 50 to nearly 20,000. This is thanks to poaching bans, as well as protection of rhinos in national parks and on reserves by rangers and guards. Efforts by zoos and other conservation organizations have also contributed to the rise in rhino populations recently.
- Learn more about the History of Rhinos
