A rhinoceros (pronounced ry-NOSS-ə-rəss) is a large animal that belongs to any of the five species that still live today (or many species that no longer exist). It is part of a group called odd-toed ungulates, which are hoofed mammals in the family Rhinocerotidae. This family is the only one in the group called Rhinocerotoidea, and all members of this group are sometimes called rhinoceroses. Two species live in Africa, and three live in South and Southeast Asia.

Rhinoceroses are among the largest animals still living today. They weigh more than half a ton when fully grown. They eat only plants, have small brains (about 400–600 grams, which is 14–21 ounces for their size), one or two horns, and thick skin that is 1.5–5 centimeters (0.59–1.97 inches) thick. Their skin is made of layers of collagen arranged in a grid-like pattern. They mostly eat leafy plants, but they can also eat tougher plants because they can digest them in their hindgut. Unlike other odd-toed hoofed mammals, the two African rhino species do not have teeth at the front of their mouths. Instead, they use their lips to pick up food.

People kill rhinoceroses for their horns, which are sold on the black market for high prices. This has caused most rhino species to be endangered. Today, the demand for rhino horns is mostly driven by wealthy buyers in China and Vietnam, where the horns are used in traditional Chinese medicine. Rhino horns are made of keratin, the same material as hair and fingernails. There is no strong evidence that using rhino horns has health benefits. In the past, Yemen was a major buyer of rhino horns, which were used to make dagger handles.

Taxonomy and naming

The word "rhinoceros" comes from Latin, which was borrowed from Ancient Greek: ῥινόκερως. This word is made up of two parts: ῥινο- (rhino-, meaning "of the nose") and κέρας (keras, meaning "horn"), referring to the horn on the nose. The name has been used since the 14th century. The plural form of "rhinoceros" can be written as "rhinoceros" or "rhinoceroses." The first rhinoceros species to be scientifically named were the Indian rhinoceros and the black rhinoceros by Carl Linnaeus in his 10th edition of Systema Naturae in 1758. Linnaeus also created the genus Rhinoceros, which was originally used for all rhinoceroses. In his early classification, Linnaeus placed the genus Rhinoceros in the group Glires, mistakenly believing rhinoceroses were closely related to rodents because Indian rhinoceroses had incisor teeth. In the 18th and early 19th centuries, scientists were unsure about the exact number of living rhinoceros species. The family Rhinocerotidae was first named in 1821 as Rhynocerotidæ by John Edward Gray in his paper "On the natural arrangement of vertebrose animals." Some sources also credit Richard Owen's 1845 work "Odontography" as the origin of the family name, which uses the modern spelling.

Description

Rhinoceroses are some of the largest living land animals, with living species weighing between 775 kilograms (1,709 lb) for the Sumatran rhinoceros and up to 2,300 kilograms (5,100 lb) for the white rhinoceros. Some extinct rhino relatives were much smaller or larger than living rhinoceroses. For example, the genus Menoceras from the Early Miocene in North America had an estimated body mass of 313 kilograms (690 lb), similar to a sheep or pig, while Elasmotherium sibiricum from the Pleistocene in Eurasia had an estimated body mass of about 4,500 kilograms (9,900 lb). Rhino skulls are usually shaped like a saddle and are low. Early rhinos had a chisel-shaped upper front tooth (I1) and a tusk-like lower second front tooth (i2), while other front teeth and canines were often absent. Black and white rhinoceroses do not have front teeth. Living rhinos have one or two horns made of tightly packed corneocytes from the skin. Horn growth is similar to human nail growth, as both are mainly made of keratin. Horns attach to a rough area on the skull. Not all rhino relatives had horns, as many extinct species, such as most members of the subfamily Aceratheriinae, did not.

Rhino brains are relatively small compared to their body size, about 531 grams (18.7 oz) in an adult black rhinoceros. Their limb bones are strong and thick. Most rhinos, both living and extinct, have three toes on each foot. Their bodies are covered in thick skin made of a dense network of collagen fibers, which is stronger and stiffer than in other mammals. The skin has deep folds and is usually gray to brown in color, with little or no hair as adults, except for eyelashes, ears, and the tail. The Sumatran rhinoceros is an exception, as it often has a lot of hair.

The black rhinoceros has 84 chromosomes (diploid number, 2N, per cell), while all other rhino species have 82 chromosomes. Chromosome differences may lead to varying counts. For example, three northern white rhinoceroses studied had 81 chromosomes.

Behaviour and ecology

Living rhinoceroses have different social behaviors depending on their species. Adult male rhinoceroses are often alone, and female Asian rhinoceroses also tend to live alone. However, some female African rhinoceroses, especially white rhinoceroses, may form small groups. Rhinoceroses eat different types of food. White rhinoceroses mainly graze, black rhinoceroses mostly browse, and Sumatran and Javan rhinoceroses eat a mix of both. Because they eat large amounts of low-quality plants, rhinoceroses spend much of their time searching for food. Rhinoceroses are hindgut fermenters, meaning they digest food in their large intestines.

All living rhinoceroses have a mating system where both males and females mate with multiple partners. Male rhinoceroses watch over females until they are ready to mate, but females may sometimes drive males away until they are ready. Males check the urine of females and curl their upper lips to determine if females are ready to mate. Males near females in heat may fight other males. These fights can be simple displays or serious battles that cause injuries. Some rhinoceroses are territorial, while others are not or only territorial depending on their environment. Females may reject males they do not like, causing the males to run or fight if cornered. During mating, the male moves his neck over the female’s back and uses it to lift his front legs before moving them behind her shoulders. Mating can last several hours. Pregnancy lasts more than a year, about 460 days in black rhinoceroses and 504 days in white rhinoceroses.

Females usually give birth in a quiet place and are protective of their young for a time after birth. Calves can stand within 30 minutes of being born and begin nursing within two hours. Mothers are strongly attached to their most recent calf. Calves often stay close to their mothers but may sometimes be left alone for long periods. Juvenile rhinoceroses are at risk from predators until they are about three years old. Mothers fiercely protect their calves from threats. In some species, mothers push away their older calves when a new calf is born. There is usually a long gap between births, but sometimes females give birth as soon as 1.5 years after their last calf. Rhinoceroses reach sexual maturity at about five to eight years old. Males in black and Sumatran rhinoceroses mature about a year after females, while male white rhinoceroses mature at around 12 years old, four years after females begin having babies.

Extant species

There are two types of white rhinoceroses: the southern white rhinoceros (Ceratotherium simum simum) and the northern white rhinoceros (Ceratotherium simum cottoni). As of 2013, the southern type had a wild population of 20,405, making them the most common rhino subspecies in the world. The northern type is very close to extinction, with only two female rhinos remaining in captivity. The name "white rhinoceros" does not have a clear explanation. One idea is that "white" comes from a word meaning "wide," but studies do not support this.

The white rhinoceros has a large body, a big head, a short neck, and a wide chest. Female rhinos weigh about 1,600 kg (3,500 lb), and males weigh about 2,400 kg (5,300 lb) on average. Some rhinos can weigh as much as 4,500 kg (9,900 lb). Their body length is 3.5–4.6 m (11–15 ft), and their shoulder height is 1.8–2 m (5.9–6.6 ft). They have two horns on their snout, with the front horn being larger. The front horn is usually about 90 cm (35 in) long and can grow up to 150 cm (59 in). A large muscular hump on their body supports their heavy head. Their color ranges from yellowish brown to slate gray. Most of their body hair is found on the edges of their ears and the bristles of their tails, with little hair elsewhere. White rhinos have a flat, wide mouth used for eating grass.

A hybrid rhino (Ceratotherium s. simum × C. s. cottoni) was born at the Dvůr Králové Zoo in the Czech Republic in 1977. Scientists have also confirmed that black rhinos and white rhinos can sometimes produce hybrids.

The name "black rhinoceros" (Diceros bicornis) was chosen to distinguish this species from the white rhinoceros. However, the two species are not truly different in color. There are four types of black rhinos: the South-central (Diceros bicornis minor), the most common, which once lived in Tanzania, Zambia, Zimbabwe, Mozambique, and South Africa; the South-western (Diceros bicornis occidentalis), which lives in dry areas of Namibia, Angola, Botswana, and South Africa; the East African (Diceros bicornis michaeli), found mainly in Tanzania; and the West African (Diceros bicornis longipes), which was declared extinct in 2011. The Tswana word "keitloa" refers to a type of black rhino in South Africa where the back horn is as long as or longer than the front horn.

An adult black rhinoceros stands 1.50–1.75 m (59–69 in) tall at the shoulder and is 3.5–3.9 m (11–13 ft) long. They weigh between 850 and 1,600 kg (1,870–3,530 lb), with some males reaching up to 1,800 kg (4,000 lb). They have two horns made of keratin. The larger front horn is usually about 50 cm (20 in) long, and some can grow up to 140 cm (55 in). A third, smaller horn may sometimes appear. Black rhinos are smaller than white rhinos and have a pointed mouth used to grasp leaves and twigs.

During the second half of the 20th century, black rhino numbers dropped from about 70,000 in the late 1960s to a low of 2,410 in 1995. Since then, their numbers have slowly increased, doubling to 4,880 by 2010. As of 2008, their population was still 90% lower than it was three generations ago.

The Indian rhinoceros, also called the greater one-horned rhinoceros (Rhinoceros unicornis), has one horn that is 20–60 cm long. It is nearly as large as the African white rhino. Its thick, silver-brown skin folds over the shoulders, back, and rump, giving it an armored look. Its legs and shoulders have wart-like bumps, and it has very little body hair. Male rhinos are larger than females, weighing 2,500–3,200 kg (5,500–7,100 lb). Females weigh about 1,900 kg (4,200 lb) and are 3–4 m (9.8–13 ft) long. The heaviest recorded Indian rhino weighed about 4,000 kg (8,800 lb).

Indian rhinos once lived in many areas from Pakistan to Myanmar and possibly parts of China. Today, they live only in protected areas of India (Assam, West Bengal, and Uttar Pradesh), Nepal, and a small area in Bangladesh.

The Javan rhinoceros (Rhinoceros sondaicus) is very close to extinction. It has one horn and a thick, dark skin. It lives in Java, Indonesia, and is one of the rarest animals in the world.

The Sumatran rhinoceros (Dicerorhinus sumatrensis) is also very close to extinction. It has two horns, with the front horn being larger (25–79 cm) and the back horn usually less than 10 cm long. Males have much larger horns than females. Their hair can be dense or sparse, and their color is reddish brown. They have short legs and a prehensile lip used for grasping. Sumatran rhinos once lived across Southeast Asia but are now found only in parts of Indonesia and Malaysia. DNA studies show they are the oldest living rhino species and are related to the extinct woolly rhino.

Evolution

The earliest members of Rhinocerotoidea appeared during the early-middle Eocene in Asia, about 54 million years ago. The family of modern rhinoceroses, Rhinocerotidae, appeared during the middle-late Eocene, around 39–40 million years ago, in both North America and Asia. Rhinoceroses migrated into Europe at the Eocene-Oligocene boundary, about 34 million years ago, as part of the "Grande Coupure" along with many other Asian species. After the end of the Oligocene epoch, around 23 million years ago, rhinocerotids became the only living family of rhinocerotoids, following the extinction of other groups like the giant paraceratheres. During the early Miocene, around 20 million years ago, rhinocerotids moved into Africa after it connected to Eurasia.

The last common ancestor of living rhinoceroses (which belong to the subgroup Rhinocerotina) is believed to have lived during the Miocene, at least 15–16 million years ago. Rhinocerotids reached their greatest diversity during the Miocene, with 4–5 species of rhinoceros often coexisting in Eurasia, up to 9 in South Asia. These included members of the living group Rhinocerotina, as well as extinct groups like Teleoceratini, Aceratheriinae, and Elasmotheriinae. Rhinocerotoids declined in diversity during the late Miocene due to unfavorable climate changes, becoming extinct in North America at the start of the Pliocene, around 5 million years ago. Teleoceratini and Aceratheriinae also became extinct by the Early Pliocene.

The earliest remains of the genus Rhinoceros (which includes the living Indian and Javan rhinoceroses) are found in Late Miocene deposits in Myanmar, dating to about 8–9 million years ago. The two modern species of Rhinoceros appeared during the Early-Middle Pleistocene. The earliest clear relatives of white and black rhinoceroses, belonging to the genera Ceratotherium and Diceros, first appeared during the late Miocene. Modern white and black rhinoceroses first appeared unambiguously during the Early Pleistocene. The earliest clear remains of Dicerorhinus (which includes the modern Sumatran rhinoceros) are from the latest Pliocene, with the modern Sumatran rhinoceros appearing during the Early Pleistocene.

Alongside modern rhinoceros species, four additional species survived into the Last Glacial Period: the woolly rhinoceros (Coelodonta antiquitatis), Elasmotherium sibiricum, and two species of Stephanorhinus—Merck's rhinoceros (Stephanorhinus kirchbergensis) and the narrow-nosed rhinoceros (Stephanorhinus hemitoechus).

Cladogram showing the relationships of recent and Late Pleistocene rhinoceros species (excluding Stephanorhinus hemitoechus) based on whole nuclear genomes, after Liu et al., 2021:

† Elasmotherium sibiricum
White Rhinoceros (Ceratotherium simum)
Black rhinoceros (Diceros bicornis)
† Woolly rhinoceros (Coelodonta antiquitatis)
† Merck's rhinoceros (Stephanorhinus kirchbergensis)
Sumatran rhinoceros (Dicerorhinus sumatrensis)
Javan rhinoceros (Rhinoceros sondaicus)
Indian rhinoceros (Rhinoceros unicornis)
† denotes extinct taxa

Family Rhinocerotidae
† Teletaceras
† Uintaceras
† Epiaceratherium
† Trigonias
† Ronzotherium
† Diceratherium
† Menoceras
† Subhyracodon
† Molassitherium
Subfamily Aceratheriinae (sometimes placed in Rhinocerotinae as Aceratheriina)
† Alicornops
† Aprotodon
† Acerorhinus
† Aphelops
† Hoploaceratherium
† Persiatherium
† Brachydiceratherium
† Diaceratherium
† Dromoceratherium
† Floridaceras
† Galushaceras
† Chilotheridium
† Mesaceratherium
† Plesiaceratherium
† Proaceratherium
Tribe Aceratheriini
† Acerorhinus
? † Aphelops
? † Hoploaceratherium
? † Persiatherium
† Aceratherium
† Subchilotherium
† Peraceras
† Chilotherium
† Shansirhinus
Tribe Teleoceratini (? sometimes placed as a separate group)
? † Alicornops
† Teleoceras
† Brachypotherium
† Prosantorhinus
Subfamily Rhinocerotinae
Subtribe Rhinocerotina (also used to encompass all modern rhinoceroses)
† Nesorhinus
Rhinoceros – Indian & Javan rhinoceros
Tribe Dicerorhinini or Subtribe Dicerorhinina (also known as the "DCS clade")
† Pliorhinus
† Coelodonta – Woolly rhinoceros
Dicerorhinus – Sumatran rhinoceros
† Dihoplus
† Stephanorhinus – Merck's rhinoceros & Narrow-nosed rhinoceros
Tribe Dicerotini/Diceroti or Subtribe Dicerotina
Ceratotherium – White rhinoceros
Diceros – Black rhinoceros
† Paradiceros
† Miodiceros
? Rhinocerotinae incertae sedis*
† Protaceratherium
† Lartetotherium
† *Gain

Predators, poaching and hunting

Adult rhinoceroses have no natural predators in the wild except humans. Young rhinos may be hunted by large cats, crocodiles, African wild dogs, and hyenas.

Although rhinos are large, aggressive, and known for being strong, they are often targeted by poachers. They visit water sources daily, making them easy to attack while drinking. As of December 2009, poaching increased worldwide, and efforts to protect rhinos have become less effective. In Zimbabwe, it is estimated that only 3% of poachers are stopped successfully. Nepal has not faced this problem as much. Poachers now use more advanced methods. South African officials called for immediate action after poachers killed the last female rhino in the Krugersdorp Game Reserve near Johannesburg. Statistics from South African National Parks show that 333 rhinos were killed in 2010, 668 in 2012, over 1,004 in 2013, and over 1,338 in 2015. Some poachers use drugs to calm rhinos and cut off their horns, which can cause them to bleed to death. In other cases, more than the horn is taken.

The Namibian government supports rhino trophy hunting to raise money for conservation. Each year, hunting licenses for five black rhinos are sold, and the money goes to the government's Game Products Trust Fund. Some conservationists and members of the public disagree with or have concerns about this practice.

Horn use

Rhinoceros horns grow from tissues under the skin and are made of hard, keratin parts. The horns attach to a layer of cells that helps them grow.

Rhinoceros horns are used in traditional medicines in parts of Asia and as handles for daggers in Yemen and Oman. Esmond Bradley Martin reported on the trade of dagger handles in Yemen, which was a major source of rhino horn demand in the late 20th century. In Europe, it was once believed that rhino horns could clean water, find poisoned liquids, and possibly act as an aphrodisiac or antidote for poison.

It is a common mistake to think that powdered rhino horn is used in traditional Chinese medicine (TCM) as a cure for cancer or as an aphrodisiac. No TCM texts ever mentioned such uses. In TCM, rhino horn is sometimes used to treat fevers and seizures, but this is not supported by scientific evidence. This practice has been compared to drinking water with fingernail clippings. In a 2021 survey, most people in China who used rhino horn said they did so for "cooling the body" or "detoxifying." In 1993, China signed the CITES treaty and removed rhino horn from its official medicine list. In 2011, the UK’s Register of Chinese Herbal Medicine officially criticized the use of rhino horn. Many TCM teachers now oppose this practice, though some TCM doctors still believe it can save lives.

Vietnam is reported to have the most rhino horn users, and their demand has caused record levels of poaching. Vietnam’s CITES authority said Hanoi saw a 77% drop in rhino horn use, but National Geographic questioned this, noting no increase in arrests or prosecutions. South African rhino horns are mostly sent to Vietnam. A single horn can be worth up to $250,000 in Vietnam, and many countries where rhinos live have stored rhino horns.

Horn trade

International trade in rhinoceros horn has been illegal since 1977 under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). In October 2016, a proposal by Swaziland to end the international ban was not accepted. In South Africa, where 80% of the remaining rhino population lives, the sale of rhinoceros horn within the country was banned in 2009. This ban was reversed in a court case in 2017, and South Africa now plans to create rules for selling rhino horn, possibly allowing exports for "non-commercial purposes." The South African government has suggested that legal trade in rhino horn could help reduce poaching and protect the species from extinction.

In March 2013, some researchers said that the best way to stop poaching might be to create a controlled trade using safe and sustainable methods for harvesting horn from live rhinos. The World Wildlife Fund does not support legalizing the horn trade, as it might increase demand. Meanwhile, the International Fund for Animal Welfare shared a report by EcoLarge, which stated that more research on economic factors is needed to support the idea of legal trade.

Conservation

The World Wide Fund for Nature states that protecting African rhinoceroses is important because they eat a lot of plants, which helps shape the African landscape and supports resources used by local people.

To stop poaching, rhinos in some areas are put to sleep and have their horns removed. In South Africa, armed rangers work to protect rhinos and sometimes stop poachers by using force. A large increase in rhino deaths in 2012 raised concerns about the species' survival. A 2025 study in the journal Science found that removing rhino horns reduced poaching by 78%.

In 2011, the Rhino Rescue Project started a method to control the illegal trade of rhino horns. This method involves injecting a mixture of pink dye and a chemical that kills ticks into the horns of living rhinos. The process is safe for rhinos but harmful to humans. It also includes placing three special tracking devices and collecting DNA samples. Because rhino horns are made of fibers, the dye spreads inside the horn but does not change its color or affect the rhino’s behavior. Experts believe that if someone eats the horn, the chemical could cause sickness, but it would not kill them. Signs at protected areas warn people about the treatment. The idea came from research about using horns to store tick medicine, and the chemical was chosen to be safe for rhinos, birds, and other animals. Supporters say the dye cannot be removed from the horns and can be seen even if the horn is broken into powder.

The UK charity Save the Rhino has criticized the horn poisoning method. They question whether the technique works as planned and whether people involved in the illegal trade would care about the effects on buyers. They also note that rhino horns are now more often bought for decoration rather than traditional medicine. Save the Rhino doubts whether the method can be used for all African rhinos because the chemical would need to be reapplied every four years. It was also reported that one rhino in 150 treated did not survive the anesthesia.

Another idea to reduce the demand for rhino horns was suggested by Matthew Markus of Pembient, a biotechnology company. He proposed creating an artificial version of rhino horns. To help authorities tell real horns from fake ones, the genetic code of the artificial horns could be recorded, similar to the DNA of living rhinos in the RhODIS system. Many conservationists were at first against the idea, but a 2016 report from TRAFFIC, which tracks wildlife trade, said it might be possible for fake horns to help protect real rhinos in the future.

Historical representations

Woolly rhinoceroses are shown in European Paleolithic art, such as in cave paintings in Chauvet Cave in France, which are about 30,000 to 40,000 years old.

A Greek historian and geographer named Agatharchides (2nd century BC) mentions rhinoceroses in his book called On the Erythraean Sea.

In Khmer art, the Hindu god Agni is shown riding a rhinoceros as his vahana. Similarly, in medieval Thai literature, Agni, known as Phra Phloeng, is sometimes described as riding a rhinoceros.

Albrecht Dürer created a famous woodcut of a rhinoceros in 1515. The image was based on a written description and a short sketch by Valentim Fernandes, a German printer living in Lisbon. Dürer did not see the animal himself, so his drawing is not entirely accurate.

Stories say rhinoceroses stamp out fires in Burma, India, and Malaysia. In Malay, the mythical rhinoceros has a special name: badak api, where badak means rhinoceros and api means fire. According to the legend, the animal would appear when a fire was lit in the forest and stamp it out. There are no recent confirmations of this happening. This story was shown in the film The Gods Must Be Crazy (1980), which features an African rhinoceros putting out two campfires.

In 1974, a lavender rhinoceros symbol began to be used as a symbol for the gay community in Boston, United States.