Five species of rhinoceros exist on Earth today, split between two continents: two in Africa and three in Asia. They range from the massive white rhino, which can weigh over 7,000 pounds, to the relatively small Sumatran rhino, the last surviving relative of the prehistoric woolly rhinoceros. Despite their size and power, most rhino species are critically endangered, with some numbering in the dozens.
Five Species, Two Continents
All living rhinos belong to the family Rhinocerotidae, which split into African and Eurasian lineages roughly 16 million years ago, after a land bridge formed between the Afro-Arabian and Eurasian landmasses. The family once included over 100 species spread across Africa, Eurasia, and even North and Central America, some of them among the largest land mammals that ever lived. Today, only five remain.
The African species are the white rhinoceros and the black rhinoceros. The Asian species are the greater one-horned (or Indian) rhinoceros, the Javan rhinoceros, and the Sumatran rhinoceros. Each belongs to a different genus, and they vary dramatically in size, appearance, and habitat.
White Rhinoceros
The white rhino is the largest of the five species, with adults weighing between 2,200 and 7,900 pounds. Its name likely comes from a mistranslation of the Dutch word “wijd” (wide), referring to its broad, flat mouth, which is built for grazing on grasses. White rhinos have two horns and a relatively calm temperament compared to their African cousin, the black rhino.
Two subspecies exist, but their fortunes differ wildly. Southern white rhinos are found across several African countries, including Botswana, Namibia, Zimbabwe, Kenya, and Zambia, and they represent the most numerous rhino population on the planet. Northern white rhinos, by contrast, are functionally extinct. Only two individuals remain, both female, living under armed guard in Kenya.
Black Rhinoceros
Despite the name, black rhinos aren’t actually black, and white rhinos aren’t white. Both are gray. The black rhino is smaller than the white and has a distinctly hooked upper lip, a feature that reflects its diet. While white rhinos graze on low grasses, black rhinos are browsers, using that prehensile lip to grab leaves, twigs, and branches from shrubs and low trees.
Black rhinos also have a reputation for being more aggressive and solitary. They inhabit a variety of landscapes across eastern and southern Africa, from savannas to dense bush. They carry two horns, with the front horn typically longer.
Greater One-Horned Rhinoceros
The greater one-horned rhino, sometimes called the Indian rhino, looks like it’s wearing a suit of armor. Deep folds in its thick skin give it a plated appearance unlike any other living mammal. As the name suggests, it has a single horn. It once roamed the entire northern floodplain of the Indian subcontinent but is now found mainly in protected areas in India and Nepal.
This is the largest of the three Asian species and the second largest rhino overall. It’s also a conservation success story: careful protection has brought its population back from the brink, though it remains vulnerable.
Javan Rhinoceros
The Javan rhino is one of the rarest large mammals on Earth. Fewer than 80 individuals survive, all of them in a single national park on the western tip of Java, Indonesia. Like the greater one-horned rhino, it has a single horn, and its skin has a similar folded appearance, though less pronounced. It lives in dense tropical and subtropical forests, making it extremely difficult to study or even observe.
Its extreme rarity and limited range make it uniquely vulnerable to a single catastrophic event, whether a tsunami, volcanic eruption, or disease outbreak.
Sumatran Rhinoceros
The Sumatran rhino is the smallest living rhino species and the most unusual. It’s the closest living relative of the woolly rhinoceros that roamed during the last Ice Age, and it’s the only Asian rhino with two horns. Sparse, reddish-brown hair covers parts of its body, another echo of its woolly ancestors.
Sumatran rhinos inhabit dense highland and lowland forests in Sumatra and Borneo, though their population has plummeted to fewer than 80 individuals. They’re solitary, elusive, and extremely difficult to breed in captivity, making conservation efforts a race against time.
What All Rhinos Share
Despite their differences, all five species share several defining traits. Their horns are made entirely of keratin, the same protein found in human fingernails and hair. Unlike the horns of cattle or antelope, rhino horns have no bone core. The keratin is especially rich in an amino acid called cysteine, which attracts iron and helps strengthen the horn’s structure. This composition is worth noting because rhino horn has no unique medicinal properties, despite the demand that drives poaching.
Rhinos have notoriously poor eyesight. Their small eyes sit on either side of their wide heads, and researchers have observed that wild rhinos often ignore stationary objects entirely, reacting only once something moves. To compensate, they rely heavily on their acute senses of smell and hearing to navigate, find food, and detect threats.
All rhinos are herbivores, though their specific diets vary by species. They’re generally solitary or live in small groups. A group of rhinos is called a crash, a fitting name for animals that can reach speeds of 30 miles per hour in short bursts despite weighing thousands of pounds.
An Ancient Lineage in Decline
A 2021 genomic study published in Cell analyzed DNA from all five living species plus three extinct ones: the woolly rhinoceros, the Siberian unicorn, and Merck’s rhinoceros. The research confirmed that the two African species form one evolutionary branch, while the Asian species split into two separate branches. The Sumatran rhino groups with the extinct woolly and Merck’s rhinos, while the greater one-horned and Javan rhinos form their own closely related pair.
Nine species survived into the Late Pleistocene, the geological epoch that ended around 11,700 years ago. Four of those went extinct during or shortly after the Ice Age. The five that remain are now under intense pressure from habitat loss and poaching. Of the five, only the white rhino (southern subspecies) and the greater one-horned rhino have populations stable enough to offer some measure of hope. The other three are critically endangered, with the Javan and Sumatran rhinos among the most threatened large animals on the planet.