White rhinoceros

Name and taxonomy

William Burchell described the southern white rhinoceros in 1817 from a spring in what is now South Africa. John Edward Gray set up the genus Ceratotherium in 1868. The name joins the Greek words for horn and beast, and simum means flat-nosed. Nobody knows for sure where the English name white came from. A popular story says settlers misheard the Dutch word wijd, meaning wide, but a review of Dutch writing found no record of that use. Square-lipped rhinoceros is a more accurate name, though it is used less often.

The species sits in the family Rhinocerotidae and the order Perissodactyla, the odd-toed hoofed mammals, with horses and tapirs. Two subspecies are recognised: the southern, C. s. simum, and the northern, C. s. cottoni, named by Lydekker in 1908. A 2010 study argued that the northern form is a full species, separate for at least one million years. Other rhino geneticists disagreed, and the IUCN still treats it as a subspecies.

Evolution and relatives

The white rhino and the black rhino, Diceros bicornis, are each other's closest relatives. Their common ancestor was probably a mixed feeder, and the two lines then split into a browser and a grazer. Fossil teeth from Makapansgat in South Africa show that early Ceratotherium still took over 30% browse. The oldest sure fossils of the living species come from Olduvai Gorge in Tanzania and are about 1.8 million years old.

For years the species was traced to Ceratotherium praecox, a rhino from about seven million years ago. A 2005 review moved that fossil to the black rhino line instead. The same review proposed a chain from C. neumayri through C. mauritanicum of North Africa to the living species. A 2011 study named C. efficax from Ethiopia and Tanzania as the earliest African member of the genus. One extinct East African form, C. germanoafricanum, looks so similar that some treat it as an ancestral subspecies.

Appearance

The white rhino has a barrel body, a huge head and a short, thick neck topped by a muscular hump. A bull measures 3.7 to 4 metres from head to rump and stands 170 to 186 centimetres at the shoulder. A cow measures 3.35 to 3.65 m and stands 160 to 177 cm. The tail adds 57 to 77 cm. Bulls average 2,000 to 2,300 kilograms and cows 1,600 to 1,700 kg. The heaviest reliable record is 3,600 kg, and claims of 4,500 kg have never been checked.

The two horns are not bone and have no bony core. They are solid keratin, the same protein as human hair and nails. The front horn is the larger and averages about 60 cm, though a cow's horn can reach 166 cm. Cows tend to carry longer, thinner horns than bulls. One horn can weigh about 4 kg.

The skin is thick and grey, with plate-like folds, and it often takes the colour of the local mud. Hair is limited to fringes on the ears and bristles on the tail. Each foot has three broad toes that spread the animal's weight. The large tube-shaped ears turn on their own, and the nostrils are the widest of any land animal. A calf is born at 40 to 65 kg, and its horns show after about six weeks.

Habitat and range

As a grazer, the white rhino needs grassland and savanna woodland with grassy openings. It does badly where winters bring hard frost or where the land is very dry. The densest populations live on savanna with fertile soil and about 700 to 800 millimetres of rain a year. It stays near water and drinks about twice a day when it can, but it can go four or five days without. In the heat of the day it moves into shade or lies in a mud wallow.

The southern white rhino once ranged across southern Africa from the Zambezi to the Orange River. By 1885 hunters had cut it to a single herd in the Umfolozi reserve in what is now KwaZulu-Natal. From that herd it has been moved back into Namibia, Botswana, Zimbabwe, Eswatini and Mozambique. It has also been introduced north of the Zambezi, into Kenya, Uganda and Zambia, beyond its old range. South Africa held about 12,968 animals in 2021, the great majority of the world total.

The northern white rhino lived in southern Chad, the Central African Republic, South Sudan, north-east Congo and Uganda. Its last wild refuge was Garamba National Park in the Democratic Republic of the Congo. A survey there in August 2005 found only four animals, and none has been seen in the wild since. White rhinos swim poorly and sometimes drown, so big rivers such as the Nile and Zambezi block their spread. GBIF holds records from 35 countries, a figure that includes zoos.

Diet and feeding

The white rhino is a pure grazer, and it is often called the largest pure grazer on Earth. Its broad flat lower lip and hard upper pad clip grass close to the ground. It prefers the shortest grasses, among them panic grass, signal grass and finger grass. The black rhino, by contrast, has a hooked lip and browses on bushes. Unlike other rhinos, the white rhino has no grasping tip to its lip.

Such a large body needs a lot of food, so the rhino grazes for about half of every day. It rests for about a third of the day, often on a breezy ridge or under a tree. Its close cropping creates grazing lawns of short, fresh regrowth that other herbivores then use. A calf tastes grass at about two months and still suckles for a year or more.

Behaviour and social life

White rhinos keep daytime hours, with feeding bouts early in the day and again towards evening. In hot summers, activity shifts towards dawn and dusk to avoid the heat. They wallow in mud in summer and roll in sand in winter, which cools the skin and drives off biting insects. They do not migrate with the seasons.

Cows and calves form groups of up to 14, though most groups are smaller. Young bulls may band together, sometimes with an adult cow, to avoid being chased by dominant males. Most adult bulls live alone, and a dominant bull holds a territory that no other dominant bull shares. He patrols the edges every day, spraying urine, scraping the ground and adding to dung piles called middens. A bull may keep 20 to 30 middens, and he can mark up to ten times an hour.

A bull's territory covers about 0.7 to 3 square kilometres, and cows range across 6 to 8 km2 that overlap freely. A losing bull leaves to find new ground, and subordinate bulls do not mark at all. Most serious fights are over a cow in season. The rhino is generally placid and walks away from trouble rather than charging. When it does run, it can reach 64 kilometres per hour in a burst and hold 48 to 50 km/h for some distance.

Communication and senses

White rhinos are short-sighted, but their hearing and sense of smell are excellent. The nasal passages are larger than the brain. Scent does most of the work of marking territory, through urine spray and shared dung heaps. A bull reads a cow's readiness to mate from the smell of her urine and dung.

The species has a range of calls. A panting call keeps group members in touch, and it varies between individuals, which probably helps them recognise one another. Courting bulls grunt, snort and make a hiccup-like throb, and cows whistle and roar back. An alarmed rhino squeals, and a threatened one bellows or growls. A bull's threat display is to wipe his horn on the ground, drop his head and flatten his ears.

Reproduction and life cycle

White rhinos breed in any month, with a peak from October to December in southern Africa. A cow first comes into season at about three and a half years but seldom breeds before five. Wikipedia gives six to seven years for a cow's first calf, and bulls do not breed until 10 to 12. Both sexes have several partners over a lifetime.

Courtship is long and rough. A bull follows a cow for days, calling as he comes, and blocks her path if she tries to leave his ground. The pair may stay together for 5 to 20 days. When she is ready, the cow curls her tail and stands stiff, and mating lasts about half an hour.

Pregnancy lasts about 16 months, or 530 to 550 days. The cow gives birth to one calf, which weighs about 40 to 65 kilograms and doubles its size by six months. The calf is unsteady for its first two or three days and then walks in front of its mother. It is weaned from about a year and stays with her for two to three years, until she drives it off before the next birth. A cow can breed into her forties, and wild rhinos live 40 to 50 years.

Predators and threats

An adult white rhino has no natural predator. One lion pride did kill a sick bull of 1,540 kilograms in Mala Mala, South Africa, but such cases are extremely rare. Lions take a calf now and then, and spotted hyenas have left rhinos with torn ears and tails. A cow guards her calf closely and charges anything that comes within about 30 to 40 metres. Other deaths come from drowning, getting stuck in mud, falls and bush fires.

Humans are the only serious threat, and poaching for the horn is the reason. Horn is sold into some traditional Asian medicines and, more and more, for carvings and as a status symbol. It has no proven medical effect, because it is only keratin. Criminal syndicates now equip poachers with night vision, silenced rifles, tranquillisers and even helicopters. The rhino's size, poor eyesight and calm nature make it an easy target.

Population and conservation

The southern white rhino is the great success story of rhino conservation. In 1885 only about 20 to 50 survived in the Umfolozi reserve. Strict protection, then moving surplus animals to new reserves, rebuilt the population. Numbers in one relocation programme grew from 337 to 1,876 between 1973 and 1993. By the end of 2023 about 17,464 lived in the wild, more than all other rhino subspecies together.

Poaching surged in the early 21st century, and in South Africa it nearly doubled in 2013 over the year before. Kruger National Park lost about 60% of its white rhinos between 2013 and 2021, down to about 3,529. Reserves now fence the land, post armed guards and cut horns off in advance to make the animals worthless to poachers. Zoos held more than 1,000 southern white rhinos in 2021, all of them this subspecies.

The northern white rhino fell from about 500 in 1968 to a handful in captivity. In 2009 four were flown from Dvur Kralove Zoo in the Czech Republic to Ol Pejeta in Kenya to encourage breeding. The last male, Sudan, was put down in March 2018 because of old age. Two females, Najin and Fatu, remain, under armed guard around the clock. Scientists have made embryos from their eggs and frozen sperm and plan to implant them in southern white surrogates.

Relationship with humans

Colonial hunters shot white rhinos almost to extinction in the 19th century. Today the animal earns money alive. Ecotourism built around rhinos supports parks such as Kruger, where ticket prices tripled in a decade. Owners may buy and sell southern white rhinos, and a small trophy hunt has been permitted since 1968. That trade gives private landowners a reason to breed and guard them.

CITES banned international trade in rhino products in 1977. South Africa, Zimbabwe and Namibia have argued against the ban, because they hold horn stocks seized from poachers. Cattle egrets and Cape starlings pick insects from the rhino's back. Oxpeckers were thought to help too, but studies found they open wounds and eat earwax as well as ticks. Rhinos in Kruger have rammed cars a few times, most likely startled by engine noise, but no one has died.

In culture and myth

The San painted rhinos on rock walls across southern Africa, alongside the other animals they hunted. In a Tswana tale, the rhino and the elephant compete to be the strongest animal. Zulu tradition casts the rhino as a guardian of springs and rivers. Pliny and other Roman authors wrote about the rhinoceros, and some scholars trace the unicorn legend to those accounts. Albrecht Durer's famous woodcut of 1515 shows an Indian rhino, not the African species.

Across parts of Asia people kept rhino charms against evil spirits, and horn was wrongly held to cure fever and reveal poison. That belief still drives the poaching that threatens the species. Modern spirit-animal blogs read the rhino as strength and steadiness, and a white one as purity, but these ideas appear to be recent inventions. Sudan, the last northern male, became a symbol of extinction in newspapers around the world after his death.