Rhinoceroses are one of the largest remaining megafauna, with all of the species reaching one ton or more in weight. They are herbivores and generally feed on leafy material although they have a hindgut that allows them to subsist on more fibrous plant matter, if necessary. Two of the rhinoceros species are native to Africa and three to southern Asia. Rhinoceroses are and have been killed in the past for their valuable horn, putting at risk their survival. The Javan, Sumatran and Black Rhinoceros are listed as “critically endangered” while the Indian Rhinoceros is considered as “vulnerable” and the White rhinoceros as “threatened”.
Rhinoceros are herbivorous mammals that belong to the family Rhinocerotidae and to the order of Perrisodactyla. This order is made up of browsing and grazing mammals such as horses, tapirs and rhinoceros. This group of animals is characterized by the curious fact that their hooves have an odd number of toes. The middle toe on each hoof is usually larger than its neighbors. The Latin word “Perissodactyla” may be divided out into two parts; “perissos” meaning “abundant or excessive” and “daktulos” meaning “toes”.
The living perissodactyls are a diverse group, with no generalized appearance, but are on the whole rather large in size ranging from the 180kg Mountain tapir to the 2,273kg White rhinoceros. The order in itself may be separated into two sub-orders, the first known as “Hippomorpha” that encompasses one-toed fast runners with long legs such as horses, donkeys and zebras. Members of the second sub-order, “Ceratomorpha”, have several functional toes and are on the whole heavier and move more slowly than the Hippomorpha. This sub-order is made-up of two extant families, which are the tapirs and rhinoceros.
Odd-toed ungulates have rather simple stomachs. They are hindgut fermenters, digesting plant cellulose in a pouch-like extension of the large intestine called caecum (“cave”).
There are four extant genera and five extant species of rhinoceros
- Ceratotherium simum or White rhinoceros, that has two horns.
- Diceros bicornis or Black rhinoceros, that has two horns.
- Dicerorhinus sumatrensis ou Sumatran rhinoceros, that has two horns.
- Rhinoceros sondaicus ou Javan rhinoceros, that has one horn.
- Rhinoceros unicornis ou Indian rhinoceros, that has one horn.
Asian rhinoceroses are much related to each other. It is believed that they separated from African Rhinos about 26 million years ago.
Asia: The Sumatran rhino (Dicerorhinus sumatrensis) is considerably threatened and is the only survivor of the oldest group, the Dicerorhinini..
The genus Rhinoceros, consisting of two species, the Indian rhinoceros (Rhinoceros unicornis) and Javan rhinoceros (Rhinoceros sondaicus), is also endangered.
These two Asian genera separated from each other about 10 million years.
Africa: The two African genera, the White rhinoceros (Ceratotherium simum) and Black rhinoceros (Diceros bicornis), diverged about 5 million years. They differ from each other in their feeding behavior. While the white rhinoceros grazes on grass, the black rhino feeds on leaves. Black rhinos are able to draw branch tips into their mouths thanks to their forward pointing upper lip.
Young white rhinoceroses walk in front of their mother, while young black rhinoceroses do so behind them. They say, in Africa, that white rhinoceroses are like white women who push their children in a stroller in front of them while black women are like black rhinos in than they carry their babies on the back.
In reality both white and black rhinoceroses are gray. The name actually comes from an old mistranslation of the Dutch “weit”, which means “wide” and refers to the large grass- grazing mouth of rhinos. When the British colonized southern Africa, they translated the “weit” to “white”.
Rhinos can measure up 5m long and 1.80m high and weigh up to as much as two tons. They are the largest living land mammals after the elephant.
The main visible characteristic of rhinos is the fact that their horns are located on their nose. Depending on the species they are either one or two-horned. Curiously enough, fossil rhino species did not have a horn.
We are able to distinguish the rhinoceros horn by the presence of hair covering it and its filled interior, which differentiates it from the hollow ivory horns. Rhinoceros horns are generally of a dark color, which may turn brown in some individuals.
Rhinos have a large body and thick short legs. Each foot has three toes each ending in a little toe. Their fingerprint resembles that of a cloverleaf. Their skin is thick and either gray or brown colored. In Asian species, the skin at the bottom of the neck and legs is very wrinkled and feels like a shield.
The rhinoceroses´ eyesight is generally weak. This disadvantage is however offset by the fact that they have an acute sense of smell and excellent hearing.
Rhinos are normally solitary, however in the savannah they can sometimes be seen in small herds.
They are both polygamous and polyandrous. Males and females have several partners.
If a female is in heat, males may confront each other and fight. The winner will then carry out a curious courtship display: it will mark its territory with urine and feces and make its tail act like a fan. In addition, the two partners may then chase and fight each other before mating.
Baby rhinos are born after a gestation period of 15 to 18 months. They will then spend up to two and a half years with their mother, following her shadow wherever she might go. Females are especially aggressive during this period, protecting their young even from members of their own species, which she will chase way.
During the day rhinos sleep. They are especially active at dusk and during the night.
Rhinos are scared of humans and try to avoid them whenever possible. They only attack when they feel threatened. Very rarely do these attacks cause serious injuries.
Rhinoceroses can run very fast and can reach speeds of about 45 km / h.
Young rhinos can be the preys of big cats, while adult rhinoceroses have no enemies except for humans.
All rhinoceros species are presently endangered and have therefore become the focus of local programs and reintroduction projects.
Although rhinos are known to be large and resistant animals, they can be easily poached, especially during their daily visits to the different water points.
Mating behavior in rhinoceroses can last over half an hour. This is why many have considered rhinoceros horns as aphrodisiacs or to contain therapeutic effects. Consequently, many rhinos have been killed because of this belief. For example between 1980 and 1984, half of the black rhino population was sacrificed.
Only 3% of poachers are arrested. This highlights the need to undertake urgent effective measures to curb the rhino poaching activity.