Rhinoceros (genus)

Indian rhinoceros ( Rhinoceros unicornis )

• Indian rhinoceros ( Rhinoceros unicornis )
• Javan rhino ( Rhinoceros sondaicus )

Rhinoceros is a genus of the family of rhinos, which in turn belongs to the odd-toed ungulates. The genus includes the one-horned rhinos in Asia and represents the Rhinoceros and the Javan rhino two are still alive today, but endangered species.

Features

The genus Rhinoceros comprises relatively large rhino representatives that achieve a head-body length of 300-380 cm and a weight of each about 2 t, the rhinoceros represents the larger of the two extant species dar. The body is built tough and has short and strong limbs. The head, which reaches a length of 50 to 65 cm, is relatively large, but compared to the other extant rhinos due to cuts in the face area smaller than this. Most striking here is the clear wedge-shaped outline of the skull with a narrow but well rounded nose and a short and fairly to slightly obtuse designed occiput, which has a strong bead. Due to the shape of the occipital bone Rhinoceros has a relatively high head carriage, which surpasses all other rhino species today. In addition, the front line between nose and occiput has a significant saddling. Of the other extant genera Rhinoceros Rhinoceros distinguishes itself further by very clearly pronounced skin folds, which are located in the neck and on the upper ends of the limbs, or lead to the body. Other features are distinctive skin defects, such as wart-like knobs or pentagonal or hexagonal segment formations, which also does not occur with other rhino lines. A significant difference is the presence of only a single horn, which sits on the nose ( Nasalhorn ), apart from the two-horned Rhinoceros what rhinos in Africa and Asia. Composed of keratin horn is also normally the shortest of the rhino species and is up to 60 cm long. It is cone-shaped and rises steeply, more rarely it is bent at the top to the back. In the teeth structure Rhinoceros has the most comprehensive front teeth with a maximum of two pairs of incisors, the lower outer incisors are elongated dagger -like and project forward, the upper have a platy shape and square to the jaws. The other extant rhinoceros species have, however, a maximum of one pair or no incisors. The premolars and molars are similar to individual tooth characteristics to those of the other rhinos today. The premolars are clearly molarisiert so that they are largely the same, the posterior teeth.

Distribution and habitat

The distribution of Rhinoceros limited today to the northern areas of the Indian subcontinent and the western tip of Java island in the Malay Archipelago. The preferred habitats are wooded open landscapes, riparian forests, and dense tropical rain forest. In historical times, the spread was much wider and the genus also occurred in Indochina. A common area of use of the two extant species came here before in the eastern part of India and in Bangladesh. However, the largest expansion reached the genus in the Pleistocene, where they South and Southeast Asia as well as the populated southern areas of East Asia, with different styles and partially overlapping habitats large parts.

Way of life

Like all rhinos are the representatives of Rhinoceros crepuscular and nocturnal. During the day they rest or wallow and bathe. Furthermore, they are territorial and solitary, group formations are primarily between mother and calf before. Individual territories are marked with urine and feces. The intraspecific communication therefore usually takes place through the sense of smell, but there are also numerous and various vocalizations, whose intensity varies according Nashornart. During the rut it comes to fighting among the bulls, which are rarely carried out with the horns but with the sharp mandibular incisors. The gestation period usually lasts 16 to 18 months. There is always only one calf born and nursed until the age of about a year. This then is still a maximum of two years with the mother until it is sold by her before the birth of the next calf. Life expectancy is around 40 years.

Nutrition

Members of the genus Rhinoceros are herbivores and largely specializes in soft plant food like leaves, twigs or bark, which they graze due to the high position of the head of medium-high shrubs or small trees. The food is thereby pulled off with the help of the pointed upper lip. Only the rhinoceros differs especially in times of drought in part of tougher grass food. Being a good swimmer is able to take this additionally below the water surface food, which has been known by any other Nashornart. Furthermore, salt licks are very important.

System

Rhinoceros is part of the subtribes of Rhinocerotina within the subfamily Rhinocerotinae. The Schwesterklade form the Dicerorhinina with the Sumatran rhino. The two lines separated after investigations on the mitochondrial DNA in the late Oligocene 26 million years. The genus Rhinoceros belong to the species living today rhinoceros (R. unicornis ) and Javan rhino (R. sondaicus ). The splitting into two species took place according to the same studies in the late Miocene epoch, about 12 million years ago.

Fossil are a dozen or more species have been described, most of which are today but asked for Rhinoceros. The few remaining fossil species are also subject in the professional world also a strong controversy. The main problem is the status of R. philippinensis, which is known for several jaw fragments of the island of Luzon and was first described by Ralph Koenigswald 1956. Many paleontologists keep the finds, however, due to their isolated geographical position outside the islands of Sundaschelfs very doubtful. Very different is also the status of R. sivalensis judges which is based on a description of Hugh Falconer and Proby Thomas Cautley from 1847 and was originally placed in the ancestral line of the rhinoceros. Today, some researchers want to assign the extant Rhinoceros representatives of this type more, depending on the view it belongs to the rhinoceros or the Javan rhino. Also controversial is R. sinensis, which was described in 1870 by Richard Owen basis of some dental remains from southern China and is the most common fossil Nashornart the Pleistocene in this region today. The special Hochkronigkeit the molars may be close to a specialized grazers, however, there is still no complete skull. In addition, the taxon has been repeatedly used as a " trash can " for all discovered Pleistocene rhinoceros finds in southern China, so that the independence of the species is not understood.

Phylogeny

The genus Rhinoceros fossil is first detected in the late Pliocene 3.3 million years ago in the Siwaliks of South Asia. The Basalform is assigned sivalensis R.. A possible predecessor shape is the gigantic Punjabitherium, also lived in the Siwaliks in the Pliocene. From Rhinoceros is Punjabitherium differs by less short skull and the presence of a second horn on the forehead. Similarities provide, inter alia, is the merger of the bone plug below the ear canal and the significantly saddled upper skull, which are all Rhinocerotina own. But since Punjabitherium still had a longer snout and above all, much hochkronige teeth, it's probably just a sister taxon with common ancestors. This is perhaps the most occurring since the Middle Miocene Gaindatherium, also from the Siwaliks, which is at the basis of the Rhinocerotina.

R. sivalensis lived largely in the late Pliocene. Among the earliest evidence of the Javan Rhino include finds from Sangiran in Java and from a terrace of the Irrawaddy in Burma, both belonging to the Frühpleistozän. Also in late Frühpleistozän or not until the early Middle Pleistocene R. sinensis is detected in the southern East Asia, so among other things, on the early human reference Yuanmou in Yunnan Rrovinz first time. From the Middle Pleistocene the first clear evidence of the rhinoceros both in India on the Narmada River and on Java is then recorded. Later in the Central and Jungpleistozäns Rhinoceros occurs in the entire space of South and Southeast Asia and the southern East Asia and colonized different islands of Sundaschelfs. At this time, divide the different types still common habitats in Indochina. At the beginning of the Holocene, only tank and Javan rhinoceros are then detectable. Here, they were pushed back by increased hunting especially in historical time more and more on today's remaining refuges.

Threat and protection

The two extant species of the genus Rhinoceros are threatened with extinction. The IUCN leads the rhinoceros as endangered, while the Javan rhino is considered critically endangered. Currently, both rhino species live freely only in several national parks. Inventory counts and estimates the end of 2010 resulted in more than 2,800 Indian rhinos in India and Nepal, and only around 40 Javan Rhinos in the west of the island of Java as a last refuge. A small population of Java rhinos in Cat Tien National Park in southern Vietnam was declared in October 2011 by WWF experts lapsed. Thus, the Javan rhinoceros is one of the rarest large mammal species in the world. Special breeding and repopulation projects are intended to stabilize the stock of both species and lift.