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All About Rhinos

Updated: Aug 5, 2018

by Science Writer, Graeme Gissing


Evolutionary History of Rhinos


For currently existing rhino species, these large herbivorous mammals are correctly envisioned as roaming either the grasslands of sub-Saharan Africa or pushing their way through the tropical forests of Asia. However, today’s rhinos represent only a small fraction of the historical diversity associated with the Family Rhinocerotidae. Indeed, modern rhinos are part of an ancient mammalian lineage which originated in the Eocene epoch some 40 million years ago. Not only ancient, this group was also highly successful, consisting of 142 species across 41 genera.


One of these prehistoric rhinos, Paraceratherium, remains the largest land mammal to have ever roamed the Earth, and would tower over an African elephant. They were also widely distributed across Europe, North America, Africa, and much of Asia. The last of these prehistoric rhinos, the cold-adapted woolly rhino, roamed the Tibetan plateau, Siberia, and throughout northern Asia until as recently as 10,000 years ago. The remaining extant (living) rhinos now consist of five species across four genera; the white and black rhinos of Africa, and the greater one-horned, Javan, and Sumatran rhinos of Asia.



Rhino Conservation Status


From a conservation perspective, three of the five rhino species (the black, Javan, and Sumatran) are critically endangered and in imminent risk of extinction. While the greater one-horned and white rhinos are not considered critically endangered by the International Union for Conservation of Nature (IUCN), all five species are covered by Appendix I under the Convention on International Trade in Endangered Species (CITES) and considered to be species threatened with extinction.


In light of the current poaching crisis in Africa, black and white rhinos have, quite rightly, become regularly featured in news coverage and documentaries illuminating their plight. However, the three critically endangered species seem to gain less traction and are woefully underrepresented in both the conservation and public consciousness. Therefore, to provide a complete picture of these amazing animals and raise awareness for the lesser-known species, each is covered here in a brief species profile.

Javan Rhinoceros (Rhinoceros sondaicus)


A shy and secretive species, the Javan rhino is also one of the most endangered large mammals on the planet. As recently as 2006, it was believed that two distinct populations of Javan rhinos existed, with the largest group of 60 individuals found on the island of Java, Indonesia. Another, much smaller, population of 6 individuals was known to occur in the Cat Tien National Park in Viet Nam. Unfortunately, the last Javan rhino from the smaller population was killed for its horn in 2009 and this species is now extinct in Vietnam. Intimately associated with dense forest and water, this one-horned species is now confined solely to the very western tip of Java in its last remaining habitat refuge, the Ujung Kulon National Park.


Sumatran Rhinoceros - Photo Credit: Charles W. Hardin

Sumatran Rhinoceros (Rhinoceros sondaicus)


The smallest rhino species, the Sumatran rhino is the only species to exhibit a somewhat woolly appearance due to the vestiges of an ancestral hairy coat, an indication of its northern past. Once widely distributed throughout South-east Asia and as far north as the Himalayan foothills, the Sumatran rhino now exists in small isolated populations in Indonesia and Malaysia. Believed to be confined to the Malay Peninsula, Sumatra, and Borneo, total population estimates range between 100-200 individuals. However, recent evidence suggests that this species may now be extinct on the Malay Peninsula and Borneo, leaving Sumatra as the last home for the small remaining population of less than 100 individuals.

Greater One-Horned Rhinoceros (Rhinoceros unicornis)


One of only two rhinos bearing a single horn, this species is characterized by its armour-like appearance due to deep folds in the skin and dermal protuberances resembling rivets. Like other rhinos, this species was once widely distributed but now exists in two main strongholds, India and Nepal.

As the greater one-horned rhino is a habitat specialist associated with floodplains and riverine forests, increasing agricultural conversion has dramatically reduced their available habitat. In conjunction with poaching, these changes represent a serious threat to this species’ long-term survival. With an estimated global population of only 3,300 remaining, one-horned rhinos are now largely restricted to protected areas such as the Kaziranga National Park in India (ca. 2,300 individuals or 70% of the total population) and the Chitwan National Park in Nepal (ca. 600 individuals).



White Rhinoceros - Photo Credit: Glen Carrie

Southern White Rhinoceros (Ceratotherium simum)


This is the largest rhino species with males reaching up to 2300 kg, the most social of the rhinos, and the most abundant. As grazers of the sub-Saharan grasslands and plains, they can be distinguished from black rhinos by their wide and square upper lip which is ideally suited to cropping grass. Although still under the constant threat of poaching and habitat loss, few people are aware that the Southern white rhinoceros is a shining example of a conservation success story. Driven by heavy hunting, this species was truly on the brink of extinction with fewer than 200 individuals remaining by the start of the 20th century. Today, their population now exceeds 20,000 individuals.


Black Rhinoceros - Photo Credit: Andy Martin

Black Rhinoceros (Diceros bicornis)


Also known as the hook-lipped rhinoceros, this species is associated with thorn-bush habitat and uses its hook-like prehensile lip to pluck vegetation from shrubs and bushes. Unlike the success story for white rhinos, this critically endangered species declined dramatically throughout the 20th century. From an estimated 100,000 individuals in the 1960s, relentless hunting and loss of habitat reduced the population by a staggering 96% by 1995 and in just the two decades, from 1970-1990, twelve African countries lost their entire black rhino populations.

Whereas the white rhino is known to be placid and social, the black is equally notorious for its aggressive and solitary nature. Males establish territories that they vigorously defend and mark by concentrating their defecation in what are called middens. To ensure that the territory is clearly marked, they also frequently use sharp kicking and scraping motions to scatter their feces.

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As a group, there is little doubt that rhinos are among the most iconic flagship wildlife species for conservation. However, each individual species has characteristics that make them unique in both character and conservation needs. As living representatives of a mammalian group that has existed for 40 million years, it is not only our responsibility, but our duty, to ensure that these incredible animals are preserved for future generations.


Individual IUCN Red List Rhino Species Profiles

Javan Rhinoceros Sumatran Rhinoceros Greater One-Horned Rhinoceros Southern White Rhinoceros Black Rhinoceros

References

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Cerdeño, E., 1998. Diversity and evolutionary trends of the Family Rhinocerotidae (Perissodactyla). Palaeogeography, Palaeoclimatology, Palaeoecology, 141(1-2), pp.13-34.

Emslie, R.H., Milliken, T., Talukdar, B., Ellis, S., Adcock, K. and Knight, M.H., 2016. African and Asian Rhinoceroses – Status, Conservation and Trade: a report from the IUCN Species Survival Commission (Iucn Ssc) African and Asian Rhino Specialist Groups and Traffic to the Cites Secretariat Pursuant to Resolution Conf. 9.14 (Rev. Cop15). In Geneva: Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Secretariat (Vol. 1).

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Subedi, N., Lamichhane, B.R., Amin, R., Jnawali, S.R. and Jhala, Y.V., 2017. Demography and viability of the largest population of greater one-horned rhinoceros in Nepal. Global Ecology and Conservation, 12, pp.241-252.

Subedi, N., Jnawali, S.R., Dhakal, M., Pradhan, N.M., Lamichhane, B.R., Malla, S., Amin, R. and Jhala, Y.V., 2013. Population status, structure and distribution of the greater one-horned rhinoceros Rhinoceros unicornis in Nepal. Oryx, 47(3), pp.352-360.

Talukdar, B.K., 2013. Asian rhino specialist group report. Pachyderm 53, 25-27.