Sumatran rhinoceros  (Dicerorhinus sumatrensis)

Classified as Critically Endangered (CR) on the IUCN Red List (1), and listed on Appendix I of CITES (3).

This prehistoric-looking, armour-plated giant is the most endangered of all five rhinoceros species (4). Despite being the smallest of all the living rhinos (5), the Sumatran rhinoceros is still an immense animal, with leathery, dark grey-brown skin, measuring up to 16 millimetres thick (2). This thick skin has a covering of reddish-brown hair, which is long and dense on calves and young adults, but becomes sparser and blacker as the rhino ages (2). The other rhinoceros species do not have such copious hairs, and thus the Sumatran rhinoceros is often called the ‘hairy rhino’ (6). A large fold of skin extends across the back, behind the shoulder (7), and thick, wrinkles of skin encircle the eye (2). The Sumatran rhinoceros is the only rhino in Asia which bears two horns (4); in fact, the genus name Dicerorhinus comes from the Latin word for two (di), horn (ceros) and nose (rhinos) (6). However, the second horn can be so short, rarely measuring more than ten centimetres, that often it appears to be single-horned with just the first horn, measuring up to 30 centimetres, showing clearly (7).

The Sumatran rhinoceros once had an enormous range; from the Himalayan foothills, east to southern China, Myanmar, Thailand, Cambodia, Lao PDR, Vietnam and Peninsular Malaysia, as well as the islands of Sumatra and Borneo in Indonesia (1). Today, however, this species is only found in small pockets of its former range (4).

There are three recognised subspecies of the Sumatran rhinoceros: Dicerorhinus sumatrensis lasiotis, Dicerorhinus sumatrensis sumatrensis, and Dicerorhinus sumatrensis harrissoni (1). Today, it is thought that D. s. lasiotis is probably extinct, although populations may survive in northern Myanmar (1). D. s. harrissoni formerly occurred throughout the island of Borneo, but now is mainly found in Sabah (Malaysia), although a few individuals may still survive in Sarawak (Malaysia) and Kalimantan (Indonesia) (1). D. s. sumatrensis currently occurs only in parts of Sumatra and Peninsular Malaysia (1).

This species can live in a wide range of habitats, from low, swampy areas, to forest high in the mountains (2). However, it is mainly found in primary forest in hilly areas, close to water, and also depends on the presence of a salt lick (1) (2).

During the heat of the day, the Sumatran rhinoceros spends most of its day wallowing in pools of rainwater or other muddy pits, which have often been dug, or deepened, by the rhino itself (2). The rhino will often have cleared the area surrounding the wallow of vegetation, providing space in which to rest (2). This wallowing behaviour is thought to either cool the animal, or provide protection against insects (2). The Sumatran rhinoceros becomes more active in the cool of the night, and it feeds before dawn and after sunset, searching out fruits, bamboo, leaves, twigs and bark to eat. Sometimes is may also eat crops (2). For such a huge animal, it can tackle steep slopes with surprising agility and is even capable of swimming (2).

The Sumatran rhinoceros is an elusive animal, possibly due to its rarity, and its presence is most often detected by the tracks it leaves behind, rather than being sighted (7); as a consequence, details of its life history are scarce (1). The Sumatran rhinoceros is a largely solitary animal, although females are often found accompanied by their offspring. Each rhino has a permanent home-range, that includes a salt lick, and males will visit a female’s territory for mating (2). It is thought that the gestation period is probably 15 to 16 months (1), with most births taking place during the period of heaviest rainfall, from October to May (2). The calf will typically stay with its mother until 16 to 17 months of age. The Sumatran rhinoceros is thought to begin to breed at seven or eight years old, with a gap of at least three to four years between each birth (2).

The Sumatran rhinoceros was driven from large regions of its former range as a result of the habitat destruction and hunting (2). Today, the small, isolated populations that remain continue to be primarily threatened by poaching (1), as sadly, the Sumatran rhinoceros is one of the unfortunate animals that is highly valued in traditional Asian medicines. Many parts of its body are believed to have aphrodisiac and medicinal properties, but its distinctive horn is most in demand, and ends up either a powdered ingredient in medicines, or artistically carved (2) (5). The populations of the Sumatran rhinoceros are now so small that breeding has become a rare activity and successful births are infrequent; as a result, inbreeding depression has become a real and serious risk (1). The small numbers mean that even the death of a single animal brings the species a step closer to extinction (5).

Despite being listed on Appendix I of the Convention on International Trade in Endangered Species (CITES) since 1975 (which prohibits trade in the species) (3), and being legally protected in all the countries in which it occurs (1), the Sumatran rhinoceros is still in a precarious situation. International efforts to prevent poaching of this rare species are underway (1), and their success is imperative if this species is to survive.

Efforts to conserve the Sumatran rhinoceros in the past have not proved successful. An expensive programme undertaken in the 1980s and 1990s to capture wild rhinos and relocate them to breeding centres across the world, was deemed by many to be disastrous (5). Many of the captured rhinos died (5), and only more recently (in 2001 and 2004) have successful births arisen from these captive breeding programmes (1) (5). Today, many scientists believe that capturing more rhinos for the breeding programme would just be sending this species to its death (5), and therefore anti-poaching efforts are currently the primary conservation focus (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

Help efforts to conserve the Sumatran rhinoceros by supporting:

• The International Rhino Foundation:
  www.rhinos-irf.org

To find out more about Sumatran rhinoceros conservation projects, see:

• Mohamed bin Zayed Species Conservation Fund
  http://www.speciesconservation.org/projects/Sumatran-rhino/694
• EDGE of Existence:
  http://www.edgeofexistence.org/mammals/species_info.php?id=6