The Sumatran Rhinoceros is the world’s smallest, and most endangered, living rhinoceros species. For these herbivorous animals, foraging normally takes place during the night or in the early, cool morning hours; days are spent in mud wallows or shallow ponds to cool and protect their leathery skin. This solitary shy creature distinctively mark their territories with soil scrapes, feces and urine. The rapid recent decline in species population was fueled largely by widespread poaching for body parts, especially their horns which are believed by some cultures to have herbal or medicinal qualities. Fewer than 275 of the fascinating creatures now remain in the wild.
The creature’s squat, hefty body is reddish-brown in color and may be covered in long hair to a degree that it has also been known as the hairy rhinoceros. It is the only Asian rhinoceros that has two horns, with the posterior horn being much reduced and occasionally absent. Two deep skin folds encircle the body, one immediately behind the front legs, and the other in front of the rear legs (these deep folds are a key distinguishing characteristic of the species). They are between two to three meters in length from head to tail with a height of 1.0 to 1.5 meters. The red-brown skin is an average of 16 millimeters thick and has a leathery texture that causes considerable wrinkling.
The Sumatran Rhino once ranged from the Himalayan foothills to southern China and across the present day countries of Thailand, Vietnam, Myanmar, Cambodia, Indonesia, and Peninsular Malaysia as well as the island of Borneo. Although earlier species populations once existed in other locales, the rhino is now regionally extinct in Bangladesh, Cambodia, India, Thailand, Vietnam, and other regional states.
There are estimated to be fewer than 275 Sumatran Rhinoceros left in the wild, with an additional twenty or so in captivity (mostly in Indonesia and Malaysia). Through the late-20th century, population size was estimated to be falling at 50% per decade, driven largely by poaching and secondarily by habitat destruction and habitat fragmentation; this rapid decline has slowed over the past decade due to enhanced protection. The species is currently found only in Indonesia and Malaysia, although some individuals may still exist in Myanmar. It is estimated that around 50 individuals survive in the Eastern Malaysian state of Sabah, mostly in the Danum Valley and Tabin National Park. Populations in Peninsular Malaysia may still exist, but in very small numbers.
The Sumatran Rhino lives in various forest environments, including tropical rainorests and mountain moss forests, it is occasionally seen along forest margins or in secondary forests and is found to be somewhat resilient to moderate timber change. They live mostly in hilly regions with plentiful water sources; the species tends to move uphill during rainy seasons to avoid lowland flooding. The shy nature of the creatures have caused them to move to higher altitudes in response to human encroachment.
The shy Sumatran Rhinoceros is dependent on salt licks to obtain minerals. The presence of salt licks in an environment is an absolute requirement for this species survival. Feeding normally occurs before dawn and sunset; moreover, the creatures are prodigious walkers and move mostly at night.
The animals are entirely herbivorous, preferring young saplings, leaves, and plants in secondary growth. Moving in a zig-zag path, the animal samples a food item before taking a large bite. Young saplings are the dominant food source, with the trees first bitten off, trampled upon, and, finally, devoured. Adults are estimated to consumer an average of fifty kilograms of food per day. Wild mangoes, bamboos, and figs appear to be the animal’s favorite foods.
Males are generally solitary, while females are generally seen with offspring and may overlap territory with males. The range size for females is estimated to be no more than 500 to 1000 hectares, with males ranging much further. The rhino’s most well-known behavior regards its marking habits, with trails marked by feces, urine and soil scraps. Territorial marking also occurs by the twisting and breaking of saplings along the territory borders; these rhinos will change direction if they come upon broken trees. When threatened the response is to spray urine and defecate multiple times; in rare instance the rhinos can become aggressive and hostile.
During the day the animal is most commonly found in wallows near streams or shallow ponds, the water serving to cool the animal and the mud preventing the leathery skin from drying and cracking.
Males remain generally solitary, except for mating. Sexual maturity is estimated to occur at six to seven years for females and ten years for males, with gestation lasting about 16 months. The species is believed to live to an age of 35-40 years. Most births take place between October and May, which coincides with the rainy season; immediately after birth the baby is hidden in dense vegetation while the mothers grazes; the calf is nearly one meter long and 25 kilograms in body mass at birth. Weaning takes place around 16 months.
The Sumatran Rhinoceros is listed as Critically Endangered on the IUCN Red List. The species has been listed on the CITES Appendix I since 1975, and is legally protected in all states in which it is presently found. An international program is currently underway in Indonesia and Malaysia to protect the species, and Rhino Protection Units have greatly contributed to a reduction in poaching in Sumatra. The primary threat to the Sumatran Rhinoceros is poaching; therefore, extensive anti-poaching campaigns are critical if the species is to survive. Both Indonesia and Malaysia are also working to develop breeding centers; recent successes in captive breeding of the species have offered some hope. In 2001, the Cincinnati Zoo had successful captive births, one of these offspring was subsequently sent to a breeding center in Sumatra.
In addition to poaching impacts, driven largely by the demand for rhino horns (for the purported medicinal qualities), decimated populations sizes have led to low breeding activity and high risk of inbreeding depression.
References and Further Reading
- IUCN. 2010. IUCN Red List
- Sumatran rhinoceros. 2011. Encyclopedia of Life