Sumatran Rhinoceros

Quick Take

• The Sumatran rhino is technically the closest living relative to an iconic Ice Age giant, and the connection is stranger than you would expect. See the woolly rhino connection →
• Its population has collapsed far faster than most conservationists predicted, a decline so severe that the numbers today are alarming enough to reframe what 'endangered' really means. Explore the population collapse →
• One daily habit shared by all Sumatran rhinos turns out to be critical for their survival, as captive rhinos learned the hard way. Discover the mud-wallowing habit →
• The captive breeding program launched to save the species had a success rate that should have worked, but it largely failed for a reason few anticipated. Review the captive breeding failures →

The Sumatran rhinoceros is the last “hairy” rhinoceros left on Earth. The smallest species of rhinoceros, the Sumatran rhino may very well be the most endangered large mammal in the world today.

Incredible Sumatran Rhino Facts

• The Sumatran rhino is believed to be the closest living relative to Woolly rhinos that were covered in fur and went extinct approximately 14,000 years ago.
• The Sumatran rhino may be the most endangered large mammal in the world, with potentially as few as 34 to 47 individuals remaining.
• Among rhinos, the Sumatran is by far the smallest species surviving today. On average, Sumatran rhinos weigh just ¼ as much as white rhinos.

Classification and Scientific Name

The scientific name of the Sumatran rhinoceros is Dicerorhinus sumatrensis. The genus Dicerorhinus is Greek for “two-horn-nose”, although the Sumatran rhinoceros is the last living species of this genus.

Sumatrensis means “of Sumatra” as the species was first located on the island (though its original range stretched far beyond Sumatra).

Appearance

The Sumatran rhinoceros is the smallest of the five rhinoceros species, with a body length of less than 250cm (about 8.2 feet). At the shoulders, a Sumatran rhino typically stands between 112 and 150 cm (approximately 3.7 to 4.9 feet) in height.

The smallest of all rhino species, Sumatran rhinos weigh between 500 and 960 kg (1,100 lbs to 1,800 lbs). It is unique among rhino species in that it has reddish hair that can cover a large portion of its body.

The Sumatran rhinoceros has relatively poor eyesight, relying more on hearing and smell to detect what is going on around it. The ears of the Sumatran rhinoceros possess a relatively wide rotational range to detect sounds, and it also has an excellent sense of smell to readily alert it to the presence of predators.

Horn

The Sumatran rhinoceros uses its horns for defense, intimidation, digging up roots, and breaking branches during feeding. Its horns are made from keratin and are therefore very strong. The horns are used in traditional medicine, and many Sumatran rhinos have been illegally hunted for them.

Unlike the other Asian rhinoceros species, the Sumatran rhinoceros has two horns like the white and black rhinos found on the African continent. However, its horns are generally much smaller than those of those species.

While the largest ever recorded Sumatran rhino horn measured 32 inches (81 cm), their horns generally measure less than 10 inches (25 cm) in length. The front horn of Sumatran rhinos is longer, while the back horn is often less than an inch (2.5 cm) in length.

Behavior

The Sumatran rhinoceros is a solitary animal and only comes together with other Sumatran rhinos to mate.

Sumatran rhinos spend a long portion of their day in mud wallows that they utilize their feet and horns to deepen. Layers of mud not only help protect the Sumatran rhino from biting insects, but also regulate skin temperature. Sumatran rhinos kept in captivity that lacked sufficient daily wallowing suffered from chronic skin problems as a result.

The Sumatran rhino is also notably diligent about marking its territory and trails through feces, urine, and even scraping trees. the large territory of each Sumatran rhino (up to 19.3 square miles for males; up to 50 square miles for females) helps explain why sightings of these animals are so rare.

Habitat

The Sumatran rhinoceros primarily inhabits dense lowland rainforests, tall grass and reed beds abundant in rivers, large floodplains, wet areas with many mud wallows, swamps, and cloud forests. The range of the Sumatran rhinoceros once stretched from India, through south-east Asia and down to Sumatra, but today, the Sumatran rhinoceros is only found on the islands of Sumatra and Borneo.

Diet

The Sumatran rhinoceros is a herbivorous animal, meaning that it sustains itself on a purely plant-based diet. Sumatran rhinos browse the densely vegetated subtropical forest for leaves, flowers, buds, fruits, berries, and roots, which they dig up from the ground using their horns.

Population

Today, the Sumatran rhino may be the most endangered large mammal on Earth. In 1986, the IUCN estimated there were between 425 and 800 Sumatran rhinos left. By 2009, the International Rhino Foundation estimated its population had shrunk to as few as 250 individuals.

Today, the International Rhino Foundation estimates fewer than 80 Sumatran rhinos are left, and that number could be as low as 30 individuals that live across four fragmented national parks.

While the Sumatran rhino population today continues decreasing due to loss of habitat and poaching, the species has long been on the brink of extinction. A study from Current Biology estimated that only 700 individuals were left after major climate changes about 9,000 years ago and have struggled to rebound since.

Predators

Due to its large size, the Sumatran rhinoceros’s only real predators in the wild are large wild cats such as tigers that will prey on the Sumatran rhino calves and weak individuals. With the Sumatran Tiger numbering no more than 500 individuals across the island and confined to small, isolated pockets, its encounters with Sumatran rhinos today are likely rare.

Humans are the biggest threat to the Sumatran rhinoceros, as it has been hunted to the brink of extinction for its horns.

Reproduction and Life Cycles

The female Sumatran rhinoceros gives birth to a single calf after a gestation period that is over a year long (approximately 15 to 16 months). The Sumatran rhinoceros calf remains with its mother until it is at least 2 years old and big enough to become independent.

The longest surviving Sumatran rhino in captivity is estimated to be about 35 years of age, as of 2020. It is believed that in the wild, Sumatran rhinos can live to about 45 years of age.

Sumatran Rhinos in Zoos

In 1984, a program to capture and breed Sumatran rhinos was launched. Unfortunately, of the 46 captured for breeding purposes, only five are still alive today, and only four calves were born and survive today. The last Sumatran rhino in the Western Hemisphere (8-year-old Harapan) was moved back to Indonesia from the Cincinnati Zoo in 2015.