SUMATRAN RHINOCEROS: CHARACTERISTICS, BEHAVIOR, MATING

SUMATRAN RHINOS

Sumatran rhinos

Sumatran rhinoceroses (Dicerorhinus sumatrensis) are the smallest and hairiest of the five rhino species. It is believed they may be related to the extinct woolly rhinoceros, which was around for around for 20 million years. Sumatran rhinos are also the most endangered rhino of one of the world's rarest animals. According to Save the Rhino, as of 2022, there were only 35 to 50 Sumatran rhinoceroses in the wild and a few in zoos and sanctuaries. Their numbers have declined quickly. In the late 2000s it was estimated there were 200 Sumatran rhinoceroses.

Sumatran rhinos usually live in dense tropical forest, both lowland and highland, on Sumatra and are generally animals, according to the International Rhino Foundation (IRF). Females give birth to one calf every three to four years after gestation period as long as 16 months. Their average lifespan in the wild is estimated be 32 years. Their average lifespan in captivity is 32.7 years. Habitat loss has driven them to occupy smaller areas of the Indonesian jungle and conservationists are concerned about the survival of the species. “As this reclusive species seems to disappear further into dense jungles, direct sightings have become rare and indirect signs like footprints are getting harder to find,” the IRF said. [Source: Heather Chen, CNN, October 3, 2023]

Little is known about the Sumatran rhino. It is rarely seen in the wild and likes dense forests. One scientist who spent three years studying them in northern Sumatra’s Gunung Leuser National Park — one of the areas they are said to be most plentiful — only saw one once when it charged through his camp unexpectedly. Most of what is known about them has been deduced from specimens kept in captivity.

Websites and Resources on Animals: International Rhino Foundation rhinos.org ; Save the Rhino International savetherhino.org; Animal Diversity Web animaldiversity.org ; BBC Earth bbcearth.com; A-Z-Animals.com a-z-animals.com; Live Science Animals livescience.com; Animal Info animalinfo.org ; World Wildlife Fund (WWF) worldwildlife.org the world’s largest independent conservation body; National Geographic National Geographic ; Endangered Animals (IUCN Red List of Threatened Species) iucnredlist.org

Woolly Rhinos and the Sumatran Rhinoceros

Sumatran rhinoceros may have evolved from woolly rhinos. According to the International Rhino Foundation: “The Woolly Rhino (Coelodonta antiquitatis) first appeared some 350,000 years ago and may have survived until as recently as 10,000 years ago. Their fossils are fairly common and have been discovered throughout Europe and Asia. Well-preserved remains have been discovered frozen in ice and buried in oil-saturated soils. In Ukraine, a complete carcass of a female Woolly Rhino was discovered buried in the mud. The combination of oil and salt prevented the remains from decomposing, allowing the soft tissues to remain intact. [Source: International Rhino Foundation \=]

“A herbivore who grazed on grass, shrubby sprouts, forbs (small herbaceous plants), lichens and mosses. Woolly Rhinos had a broad front lip. The horns of Coelodonta antiquitatis fossils show abrasion marks that were presumably caused by to and fro motion of the head as it pushed the snow away while searching for grass. The Woolly Rhino lived just as their recent relatives do, alone or in very small family groups. Coelodonta antiquitatis were hunted by early humans and they were depicted on the walls of caves in France 30,000 years ago. The Sumatran rhino, Dicerorhinus sumatrensis, is the last representative of the Woolly Rhino family. \=\

“Once common throughout Northern Europe and Eastern Asia (especially in what is now Russia). Coelodonta antiquitatis' range extended from South Korea to Scotland to Spain. In the latter part of the Pleistocene Period, the Woolly Rhino may have had the largest range of any known rhinoceros, living or extinct. The Woolly Rhinos frequently inhabited the same areas as Woolly Mammoths, however they apparently never managed to move across the Bering Strait (Bering Land Bridge) and extend their range into North America. \=\

Sumatran Rhinoceros Habitat and Where They Are Found

Sumatran rhino range

The Sumatran rhino is found in small, fragmented populations on the islands of Sumatra (Indonesia) aas well as a recently identified individual or group in Indonesian Borneo. Many of these found in Sumatra live near Mount Leuser, Way Kambas and Bukit Barisan Selatan. Those that lived in Malaysian Borneo and Peninsular Malaysia are now thought to be gone now.

The Sumatran rhinoceros lives in both lowland and highland tropical rain forests. They can live in a variety of habitats. Mainly they are found in dense forests, mountain moss forests and hilly areas close to water beds but there is also evidence they live in margins of forests and areas with dense secondary vegetation. Sumatran rhinos also have been sighted in coastal swamps and in the sea. [Source: Nghi Tran, Animal Diversity Web (ADW) /=]

Sumatran rhinoceroses used to inhabit a large range that extended from the foothills of the Himalayas of Bhutan through Myanmar (Burma), Thailand, Malaysia and into Sumatra and Borneo. They may have also lived in Vietnam and Indonesia. Up until fairly recenly they were found in peninsular Malaysia, coastal areas of Sumatra, particularly in the west and south, and dense forest in very high altitudes in Sabah, Malaysia in northeast Borneo.

Sumatran Rhinoceros Characteristics

Sumatran rhinos, as we saiad earlier, are the world’s smallest rhinos, with an average body length of around 2.5 meters (8.2 feet) A mature Sumatran rhino typically stands about one to 1.5 meters (50 to 75 inches) at the shoulder, with a body length of 2.4 to 3.15 meters (94 to 124 inches) and weighs around 600 to 950 kilograms (1,320 to 2,095 pounds), with a range of 800 to 2000 kilograms (1762 to 4405 pounds).. Like the African species, it has two horns; the larger is the front (25 to 79 centimeters), with the smaller usually less than 10 centimeters long. Sexual Dimorphism (differences between males and females) is present: Ornamentation is different. The males have much larger horns than the females.

Hair can range from dense (the densest hair in young calves) to scarce. The color of these rhinos is reddish brown. They have relatively few skin wrinkles except around the neck. Their body is short and has stubby legs. They also have a prehensile lip. Under ceratin conditions it will grow a thick coat of hair like that of the long-extinct woolly rhino.

According to Animal Diversity Web: Sumatran rhinoceroses are thick-statured and short-bodied The species can be easily recognized by the two deep skin folds encircling the body between the legs and the trunk, and its thick fur of short stiff hairs. Two horns decorate the snout, although the frontal horn is much more conspicuous than the nasal horn. An average of 16 millimeters thick, the skin of the Sumatran rhino is thick and leathery, causing it to wrinkle at the edges. The muzzle is rounded and unwrinkled. In adults, body color is generally dark gray or brown. Its dental formula is 1/0, 0/1, 3/3, 3/3. [Source: Nghi Tran, Animal Diversity Web (ADW) /=]

Sumatran Rhinoceros Food and Eating Behavior

Sumatran rhinoceroses are herbivores (primarily eat plants or plants parts), but are also recognized as folivores (eat leaves), frugivores (eat fruits), lignivores (eat wood). Among the plant foods they eat are leaves, saplings, plants in secondary growth, wood, bark, or stems seeds, grains, and nuts fruit. [Source: Nghi Tran, Animal Diversity Web (ADW) /=]

When feeding, Sumatran rhinoceroses moves in a zig-zag fashion, sampling the potential food items in sight before it takes in mouthful quantities. According to Animal Diversity Web: Young saplings serve as the major food source and are systematically prepared for consumption; the young trees are bitten off, trampled upon, and then eaten. These rhinos take in fruits, twigs, and bark.

Favored foods, such as wild mangoes, bamboos, and figs are preferred. Rhinos get minerals, mainly sodium and calcium, from drinking from salt springs. Daily food consumption in adults averages 50 kilograms. In captivity, they are pretty picky about what they eat. They prefer fresh Ficus browse. If they don’t get that they often won’t eat.

Sumatra Rhinoceros Behavior

The Sumatran rhinoceros is a solitary species. Both males and females maintain permanent home ranges, but males defend a larger territory than females. Roaming across a grazing territory of about 16 square kilometers, these animals spend much of their day in wallows and browses on twigs, leaves, fruits, saplings and tender fruit. They are used to the shade. Captive Sumatra rhinoceroses exposed to long periods in the sun developed eye problems.

Nghi Tran wrote in Animal Diversity Web: As boundaries of home ranges overlap, Sumatran rhinos occasionally meet, but they do not stay together for any considerable length of time. During mating periods, males and females come together to mate and form short term bonds. [Source: Nghi Tran, Animal Diversity Web (ADW) /=]

The Sumatran rhinoceros is well-known for its marking behavior. The animal marks it trails with feces, urine and soil scraps. These traces serve as visual and olfactory signals for passing rhinos. The most common method of territorial marking is a scrape made by a single movement of the hind feet into the ground, resulting in a bare patch of soil. Feces are often deposited in the scrape and urine is sprayed and splashed over vegetation. This species also delimits its territory by twisting and breaking saplings; Sumatran rhinos change directions when they encounter broken trees in their way. When disturbed or threatened by human encounters, the animals spray copious urine and defecate several times. The behavior serves to temporarily attract attention from the intruders while traveling young, if present, seek cover. In some situations, these rhinos can become aggressive and hostile. /=\

The species is an inexhaustible walker. It feeds before dawn and before sunset, and moves mostly by night. It can also swim well. During the day, the animal is often found in rain ponds or wallows that are dug out near streams. Wallows serve to cool the animal; in addition, the mud from the wallows prevents the animal's skin from cracking and drying. The species is known to make patterned seasonal movements. It travels along hills when the lowlands are flooded, descending when the weather is cool and relatively dry, returning to high ground to escape summer insects, particularly horse flies. /=\

Sumatra Rhinoceros Reproduction, Sex and Offspring

Due to their hidden nature, the mating period of Sumatra rhinoceroses is not known. However, it is known that most births occur from October to May, the months of heaviest rainfall. The gestation period is 475 days. Typically one calf is born and it stays with its mother for 18 months. During the first few days after birth, young are hidden in dense vegetation near salt licks while the mother browses. After two months, young start wandering with theirits mother. At birth, the newborn is 60 centimeters tall and 90 centimeters long, weighing approximately 25 kilograms. It has a coat of crisp and black hair that later becomes long and shaggy. During earlier stages of development, young may associate with one another, but they eventually become solitary. Weaning takes place at 16 to 17 months. Interbirth intervals last at least three to four years in part because of the long gestation period and nurturing time spent with young. Sumatra rhinoceroses reach sexual maturity at age seven to eight. [Source: Nghi Tran, Animal Diversity Web (ADW) /=]

The female shows little sign of estrus and is believed to be an induced ovulator (the egg is only reduced after the make begins showing interest in her). This is unique among rhinos. If male and female arr together at the wrong time they will fight. At the right time he will follow the female around. The male with follow the female around for about 15 minutes with nose to tail. When she stops he mounts her and stays mounted for anywhere from 20 to 50 minutes.

Paul Watson wrote in the Los Angeles Times, “In the forest, a Sumatran male rhino goes looking for a female when he senses she is in heat, which occurs roughly every three weeks. Zoo rhinos often suffered serious injuries until experts figured out when it was safe to nudge them toward mating, Marcellus Adi Riyanto of the Sumatran Rhino Sanctuary said. If the timing is bad, they fight when they meet. They might even kill each other," said Riyanto, who has seen a female chomp a deep gash 8 inches long in a pushy male. "Even if the timing is right, they still have rituals. The female is always looking for a good male. She will persuade the male to fight. If the male is strong enough, he will chase her." And only then does she give in to his advances. [Source: Paul Watson, Los Angeles Times, April 26, 2007]

Image Sources: Wikimedia Commons

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated December 2024