Sumatran rhinoceroses (Dicerorhinus sumatrensis) had a historic range that included Assam, Burma and Indochina to Malaysia, and areas in northern Sumatra and northwestern Borneo. However, their current range is more restricted, and they are uncommon throughout this range. As of 1992, there were small populations of 50 individuals each in Borneo, Sumatra, and Malaysia. Smaller populations of around 10 individuals were reported in Thailand, Burma and Indochina. As of 2015, most populations are restricted to national parks in Sumatra and Malaysia, although there are a few groups found in the wild near the border of Thailand and Malaysia. (Corbet and Hill, 1992)
Sumatran rhinoceroses live in upland forests around Peninsular Malaysia, Sumatra, and Borneo, at elevations up to 2,000 m above sea level. In these areas, rainfall is plentiful. Specific habitats include dense highland and lowland tropical and sub-tropical forests. Although they prefer upland habitats, Sumatran rhinoceroses are found occasionally in swampy wetlands. In Borneo and Sumatra, they are found most often in lowlands by the Sundaland River and in swamps. (Corbet and Hill, 1992; Foose and van Strien, 1997)
Sumatran rhinoceroses are the smallest species of rhinoceros (family Rhinocerotidae). They are also commonly called hairy rhinoceroses, due to the dense hair that covers their body, which helps keep mud caked on their bodies to keep them cool in the hot summer.
Distinct characteristics of Sumatran rhinoceroses are fringed ears, reddish-brown skin covered in long hair, and wrinkles around their eyes. Sumatran rhinoceroses have two horns on their heads. In males, the front horn usually ranges from 25 to 80 cm long and the posterior horn grows no larger than 10 cm. In females, both horns are significantly reduced, and appear as short knobs. Newborn calves are covered in thick hair, which is a light reddish-brown color. As calves approach adulthood, their hair becomes sparser and darker, eventually turning black upon maturity.
Sumatran rhinoceroses grow 2 to 4 m long and 1 to 1.5 m tall at their shoulders. Their tails can grow up to 70 cm. Mature adult Sumatran rhinoceros can around 600 to 1,000 kg. At birth, calves weigh 40 to 50 kg. (Cave, 2009; Morris, 1995; Roth, 2006; Strien, 1986)
Although they have never been observed mating in the wild, Sumatran rhinoceroses are considered to be polyandrous. When they are ready to mate, both female and male Sumatran rhinoceroses become more aggressive than usual. Females will indicate that they are in estrus by vocalizing, spraying their urine on objects in their environment, and raising their tails near males. Males use their snouts to nudge the backsides of females and, if a female is receptive to mating with a male, then the male will mount the female. Sumatran rhinoceroses mate every 3 to 4 years, primarily due to long periods of gestation (15 to 16 months) and maternal care (2 to 3 years) associated with each offspring. (Bosi, 1998; Roth, et al., 2004)
Reproduction of Sumatran rhinoceroses has never been observed in the wild. All known observations of reproduction were recorded in captivity. Sumatran rhinoceroses are solitary animals, who only come together to reproduce. Females reach sexual maturity around 6 to 7 years old, and males reach sexual maturity around 10 years old. Females will not come into estrus until they sense nearby males. Sumatran rhinoceroses have a gestation period of 15 to 16 months. Females give birth to one calf at a time, every 3 to 4 years. Calf will range from 40 to 60 kg at birth. They are fully dependent on their mothers for 2 to 3 years. (Schwarzenberger, et al., 2000; Zahari, et al., 2005)
Calves are weaned around 18 months, but stay close to their mothers for 2 to 3 years. Many female Sumatran rhinoceroses will come together to raise their calves. The only time female Sumatran rhinoceroses congregate is when they are with their calves. Once their calves are independent, females return to a solitary lifestyle. Once male Sumatran rhinoceroses mate, they do not invest any more time in their offspring. (Bosi, 1998; Zahari, et al., 2005)
There is limited information on lifespans of Sumatran rhinoceroses in the wild. However, it is estimated that they can live 30 to 45 years in the wild. In captivity, the oldest an individual has lived is 32 years and 8 months. (Rabinowitz, 1995; Roth, 2006; Strien, 1986)
Despite their size (up to 1,000 kg), Sumatran rhinoceroses are rather quick and quiet. They have been observed to reach speeds of 40 km/hr. As young adults, male Sumatran rhinoceroses can be very aggressive towards females. During altercations, young males are known to injure and kill females.
Even though Sumatran rhinoceroses are solitary, they are not aggressive about defending their territory; often males will have territories that overlap with other males.
In hot weather, Sumatran rhinoceroses will wallow in mud pits to help maintain a constant body temperature and avoid overheating. They also wallow in mud to protect their skin from parasites and insects. When mud pits are not available, Sumatran rhinoceroses make small puddles in mud pits by digging with their legs or horns. (Cave, 2009; Hutchins and Kreger, 2006; Strien, 1986)
Male and female Sumatran rhinoceroses have home ranges of different size. Males have average home ranges of around 50 km², whereas females have home ranges of around 10 to 15 km². Sumatran rhinoceroses mark their territorial boundaries using urine and feces. They also use their hind legs to scrape territory markers. However, they do not aggressively defend these areas. (Cave, 2009)
While most rhinoceros species (family Rhinocerotidae) primarily use scent and body language to communicate with conspecifics, Sumatran rhinoceroses also use vocalizations. Sumatran rhinoceroses have three distinct calls: "eeps", "whale calls", and "whistle-blows". Eeps are the simplest and most common call type, consisting of short "eep" sounds. Whale calls sound similar to the calls of humpback whales (Megaptera novaeangliae). Finally whistle-blow calls are loud whistling calls at low or high tones.
Although the purposes of these calls are poorly studied, eeps are considered to be how they communicate during most intraspecific encounters. Whale calls have only been heard from male Sumatran rhinoceroses, but their functions are still unknown. Whistle-blow calls can travel long distances without attenuating, and are used most often when Sumatran rhinoceroses are communicating in the dense forest environments. It is also used less often to mark territory boundaries. Sumatran rhinoceroses also use their urine to indicate their territory boundaries and to communicate that they are ready to mate. (von Muggenthaler, et al., 2003)
Sumatran rhinoceroses are browsers, eating small trees, shrubs, and herbs. Sumatran rhinoceroses do not have specific periods of feeding; they alternate the times that they feed depending on when they are traveling. Sumatran rhinoceroses are generalist herbivores and will sample any plant along the route they are traveling. However, Sumatran rhinoceroses mostly feed on leaves and twigs from saplings and small trees. In lowlands and valleys, Sumatran rhinoceroses primarily feed on herbaceous undergrowth. The undergrowth has more nutritional value due to the rich soil and thickness of the undergrowth. In Malaysia, as much as 98% of the diets of Sumatran rhinoceroses consists of saplings, because dense forest cover restricts herbaceous undergrowth.
Food availability varies depending on where Sumatran rhinoceroses are feeding. At higher elevations (close to 2,000 m) sapling trees and herbaceous undergrowth are abundant year-round. Sumatran rhinoceroses in these areas do not travel far, indicating that food is not a limiting factor. (Corbet and Hill, 1992; Strien, 1986)
Sumatran rhinoceroses do not have many predators, except for humans (Homo sapiens) and Sumatran tigers (Panthera tigris sumatrae). Sumatran tigers do not actively hunt Sumatran rhinoceroses, but will opportunistically attack stranded calves. (Cave, 2009)
Sumatran rhinoceroses are large herbivores, which likely play a role in controlling understory vegetative growth and forest succession patterns.
Protozoans are present in the feces of Sumatran rhinoceroses. Trypanosomes also infect Sumatran rhinoceros. The most common trypanosome found in the rhinoceroses is Trypanosoma evansi, which is found in the bloodstream. These trypanosomes eventually kill their hosts by traveling to the brain and causing tumors, hemorrhaging, and labored breathing. (Octalia, et al., 2008)
Sumatran rhinoceroses have been hunted by humans for hundreds of years. Body parts such as the horns are used for tribal practices and traditional medicine in some Asian cultures. Sumatran rhinoceros horns and other body parts have been used to treat different aliments such as fevers and strokes. Their horns were also once considered an aphrodisiac.
The horns of Sumatran rhinoceroses can be worth up to $50,000 USD per kg on the black market. (Corbet and Hill, 1992; Foose and van Strien, 1997)
Sumatran rhinoceroses can inadvertently trample or consume agricultural crops in areas where there range overlaps with human settlements. (Corbet and Hill, 1992; Foose and van Strien, 1997; Roth, et al., 2004)
Sumatran rhinoceroses are listed as "critically endangered" according to the IUCN Red List and is listed under Appendix I of CITES, prohibiting international trade for any commercial reason. Sumatran rhinoceroses can be imported or exported for research purposes with proper documentation and government approval.
In 2008, there were an estimated 250 Sumatran rhinoceroses remaining in the wild. The main reasons for their low population sizes are poaching and habitat loss due to deforestation.
For hundreds of years, Sumatran rhinoceros horns and other body parts have been used for medicine in Asia to treat different aliments, such as fevers and strokes. Hunting Sumatran rhinoceroses is illegal today, but humans still poach them for their horns. Another way humans are harmful to Sumatran rhinoceroses is by logging and burning down their forest habitats to clear land for plantations that produce palm oil (Elaeis guineensis). Extant populations of Sumatran rhinoceroses are concentrated in protected areas, which can lead to the spread of diseases and make them easier targets for poachers.
The Rhino Protection Unit is the most involved organization that is trying to stop poaching of Sumatran rhinoceroses. Advocates in this unit have been working with the government of Indonesia to construct laws and penalties for poaching Sumatran rhinoceros.
There are zoos that have Sumatran rhinoceroses in breeding programs in attempts to increase numbers. The most successful zoo is the Cincinnati Zoo, where the breeding program is led by CREW (Lindner Center of Conservation and Research of Endangered Wildlife). In 2000, the Cincinnati Zoo successfully mated two Sumatran rhinoceros. There was another successful mating of Sumatran rhinoceros in 2013. Because there are such low numbers in the wild, inbreeding occurs and many calves do not survive. Calves can be born and introduced to the wild to expand the population. (Carwardine, 2015; Hutchins and Kreger, 2006; Rabinowitz, 1995; Scott, et al., 2004; Strien, 1986)
Nick Succop (author), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Emily Clark (editor), Radford University, Cari Mcgregor (editor), Radford University, Jacob Vaught (editor), Radford University, Galen Burrell (editor), Special Projects.
uses sound to communicate
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
an animal that mainly eats leaves.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly plants or parts of plants.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
found in the oriental region of the world. In other words, India and southeast Asia.
Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).
reproduction that includes combining the genetic contribution of two individuals, a male and a female
one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
uses sight to communicate
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