Geographic Range
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.
Habitat
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.
- Habitat Regions
- tropical
- Terrestrial Biomes
- savanna or grassland
- forest
- Wetlands
- swamp
Physical Description
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.
- Other Physical Features
- endothermic
- homoiothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
- ornamentation
Reproduction
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.
- Mating System
- polyandrous
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.
- Key Reproductive Features
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
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.
- Parental Investment
- female parental care
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- female
-
provisioning
-
pre-independence
-
protecting
- female
-
protecting
- extended period of juvenile learning
Lifespan/Longevity
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.
Behavior
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.
Home Range
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.
Communication and Perception
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.
Food Habits
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.
- Plant Foods
- leaves
- roots and tubers
- wood, bark, or stems
Predation
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.
Ecosystem Roles
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.
- Trypanosome ( Trypanosoma evansi )
- Protozoa
Economic Importance for Humans: Positive
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.
- Positive Impacts
- body parts are source of valuable material
- source of medicine or drug
Economic Importance for Humans: Negative
Sumatran rhinoceroses can inadvertently trample or consume agricultural crops in areas
where there range overlaps with human settlements.
- Negative Impacts
- crop pest
Conservation Status
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.
Additional Links
Contributors
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.
- oriental
-
found in the oriental region of the world. In other words, India and southeast Asia.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- tropical savanna and grassland
-
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.
- savanna
-
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.
- temperate grassland
-
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.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- swamp
-
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
- endothermic
-
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.
- bilateral symmetry
-
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.
- sexual ornamentation
-
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.
- polyandrous
-
Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).
- female parental care
-
parental care is carried out by females
- diurnal
-
- active during the day, 2. lasting for one day.
- motile
-
having the capacity to move from one place to another.
- solitary
-
lives alone
- visual
-
uses sight to communicate
- acoustic
-
uses sound to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- drug
-
a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease
- herbivore
-
An animal that eats mainly plants or parts of plants.
- folivore
-
an animal that mainly eats leaves.
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
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