Rhinoceros

Diversity

The genus Rhinoceros contains two species, Rhinoceros sondaicus and Rhinoceros unicornis . Rhinoceros species are large, herbivorous mammals that are native to Southeast Asia. They can be found in tropical grasslands, forests, and even dense rainforests. Rhinoceros is the only genus in Rhinocerotidae to possess one horn, incisors, and lower canines. Both species are very similar in appearance to one another, with R.unicornis being much larger in size. Individuals of R.unicornis can weigh up 3000 kg, making it one of the largest members of the Family Rhinocerotidae . Both species are endangered, with R.sondaicus being critically endangered with only 60 individuals remaining.

Geographic Range

Rhinoceros species are native to Southeast Asia. Rhinoceros unicornis occupies the grasslands and forests of Northern India and Southern Nepal. The species once roamed from Pakistan in the West to the Indian-Burmese border in the East, inhabiting the river basins of the Indus, Ganges, and Brahmaputra. Rhinoceros sondaicus currently occupies a single national park, Ujong Kulong, in West Java, Indonesia. R.sondaicus was thought to have been the most widespread species in Rhinocerotidae , ranging from India to Vietnam, and throughout Sumatra and Borneo, until its recent decline.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

Rhinoceros species occupy tropical ecosystems. They prefer having a source of water nearby, to create features such as muddy riverbanks, or mud pits to wallow in during the heat of the day. Rhinoceros unicornis occupies the grasslands surrounding great river systems today but has occupied nearby forests in the past. The species is mainly a grazer, but has the ability to browse on fruits, branches, and the occasional cultivated crop. Rhinoceros sondaicus occupies the lowland tropical rainforest of West Java, but historically occurred in a variety of habitats including mixed forests, grasslands, and even rugged mountainous areas. Not much is known about their preferred habitat since only a single population remains. The species is thought to be a browser, preferring all things woody, and eating very little grass.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• rainforest rainforest

Systematic and Taxonomic History

Rhinoceros is a member of the Family Rhinocerotidae. Four genera are found in the family: Rhinoceros , Dicerorhinus , Diceros , and Ceratotherium . Rhinoceros is a sister group with Dicerorhinus , according to both molecular and morphological data (Tougard et al. 2001, Groves 1983). It is estimated that Rhinoceros diverged from the other genera approximately 26 million years ago (Tougard et al. 2001). Rhinoceros has always been clearly distinguished as being distantly related from the African genera, Diceros and Ceratotherium , but it was unknown where Dicerorhinus fit in. Only recently was it clarified that Rhinoceros and Dicerorhinus were sister groups. The Family Rhinocerotidae is in the Order Perissodactyla . Family Tapiridae appears to be the sister taxon to Rhinocerotidae (Tougard et al. 2001). Rhinoceros was originally described by Linnaeus in 1758, and has kept the name since. Other synonyms listed below have been used, but never significantly.

Physical Description

Rhinoceros species are large mammalian megaherbivores, and the only genus in Rhinocerotidae to possess one horn, incisors, and lower canines. Their horn is not made of bone, but of densely packed keratin, and continuously grows as a result. Females of Rhinoceros sondaicus possess either no horn at all or just a small knob. Both species are similar in appearance, with Rhinoceros unicornis being much larger. Weighing up to 3000 kg, it is one of the largest rhinoceros species. Males of R.unicornis are much larger than females, but not enough data is present to determine if there is any dimorphism in R.sondaicus . Both species possess thick folds in their gray skin, giving the illusion that the animals are wearing armor. R.sondaicus has shallower skins folds of the two species. Both species possess a prehensile upper lip, used to pull in browse.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Rhinoceros sondaicus has a brief courtship period before mating, and is the only time males and females have been seen together. Rhinoceros unicornis is a solitary species, with males and females only coming together to mate. They are known for their brutal fighting between males, that may lead to the death of one of the males. Males fight for the right to mate with females. Thick skin folds are used for protection from each other, both males and females, during fighting for the right to mate or fighting with their mate. They use their incisors in the front to gore their counterparts. R.sondaicus males and females spare or skirmish with one another before mating, but not to the extent of R.unicornis .

Both species have a long gestation period, 15-16 months for R.unicornis and 16-19 months for R. sondaicus , resulting in a single offspring. Rhinoceros sondaicus females give birth every 4-5 years while R. unicornis females give birth every 3-4 years. Both species wean anywhere from 12-24 months. Both species reach sexual maturity at 5-7 years for females and around 10 years for males.

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Both species of Rhinoceros exhibit extensive parental investment from the females. Calves will spend the first year and a half with their mothers before being pushed away. Calves rely strictly upon their mother's milk for the first 3-5 months before they can forage on their own. Females provide milk and protection from predators for the first 12-24 months. Anywhere along that time frame will calves wean and be pushed away by their mothers. Males play no role in the rearing of young.

• Parental Investment
• female parental care female parental care
• pre-independence
  • protecting
    • female
• extended period of juvenile learning

Lifespan/Longevity

Rhinoceros species have a lifespan of 30-40 years in the wild. The oldest individual of Rhinoceros unicornis recorded reached 40 years old (von Houwald 2018). Rhinoceros sondaicus has appeared so rarely in captivity, that not much is known about their longevity there.

Behavior

Rhinoceros species are solitary. Groups will only be seen during mating, a mother and calf, and small groups of adolescent males. Rhinoceros males occupy a territory, with females moving freely about. Rhinoceros unicornis males have constantly changing territories depending on the season with possible overlap of territories with other males, and will defend their territory aggressively from other males (von Houwald 2018, Talukdar et al. 2008). Rhinoceros sondaicus males have large territories, with only a single male occupying each range (van Strien 2012). Rhinoceros species are active throughout the day and night. Both species will use mud wallows frequently to escape high temperatures.

• Key Behaviors
• terricolous
• diurnal diurnal
• motile motile
• solitary solitary

Communication and Perception

Rhinoceros species have poor eyesight, but rely on their developed hearing and sense of smell. Both species communicate with others in their species mainly through scents, along with some vocalizations. Rhinoceros unicornis leave dung heaps at the edge of their territories, and then walk through it to spread the scent around even further. Some individuals leave dung heaps on top of other individuals dung heaps, resulting in a pile that can be 5 meters wide (von Houwald 2018). Rhinoceros sondaicus leaves dung heaps to mark its territory, as well as a substance it projects from snorting to create scent markers (Groves and Leslie 2011). Rhinoceros unicornis has 12 different vocalizations recorded, ranging from snorts, honks, and even roars (von Houwald 2018). Rhinoceros sondaicus is much less vocal, with only 5 vocalizations (Groves and Leslie 2011).

• Communication Channels
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks

• Perception Channels
• tactile tactile
• chemical chemical

Food Habits

Rhinoceros species are generalist browsers with a prehensile upper lip. Their prehensile upper lip allows them to grasp woody branches and pull them into their mouth. Rhinoceros unicornis eats grass, woody twigs and branches, and semi-aquatic plants (von Houwald 2018, Larie et al. 1983). Rhinoceros sondaicus eats strictly vegetation from woody plants, or leaves, twigs, and branches (Groves and Leslie 2011).

• Primary Diet
• herbivore herbivore
  • folivore folivore
  • lignivore

Predation

Rhinoceros species have few predators. As with all rhino species, adults are so large that they don't have any predators. Rhinoceros sondaicus has no remaining predators in its current habitat, as tigers have become extinct on the island of Java (Groves and Leslie 2011). Rhinoceros unicornis may have tigers prey upon their young, usually 6 months or younger (Groves and Leslie 2011). The rhino is famous for its horn, but they don’t use it to protect themselves. The only time is when mothers must fend off a predator that is pursuing their calf.

Ecosystem Roles

Rhinoceros species are large megaherbivores that have a variety of impacts on their ecosystem. The main impact is upon the vegetation, as animals of their size eat significant amounts of vegetation that could alter the landscape if left unchecked. Rhinoceros unicornis creates paths in the forest they occupy (van Strien 2012). Rhinoceros unicornis has a close relationship with the cattle egret. Cattle egrets will follow rhinos around, waiting to eat any invertebrates the large mammals may kick up. Rhinoceros sondaicus creates mud wallows, that a variety of species use when the rhinos aren't around (Groves and Leslie 2011).

• Ecosystem Impact
• creates habitat

Economic Importance for Humans: Positive

The main economic importance of Rhinoceros species is tourism. Rhinoceros sondaicus is in such an isolated location, and under such heavy protection since there is only one population left, that they have almost no interaction with humans. A good example of the separation between R.sondaicus and humans is just how little we know about the life history of this species. Rhinoceros unicornis has become a very popular ecotourism attraction in India and Nepal. An entire tourism industry is starting to emerge outside of the national parks in India and Nepal where R.unicornis is found.

• Positive Impacts
• ecotourism ecotourism

Economic Importance for Humans: Negative

Rhinoceros unicornis is found increasingly in human-wildlife conflicts as its numbers rise. Individuals find their way into local community's crops routinely, causing thousands of dollars of damages. Being such a large animal, there have been numerous human fatalities recorded at the hands of R.unicornis .

• Negative Impacts
• injures humans
• crop pest

Conservation Status

Rhinoceros species are two of the most endangered species in the world, with the main cause being habitat loss. Rhinoceros unicornis is listed as threatened, with 3,200 individuals remaining (Talukdar et al. 2008). R.unicornis dropped down to only 200 individuals in the early 1900's mainly due to over harvesting and the transformation of their alluvial plain habitat to farmland (Talukdar et al. 2008). Now they have a stable population, but little habitat to occupy. The main threat to R.unicornis in the future will be poaching for their horn that is used in traditional Chinese medicine, and further habitat loss. Future conservation actions look at expanding their population by reintroducing R.unicornis to more of its former range (Talukdar et al. 2008). Rhinoceros sondaicus is one of the most endangered mammals in the world, and is listed as critically endangered. With a single population of about 65 individuals, this species is in desperate need of help. The population is safeguarded by Rhino Protection Units to prevent poaching, but the major concern comes from their location. They reside in Ujung Kulon National Park, at the foot of the famous and massive volcano Krakatau. If the volcano were to erupt, or create a tsunami that devastates the park, we could lose the species. Current efforts look to reintroduce the species to a second location, so that the population has an opportunity to grow (van Strien et al. 2008).

Other Comments

The word "Rhinoceros" is of Greek origin. "Rhino" meaning nose, and "cero" meaning horn. All Rhinos have 3 toes, and are members of the Family Perissodactyla, which is known as the "odd-toed" ungulates. Rhinoceros is closely related to the extinct genera: Gaindetherium and Punjabitherium (Groves 1983).

Additional Links

Encyclopedia of Life

Contributors

Evan Smith (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

Cerdeno, E. 1995. Cladistic Analysis of the Family Rhinocerotidae. American Museum Novitates , 3143: 1-25.

Dinerstein, E. 2011. Handbook of The Mammals of the World Volume 2 . Unknown: Lynx Edicions.

Dinerstein, E. 2018. Rhinoceros. Britannica. Accessed February 05, 2018 at https://www.britannica.com/animal/rhinoceros-mammal .

Groves, C. 1983. Phylogeny of the living species of Rhinoceros.

Groves, C., P. Grubb. 2011. Ungulate Taxonomy . Baltimore, Maryland: The Johns Hopkins University Press.

Groves, C., D. Leslie. 2011. Rhinoceros sondaicus. Mammalian Species , 43: 190-208.

Laurie, A. 1982. Behavioural ecology of the Greater one-horned rhinoceros. Journal of Zoology , Volume 196, Issue 3: 307-341.

Laurie, W., E. Lang, C. Groves. 1983. Rhinoceros unicornis. Mammalian Species , 211: 1-6.

New World Encyclopedia contributors, 2009. Rhinoceros (genus). New World Encyclopedia. Accessed February 05, 2018 at http://www.newworldencyclopedia.org/entry/Rhinoceros_(genus) .

Talukdar, B., R. Emslie, S. Bist, A. Choudhury, S. Ellis. 2008. "IUCN Red List: Rhinoceros unicornis" (On-line). Accessed February 05, 2018 at http://www.iucnredlist.org/details/19496/0 .

Tougard, C., T. Delefosse, C. Hanni, C. Montgelard. 2001. Phylogenetic Relationships of the Five Extant Rhinoceros Species (Rhinocerotidae, Perissodactyla) Based on Mitochondrial Cytochrome b and 12S rRNA Genes. Molecular Phylogenetics and Evolution , Volume 19, Issue 1: 34-44.

van Strien, N., R. Steinmetz, B. Manullang, H. Sectionov, W. Isnan. 2008. "IUCN Red List: Rhinoceros sondaicus" (On-line). Accessed February 05, 2018 at http://www.iucnredlist.org/details/summary/19495/0 .

van Strien, N. 2012. "Save the Rhino" (On-line). Accessed February 25, 2018 at https://www.savetherhino.org/rhino_info/species_of_rhino/javan_rhinos/factfile_javan_rhino .

von Houwald, F. 2018. "Save the Rhino" (On-line). Accessed February 25, 2018 at https://www.savetherhino.org/rhino_info/species_of_rhino/greater_one-horned_rhinos/factfile_greater_one-horned_rhino .