The Indian rhinoceros (Rhinoceros unicornis), also known as the great one-horned rhinoceros and the Asian one-horned rhinoceros, is a massive and impressive creature with an intriguing natural history. This species is long lived, has an intricate social structure, shows strong maternal care, and is an important part of its ecosystem. Unfortunately, wild populations have significantly declined mostly due to habitat destruction and poaching.
With a distinctive armored look unique to this species of rhino, the Indian rhinoceros is also the largest member of the Rhinocerotidae family. Adult males weigh 4,400 to 6,000 pounds and reach heights of up to 7½ feet. Females average a mere 3,500 pounds and tend to be shorter than the males. Characteristics unique to both members of the genus Rhinoceros, the other member being the Javan rhinoceros (R. sondaicus), are having a single horn (made of keratin) and the presence of lower incisors and canines. The Indian rhinoceros has a prehensile upper lip distinguishing it from the Javan rhinoceros.
The Indian rhinoceros has a long lifespan of 30 to 45 years. Zoologists estimate the age of an individual in the wild visually by evaluation of facial wrinkles, erosion of the horn, number of scars on the body, and by body size.
Unlike other Asian Rhinocerotidae, the Indian rhinoceros’s range is more limited due to its preference for flood plains and the surrounding forest tracts. Prior to the 1900’s its range was extensive, stretching from northern Pakistan through northern India to northern Myanmar. Due to poaching, habitat loss, and civil war, today’s population of Indian rhinoceros is limited to very small parcels of its historical range.
The females have their first calf usually around the age of seven, after a 15½-month pregnancy. They generally give birth to one calf every 2½ years. Mating season lasts from February through April and it is not a quiet affair. Males will aggressively chase a female over a mile to catch her and often injure her in the process. The actual birth happens quickly, taking only 30 minutes from the first signs of labor to delivery of the calf. The calf will nurse for up to a year, although it starts to eat grasses after one week of age, and remains with the mother for 4 years.
These large mammals are obligate herbivores with a varied diet of grasses and shrubs. An important and highly nutritious food source is Saccharum spontaneum (elephant grass). They will also eat twigs, bamboo shoots, water hyacinths, and some fruits. The eating habits and movements of the Indian rhinoceros and other mega fauna determine the forest structure of the area. Because the rhinos eat the tops of seedlings, many of the area plants have adapted by growing outwards. Trees will grow in clumps due to the rhinoceros’ dispersal of the seeds via dung piles. The fruit tree Trewia nudiflora depends on the Indian rhinoceros as its main seed disperser because the seeds are too large and hard for other animals to utilize.
As a territorial species, these rhinos live solitary lives except when the mother is with a calf and as sub-adults. Females maintain territories that are loosely structured and overlap with other rhinos. They do come together to share community wallows. Sub-adults, rhinos ages four to six years, will form same sex groups but do try to stay close to their mother’s territory.
The male society is a volatile and dangerous one. Male Indian rhinoceroses have a dominant hierarchy with the dominant male being the main breeder. The dominant male will kill young of other males and will remain in the dominant position only an average of eight months at a time. Males mark their territories with dung piles and use a squirt-urination display to show their dominance. The squirt-urination display is a strategic wide spray of urine directed towards the back of the rhino.
Male to male aggression accounts for half of all male deaths. Males will even attack another male during copulation to be able to mate with the female. The tusk-like incisors are the main weapon used during combat (not the horn). Size of incisors directly corresponds to dominance. Those with longer, by even a centimeter, and intact incisors will be in a dominant position more often and for longer periods of time. Having a broken or intact horn makes no difference as to the male’s dominant status.
Indian rhinoceros’s have an assortment of vocalizations used for communication. A snort is a greeting. Honks are loud, travel long distances, and are usually made during fights by the subordinate. A bleat indicates submission during a courtship chase. A squeak-pant is made by males during a courtship chase. Roars are usually made by a mother protecting her baby. Mother and baby use a moo-grunt as a contact call.
The Indian rhinoceros is listed as endangered by the United States Fish and Wildlife Service, International Union for Conservation of Nature and Natural Resources (IUCN) Red Data Book, and the Convention for International Trades of Endangered Species (CITES). Estimates put its population at only 900 surviving in 1970. This number increased to about 2,700 individuals in 2010. Prior to the 1900’s researchers believe that, although not as numerous as other Rhinocerotidae, its population was much more abundant than it is today. Current efforts to preserve the Indian rhinoceros focus on protecting the wild populations from poachers (a single horn sells for up to $30,000 per kilogram), research, developing partnerships with local people, and sustainable farming. In addition, ecotourism has provided economic incentives for the local people to protect the rhinoceros population. However, the downside of ecotourism is that tourists have at times disrupted the behavior of the Indian rhinoceros by getting too close.
Like other large herbivorous mammals, the Indian rhinoceros is an animal that tends to capture people’s interest. Its natural behaviors are representative of a complex animal society. Its large size and eating habits shape the habitat in which they live. As an endangered species, it may be headed for extinction. If the Indian rhino does disappear, not only will its unique presence be lost, but there will be permanent changes to the habitat that it has so much impact on. It is the hope of international rhinoceros researchers and conservation organizations that this species will not go the way of the prehistoric woolly rhinoceros.
- Dinerstein, Eric 1992. Effects of Rhinoceros unicornis on Riverine Forest Structure in Lowland
Nepal. Ecology, 73(Tougard et al., 2001):701-704
- Dinerstein, Eric, 2003. The Return of the Unicorns: The Natural History and Conservation of the
Greater One-Horned Rhinoceros. Columbia University Press, New York, 316 pp.
- Dinerstein, Eric 1991. Sexual Dimorphism in the Greater One-Horned Rhinoceros (Rhinoceros
unicornis). Journal of Mammalogy, 72(3):450-457
- Laurie, W. A., Lang, E. M., and Groves, C. P., 1983. Rhinoceros unicornis. Mammalian Species,
- Lott, Dale F. and McCoy, Michael 1994. Asian rhinos Rhinoceros unicornis on the run? Impact
of Tourist visits on One Population. Biological Conservation, 73(1):23-26
- Macdonald, David Dr. 1995. The Encyclopedia of Mammals. Facts on File, Inc. New York,