Greater One-horned Rhinoceros

About the greater one-horned rhinoceros

The greater one-horned rhinoceros, also called the Indian rhinoceros or great Indian rhinoceros, is the second-largest living rhino species and the largest rhino in Asia. Only the white rhinoceros outweighs it. Among terrestrial mammals native to Asia, it ranks second in size only to the Asian elephant. Bulls have a head-and-body length of 368–380 cm and a shoulder height of 163–193 cm, averaging about 2,070–2,200 kg. Cows are smaller, at 310–340 cm long, 147–173 cm at the shoulder, and around 1,600 kg. The largest individuals on record reportedly reached 436 cm in body length, 206 cm at the shoulder, and up to 4,000 kg.

Its defining feature is a single horn on the snout, present in both bulls and cows but absent in newborn calves. The horn is pure keratin, starts to show after about six years, and typically reaches around 25 cm in adults, though the longest recorded horn measured 57.2 to 61.6 cm and weighed just over 3 kg. In captive animals the horn is often worn down to a thick knob.

The species' thick, grey-brown skin is folded into pinkish creases; bulls have especially large neck folds. Rich blood vessels beneath these folds give them their pink color, and the extra surface area helps the animal regulate body temperature. The skin is otherwise nearly hairless apart from the eyelashes, ear fringes, and tail brush, and its upper legs and shoulders are covered in wart-like bumps. Despite its thickness, the skin does not protect against bloodsucking Tabanus flies, leeches, and ticks. In the wild, the greater one-horned rhinoceros lives in the alluvial grasslands and riverine habitats of the Indo-Gangetic Plain, along the Ganges and Brahmaputra river systems.

Behavior and diet

Bulls are usually solitary, associating with other rhinos mainly during the breeding season. Cows form groups with their calves, and subadults sometimes gather in groups of up to six, congregating at wallows and grazing areas. The species is most active in early morning, late afternoon, and at night, resting during the heat of the day. Rhinos bathe regularly, and the folds in their skin trap water, holding moisture even after they leave a wallow. They are strong swimmers and can run up to 55 km/h (34 mph) over short distances. Hearing and smell are excellent, but eyesight is comparatively poor. At least ten distinct vocalizations have been recorded, including snorting, honking, bleating, roaring, and rumbling, and bulls also communicate by urinating backward as far as 3–4 meters and by marking rhino latrines with scent from pedal glands.

As a grazer, the greater one-horned rhinoceros feeds mainly on grasses, using its semi-prehensile lip to grasp stems, bend them down, and bite off the top. For very tall grasses or saplings, it may walk over the plant and use its body weight to push the top within reach of its mouth — a technique mothers also use to make food accessible to calves. Beyond grass, the diet includes twigs, leaves, branches of shrubs and trees, flowers, fruits, and submerged or floating aquatic plants. Feeding happens mainly in the mornings and evenings.

Females give birth to a single calf after a gestation of about 15.7 months, with birth intervals of 34 to 51 months. Mothers stay close to their calves for up to four years, sometimes allowing an older calf to remain nearby once a new one is born. Adult rhinos have few natural predators; tigers occasionally kill unguarded calves, but grown rhinos are rarely taken due to their size.

Range and habitat

The greater one-horned rhinoceros once ranged across the entire northern part of the Indian subcontinent, following the Indus, Ganges, and Brahmaputra river basins from Pakistan to the India–Myanmar border, including Bangladesh and parts of Nepal and Bhutan. Habitat destruction and hunting drastically reduced this range over the 19th and 20th centuries. Today the species survives in a few pockets: the Terai grasslands of southern Nepal, northern West Bengal, and the Brahmaputra Valley of Assam in India, along with a small, non-permanent presence in Bhutan's Manas National Park area.

Its remaining habitat consists of alluvial grasslands and adjoining forest and wetland along these river systems, and it is now largely confined to about a dozen protected areas spread across northern India and southern Nepal. Because this habitat sits within human-dominated landscapes, rhinos frequently range into cultivated fields, pastures, and secondary forest surrounding the protected core areas.

Conservation status

The greater one-horned rhinoceros is listed as Vulnerable on the IUCN Red List. Its population is fragmented and restricted to less than 20,000 km², a fraction of its historical range, largely as a result of past hunting and agricultural expansion. In the early 1990s the global population was estimated at just 1,870 to 1,895 individuals, down from as few as 100 in the early 1900s. Conservation measures by the governments of India, Nepal, and Bhutan have since driven a substantial recovery: a March 2025 census put the population at roughly 4,075 individuals, with about 3,323 in India and 752 in Nepal. Poaching for the horn remains an ongoing threat, and the species is also vulnerable to diseases such as anthrax and infections carried by leeches, ticks, and nematodes.