Sumatran rhinos are the smallest of the living rhinoceroses and the only Asian rhino with two horns.
They are covered with long hair and are more closely related to the extinct woolly rhinos than any of the other rhino species alive today. Calves are born with a dense covering that turns reddish brown in young adults and becomes sparse, bristly and almost black in older animals.
The front horn is usually 25-80 cm long, while the posterior horn is usually quite small and often no more than 10 cm.
Adult males grow to between 2-4m in length and reach up to 1-1.5m in height. They can weigh as much as 950kg, considerably less than their larger relatives elsewhere in Asia and Africa.
Sumatran rhinos prefer lower altitudes, especially secondary forests where low-growing plants are more abundant. Their habitat ranges from lowland swamps to montane forests, but they generally favour forests with thick vegetation.
In the wild, Sumatran rhinos live at low densities and are mostly solitary. Females are thought to be territorial and to avoid one another. Adults of both sexes regularly mark their ranges with scrapes, saplings, faeces, and urine.
Females are thought to reach sexual maturity at 6-7 years, while males reach sexual maturity at 10 years.
Sumatran rhinos give birth to one calf at a time, every 3-4 years. Calves are born from October to May, which corresponds with the region's rainy season. Calves gain independence at 16-17 months and may join other juveniles before taking up a solitary lifestyle.
Their life span is thought to be similar to other rhinos at around 35-40 years.
The Sumatran rhino is a browser and feeds on fruit (especially wild mangoes and figs), leaves, twigs, and bark. Sometimes the animal will venture into cultivated areas to eat crops.