Sumatran rhinoceros

Sumatran rhinos eat plants.

They munch leaves, twigs and young trees.

Sumatran rhinos are browsers: they eat leaves and twigs rather than grass. Their favorite foods are the leaves and twigs of saplings, which are young trees, and small bushes.

They are not fussy. A Sumatran rhino tastes almost any plant along the path it is walking, and its diet can include more than 100 kinds of plants. In valleys and lowlands, it also eats low plants growing on the forest floor.

The species is a generalist browser with a very varied diet that may include more than 100 plant species (International Rhino Foundation). Animal Diversity Web describes it feeding mostly on leaves and twigs of saplings and small trees, sampling plants along its travel routes rather than at fixed feeding times. In lowlands and valleys it takes more herbaceous undergrowth; in parts of Malaysia, saplings once made up as much as 98 percent of the diet because dense canopy limited undergrowth.

At higher elevations, near 2,000 meters, saplings and undergrowth were abundant all year, and rhinos there did not travel far to feed.

Sumatran rhinos like to live alone.

They make squeaks and whistles to talk to each other in the forest.

Sumatran rhinos usually live alone. Mothers stay with their calves, and males and females meet only to have babies. A male's home area is about 50 square kilometers, and a female's is about 10 to 15.

They are chattier than other rhinos. Scientists have described three kinds of calls: short 'eeps', 'whale calls' that sound like a humpback whale, and loud 'whistle-blows' that carry far through the thick forest. They also mark their areas with dung and urine, and scrape the ground with their back feet.

The species is generally solitary (International Rhino Foundation); females associate only with their calves, and adults meet to breed. Home ranges average about 50 square kilometers for males and 10 to 15 square kilometers for females, and overlapping male ranges are not aggressively defended (Animal Diversity Web). Boundaries are marked with urine, feces and hind-foot scrapes.

Unusually for rhinos, Sumatran rhinos are vocal. Three call types are described: simple 'eeps', the most common call; 'whale calls', heard only from males and of unknown function; and 'whistle-blows', which travel long distances in dense forest. The purposes of these calls are still poorly studied.

Only a few Sumatran rhinos are left.

People protect their forests. Some rhinos live in a special safe park, where babies are born.

The Sumatran rhinoceros is Critically Endangered, the highest risk level for animals still living in the wild. In its 2019 assessment, the IUCN estimated only about 30 grown-up rhinos left in the wild. For many years people hunted rhinos for their horns, and forests were cut down for farms and plantations. Now the few rhinos left live in small groups, far apart from each other.

To help, rangers guard the forests, and some rhinos live at the Sumatran Rhino Sanctuary in Way Kambas National Park, where calves have been born.

The IUCN lists the species as Critically Endangered (Ellis and Talukdar; assessed 29 May 2019, published 2020), estimating about 30 mature individuals in a severely fragmented, decreasing population. Recorded threats include hunting and trapping, logging, crop plantations and fire. Poaching for horns used in traditional medicine and forest clearing for palm oil drove the long decline (Animal Diversity Web). The International Rhino Foundation reports Asian Rhino Specialist Group estimates of 34 to 47 wild rhinos in up to four isolated populations, only one of them (in Gunung Leuser) thought large enough to be viable, and no evidence of poaching for over a decade.

A managed breeding program supports an insurance population. By 2022, six calves had been born in managed breeding in the last century, the first at the Cincinnati Zoo in 2001 (Cincinnati Zoo). The species is on CITES Appendix I.