Javan rhinoceros: rare and vital rainforest grazers

One Earth's “Species of the Week” series highlights the flagship species of each of the 844 unique ecoregions contained within Earth’s bioregions.

With a small, black horn at the tip of their snout, leathery skin folds giving an armored appearance and weighing over two tons, the Javan rhinoceros is a fascinating sight to behold in the dense jungle of Ujung Kulon National Park. Once, this great species roamed the islands of Java and Sumatra, throughout Southeast Asia, and into India and China, but now are only found on the tip of the Banten Province in Indonesia. 

The rarest of the five rhino species, there are only 75 Javan rhinos currently living. Like all rhinoceroses, Javan rhinos are vital grazers. They eat large amounts of vegetation which helps the forest stay healthy so it can house more biodiversity, sequester more carbon, and produce more oxygen.

The second smallest species of rhino, Javan rhinoceros can reach a height of 1.7 m (5.6 ft) and weigh up to 2,300 kg (5,070 lb). They have the smallest horns of the Rhinocerotidae family, measuring less than 20 cm (7.9 in) in length. Like the Indian rhino, the Javan rhinoceros has a single horn compared to the other three species which have two. Only males in this species develop horns, female Javan rhinoceroses are the only extant rhinos that remain hornless into adulthood. Javan rhinoceroses do not use their horns for fighting, but rather use them to scrape mud, pull down plants for eating, and open paths through thick vegetation.

Leaves, shoots, twigs, and fallen fruit make up the majority of the Javan rhinoceros’ diet. It is the most adaptable feeder of all rhinos with biologists identifying more than 300 different species they consume. Eating an estimated 50 kg (110 lb) of food in a day, Javan rhinoceroses help make room for new plants to grow. 

They also knock down and trample vegetation with their large bodies and wallow in the mud. This helps keep the Javan rhino’s body temperature cool and prevents diseases, but for the ecosystem, their motion provides a natural pruning system that allows the forest to stay strong, store CO₂, and pump out clean air.

For millions of years, Javan rhinos have played this essential role in their ecosystem, but human caused habitat destruction and mass amounts of poaching have decreased their numbers drastically. Their horns are highly revered in traditional Chinese medicine despite research indicating no medicinal value. The International Rhino Foundation and the staff of Ujung Kulon National Park work together to protect the remaining members of this critically endangered species. Success comes slowly, as Javan rhinos are mostly solitary and females only gestate every 2-3 years, but a recent birth is what propelled their new population to 75 individuals.