Javan Rhinoceros

Quick Take

• A catastrophic volcanic eruption in 1883 accidentally became the Javan rhino's greatest lifeline, yet that same volcanic region still threatens to erase them entirely. How Krakatoa shaped their refuge →
• Only 72 of these rhinos survive, yet they owe their existence to a disaster that killed thousands of humans. Here is the unlikely chain of events that made their refuge possible. See the current population →
• Female Javan rhinos break one of the most iconic rules of their own species, which is something even dedicated wildlife fans rarely know. Discover the horn difference →
• With 145 million people sharing an island the size of Arkansas and zero captive individuals for breeding, the math for this species' survival looks impossible. So why are scientists cautiously hopeful? Explore the survival challenges →

The Javan rhinoceros (also known as the lesser one-horned rhinoceros and the Sunda rhinoceros) is a species of rhinoceros native to Southeast Asia. The Javan rhinoceros is thought to be most closely related to the Indian rhinoceros, both of which have only one horn.

As of 2019, it’s estimated that just 72 Javan rhinos survive in a single national park named Ujung Kulon on the westernmost tip of the Indonesian island of Java. However, with no poaching of the species reported in more than 25 years at Ujung Kulon, there’s hope for the species’ survival.

Incredible Javan Rhinoceros Facts

• The Javan rhinoceros once roamed from India to Vietnam, and south to the islands of Indonesia. The last mainland Javan rhino was poached in 2010, leaving the subspecies of mainland Javan rhinos extinct.
• Female Javan rhinos often lack a horn or have a small “nub.”
• Today, the Javan rhino is found in only a single national park that sits 37 miles (60 km) from an active volcano that erupted as recently as December 2019.

Scientific Name and Evolution

The scientific name for the Javan rhinoceros is Rhinoceros sondaicus. Along with the Indian rhinoceros, the Javan rhino is in the genus Rhinoceros, which is Greek for ‘nose’ and ‘horn’ and comprises the two species of one-horned rhinos. Sondaicus refers to ‘Sunda,’ a name for Southeast Asia where Javan Rhinos historically lived.

Javan Rhinos are more closely related to Indian Rhinos, of course, and may have diverged from them in evolution around 11 million years ago. While they have their differences from the other species of rhinos, they all evolved a thick, protective hide to defend themselves from would-be attackers. Combined with their imposing horns, there are few animals on Earth that could survive a rhino’s charge and gore.

Appearance

The Javan rhino is smaller than the Indian rhinoceros, weighing 900 to 2,300 kg (1,984 to 5,071 lbs). Its length ranges from 2 to 4 m (6.6 to 13.1 ft).

The Javan rhino closely resembles Indian rhinos. Both species have a single horn, though female Javan rhinos often lack a horn or have a small “nub” on their nose. In addition, the Javan rhino’s skin folds aren’t as pronounced as the Indian rhino’s. This gives the species less of a look of having “body armor.”

Due to the extreme rarity of Javan rhinos, they’ve been studied the least of all rhino species. Today, few pictures are taken of Javan rhinos, with most studies coming from camera traps in the dense forests they inhabit in Ujung Kulon National Park.

Habitat

The Javan Rhino primarily inhabits dense lowland rain forests, tall grass, and reed beds that are plentiful with rivers, large floodplains, or wet areas with many mud wallows. The range of the Javan rhinoceros once stretched from Bengal, through Southeast Asia, and down to Sumatra, but today, the Javan rhinoceros is only found on the island of Java.

Where the Javan rhinoceros is found today: Ujung Kulon

Today, the Javan rhino is known to survive in just a single habitat, the Ujung Kulon National Park on the western edge of the island of Java. The national park encompasses a total area of approximately 1,229 square kilometers (474 sq. miles), including both land and marine areas, which means all Javan rhinos live within a remarkably small and confined refuge.

While Javan rhinos were either hunted to extinction or lost their habitat across Southeast Asia, they survived in Ujung Kulon due to unique circumstances. In 1883, a massive volcano named Krakatoa erupted off the coast of Indonesia and decimated surrounding areas. After the event, humans fled the area, but rhinos and many other wildlife species began repopulating the area.

Today, Ujung Kulon provides a protected environment that has allowed Javan rhino populations to stabilize, but it can only support a limited number of rhinos within its borders.

Population

The population of Javan rhinos was estimated at 72 individuals by the International Rhino Foundation in 2019.

While this population makes the Javan rhino one of the most critically endangered mammals on Earth, it has been stable for more than 30 years, and its population has increased from an estimated 50 individuals in the past decade.

Extinct Javan rhino subspecies

Historically, there were three subspecies of Javan rhinoceros. In addition to the subspecies that survive today, there were the Indian Javan rhinoceros and the Vietnamese Javan rhinoceros.

Today, both the Indian Javan rhinoceros and the Vietnamese Javan rhinoceros have been declared extinct. A small population of Javan rhinos was found in Vietnam’s Cat Tien park, but the last surviving member of the subspecies was found poached in 2010.

Diet

The Javan rhino is a herbivore that browses across shrubs, bushes, and saplings. Javan rhinos browse the densely vegetated subtropical forest for leaves, flowers, buds, fruits, berries, and roots, which they dig up from the ground using their horns.

Because Javan rhinos are restricted to a small habitat, it is difficult to know how varied their diet was across their historical range. Since Javan rhino populations once ranged as far as the dense grasslands of India, the species likely grazed as well.

Predators

The Javan rhino faces few predators in the wild. Javan tigers existed in parts of Java until the late 1960s, but the last confirmed sighting was in 1976, and the subspecies has since been declared extinct. A small population of Javan leopards survives in Ujung Kulon and could prey on rhino calves and weaker individuals.

With no human poaching reported in the rhino’s surviving habitat in the past 25 years, its greatest threat today is a lack of genetic diversity that threatens breeding numbers.

Reproduction and Life Cycles

With an extremely small population and long gestation periods, the birth of any Javan rhino is closely monitored. In December 2019, four new calves were spotted, increasing the population to an estimated 72 rhinos.

Like all rhino species, the Javan rhino has a long gestation period, making repopulating challenging. Since no Javan rhinos are held in captivity, their gestation period isn’t precisely known. However, it’s believed to be roughly 15 to 16 months.

Facts

• Living in the shadow of a volcano: The remaining Javan rhino population survived after repopulating an area devastated by the eruption of the volcano Krakatau in 1883. However, the species today faces the threat of natural disasters as a nearby volcano named Anak Krakatau continues to erupt.
• A close scare in 2018: Anak Krakatau lies just 37 miles (60 km) from the coast of the Javan rhino’s single remaining habitat. In December 2018, the volcano erupted and unleashed a tsunami that killed at least 222 people across the Indonesian islands of Java and Sumatra. It’s believed no Javan rhinos were harmed, but the event demonstrates the risks that remain with all rhinos living in a habitat that’s susceptible to natural disasters.
• 145 million people and 72 Javan rhinos: One of the challenges to repopulating the Javan rhino is the loss of suitable habitats across Java. The island is only about the size of Arkansas (population: 3 million), but is home to about 145 million people. This growth in population has left few suitable habitats for large Javan rhino populations.