Once the most widespread of Asian rhinoceroses, the Javan rhinoceros ranged from the islands of Java and Sumatra, throughout Southeast Asia, and into India and China. The species is critically endangered, with only one known population in the wild, and no individuals in captivity. It is possibly the rarest large mammal on earth, with a population of as few as 58 to 61 in Ujung Kulon National Park at the western tip of Java in Indonesia. A second population in Cat Tien National Park in Vietnam was confirmed as extinct in 2011. The decline of the Javan rhinoceros is attributed to poaching, primarily for their horns, which are highly valued in traditional Chinese medicine, fetching as much as US$30,000 per kg on the black market. As European presence in their range increased, trophy hunting also became a serious threat. Loss of habitat, especially as the result of wars, such as the Vietnam War, in Southeast Asia, has also contributed to the species' decline and hindered recovery. The remaining range is within one nationally protected area, but the rhinos are still at risk from poachers, disease, and loss of genetic diversity leading to inbreeding depression.
The Javan rhino can live around 30–45 years in the wild. It historically inhabited lowland rain forest, wet grasslands, and large floodplains. It is mostly solitary, except for courtship and offspring-rearing, though groups may occasionally congregate near wallows and salt licks. Aside from humans, adults have no predators in their range. The Javan rhino usually avoids humans, but will attack when it feels threatened. Scientists and conservationists rarely study the animals directly due to their extreme rarity and the danger of interfering with such an endangered species. Researchers rely on camera trapsand fecal samples to gauge health and behavior. Consequently, the Javan rhino is the least studied of all rhino species. Two adult rhinos with their calves were filmed in a motion-triggered video released on February 28, 2011, by WWF and Indonesia's National Park Authority, which proved it is still breeding in the wild. In April 2012, the National Parks Authority released video showing 35 individual Javan rhinos, including mother/offspring pairs and courting adults.
The Javan rhino is smaller than the Indian rhinoceros, and is close in size to the black rhinoceros. It is the largest animal in Java and the second-largest animal in Indonesia after the Asian elephant. The body length of the Javan rhino (including its head) can be up to 2 to 4 m (6.6 to 13.1 ft), and it can reach a height of 1.4–1.7 m (4.6–5.6 ft). Adults are variously reported to weigh between 900 and 2,300 kg (2,000 and 5,100 lb), although a study to collect accurate measurements of the animals has never been conducted and is not a priority because of their extreme conservation status. No substantial size difference is seen between genders, but females may be slightly bigger. The rhinos in Vietnam appeared to be significantly smaller than those in Java, based on studies of photographic evidence and measurements of their footprints.
Like the Indian rhino, the Javan rhinoceros has a single horn (the other extant species have two horns). Its horn is the smallest of all extant rhinos, usually less than 20 cm (7.9 in) with the longest recorded only 27 cm (11 in). Only males have horns. Female Javan rhinos are the only extant rhinos that remain hornless into adulthood, though they may develop a tiny bump of an inch or two in height. The Javan rhinoceros does not appear to often use its horn for fighting, but instead uses it to scrape mud away in wallows, to pull down plants for eating, and to open paths through thick vegetation. Similar to the other browsing species of rhino (the black, Sumatran, and Indian), the Javan rhino has long, pointed, upper lips which help in grabbing food. Its lower incisors are long and sharp; when the Javan rhino fights, it uses these teeth. Behind the incisors, two rows of six low-crowned molars are used for chewing coarse plants. Like all rhinos, the Javan rhino smells and hears well, but has very poor vision. They are estimated to live for 30 to 45 years.
Its hairless, splotchy gray or gray-brown skin falls in folds to the shoulder, back and rump. The skin has a natural mosaic pattern, which lends the rhino an armored appearance. The neck folds of the Javan rhinoceros are smaller than those of the Indian rhinoceros, but still form a saddle shape over the shoulder. Because of the risks of interfering with such an endangered species, however, the Javan rhinoceros is primarily studied through fecal sampling and camera traps. They are rarely encountered, observed or measured directly.
Distribution and Habitat Edit
Even the most optimistic estimate suggests fewer than 100 Javan rhinos remain in the wild. They are considered one of the most endangered species in the world. The Javan rhinoceros is known to survive in only one place, the Ujung Kulon National Park on the western tip of Java. The animal was once widespread from Assam and Bengal (where their range would have overlapped with both the Sumatran and Indian rhinos)eastward to Myanmar, Thailand, Cambodia, Laos, Vietnam, and southwards to the Malay Peninsula and the islands of Sumatra, Java, and possibly Borneo. The Javan rhino primarily inhabits dense, lowland rain forests, grasslands, and reed beds with abundant rivers, large floodplains, or wet areas with many mud wallows. Although it historically preferred low-lying areas, the subspecies in Vietnam was pushed onto much higher ground (up to 2,000 m or 6,561 ft), probably because of human encroachment and poaching.
The range of the Javan rhinoceros has been shrinking for at least 3,000 years. Starting around 1000 BC, the northern range of the rhinoceros extended into China, but began moving southward at roughly 0.5 km (0.31 mi) per year, as human settlements increased in the region. It likely became locally extinct in India in the first decade of the 20th century. The Javan rhino was hunted to extinction on the Malay Peninsula by 1932. The last ones on Sumatra died out during World War II. They were extinct from Chittagong and the Sunderbans by the middle of the 20th century. By the end of the Vietnam War, the Vietnamese rhinoceros was believed extinct across all of mainland Asia. Local hunters and woodcutters in Cambodia claim to have seen Javan rhinos in the Cardamom Mountains, but surveys of the area have failed to find any evidence of them. In the late 1980s, a small population was found in the Cat Tien area of Vietnam. However, the last individual of that population was shot in 2010. A population may have existed on the island of Borneo, as well, though these specimens could have been the Sumatran rhinoceros, a small population of which still lives there.
The Javan rhinoceros is a solitary animal with the exception of breeding pairs and mothers with calves. They sometimes congregate in small groups at salt licks and mud wallows. Wallowing in mud is a common behavior for all rhinos; the activity allows them to maintain cool body temperatures and helps prevent disease and parasite infestation. The Javan rhinoceros does not generally dig its own mud wallows, preferring to use other animals' wallows or naturally occurring pits, which it will use its horn to enlarge. Salt licks are also very important because of the essential nutrients the rhino receives from the salt. Male home ranges are larger at 12–20 km (7.5–12.4 mi)²) compared to the female, which are around 3–14 km (1.9–8.7 mi)²). Male territories overlap each other less than those of the female. It is not known if there are territorial fights.
Males mark their territories with dung piles and by urine spraying. Scrapes made by the feet in the ground and twisted saplings also seem to be used for communication. Members of other rhino species have a peculiar habit of defecating in massive rhino dung piles and then scraping their back feet in the dung. The Sumatran and Javan rhinos, while defecating in piles, do not engage in the scraping. This adaptation in behavior is thought to be ecological; in the wet forests of Java and Sumatra, the method may not be useful for spreading odors.
The Javan rhino is much less vocal than the Sumatran; very few Javan rhino vocalizations have ever been recorded. Adults have no known predators other than humans. The species, particularly in Vietnam, is skittish and retreats into dense forests whenever humans are near. Though a valuable trait from a survival standpoint, it has made the rhinos difficult to study. Nevertheless, when humans approach too closely, the Javan rhino becomes aggressive and will attack, stabbing with the incisors of its lower jaw while thrusting upward with its head. Its comparatively antisocial behavior may be a recent adaptation to population stresses; historical evidence suggests they, like other rhinos, were once more gregarious.
The Javan rhinoceros is herbivorous, eating diverse plant species, especially their shoots, twigs, young foliage and fallen fruit. Most of the plants favored by the species grow in sunny areas in forest clearings, shrubland and other vegetation types with no large trees. The rhino knocks down saplings to reach its food and grabs it with its prehensile upper lip. It is the most adaptable feeder of all the rhino species. Currently, it is a pure browser, but probably once both browsed and grazed in its historical range. The rhino eats an estimated 50 kg (110 lb) of food daily. Like the Sumatran rhino, it needs salt in its diet. The salt licks common in its historical range do not exist in Ujung Kulon, but the rhinos there have been observed drinking seawater, likely for the same nutritional need