The Javan rhinoceros ( Rhinoceros sondaicus ), also known as the lesser one-horned rhinoceros or Sunda rhinoceros, is a critically endangered member of the rhinoceros family Rhinocerotidae. It is one of the five remaining extant rhinoceros species found in South Asia and Africa. This article explores the Javan rhinoceros's diet, habitat, and the conservation efforts aimed at protecting this rare species.
Physical Characteristics
The Javan rhinoceros is among the smallest of the rhino species. They can reach a height of 1.4-1.7 m (4 ft 7 in - 5 ft 7 in) at the shoulder and a body length of 2 to 4 m (6.6 to 13.1 ft), including the head. Adults typically weigh between 900 and 2,300 kg (2,000 and 5,100 lb). No substantial size difference is seen between genders, but cows may be slightly bigger. They possess a single horn, usually less than 20 cm (7.9 in) long, with the longest recorded at only 27 cm (11 in). Only bulls have horns; cows 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 rhino's skin is hairless, splotchy gray or gray-brown, and 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 Javan rhinos are smaller than those of the Indian rhinoceros but still form a saddle shape over the shoulder.
Like other browsing rhino species, Javan rhinos have a long, pointed upper lip, which assists in grabbing food. Their lower incisors are long and sharp and are used when they fight. Behind the incisors, two rows of six low-crowned molars are used for chewing coarse plants. Like all rhinos, Javan rhinos smell and hear well but have very poor vision.
Historical and Current Habitat
Historically, the Javan rhinoceros ranged throughout Southeast Asia, from near Calcutta in India, throughout Bangladesh, southern China, Laos, Vietnam, Cambodia, Myanmar, Thailand, Peninsular Malaysia, the large island of Sumatra, and the western half of Java. The species is found in the oriental region of the world. However, the Javan rhino's range has been shrinking for at least 3,000 years. The northern range of the rhinoceros extended into China around 1000 BC 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 and was hunted to extinction on the Malay Peninsula by 1932. The last ones on Sumatra died out during World War II. By the end of the Vietnam War, the Vietnamese rhinoceros was believed extinct across all of mainland Asia.
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Today, the Javan rhino exists in a single population in Ujung Kulon National Park (UKNP) on the westernmost tip of Java, Indonesia. This national park measures only about 498 square kilometers (192 sq. miles).
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. They used to live in a variety of tropical landscapes, both lowland and highland, from the mangroves of the Sunderbans in India and Bangladesh and the mountains of southern China to the sub-montane shrubs on the highest volcanoes of Java.
Diet and Feeding Habits
The Javan rhinoceros is an herbivore, but does not eat grasses. This rhino may resort to extreme methods to access food and may knock down saplings to reach its food and grabs it with its prehensile upper lip. The Javan rhino's diet is characterized by high species diversity. Biologists have documented over 300 different species they consume. Hundreds of food plant species have been recorded, but about 40% of the quantity of food eaten comes from a few preferred and common plant species. The rhinos eat mostly leaves, young shoots, and twigs. Most of the plants eaten by rhinos grow in unshaded locations, in vegetation without tall trees, gaps created by fallen trees, and shrubland without trees.
The Javan rhino 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. They consume large amounts of vegetation, ensuring the forest remains healthy, fostering more biodiversity, and aiding in carbon sequestration.
Behavior and Social Structure
The Javan rhinoceros is generally solitary, except for breeding pairs and mothers with calves. Cows will stay with the calf for up to two years post-partum. They sometimes congregate in small groups at salt licks and mud wallows. Calves leave the mother shortly after walking is achieved, which is 1-2 hours after birth. Researcher Yahya found no difference in wallowing behavior between the sexes. 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.
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In Ujung Kulon National Park, individuals move 0.4-3.8 km per day. Bull home ranges are larger at 12-20 km2 (4.6-7.7 sq mi) compared to the cow, which are around 3-14 km2 (1.2-5.4 sq mi). Bull territories overlap each other less than those of the cow. Bulls 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. The Javan rhino does not defend a specific territory.
The Javan rhino is much less vocal than the Sumatran; very few Javan rhino vocalizations have ever been recorded. The rhino does not have strong visual perception. Typical gestures include moving their ears. Vocalizations include a "shriek," "lip vibrations" and a "snort".
Threats and Conservation Status
The IUCN Redlist placed the Javan rhino as critically endangered in 2008. The main factor in the continued decline of the Javan rhinoceros population has been poaching for horns, a problem that affects all rhino species. The horns have been a traded commodity for more than 2,000 years in China, where they are believed to have healing properties. Of Asian rhino species, horns are worth up to 10 times their African counterparts and are used for medical purposes in Chinese remedies as a fever reducer. The horn is composed of non-medicinal substances from the high concentration of calcium. Loss of habitat because of agriculture has also contributed to its decline, though this is no longer as significant a factor because the rhinoceros only lives in one nationally protected park. Deteriorating habitats have hindered the recovery of rhino populations that fell victim to poaching.
The biggest threat to the Javan rhino is the very small size of the remaining population and a lack of suitable habitat to support their expansion. This leads to inbreeding and loss of genetic variability and vitality. Beyond poaching, habitat destruction and loss for agriculture and development are further threats to the rhino population.
The Javan rhino is listed under Appendix I of CITES, meaning commercial international trade is generally not allowed. The Endangered Species Act was passed, and the Javan rhino is endangered under the list of Endangered Foreign Species.
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Even with all the conservation efforts, the prospects for their survival are grim. Because the population is restricted to one small area, they are very susceptible to disease and inbreeding depression.
Conservation Efforts
The International Rhino Foundation, in conjunction with the staff of Ujung Kulon National Park, is committed to safeguarding the remaining members of this critically endangered species. Success is gradual; Javan rhinos are primarily solitary creatures, and females only reproduce every 2-3 years. However, a recent birth has increased their population to 75 individuals.
Park authorities in Ujung Kulon have stepped up their monitoring systems and now have camera traps covering the entire park. Additionally, the removal of the invasive Arenga palm from the area helps promote better food availability for Javan rhinos.
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