Javan rhino, Sunda rhinoceros, Lesser one-horned rhinoceros
The Javan rhinoceros (Rhinoceros sondaicus) is a very rare member of the family Rhinocerotidae and one of five extant rhinoceroses. Once the most widespread of Asian rhinoceroses, it is now critically endangered, with only one known population in the wild, and no individuals in captivity. It is possibly the rarest large mammal on Earth.
Javan rhinos are smaller than the Indian rhinoceros and are close in size to the Black rhinoceros. They have 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. 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. Javan rhinos do not appear to often use their horn for fighting but instead use it to scrape mud away in wallows, to pull down plants for eating, and to open paths through thick vegetation. Javan rhinos have a long, pointed, upper lip which helps in grabbing food. Their lower incisors are long and sharp; when Javan rhinos fight, they use these teeth. 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. Their 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 Javan rhinos are smaller than those of the Indian rhinoceros, but still, form a saddle shape over the shoulder.
Javan rhinos live only in the Ujung Kulon National Park in the very western part of Java. They inhabit dense, lowland rainforests, grasslands, and reed beds with abundant rivers, large floodplains, or wet areas with many mud wallows.
There are still big gaps in information about Javan rhinos, as they are very difficult to study, and very little is known regarding their social behavior. They are solitary animals, except for breeding pairs and mothers with young. Their range extends from 3 to 20 sq m, and various groups have ranges that overlap each other. Javan rhinos sometimes gather in groups at salt-licks and wallows, the latter allowing them to maintain a cool body temperature and helping to prevent parasite infection and disease. Javan rhinos generally do not dig mud wallows themselves, preferring to use those of other animals or naturally occurring pits, enlarging them with their horn. They are much less vocal compared to related species, and very few vocalizations from Javan rhinos have been recorded.
Javan rhinos are herbivores (folivores, frugivores). They mostly eat by browsing consuming leaves, twigs, young shoots, and fallen fruit.
Javan rhinos live in very dense jungles and they have never been bred in captivity, so very little information is to hand with regard to their mating system. Pairs form for mating, which might mean that Javan rhinos are polygynous. The mating season is roughly from July through to November. Gestation is for 16 months, and births occur every four to five years. A single rhinoceros is born at one time. A young rhino is active soon after birth. It will be nursed by its mother for up to one to two years. Females reach maturity when they are three to four years old, and males after six years.
The huge decline in Javan rhinoceros numbers has been mostly attributed to being hunted for its horn and other body parts to be used for traditional Chinese medicine. Habitat loss from logging and development has had a big impact on the species, and it has also suffered from disease and natural disasters, either of which could destroy an entire population.
According to the IUCN Red List resource, the total population size of the Javan rhino is 68 individuals. All of them live in Ujung Kulon National Park on the western tip of Java. Currently, this species is classified as Critically Endangered (CR) on the IUCN Red List and its numbers today are stable.
