Javan rhinoceros

Javan rhinoceros Temporal range: Early Pleistocene – Recent 1.5–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
R. s. sondaicus in the London Zoo from March 1874 until January 1885
Conservation status
Critically Endangered  (IUCN 3.1)[2]
CITES Appendix I (CITES)[2]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Perissodactyla
Family:	Rhinocerotidae
Genus:	Rhinoceros
Species:	R. sondaicus[1]
Binomial name
Rhinoceros sondaicus[1] Desmarest, 1822[3]
Subspecies
Rhinoceros sondaicus sondaicus Rhinoceros sondaicus annamiticus† Rhinoceros sondaicus inermis †
Javan rhinoceros range

The Javan rhinoceros (Rhinoceros sondaicus), Javan rhino, Sunda rhinoceros or lesser one-horned rhinoceros is a critically endangered member of the genus Rhinoceros, of the rhinoceros family, Rhinocerotidae, and one of the five remaining extant rhinoceros species across South Asia and Africa. The Javan rhinoceros is one of the smallest rhinoceros species, along with the Sumatran, or "hairy", rhinoceros. They are superficially similar to Indian rhinos, as they have plate-like, "armored" protective skin folds, but are slightly smaller in size, at just 3.1–3.2 m (10–10 ft) long and 1.4–1.7 m (4.6–5.6 ft) tall, on average. The heaviest specimens weigh around 2,300 kg/2.3 tonnes (2.54 short tons), similar to a black rhinoceros.^[4] However, unlike the long and potentially lethal horns of the black or white rhinoceroses of Africa, the Javan species' single, somewhat blunted horn (only present on males) is usually shorter than 25 cm (9.8 in).

Up until the mid-19th to about the early 20th century, the Javan rhinoceros had ranged beyond the islands of Java and Sumatra and onto the mainland of Southeast Asia and Indochina, northwest into East India, Bhutan, and the south of China. Today, it is the rarest of all rhinoceros, and among the rarest of all living animal species, with only one currently known wild population, and no individuals successfully kept in captivity. It is among the rarest large mammals on the planet Earth,^[5]: 21 with a population of approximately 74 rhinos within Ujung Kulon National Park, at the far western tip of Java, Indonesia.^[6] In 2023, the Indonesian authorities captured two gangs of poachers who confessed to killing 26 rhinos from 2019-2023 ^[7]. No census has been released since 2019. The Javan rhinoceros population in Vietnam's Cat Tien National Park was declared locally extinct in 2011.^[8]

The decline of the Javan rhinoceros is primarily attributed to poaching, for the males' horns, which—despite merely being composed of keratin—are highly valued in traditional Chinese medicine, fetching as much as US$30,000 per kg on the black market.^[5]: 31 As the presence of colonial Dutch and other Europeans in its range increased, peaking in the 1700-1800s, trophy hunting also became a serious threat. Loss of habitat and massive human population growth (especially post-wartimes, such as the Vietnam War) have also contributed to its decline and hindered the species' recovery.^[9] The remaining range is within one nationally-protected area, and Ujung Kulon is also a UNESCO World Heritage Site. Nonetheless, rural, potentially rugged park boundaries mean that law enforcement cannot be equally present in all places at all times; in some areas, this lack of security still places the species at risk from poachers, disease exposure and, ultimately, loss of genetic diversity—leading to genetic "bottlenecking" (i.e., inbreeding depression).^[10]

The Javan rhinoceros can live around 30–45 years in the wild. It historically inhabited dense lowland rainforest, wet grasslands, and vast floodplains at forest-edges. It is mostly solitary, except for courtship and rearing offspring, though groups may occasionally congregate near wallows and salt licks. Aside from humans, whom they usually avoid, adult rhinos have no natural predators in their range. Very small juveniles may be preyed upon, if left unsupervised, typically by leopards, Sumatran tigers or, rarely, crocodiles. Scientists and conservationists rarely study the animals directly due to their extreme rarity and the danger of interfering with such an endangered species. Researchers instead rely on camera traps and fecal samples to gauge health and behavior. Consequently, Javan rhinos are the least-studied of all rhinoceros species. Two adult female Javan rhinoceroses, each with a calf, were filmed using a motion-triggered trail camera, the video being released on 28 February 2011 by WWF and Indonesia's National Park Authority, proving they are still breeding in the wild.^[11] In April 2012, the National Parks Authority released further trailcam videos showing 35 individuals, including mother-offspring pairs and courting adults.^[12]