The Sunda clouded leopard (Neofelis diardi) is a medium-sized wild cat that lives in Borneo and Sumatra. It is listed as Vulnerable on the IUCN Red List since 2015 because there are likely fewer than 10,000 adult individuals, and their numbers are decreasing. On both islands, the cats face threats from deforestation, which causes them to lose their homes. Scientists classified it as a separate species in 2006, after a study showed it is different from the clouded leopard found in mainland Southeast Asia. The Sunda clouded leopard has darker fur with smaller cloud-like patterns. It is also called the Sundaland clouded leopard, Enkuli clouded leopard, Diard's clouded leopard, and Diard's cat.

Characteristics

The Sunda clouded leopard has a body color that is grayish yellow or gray. It has two lines running down its back and small, irregular cloud-shaped patterns on its shoulders. These cloud markings often have spots inside them and form two or more rows that line up vertically from the back to the sides. It can purr because its hyoid bone is hard and does not move. Its eyes change shape to narrow vertical slits.

The leopard has a strong, sturdy body and weighs about 12 to 26 kilograms (26 to 57 pounds). Its canine teeth are 2 inches (5.1 centimeters) long, which are longer than the canine teeth of any other living cat when compared to the length of its skull. Its tail can grow as long as its body, which helps with balance.

Distribution and habitat

The Sunda clouded leopard lives only on the islands of Borneo and Sumatra. In Borneo, it is found in lowland rainforests and in smaller numbers in forests that were cut down, but only below 1,500 meters (4,900 feet). In Sumatra, it is more common in hilly and mountainous areas. It is not known if it still lives on the Batu Islands near Sumatra.

Between March and August 2005, researchers found clouded leopard tracks in the Tabin Wildlife Reserve in Sabah. In a 56-kilometer (22 square mile) area, scientists estimated there were five leopards based on tracks from four confirmed animals. The density was estimated at eight to 17 leopards per 100 kilometers (39 square miles). The total population in Sabah is estimated to be between 1,500 and 3,200 leopards. Of these, about 275 to 585 live in protected reserves large enough to support a long-term population of more than 50 individuals. Outside protected areas in Sabah, the density is likely much lower, with about one leopard per 100 kilometers (39 square miles).

In Sumatra, the Sunda clouded leopard has been found in Kerinci Seblat, Gunung Leuser, and Bukit Barisan Selatan National Parks. It probably lives in smaller numbers there compared to Borneo. One possible reason for the lower density of about 1.29 leopards per 100 kilometers (39 square miles) is that on Sumatra, it shares its habitat with the Sumatran tiger, while on Borneo, it is the largest carnivore.

Fossils of clouded leopards were found on Java, where the species may have gone extinct during the Holocene period.

Ecology and behaviour

The habits of the Sunda clouded leopard are not well understood because the animal is shy and elusive. It is believed to live alone most of the time. The leopard hunts mostly on the ground and uses its ability to climb trees to stay safe from threats.

The diet of Sunda clouded leopards is not fully understood, but studies show they eat sambar deer, muntjacs, Bornean bearded pigs, mouse deer, porcupines, and primates.

Taxonomy and evolution

In 1823, Georges Cuvier gave the scientific name Felis diardi to honor Pierre-Médard Diard, who sent a skin and a drawing from Java to the National Museum of Natural History in France. Later, in 1917, Reginald Innes Pocock classified Felis diardi as a subspecies of the clouded leopard.

Studies of hair samples from mainland and Sunda clouded leopards showed differences in mitochondrial DNA, nuclear DNA, and other genetic markers. These differences suggest the two groups separated between 2 and 0.9 million years ago. Their most recent shared ancestor likely crossed a now-submerged land bridge to reach Borneo and Sumatra. A study of fur patterns in 57 clouded leopards from across their range found that the two groups differ mainly in the size of their cloud-like markings. Because of this, the genus Neofelis was reclassified into two species: N. nebulosa on the mainland and N. diardi in Sumatra and Borneo.

Analysis of genetic material, skull and jaw features, and teeth shows that the Sunda clouded leopard has two distinct subspecies with separate evolutionary histories:
– Bornean clouded leopard (N. d. borneensis)
– Sumatran clouded leopard (N. d. diardi)

Both populations are believed to have split during the Middle to Late Pleistocene. This event likely coincided with the massive eruption of the Toba Volcano in Sumatra 69,000–77,000 years ago. One possible explanation is that clouded leopards from Borneo moved to Sumatra during periods of low sea levels in the Pleistocene, but rising sea levels later separated them from their original group.

Threats

Sunda clouded leopards are tree-dwelling animals that live only in forests. They are in danger because forests are being destroyed in Indonesia and Malaysia.

Since the 1970s, many forests in southern Sumatra, especially lowland tropical evergreen forests, have been cleared. Forests are broken into smaller pieces, and farms are built near wildlife areas, making animals more at risk from humans. Borneo has one of the fastest rates of forest loss. In the mid-1980s, forests covered almost three-fourths of Borneo, but by 2005, only about half of the island remained forested. Forests and land are being used for human homes. Illegal trade of wildlife is common in many areas.

The number of Sunda clouded leopards in Sumatra and Borneo has likely decreased because of forest loss, changes to forest land, illegal logging, people moving into forest areas, and possibly hunting. In Borneo, forest fires are an extra danger, especially in Kaltimantan and Sebangau National Park.

There are reports of people illegally hunting Sunda clouded leopards in Brunei’s Belait District. Locals are selling their fur for high prices.

In Indonesia, Sunda clouded leopards are threatened by illegal hunting and trade. Between 2011 and 2019, authorities found parts of 32 leopards, including 17 live animals, six skins, several teeth, and claws. One live leopard found in Jakarta was ordered by a buyer from Kuwait.

Conservation

Neofelis diardi is protected under CITES Appendix I and is completely protected in Sumatra, Kalimantan, Sabah, Sarawak, and Brunei. Sunda clouded leopards live in most protected areas along the mountain range in Sumatra and in most protected areas on Borneo.

Since November 2006, the Bornean Wild Cat and Clouded Leopard Project, located in the Danum Valley Conservation Area and the Tabin Wildlife Reserve, studies the behavior and habitat of five species of Bornean wild cat—bay cat, flat-headed cat, marbled cat, leopard cat, and Sunda clouded leopard—and their prey, with a focus on the clouded leopard. The project also investigates how changes to habitats affect these animals, raises awareness about the need to protect Bornean wild cats using the clouded leopard as a key example, and examines threats to these cats from hunting and trade in Sabah.

The Sunda clouded leopard is a main focus of the Conservation of Carnivores in Sabah project, which began in northeastern Borneo in July 2008. The project team studies how different types of forest use affect the number and density of wild cats in three forest reserves. They plan to evaluate the conservation needs of these cats and create specific conservation plans with other researchers and local groups.

Names

The scientific name of the genus Neofelis is a combination of the Greek word "neo-" meaning "new, fresh, strange," and the Latin word "feles" meaning "cat," so it literally means "new cat."

The Indonesian name for the clouded leopard, "rimau-dahan," means "tree tiger" or "tiger that lives in branches." In Sarawak, it is known as "entulu."