The saola (Pseudoryx nghetinhensis) is one of the world's rarest mammals and is found only in the forested Annamite Mountains along the border of Laos and Vietnam. It was first documented by scientists in 1992, making it one of the most recent discoveries among large terrestrial mammals. The saola is the only species in its genus, representing a unique evolutionary branch within the cattle family.
Adult saolas weigh about 80 to 100 kilograms and have a short, dark brown coat with distinctive white facial markings. Both males and females possess two long, nearly parallel horns that can reach 35 to 50 centimeters in length. They are believed to inhabit dense evergreen or mixed forests at mid-elevations, feeding primarily on leaves and other vegetation. Observations indicate that saolas are solitary or occur in small groups and are highly secretive, seldom approaching human settlements.
The species is listed as critically endangered by the International Union for Conservation of Nature (IUCN). Fewer than 100 individuals are thought to remain, and the actual number may be much lower. Major threats include hunting, especially through the widespread use of wire snares, and habitat loss due to deforestation, and infrastructure development.
Because saolas live at very low densities and avoid humans, population surveys are difficult, and most of the available information comes from camera-trap photographs and reports from local communities. Saolas are so elusive that very few scientists have ever seen one alive in the wild, underscoring how difficult they are to study. The most recent confirmed record was a camera-trap image from 2013 in Vietnam.
Conservation efforts are coordinated by organizations including the Saola Working Group and the Saola Foundation. Key actions include removing snares, improving law enforcement, protecting remaining forest habitats, and exploring the possibility of a carefully managed captive population in the future. No saola has been kept long-term in captivity, and all known captive individuals have died quickly, which is one reason proposals for a captive population are cautious. These measures also support other highly restricted species in the same region, such as the large-antlered muntjac (a small deer known for its dog-like bark) and the Annamite striped rabbit.
The saola's situation resembles that of other critically endangered species with extremely small and hard-to-detect populations, such as the vaquita (a species of small porpoise) in the Gulf of California and the northern white rhinoceros in Africa, each facing the risk of extinction even as conservationists continue efforts to preserve them. It is important to save the saola because it represents a unique, irreplaceable branch of life and exists only in a small part of the Annamite Mountains, so if it disappears, an entire distinct evolutionary lineage would be lost forever. Because it is likely among the most endangered of large terrestrial mammals, its survival is a test of whether we can prevent the loss of other such species on the brink of extinction.