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An Ultimate Ungulate Fact Sheet
Pseudoryx nghetinhensis
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Pseudoryx nghetinhensis [Dung, Giao, Chinh, Tuoc, Arctander and MacKinnon, 1993].
Citation: Nature, 363: 443.
Type locality: Vu Quang Nature Reserve, Vietnam 18o15' N by 105o25'E.

The saola is one of the most recently discovered large mammals, and its formal description elicited an incredible flurry of scientific interest due to its highly distinctive physical traits. In fact, the saola is so distinctive that its discovery required the creation of a new genus (Pseudoryx). Initial attempts at classifying Pseudoryx within the ungulates were all over the map: based on morphological characters, various authors allied the saola with the subfamily Bovinae (including it in each of the three tribes: Boselaphini (nilgai and chousingha), Bovini (cattle and buffalo), and Tragelaphini (spiral-horned antelope)) or with the subfamily Caprinae (specifically the Rupicaprini, closest to serows and gorals) (Schaller and Rabinowitz, 1995). Genetic analysis (based on mitochondrial DNA and rRNA genes) by Hassanin and Douzery (1999) has shown that Pseudoryx is strongly nested within the subfamily Bovinae. While these authors suggest that the saola should be placed within the tribe Bovini, the current consensus is to place Pseudoryx in its own tribe - Pseudorygini (Hernandez-Fernandez and Vrba, 2005).

Physical Characteristics

Few measurements have been made from live saolas. Weight is approximately 100 kg, body length around 150 cm, and shoulder height between 80 and 90 cm. There does not appear to be any noticeable sexual dimorphism (Schaller and Rabinowitz, 1995).

Reported measurements for saola (Pseudoryx nghetinhensis)
Source Adult Weight Head & Body Length Shoulder Height Tail Length
Dung et al., 1993 est. 100 kg ~150 cm ~80-90 cm 13 cm + tassel
Robichaud, 1998 est. 85 kg
150 cm
84 cm
23 cm

The general color of the saola is a deep chestnut brown, with individuals varying from a rich reddish brown to almost black (Dung et al., 1993; Schaller and Rabinowitz, 1995). The hair on the upper parts is short (1.5-2.5 cm long), fine, and glossy - the head and neck have especially short hairs (Dung et al., 1993; Robichaud, 1998). Considering the cool, damp weather in at least part of its range, the coat of the saola is surprisingly soft and thin (Robichaud, 1998). The underparts are also brown, but are paler than the upper body, and are covered in fluffy, almost wooly hairs about 3.5 cm in length (Dung et al., 1993; Robichaud, 1998). The anal area and inner flanks (including the scrotal skin of males) is white (Dung et al., 1993). The same pale coloration of the underparts is seen on the neck (beginning from the shoulders), and this appears as a conspicuous patch when seen from the side (Robichaud, 1998). There is no dorsal crest, but a thin (0.5 cm wide) black stripe runs along the spine from between the shoulders to the top of the tail, where it fades out (Dung et al., 1993; Robichaud, 1998). A white horizontal stripe runs across the rump, and is matched by a white band across the tail which merges with the stripe when in a relaxed position (Dung et al., 1993; Robichaud, 1998). This stripe splits the tail into three bands of color - brown at the base, white in the middle, and black towards the fluffy terminal tassel (Dung et al., 1993; Robichaud, 1998). The legs are darker than the main body, accented by two white spots above the hooves which are separated by a fine band of black (Dung et al., 1993; Schaller and Rabinowitz, 1995).

The form of the saola is similar to that of other forest-dwelling ungulates such as duikers (Cephalophinae), with a compact body and hunched back adapted for moving through dense cover (Schaller and Rabinowitz, 1995). The hunched posture causes the shoulders to sit low in comparison to the arch of the spine - an adult female examined by Robichaud (1998) had a shoulder height of 84 cm but a height of 96 cm at the tallest part of the back. The skin is 1-2 mm thick over most of the body, but thickens significantly (to around 5 mm thick) on the nape of the neck and shoulders (Schaller and Rabinowitz, 1995). Schaller and Rabinowitz suggest this thick skin may act as a shield to protect saola from being punctured by a rival's horn during intraspecific conflict (Schaller and Rabinowitz, 1995). There are no known glands on the legs (Robichaud, 1998). The dark grey hooves are approximately 6 cm in length and have rounded tips, resembling those of the lowland anoa (Bubalus depressicornis) (Schaller and Rabinowitz, 1995). The dew claws are vestigial calluses (Dung et al., 1993). Females have four nipples (Robichaud, 1998).

The head is described as "delicately shaped" by Schaller and Rabinowitz (1995), with a narrow muzzle and distinctly arched nasal bones which give the appearance of an almost bulging face (see also Dung et al., 1993). The ears are relatively small (each being about 10 cm long); they are brown behind, whitish inside, and are covered with short hair except for a long tuft on the inner surface (Dung et al., 1993). The eyes have dark brown irises and round pupils, and in a flashlight beam they reflect a glowing orange (Robichaud, 1998). The rhinarium (naked flesh of the nose) is dark brown, and the tongue is unusually long - it can extend up to 16 cm to reach the eyes and upper face (Robichaud, 1998). The lips are white, as is the underside of the chin and upper throat (Robichaud, 1998). On the underside of the muzzle is a cluster of whiskers about 2 cm long (Robichaud, 1998). The faces of both males and females are distinctly marked with white to buff patches, the most distinctive of which is a long, thin stripe above each eye (forming an "eyebrow") (Dung et al., 1993). A variable pattern of spots and slashes runs from beneath the eye to under the jaw, while a single white spot may be present on the cheek (Dung et al., 1993). On close examination, Robichaud (1998) found each white cheek mark to conceal dermal nodules 1 to 2 mm high, which were found nowhere else on the face; black whiskers 2.0-2.5 cm long protrude from most of these nodules, and the presence of a single pore at their apex may indicate a secretory function.

The maxillary glands, located just in front of the eye, are extremely well-developed (Dung et al., 1993; Dung et al., 1994) - indeed, Robichaud (1998) suggests that the saola may have the largest maxillary-preorbital gland of any extant mammalian species. Robichaud (1998) provides a detailed description of the maxillary gland and its secretion: the fleshy external part of the gland comprises a rectangular, shallow depression along the upper muzzle measuring approximately 9 cm long by 3.5 cm wide by 1.5 cm deep. The gland secretes a thick, grayish-green paste with a foul, pungent odor reminiscent of the musk of mustelids. This depression is covered by a muscular flap (0.8 cm thick) which can be raised like an awning to expose the gland. This unusual flap of skin has been misinterpreted in popular media, and the saola is sometimes referred to as an antelope with "gills".

Many detailed descriptions of the horns of the saola exist: they are the most frequently encountered evidence of this species. In adults, the two horns are long, slender, and nearly straight, with a slight curve backwards (Dung et al., 1993; Schaller and Rabinowitz, 1995). The horns are swept backwards following the profile of the face, and rest on the back when the head is tilted upwards (Dung et al., 1994). They range from nearly parallel to moderately diverging - villagers have even reported one individual with crossed horn tips - but there does not appear to be a significant difference in divergence between males and females as initially reported by Dung et al. (1993 - Schaller and Rabinowitz, 1995). In cross-section the horns are round to oval, and there is no keel on either the horn cores or the outer sheaths (Dung et al., 1993; Schaller and Rabinowitz, 1995; Robichaud, 1998). For the majority of their length the horns are smooth, although corrugations are often found within a few centimeters of the base (7 cm according to Dung et al., 1993; 2-4 cm from Schaller and Rabinowitz, 1995). The lateral and medial surfaces of horns of many individuals are rough and pitted, and it has been suggested that the smoothness of the horn sheath is the result of animals sharpening their horns by rubbing them against small trees (Dung et al., 1994; Robichaud, 1998). The horn cores extend close to the horn tips (over 80% of the horn length in both specimens measured by Schaller and Rabinowitz, 1995), and suggest that they serve a real fighting purpose, possibly as defence against predators (Dung et al., 1993; Dung et al., 1994).

The horns of most adults of both sexes are 35-50 cm long, with the longest reported set having a maximum length of 52 cm (Schaller and Rabinowitz, 1995). In Laos, eight sets of adult horns examined by Schaller and Rabinowitz (1995) had a length of 36.2-50.4 cm, averaging 44.2 cm. Eighteen sets of horns measured by Dung et al. (1993) varied in length from 32-52 cm, with an average of 41 cm. Due to the difference in horn divergence among individuals, the width between the horn tips shows considerable variation. Dung et al. (1993) reported horn tip distances of 7.5-20 cm, with an average of 13.3 cm (n=17), while skulls examined by Schaller and Rabinowitz (1995) measured between 3.5 and 18.4 cm between the horn tips (average 9.6 cm, n=7). The living female observed by Robichaud (1998) did not follow this trend - the distance between the tips of her horns was 25 cm. The basal circumference shows much less variation among individuals, ranging from 10.8 to 13.0 cm (average 11.7 cm, n=8) (Schaller and Rabinowitz, 1995).

Reproduction and Development

Given its recent discovery, the remoteness of its range, and a minimal number of scientific observations, a surprising amount of information on the reproductive cycle of P. nghetinhensis has been gathered and inferred. Most of the data is from a single pregnant female observed in life by Robichaud (1998, in central Laos) that was found to be carrying a male fetus upon her death in January 1996. Based on the size of the fetus (38 cm from nose to rump along the contour of the spine) and weight (800-1,000 grams), the pregnancy was estimated to be in its second trimester. By inferring a 33 week gestation length from similarly-sized spiral-horned antelope (the nyala Tragelaphus angasii and sitatunga Tragelaphus spekii), Robichaud (1998) estimated that the fetus would have been conceived between late August and mid-November (the mid-rainy to early dry season in Laos). Likewise, the birth would be expected to occur between mid-April and late June (the late dry season to mid wet season), an estimate which is supported by observations made by Schaller and Rabinowitz (1995). The timing of wet and dry seasons is different in Vietnam, and thus the seasonality of the saola's reproductive seasons may be different there. Based on horn length variation among animals within the same cohort, Schaller and Rabinowitz (1995) suggested that the birthing season spreads over 2 to 3 months. All of the data collected to date suggests that the saola is a seasonal breeder, with births timed to coincide with the onset of the monsoon (Robichaud, 1998). No estimate of life expectancy is available, but the adult female examined by Robichaud (1998) was estimated to be between 8 or 9 years old.


Pseudoryx nghetinhensis inhabits forested habitats in the Annamite mountains without a pronounced dry season (i.e., some rain falls in nearly every month) (Robichaud and Timmins, 2004). Most saola records are from climatically wet broadleaf evergreen forests at mid-elevation (generally at 400-800 m above sea level, sometimes up to 200 m above or below this), often dominated by the dipterocarp Hopea mollissima (Dung et al., 1993; Robichaud and Timmins, 2004). Forest blocks smaller than 25 square kilometers are not used (Timmins et al., 2008). At higher elevations, the forests are dominated by conifers - notably Fokenia hodgsoni - but, while the mountains peak at 2,200 m above sea level, there is no evidence that this species is found above 1,200 m (Dung et al., 1993; Timmins et al., 2008).

Dung et al. (1993) report that the saola uses all forest levels in differing seasons, even entering secondary lowland forests along large rivers with an altitude of only 200 m (see also Schaller and Rabinowitz, 1995). These authors suggest that these seasonal movements are dependent on water, with the saola inhabiting higher elevation during the summer months when highland streams have plenty of water, and retreating to lower elevations in the winter when the same streams dry up. Most hunted specimens have been taken in winter, when saola are in more accessible lowland terrain (Dung et al., 1994). Even so, most sightings made by locals occur in steep - but not precipitous - hills, usually in forest with a closed canopy of evergreen broad-leaved trees and an understory with saplings, bamboo, and palms (Schaller and Rabinowitz, 1995). Pseudoryx is reportedly very shy, and never enters agricultural lands (Dung et al., 1994).

Pseudoryx is surprisingly tame in the presence of humans - an observation made from captive individuals as well as local reports (Robichaud, 1998). Predators of the saola potentially include leopard (Panthera pardus) and tiger (Panthera tigris), while the defensive stance (described below) is similar to that used by other ungulates in the region when preyed upon by dhole (Cuon alpinus) (Dung et al., 1994; Schaller and Rabinowitz, 1995).

Villagers' reports suggest P. nghetinhensis feeds on the leaves of fig trees and other riverside bushes; the relatively short incisors suggest a browsing diet, supporting this theory (Dung et al., 1994). Local reports suggest that the saola is quite fond of the medicinal herb Homalomena aromatica (Araceae) (Dung et al., 1994). The saola is a rather delicate feeder - the captive female observed by Robichaud (1998) rarely jerked or pulled on vegetation while feeding, but rather chewed the petioles to separate the leaves from the stem before chewing the leaves themselves. This saola only occasionally pulled leaves into mouth using her tongue (surprising, given its length and mobility). This captive individual was fed Homalomena sp. (Araceae - later identified as the related species Schismatoglottis cochinchinensis (Araceae)), Asplenium sp. (Aspleniaceae), and an unidentified broad-leaved plant of the family Sterculiaceae, all of which are reported to be part of the diet in the wild (Robichaud, 1998; Robichaud, 1999).

Fecal deposits are composed of boluses (around eight deposited per episode), each measuring about 7.5 cm long by 4.5-6.0 cm in diameter. Each bolus is formed of smaller oval-shaped pellets (each about 1 cm by 2 cm by 0.75 cm - one bolus examined contained 46 pellets) (Robichaud, 1998). Boluses of fresh dung were eaten on one observed occasion (Robichaud, 1998). Observations of the drinking habits of the saola suggest that they can consumed large quantities of water at one time - in one 4 minute span, the captive female observed by Robichaud (1998) took nearly 60 draughts of water, pausing only five times to lick her nose and muzzle.


P. nghetinhensis appears to be a solitary species based on reports collected from locals by Schaller and Rabinowitz (1995). Adult pairs (male and female) are known, but the majority of pairs seem to be a female with her most recent offspring (Schaller and Rabinowitz, 1995). Dung et al. (1994) reported that the saola travels in small groups of two or three animals, rarely as large as six or seven.

The captive individual studied by Robichaud (1998) is the source of the majority of behavioral data on this species. Except where noted, all following data comes from this paper.

The captive saola was primarily diurnal, or diurnal and crepuscular, although the author noted a potential bias due to day-time human activity. Nonetheless, this individual fed at most times during the day and only rarely at night, and was observed to rest her chin on the ground with eyes closed most frequently during the hours of darkness. Rumination occurred most frequently in the morning. Interviews with Laotian locals indicate that this species is most active during the morning, late afternoon, and at night, but not when the sun is overhead - although camera traps have photographed active saola in midday (the daytime camera-trap image above was taken at 11h50; Robichaud, 1999). While resting, the forelegs are tucked under the body.

While relatively placid with people, dogs provoke a strong defensive reaction in this species: when faced with dogs, saola will turn to face the threat, arch the back by bringing all feet together and bow the head such that the tips of the horns point at the dogs. In the captive female observed by Robichaud, the maxillary glands were flared during such posturing, accompanied by snorting. When chased by dogs in the wild, saola are said to run to the nearest stream where they make their stand (Schaller and Rabinowitz, 1995).

Grooming with the tongue appears to be a significant activity, the main function of which (in the captive animal) was to disperse gathering flies. The eyes and face were licked the most, followed by the flanks, shoulders, and forelegs. Licking of the muzzle was also observed after feeding, drinking, and ruminating. Scent-marking was observed five times: in each instance the flap of the facial gland was raised and the inner portion of the flap touched to protruding rocks around the enclosure. The only known vocalization is a soft, monotone bleat, around one second in duration.

The postures utilized for urination and defecation were very similar, both of which involved squatting with the rear legs spread wide and the rump low to the ground. This squatting posture was sometimes held for 0.5-3 minutes before and after passing urine or feces (as is typical of bovids, passing of urine and feces were performed separately).


The saola is found in the forests along the Annamite mountain range on the border between Viet Nam and Lao People's Democratic Republic. Most scientifically-documented records of occurrence are from south of the Song Ca river in Viet Nam, although there is a small population which has been found north of the river (Dung et al., 1994; Kemp et al., 1997). Within Lao People's Democratic Republic, the saola is known from the provinces of Bolikhamxay, Khammouan, Savannakhet and Xekong, and likely lives in southern Xieng Khouang Province; in Viet Nam, the provinces of Nghe An, Ha Tinh, Quang Binh, Quang Tri, Thua-Thien Hue and Quang Nam support populations of Pseudoryx (Timmins et al., 2008). In all, the total known range of the saola encompasses only 4,000 square kilometers, although the historical range may include as much as 15,000 km2 (Dung et al., 1994; Timmins et al., 2008).

Countries: Lao People's Democratic Republic, Viet Nam (Timmins et al., 2008).

Range Map
(Redrawn from Timmins et al., 2008)

Conservation Status

P. nghetinhensis is classified as critically endangered by the IUCN (Timmins et al., 2008), and has been listed on CITES Appendix I since November 1994 (Editor's note in Schaller and Rabinowitz, 1995; CITES, 2009). "A few hundred" individuals were estimated to survive in both Viet Nam and Laos in 1995, but proper censusing is difficult due to the remoteness and ruggedness of the species' habitat (Schaller and Rabinowitz, 1995). The IUCN Saola Working Group estimates (as of 2009) probably no more than a few hundred saola remain, and possibly as few as a few tens (Saola Working Group, 2009). Available data indicate that the saola continues to decline significantly in numbers - at the dangerous level of over 80% over the course of three generations (estimated for past, present, and future by Timmins et al., 2008).

Hunting is the greatest threat to the survival of this species: hunting pressures from humans have been described as "intense", including chases with dogs and generalist snares (Timmins et al., 2008). There are fears that the saola may be snared into extinction (particularly in Viet Nam) due to a variety of more abundant wildlife species, such as wild pigs and civets (Timmins et al., 2008). In addition to eating the meat, villagers may use the facial glands of the saola for medicinal purposes (Dung et al., 1994). The saola is severely threatened by habitat destruction, with the forests within their range being cleared by timber extraction practices and for small-scale agricultural use. The creation of roads for logging trucks not only increases the among of lumber which can be exported, but also fragments the remaining forest patches and make these animals more accessible to hunters (Timmins et al., 2008).

As of 1998, thirteen saola were known to have been captured and kept in captivity, and none survived longer than five months (Timmins et al., 2008 report at least 20 captive individuals, all of which met a similar fate, save for two that were released back into the wild). In light of this mortality, the Ministry of Forestry in Viet Nam has issued a ban on further capture, trade, or holding of saola; the Ministry has also ordered that no financial compensation be paid to anyone found in possession of a saola (Robichaud, 1998).


The saola is generally considered to be the greatest animal discovery in recent times, and is so different from any currently known species that a separate genus was constructed for it. The first record of this species came to the western world in the form of three sets of horns discovered in 1992 in the Vu Quang Nature Reserve, from which the saola takes its alternate common name, the Vu Quang ox (Schaller and Rabinowitz, 1995). Very few saola have been studied alive, and much of our present knowledge comes from skeletons and tales from native villagers.

The common name "saola" [rhyming with "now, ha", and sometimes spelled "sao la"] is a native Lao name meaning "spinning-wheel posts", referring to the long, straight horns characteristic of this species (Robichaud, 1998). Similarly, the genus name Pseudoryx is based on the antelope genus Oryx, whose members (the oryxes) have extremely long, straight horns similar to those of the saola, and the Greek word pseudes, meaning false. The species name nghetinhensis describes the range of this new species: Nghe an and Ha tinh are two Vietnamese provinces (bordering on Lao People's Democratic Republic) in the core of the saola's range, with -ensis (Latin) being a suffix meaning "belonging to" (Dung et al., 1993).

Local names
Sao La [Lao, "spinning-wheel posts"] (Robichaud, 1998)
Sun Duong [Ha Tinh province, "mountain goat"] (Dung et al., 1994)
Yang [Laotian locals] (Schaller and Rabinowitz, 1995)
Saola (Timmins et al., 2008)
Vu Quang-Wildrindes (Nadler and Phuong, 1994)
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