Saola (Pseudoryx nghetinhensis)

Taxonomy

The Saola (Pseudoryx nghentinhensis) is the most recently described species of Bovidae, being discovered only in 1992 (1). The etymological meaning of Pseudoryx is false oryx since the taxon is superficially similar in appearance to oryxes. The species name nghentinhensis denotes the Vietnamese province in which it was discovered (1). The word saola on the other hand is the Lao word for the species, which predates the scientific discovery (5) and roughly translates to ‘spinning wheel posts’ due to the resemblance of the horns to this object (5). The species has not been broken into subspecies.

Preliminary DNA analysis clustered the saola within the bovines (subfamily Bovinae), though the exact placement was unclear (1). Though affinities to Caprinae have been suggested (2), it is clear from subsequent molecular analyses that the initial placement of saola within Bovinae was correct and peculiarly that it belongs to the tribe Bovini, which is composed of cattle (Bos), buffalo (Syncercus & Bubalus) and bison (Bison) (2, 3, 4). The exact placement within Bovini is less clear, Hassanin & Douzery 1999 erected the subtribe Pseudoryina exclusively for the saola, as it does not show strong similarities to any other Bovini taxon, but whether this subtribe was a sister group to the buffaloes (Bubalina) or the cattle and bison (Bovina) or an outgroup to both is unclear.

Distribution & Age

At the time of its discovery, Dung et al 1993 estimated a few hundred individuals in Northern Vietnam and it was originally classed as Endangered by the IUCN (6). Today we know the range to extend into both Vietnam and Laos, centered mostly around the Annamite mountains, though a few populations outside this mountain range exist (6). Optimistic estimates place the total population size around 750 individuals, though this number may be much lower, unfortunately, due to a shy nature, rarity, and remote habitat a reliable estimate is difficult to pin down. Currently, it is considered critically endangered (6).

It is impossible to estimate the palaeorange of the species due to the lack of fossil remains, however it is noteworthy that the saola does not seem to occupy all areas with suitable habitat in the region, so likely its range was once somewhat greater (6). Even so, it appears to be a very localized species (6). Without fossil remains the age of the species is impossible to establish.

Morphology & Ecology

At 1.5m in length, 80-90cm height at the shoulders, and 80-100kg mass (1, 5), the saola constitutes a medium-sized bovid. The overall bauplan is reminiscent of antelopes, despite the affinity to the bovini. Probably, this was a similar body shape to the ancestor of the clade (5). The saola has a relatively slim build, long legs, and a smooth, largely straight pair of horns that extend backward with an average length of about 40cm, males seemingly possess slightly longer horns than females (1).

P. nghentinhensis is found primarily in coniferous montane forests. They have been observed at various altitudes of the mountains but usually it has been reported between 500 and 800m above sea level (6) and never above 1200m. Its unclear if the natural range once extended to the foot of the mountains as the low altitudes are highly developed (6). Notably, the areas inhabited by the saola have very mild or no dry seasons (5). The habitat appears to have been especially restricted during the glacial periods, and it is suggested by Robichaud & Timmins 2004 that the current range of the Saola represents the locations of refugia during the last glacial period (5).

The species appears to mostly be solitary, though small groups do form up to 6 or 7 individuals on occasion (6). It also seems to be territorial, though this is inferred from large scent glands found in the face (6), though reportedly it moves down to more lowland areas during winter (6). The species is probably diurnal as this is when the species has been caught on camera traps and was active in captivity (6). Little more is known about the behavior of this enigmatic species.

Due to the absence of fossil assemblages from the community of the saola, it is difficult to be sure which extinct species would have co-inhabited the region. Today, though many of the megafauna species are endangered, Asian elephant (Elephas maximus), Gaur (Bos gaurus), and Sambar (Rusa unicolor) can all be found in the coniferous mountains of the Annamite mountains. The principal predators of the region are the tiger (Panthera tigris) and dholes (Cuon alpinus), though leopards (Panthera pardus) also inhabited the region in historical times.

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Citations

1.      Dung, V. V., Giao, P. M., Chinh, N. N., Tuoc, D., Arctander, P., MacKinnon, J.. (1993). A new species of living bovid from Vietnam. Nature 363. 443-445.

2.      Gatesy, J., Arctander, P.. (2000). Hidden morphological support for the phylogenetic placement of Pseudoryx nghetinhensis with Bovine bovids: A comibed analysis of Gross anatomical evidence and DNA sequences from five genes.  Systems biology 49(3), 515-538.

3.      Hassanin, A., Douzery, E. J. P.. (1999). Evolutionary affinities of the enigmatic saola (Pseudoryx nghetinhensis) in the context of the molecular phylogeny of Bovidae. Proceedings of the Royal Society of London 266, 893-900.

4.      Nguyen, T. T., Aniskin, V. M., Gerbaut-Seureau, M., Planton, H., Renard, J. P., Nguyen, B. X., Hassanin, A., Volobouev, V. T.. (2008). Phylogenetic position of the saola (Pseudoryx nghetinhensis) inferred from cytogenetic analysis of eleven species of Bovidae (Cytogenetic Genome Research 122, 41-54.

5.      Robichaud, W., Timmins, R.. (2004). The Natural History of Saola (Pseudoryx nghetinhensis) and the species distribution in Laos. Proceedings of the “Rediscovering the saola – a status review and conservation planning workship”, 14-23.

6.      Timmins, R.J., Hedges, S. & Robichaud, W.. (2020). Pseudoryx nghetinhensis (amended version of 2016 assessment). The IUCN Red List of Threatened Species 2020 (e.T18597A166485696)