Mystery pigs of tropical Asia, and capturing them on film

The increasing availability of automatic cameras (cameras set up to take photos on their own are known in the trade as camera traps) has been a great boon to field biologists, and to people interested generally in the documentation of obscure and elusive creatures. Many animals hardly ever photographed in living state have been documented by these tools, and quite a few taxa never photographed in living state at all have been captured by them too. A few examples of the latter include Lowe's servaline genet Genetta servalina lowei (camera-trapped in 2002, shown at the top of the adjacent composite), Giant (or Large-antlered) muntjac Muntiacus vuquangensis (camera-trapped in 2007, shown at bottom of composite) and Hairy-nosed otter Lutra sumatrana (camera-trapped in July 2010, shown in middle of composite). Species have also been documented in entirely new areas thanks to camera traps: witness, as one example among many, the 2008 camera-trapping of Bush dogs Speothos venaticus in the Atlantic forest of São Paolo, Brazil (Besiegel 2009).

Most exciting of all, entirely new species have also been discovered thanks to camera traps. Examples include the Grey-faced sengi Rhynchocyon udzungwensis (covered on Tet Zoo back in March 2008) and a possible new species of brocket deer from Peru (Trolle & Emmons 2004). Every now and again things that look like sasquatches and thylacines are photographed by camera traps, but no real deal so far :)

A while ago I became interested in the fact that several 'ethnoknown' pigs from SE Asia have been documented by camera traps, yet remain the source of controversy. An ethnoknown animal, for those of you unfamiliar with the term, is one that's recognised as a distinct entity by local people, but isn't necessarily a distinct taxon: an ethnoknown animal could, say, be a distinct growth stage or colour morph of a certain species, or it might not be a real animal at all (but, rather, a mythological entity or such). On the other hand, it could be an animal wholly new to science.

In Tuyen Quang Province, northern Vietnam, local people report two distinct types of pig: a common, long-snouted, long-legged form with white cheek stripes, and a short-faced, black form [drawings of the two forms are shown here, from Meijaard et al. (2002)]. In southern Vietnam, people again report two distinct pigs. The heo bac (meaning 'silver pig') is a short-snouted, whitish animal with white cheeks, while the heo den is longer-snouter and blackish. While the reported snout lengths do not tally between these forms, it is plausible that the whitish pigs from both regions represent the same taxon, as do the blackish pigs from both regions.

What might the identity be of these ethnoknown animals, and are known or unknown taxa at the bottom of the reports? This is very difficult to answer, as a tremendous amount of variability and hybridisation within wild and feral pigs in SE Asia makes identification difficult (Groves 1981). Camera traps used in Na Hang Nature Reserve in Tuyen Quang Province succeeded in photographing wild pigs that seem to correspond to these different descriptions [a camera-trapped Na Hang pig is shown below; from Meijaard et al. (2002)]. The white-cheeked heo bac might represent Sus scrofa moupinensis Milne-Edwards, 1871, a small boar from China and Vietnam with a broad, high skull.

The possibility that the small, dark heo den might represent Heude's pig S. bucculentus (also known as the Indo-Chinese warty pig) has been proposed (Meijaard et al. 2002). Named in 1892 for two skulls discovered in Vietnam, S. bucculentus remained enigmatic until 1995 when an additional skull discovered in the Annamite Mountains of Laos apparently rescued the species from oblivion, supposedly validating its existence as a distinct species (Groves et al. 1997). More recently, DNA analysis has shown that S. bucculentus fits within the range of variation present within Asian populations of S. scrofa, the widespread Eurasian wild boar, so separate species status is no longer thought likely (Robins et al. 2006). 'S. bucculentus' might not be a distinct species, but there still seems to be a population that corresponds to our concept of this animal, and it might be that this is what people have been seeing and calling the heo den.

Please note the many caveats given in the text above: the assumption that the animals from northern and southern Vietnam are the same could well be erroneous (as suggested by conflicting details of snout length), and one could argue anyway that it might not be possible to arrive at firm conclusions based on the evidence to hand. Field studies and DNA sampling of the heo bac and heo den, and their northern Vietnamese equivalents, are needed.

Controversial pigs have also been photographed in the Philippines. While searching Tawi Tawi and adjacent islands between 1995 and 1999 for birds, Desmond Allen photographed an unidentified pig on Baliungan Island (just east of Tawi Tawi) [it's shown here; from Allen (2002)]. A separate visit to Tawi Tawi by Karen Rose in 1997 revealed that "a pig present was probably of an undescribed species and ... pigs on some of the offshore islands such as Bilatan might be different again" (Allen 2002, p. 4). The high diversity of endemic pig taxa already known from the Philippines (something I plan to cover one day) renders it likely that further forms do await documentation there.

Thanks in part to the spread of feral colonies in parts of Europe and North America, the adaptability and versatility of the wild boar and its modified descendants are all too familiar. Less well known is that pigs as a whole are a surprisingly large, diverse group that have been very good at colonising islands, crossing barriers* and evolving new endemic forms, many of which are of high conservation priority. Many questions remain on the subject of pig systematics, evolution and diversity, and the documentation of local forms - aided by camera trapping techniques - remains an important (yet frequently unappreciated) area of investigation.

* Including Wallace's line (Groves 1983).

For previous Tet Zoo articles on pigs, see...

• The legend of Hogzilla
• Traumatic anal intercourse with a pig
• The deer-pig, the Raksasa, the only living anthracothere... welcome to the world of babirusas
• Are anthracotheres alive and well and living on Sulawesi? No, but it was a nice idea. Babirusas, part II
• What's with the bizarre curving tusks? Babirusas, part III
• When babirusas fight (babirusas, part IV)
• This little piggy went ploughing (babirusas, part V)
• The many babirusa species (babirusas, part VI)
• Laissez-faire lumping under fire? (babirusas, part VII)
• Babirusas can get impaled by their own teeth: that most sought-after of objects does exist! (babirusas, part VIII)
• The author caricatured. His trusty steed: a babirusa!
• Possibly the world's first knitted babirusa
• A close-up look at a Hairy babirusa

Refs - -

Allen, D. 2002. Some poorly-known pigs in the Philippines: Tawi Tawi and Tablas. Asian Wild Pig News 2 (1), 4-5.

Besiegel, B. M. 2009. First camera trap records of bush dogs in the state of São Paulo, Brazil. Canid News 12.5 (online) [free pdf here].

Groves, C. P. 1981. Ancestors for the Pigs: Taxonomy and Phylogeny of the Genus Sus. Technical Bulletin 3, Department of Prehistory, Research School of Pacific Studies, Australian National University, pp. 96.

- . 1983. Pigs east of the Wallace Line. Journal de la Société des Océnistes 77, 105-119.

Groves, C., Schaller, G., Amato, G., & Khounboline, K. (1997). Rediscovery of the wild pig Sus bucculentus Nature, 386 (6623), 335-335 DOI: 10.1038/386335a0

Meijaard, E., Oliver, W. L. R., Martin, B. & Thanh, V. N. 2002. Records and reports of pigs in Vietnam. Asian Wild Pig News 2 (2), 40-42.

Robins, J. H., Ross, H. A., Allen, M. S. & Matisoo-Smith, E. 2006. Sus bucculentus revisited. Nature 440, E7.

Trolle, M. & Emmons, L. H. 2004. A record of a dwarf brocket from Madre de Dios, Peru. Deer Specialist Group Newsletter 19, 2-5.