I’m not just interested in ‘wild’ animals – I also think domesticated animals are fascinating. After all, my general philosophy is that there’s no such thing as a boring tetrapod. If you want me to be more specific about the merits of domesticates: well, while in cases they’re not all that different from their wild brethren (yet typically far more accessible), they’ve often had all kinds of crazy morphological variation bred into them by humans. Furthermore, there’s all that docility and friendliness that (sometimes) comes as part of the domestication deal. I particularly like learning about obscure breeds of domestic animals - the ones that you don’t hear about all that often.

One of the most peculiar pigs has to be the Mulefoot hog, so named as – if you know nothing of this pig, get ready to stagger backward, clutching heart, in surprise – it’s syndactyl. That is, it’s not cloven-hoofed: the two central digits on both the fore- and hindfeet are fused into one [Mulefoot image above from One Blog for the Kids!].

The very idea of a syndactyl artiodactyl must surely be a radical one if you’re not familiar with the variation seen in domestic pig breeds, but syndactyly has actually cropped up numerous times within various different breeds (it’s also been widely reported in cattle* [syndactyl cow limb shown here; from Donal O’Toole’s Inherited and congenital diseases of food animals and horses]). Aristotle reported syndactyl pigs in Greece in 350 BC; Gesner wrote about syndactyl pigs in England, Belgium and the Netherlands; Linnaeus wrote about their occurrence in Sweden. The remains of syndactyl pigs have also been reported from various archaeological sites in Ireland, Wales, England and France: based on the frequency with which syndactyl archaeological specimens have been discovered, Madgwick et al. (2011) recently suggested that the “the condition may have been more common in the past than commonly realised” (p. 12)

* Weirdly, when cattle do possess syndactyly, they tend to express it in the right forelimb alone (Leipold et al. 1969). Why?

While it seems that syndactyly might crop up randomly within individuals of various domestic pig breeds, the American Mulefoot is special in that syndactyly (also termed syndactylism in the domestic animal/veterinary literature) is a fixed trait. It seems that the Mulefoot breed first appeared in the early 1900s in the southwest USA; it was also apparently present in Mexico at this time. In Missouri and Arkansas it was known as the Ozark hog. Over 235 herds were registered across the US by 1910, and herds were also kept in Canada. Hardy, easy to fatten, and productive, part of the breed’s popularity might also be explained by the fact that it was believed immune to swine fever, cholera and foot and mouth disease (Porter 1993). Similar beliefs were also held about syndactyl pigs in Europe: there was such demand for syndactyl pigs round about the turn of the 20th century that breeders were apparently unable to keep up with demand. Alas, none of those claims about immunity are true, though it is conceivable that syndactyl pigs are less prone to the fungal foot diseases that can occur in cloven-hoofed pig breeds [Mulefoot... foot shown here from Foust Farms].

Like so many breeds that were once fairly popular and widespread, the Mulefoot sort of went out of fashion during the later part of the 20th century. That idea about extreme immunity was no longer such a big draw, since vaccines and medicines became cheaper and more widely available.

By the 1960s, the breed would likely have been lost were it not for the efforts of R. M. Holiday in Louisiana. During the 1970s he introduced genes from a herd in North Dakota, and this unfortunately led to the incorporation of several undesirable traits into the breed, including split hooves, ‘prick’ ears and wattles. Nevertheless, by 1985, Holiday’s herd was the only one left and only 200 individuals were in existence in 2006 (there are currently about 600). For more on this breed’s history, and on its characteristics, potential significance and perpetuation, visit the website of The American Mulefoot Hog Association.

Aside from its peculiar feet, the Mulefoot isn’t that remarkable. It’s typically black (sometimes with white markings) and with floppy ears and a soft hair coat [adjacent image shows mother Mulefoot with piglets; from Deer Run Farm].

So now you know. I recently acquired Valerie Porter’s Pigs: A Handbook to the Breeds of the World and am really enjoying learning about obscure domestic pig breeds. For previous Tet Zoo articles on domestic animals, see…

Refs - -

Leipold HW, Adrian RW, Huston K, Trotter DM, Dennis SM, & Guffy MM (1969). Anatomy of hereditary bovine syndactylism. I. Osteology. Journal of dairy science, 52 (9), 1422-31 PMID: 4312935

Madgwick, R., Forest, V. & Beglane, F. 2011. Syndactyly in pigs: a review of previous research and the presentation of eight archaeological specimens. International Journal of Osteoarchaeology doi:10.1002/oa.1260

Porter, V. 1993. Pigs: A Handbook to the Breeds of the World. Helm (Mountfield, Easy Sussex).