Sheep-pig Hybrids

imageA sheep-pig hybrid? - As shown in a BBC article

EUGENE M. MCCARTHY, PHD GENETICS, ΦΒΚ

And so if, as you recently told me, a lamb with a pig’s head was born, then it is because a boar mated with a sheep.

—Polydore Vergil
Dialogues on Prodigies, III, xxvi*

Caution: This disparate cross needs further confirmation, particularly from controlled breeding experiments.

It’s well documented that sheep and pigs sometimes will mate (videos >>). Indeed, even the ancient Akkadians knew that pigs and sheep do sometimes engage in such activities (Freedman 2017, p. 6). It’s a common barnyard occurrence. And text-mining of old newspapers shows that hybrids occur as well, as indicated, for example, in the reports at right.

At one time, unusual births such as pig-sheep hybrids were regularly reported in newspapers as “freaks of nature,” an English translation of the older term lusus naturae. But at about the time of the first world war, a movement arose to suppress freak shows and news reports about such creatures as well. It was distasteful and offensive, even cruel, opponents argued, to put such things before the public. The movement was successful and after the twenties, freaks rarely came before the public eye. As a result, it has been forgotten even by biologists that strange hybrids do occur. This societally enforced ignorance results in people interpreting animals that look like sheep-pig hybrids, such as the animal pictured above, as a wooly breed of pig.

For example, in 2010 stories about woolly sheep-like pigs and sheep-pig hybrids surfaced on the internet because a zoo in the UK (Tropical Wings Zoo, South Woodham Ferrers, Essex) announced that it had imported rare “Mangalitza” pigs and that they planned to breed them. Many people thought they were sheep-pig hybrids. But a BBC story assured the public that the Mangalitza was only a breed of pig:

An extremely rare breed of curly coated pig is to be bred for the first time at a zoo in Essex.

The three Mangalitza pigs, which bear a striking resemblance to sheep, arrived at the Tropical Wings Zoo in South Woodham Ferrers, just before Easter as part of a programme to save the breed.

“At first sight people perhaps think they are sheep” said education co-ordinator Denise Cox.

“It’s not until they turn around and you see their faces and snouts that you realise they are in fact pigs.”

The breed is thought to be native to Austria and Hungary.

But how did this breed of pig obtain a fleece like a sheep’s? It seems it would take some very clever breeding to start with a near naked, bristly pig and somehow select for a dense sheep-like coat of hair. And it seems no genetic study of these “pigs” has been made. After seeing this story, a Spanish geneticist whose former lab sequenced the genomes of some Mangalitza pigs said that, although the results of the study had been compared to other breeds of pig, he did not think any comparison had been made to sheep. So it seems that it has not been shown that Mangalitzas are not sheep-pig hybrids, although it’s clear from comments on the various stories around the internet that many people think they are.

The BBC subsequently published two brief stories on “Mangalitza pigs” (in these more recent articles, by the way, they use the spelling “Mangalica”).

One of these articles, by BBC World Service broadcast journalist Lucy Hooker, is about efforts to save the breed. In that article she comments that

To the uninitiated it is a sheep-pig. In reality it is the Mangalica, a comical but appealing breed that is taking the food industry by storm.

What this comment fails to recognize is that it is well known that many breeds of domestic animals were originally produced from hybrid crosses. I discuss this fact at length, among other places, in my reference work on hybridization in birds (Handbook of Avian Hybrids of the World, Oxford University Press, 2006) and elsewhere on this website. So really, it’s entirely possible that these pigs are not only a breed, but also of hybrid origin. The two are by no means mutually exclusive, as Ms. Hooker seems to suggest.

Since this is an old breed, which has apparently existed for centuries, its origin seems to be unknown. To determine the nature of that origin, it will be necessary to carry out investigations. One obvious way of gaining information about whether these animals might be sheep-pig hybrids is genetic analysis, as mentioned above. Another is experimental mating to see whether such hybrids can be produced. It is even conceivable that breeding records survive describing how the breed was produced (as is the case with many domestic breeds derived from hybrid crosses). Certainly, there are reports about sheep-pig hybrids being produced in Mexico (see below).

But the BBC’s implication that only the uninformed would suppose that these animals might be sheep-pig hybrids (i.e., “To the uninitiated it is a sheep-pig.”) seems premature. I am a geneticist and I know about hybrids, and yet I think they probably are hybrids of that sort. Moreover, I gently object to Ms. Hooker’s statement. It treats the unknown as known and therefore tends to dampen the spirit of investigation.

The other article, which is very short, was written by Tim Muffet, a reporter for BBC Breakfast. It’s really just a bit of text to accompany a video showing how these pigs are being used to restore heath land. From the standpoint of the sheep-pig question, this video is of interest primarily because it demonstrates beyond doubt that animals, such as the one pictured at the top of this page, do actually exist. Mere pictures can easily be faked. Videos, especially videos from a reliable source like the BBC, cannot.

The video evidence is also relevant because individual variation can be seen in the animals shown, with some looking identical to the very sheep-like animal shown above with its curly white fleece, to animals with sparser straight, black pelts more similar to that of European boars. This is exactly the sort of variation that occurs in a wide variety of hybrid crosses, where some individuals are more similar to one of the two parents that originally crossed to produce them, while others are more similar to the other. Such variation is especially characteristic of later-generation hybrids, the descendants of the first-generation, or F₁, hybrids produced by the original cross.

In the video accompanying Ms. Hooker’s article, it can also be seen that these animals have dark red meat like that of a sheep, not the light-colored meat typical of most pigs.