Specimen of the Week 285: The Pig Skull
By Will J Richard, on 31 March 2017
Hello internet-folk. Will Richard here blogging a blog again. And for this blog I’ve chosen a specimen that nobody bothers with. We’ve got loads and they’re not exactly hard to find: flat-nosed, famously greedy and surprisingly intelligent it’s the…
**Domestic pig skull**
The domestic pig (Sus scrofa domesticus) is an omnivore originally domesticated from wild boar about 13,000 years ago in western Asia. Alongside their ability to survive on human refuse, pigs live happily in small groups and have large litters: more than ten piglets is not uncommon. This made them both easy to domesticate and productive to keep. Since then they have been selectively bred for generations and there are now more than 70 recognised breeds. Although their characteristics do vary there has been a general trend towards making pigs bigger, more fecund and more docile. Males (boars) are about a third larger than females (sows). They regularly reach weights of 350 kilogrammes though, according to what is undoubtedly the best Wikipedia page ever; “List of pigs”, the world record holder “Big Bill” weighed over a tonne.
Today they are widely farmed, primarily for their meat and skin, and the global population is estimated to be more than a billion. Despite this, and our long association, we know surprisingly little about their intelligence, wellbeing and behaviour. A comprehensive literature review published in 2015 makes a compelling case, drawing realistic cognitive comparisons for pigs with traditionally “clever” animals like dogs and even chimpanzees. If further research, as the authors recommend, upholds this, then surely we need to re-think a few things…
The government’s “Code of recommendations for the welfare of livestock: pigs” states that: “The dimension of any stall or pen used for holding individual pigs in accordance with these regulations shall be such that the internal area is not less than the square of the length of the pig, and no internal side is less than 75% of the length of the pig, the length of the pig in each case being measured from the tip of its snout to the base of its tail while it is standing with its back straight.”
Now, if we accept the theory that pigs and chimpanzees are comparably intelligent let’s imagine applying these rules to both. An adult bonobo, a highly-intelligent, small chimpanzee, is about 1.2 metres tall and so could, therefore, be kept in a 1.2 x 1.2 metre pen (1.44m2). For reference, the size of the UK’s standard bath tub is 1.19m2.
To take another chunk on environmental enrichment: “Objects such as footballs and chains can satisfy some of the pig’s behavioural needs, but can quickly lose their novelty factor. The long-term use of such items is not, therefore, recommended unless they are used in conjunction with [straw], or are changed on a weekly basis.” To continue the comparison: these regulations would be ok with keeping an intelligent, gregarious bonobo in a large, bare bath provided it was given a different football every Monday.
The idea that pigs and chimpanzees think similarly might seem far-fetched, and perhaps it is. We will not know until more work has been done, but the thought of keeping a chimp in a bath with no other stimulation than a football is, I hope, shocking. It was to me. If that is shown to be comparable to how we currently house pigs on an industrial scale, then I think the Code of recommendations might need a re-write.
Marino, Lori; & Colvin, Christina M. (2015). Thinking Pigs: A Comparative Review of Cognition, Emotion, and Personality in Sus domesticus. International Journal of Comparative Psychology, 28.
Will Richard is Visitor Services Assistant at the Grant Museum of Zoology