The Diets of Parallel Pigs

Peccaries from South America

The word "ungulate" refers to a broad category of mammals that are generally large and herbivorous. They form a natural evolutionary group, although only if you include the cetaceans, which are descended from vaguely hippo-like ancestors. The word comes from the Latin word for "hoof", and the great majority of living ungulates have hooves of one kind or another. Even ignoring the cetaceans there are exceptions, but it doesn't take a great stretch of the imagination to see that camels, for instance, are at least the same general kind of animal as deer or cows.

All living ungulates can be placed into one of two mammalian orders: the artiodactyls, which includes the cloven-footed kinds, and the perissodactyls, which includes, among others, the horses. If you start looking at fossils, however, it becomes clear that other ungulate orders once existed. Most were very early, dying out in the first half of the Age of Mammals, representing early branches in the great ungulate family tree that ultimately proved unsuccessful.

Oligocene (Pt 3): From Musk Deer to Hell-Pigs

Entelodon

The Grande Coupure that marked the beginning of the Oligocene in Europe did not have as dramatic an effect on the cloven-hoofed animals as it did on some other mammalian groups. But the change was nonetheless noticeable, with several primitive forms that had once inhabited the continent suddenly dying out as it merged with Asia. Others, however, survived through the break, and the absence of their earlier competitors may even have helped them prosper.

These include the gelocids, which first appeared close to the end of the previous epoch. Few of the known fossils of these animals are in good condition, and there is some debate as to whether they are a true group of animals at all, or just a vague term used to collect similar-looking creatures that we can't place elsewhere. That aside, we can at least say that they physically resembled (but were probably not related to) musk deer. That is, they were relatively small, hornless animals with long legs suited for running fast, but lacking the large fang/tusks that mark true musk deer. They did well enough that some, such as Pseudogelocus, are known not only from France and Germany, but also Mongolia, suggesting that they crossed over in the opposite direction to most other mammal groups.

Are Animals Darker in the Tropics?

In 1833 Prussian ornithologist C. L. Gloger published the book Das Abändern der Vögel durch Einfluss des Klimas (roughly "the modification of birds by climatic influences"). In this, he put forward a proposal that the plumage of birds living in hot, humid, environments tends, on average, to be darker in colour than that of those which do not. In 1929, biologist Bernhard Rensch formalised this as "Gloger's Rule", one of a number of zoological "rules" that seemed to be true more often than not but for which there was not necessarily a clear explanation.

Crucially for this blog, it seemed to be true of the skin and hair of mammals as well. This observation raises a number of questions, of which the first is clearly "is it true?" 

Miocene (Pt 23): Giraffes Become Tall, Hippos Stay Dry, and Antelopes... Get Eaten

Palaeotragus, a short-necked giraffe

About half-way through the Late Miocene, around 8 million years ago, worldwide temperatures began to drop significantly, and even tropical Africa did not escape the effects. In its case, this didn't lead to cold and barren steppelands, and, indeed, the world may still have been slightly warmer than it is today, but there is evidence of the expansion of grasses across many parts of the continent. Perhaps enhanced by the closure of the Mediterranean Sea during the Messinian Salinity Crisis and disruption of the monsoons, North Africa also became much drier than before, although whether the Sahara as we know it today dates back quite that far remains controversial; there is some evidence of sand dunes that far back, but also of numerous rivers crossing the region.

These changes in climate also affected the animal life on the continent, to the benefit of some and the detriment of others. Pigs are omnivorous animals, and one might expect them to have survived such changes relatively unscathed. In a sense, this is true, since they remained common on the continent, but the nature of particular species living there did change.

Like a Hole in the Head: What's the Point of Sinuses?

We're probably all generally familiar with the existence of what are technically termed paranasal sinuses. That's largely because the inflammation of them, known as sinusitis, affects as many as 1 in 8 Americans, and presumably a similar number of people elsewhere, at least in the west. The term 'sinus' just means an empty space in something, and in the case of the paranasal sort, those spaces are inside the bones of our skull, connected by narrow passages to the nasal cavities.

The existence of these passages is important, ensuring that the sinuses are drained of mucus and filled with air... and also allowing any germs that you might have breathed to get into them and make what would otherwise only affect your nose into something worse. But why do we have sinuses at all?

Miocene (Pt 20): Unicorn-Pigs and the First Hippos

Prodeinotherium

Pigs seem to have been another example of animals crossing over from Asia when that continent collided with Africa around 17 million years ago. The oldest fossil pigs in Africa date from about that time and are represented by Kenyasus from Kenya and Nguruwe from Namibia and South Africa. These were relatively small, short-snouted pigs with a primitive appearance similar to that seen in their presumed Asian ancestors.

Because of these primitive features, determining exactly where they fit in the pig family tree isn't a simple matter, but they are often placed with a group called the kubanochoerines. Assuming this is correct (and it's far from settled) they must have evolved fairly rapidly into much larger and more distinctive animals. The best-known member of the group is the giant "unicorn-pig" Kubanochoerus, which lived in China during the Late Miocene. This was an exceptionally large, long-legged animal, perhaps standing 120 cm (4 feet) high at the shoulder and - even more dramatically - sporting a long pointed horn that projected from the centre of its forehead.

Not the Pig Family: Fossil Peccaries and More

Mylohyus

Today, there are only three recognised living species of peccary, the smallish pig-like animals that inhabit the Americas... and one of those is endangered. However, these are but the last remnants of a once much larger group with a fossil history that stretches back even further than that of the true pigs.

While pigs date back, at the best, to the end of the Oligocene epoch, the oldest known peccary fossil dates from the end of the epoch before that, the Eocene. This implies that the ancestors of the peccaries entered North America from Asia between 36 and 34 million years ago. The fossil in question belongs to a species known as Perchoerus minor, and it's also worth noting that it is also the smallest peccary known... in fact, it was about the size of a typical house cat.

The Pig Family: Fossil Pigs

Kubanochoerus, the unicorn-pig

There are seventeen widely accepted species of pig alive today. Although some, notably the wild boar and the two kinds of warthog, are doing absolutely fine in the grand scheme of things, many are threatened to varying extents by hunting and loss of habitat. Three - the pygmy hog and the Visayan and Javan warty pigs - are formally listed as endangered species by the IUCN, and many of the others are just outside that category. On the bright side, no clearly identified species of pig has actually slipped over the line into extinction in the last few thousand years. But, of course, if you go back a few million years, it's a rather different story.

Indeed, in some respects, the pig family as it exists today is a shadow of its former self. Pigs have always been reasonably successful animals (at least, without human interference), given their adaptability, moderate intelligence, and willingness to eat just about anything. But, in the past, they were more varied than today. In total, there are five generally recognised subfamilies within the overarching pig family - and all but one of them are known only from fossils.

The Pig Family: Peccaries Are Not Pigs

Over the the year so far, this series has described every living species of pig. Yet there are some animals that might seem to be missing. Found across much of Latin America, and up into the southwestern USA, we can find animals known as peccaries. These certainly look like pigs, and, unlike razorbacks, which can also be found in the US, they are genuinely wild animals, not the descendants of domesticated ones that happen to have escaped.

The reason I haven't mentioned them so far is, as the title of the post makes apparent, that they aren't actually pigs. So why the heck not, and what are they, if they're not pigs?

The Pig Family: The Strange Case of the Sulawesi Pig-Deer

Sulawesi babirusa

Warthogs are fairly odd-looking animals, as are forest hogs, among others. But, at least to my mind, when it comes to wild pigs, nothing quite beats the babirusas.

These strange looking pigs inhabit the island of Sulawesi in Indonesia. Unlike most of the others in the group, this has been an island for far longer than pigs have been in existence - when sea levels were lower, most islands to the west were joined with Asia, and those to the east with Australia, but the waters around Sulawesi are so deep that it remained isolated. I've mentioned this before, in the context of warty pigs, so it's interesting to note that those channels must have been crossed by wild pigs on no less than three occasions (the third sort of Sulawesian pig, Celebochoerus, died out in the Ice Ages).

The Pig Family: Warthogs

Common warthog

Warthogs are, quite possibly, the best known species of wild pig after the wild boar itself. They are relatively common animals, readily observed in the habitats where they live (rather than hiding in dense thickets, say) and, perhaps above all, they have a striking and distinctive appearance.

The common warthog (Phacochoerus africanus) is widespread across sub-Saharan Africa, and is currently thought to have four different subspecies. Unlike other African hogs, they inhabit lush grasslands and open savanna, country dotted with trees and waterways, but neither densely forested nor the truly arid terrain of veldt or desert. Two subspecies live in the north, in the Sahel belt that separates the Congo rainforest from the Sahara, and are found right from the Atlantic coast of Mauritania to the shores of the Red Sea in Eritrea. The others are found across East Africa and pretty much the entire south of the continent outside the deserts, reaching as far as South Africa.

The Pig Family: Bush Pig, Bushpig, Red River Hog

Red river hog (boar)

As zoological knowledge has advanced, the number of species that we know about has changed regularly, and not just because we keep discovering new ones. Animals that we knew about, but previously thought were subspecies get promoted to full species, and animals that we thought were separate species turn out not to be.

In fact, over time, we can sense something of a trend here. Beginning with Linnaeus in 1758, several new species are named, often by naturalists unaware, in the days before fully up-to-date reference libraries, let alone the internet, that somebody else had already given a name to the same thing. That process continues through the 19th century, with minor differences being seized on as evidence of speciation, even where it was possible to make decent comparisons. Through the 20th century, the number of genuinely new species being discovered dramatically tails off (at least, for mammals), but there's also a tendency to tidy up the great mass of inherited names from the past, merging similar animals together. Finally, from the late 20th century onwards, an increasing understanding of genetics results in numerous subspecies being promoted, often with our Victorian predecessors turning out to have been right all along.

The Pig Family: The World's Largest and Smallest Pigs

Pygmy hog

By some definitions, the term "pig" can really only be applied to those species that are most closely related to the domestic animal; those included within the genus Sus. This includes the wild boar, and the various kinds of warty and bearded pig that inhabit the Indonesian and Philippine islands.

But these are not the only pig-like animals to inhabit Asia. In 1847, Brian Hodgson, a naturalist and former colonial administrator who was living in Darjeeling at the time, described and named the pygmy hog (Porcula salvania), an animal he considered so different from regular pigs in the shape of its teeth and feet that he placed it in its own, newly defined, genus, Porcula. (The scientific name, incidentally, translates as "piglet from the Sal Van", the latter being a forest that only coincidentally sounds like the Latin "silvae" meaning "woodland").

The Pig Family: Threatened Pigs of the Philippines

Visayan warty pig (female)

When the animal we now know as the Sulawesi warty pig was first described, back in the 19th century, it was thought that it lived, not only on the island of Sulawesi, but also on a whole chain of islands to the north - the Philippines. But the pigs there didn't look exactly the same as those to the south, so in 1886, German zoologist Alfred Nehring proposed that they be regarded as a distinct subspecies.

And so things remained for a hundred years, until scientists began to look more closely at the animal's genetics. When they did so, they discovered something fairly surprising. Pigs typically have 38 chromosomes (compared with 48 in humans), but it turned out that the warty pigs from the Philippines had only 36 - an entire pair had disappeared, its genetic material shuffled around elsewhere in the genome.

The Pig Family: Wild Pigs of Indonesia

Bearded pig

Thanks to their adaptability, wild boar are a remarkably widespread species, being found from Portugal to Japan. All of their close living relatives, however, are much more restricted, each being isolated on different islands or island chains off the south-east coast of Asia.

The largest such island, and, indeed, the third largest island in the world, is Borneo. This is home to the bearded pig (Sus barbatus), which is also found, not only on the neighbouring island of Sumatra, but also on the Malaysian mainland. The Bornean and Sumatran forms of the animal are widely regarded as different subspecies - the latter going by the rather brilliant name of S. b. oi - although quite which of these two the Malaysian pigs belong to has been a matter of mild controversy.

Miocene (Pt 6): The Coming of the Mice

Palaeotragus

The Early and Mid parts of the Miocene epoch were, for the most part, times when the world was much warmer than it is today. It wasn't a steady pattern, however, and I've already described how the fluctuations in climate, over the course of many millions of years, affected the rodents of Europe. It was a time when the most common small mammals in Europe were not mice and voles, but dormice, accompanied by early hamsters, squirrels, and the gliding eomyids.

By 10 million years ago, however, the colder, drier climate had become locked in for the long term. We know that the forests of Europe changed dramatically at this time, the old subtropical trees, such as figs and palms, being replaced by oak, alder, and elm. Likely as a result of this change in the available food supply, most of the dormice died out, leaving only a few close relatives of the relatively small number of species we have today.

The Pig Family: Wild Boar and the Domestication of Pigs

European wild boar

Generally speaking, the wild ancestors of agricultural animals have not fared particularly well. Wild goats are a threatened species, wild horses are an endangered one, camels are doing even worse, and wild cattle have been extinct for centuries. Wild sheep haven't done quite so badly, although they're hardly widespread, but, in general, one of the main problems facing such animals is that the sort of places they like to live are exactly the ones we want to turn into agricultural land to raise their domesticated kin.

Indeed, only two wild ancestors of widely domesticated herbivore are doing well: chickens and pigs. (This may, of course, depend on your definition of "widely"; I'm ignoring, say, rabbits). Indeed, the wild ancestor of the domestic pig is not only reasonably common, it's the single most widespread of any species of wild pig.

The Pig Family: Suids, Suines, and Swine

The pigs occupy an an interesting position in the mammalian family tree. The pig family, or Suidae, belongs to the order Artiodactyla, consisting of the cloven-footed mammals and a few of their closest relatives. (I will, at this point, note that I'm going to be using "artiodactyl" in the traditional, non-molecular sense, in this post. Paraphyly be damned, at least for today.)

This is unsurprising, given that pigs do, indeed, have cloven hooves. However, there are other features that almost all artiodactyls have in common, most significantly, that they are purely herbivorous animals with multi-chambered stomachs that they use to "chew the cud". Pigs, however, do not, and while they may not be the only non-ruminating artiodactyls, they are by far the most species-rich group to fit this description.

Traditionally, this was thought to be because they are more "primitive", having evolved before their relatives got round to developing more complex digestive systems. In a more modern way of looking at things, we'd instead note that, compared with other artiodactyls, pigs are omnivorous; they haven't developed more efficient ways of digesting tough plant matter because they don't need to. That they've survived as well as they have, evolving over many millions of years without ever being wiped out, shows that this has been a pretty successful tactic for them.

Miocene (Pt 2): Before There Were Mice

Heteroprox

After a brief cold snap at the very dawn of the epoch, the world of the Miocene warmed rapidly. Europe became, if not truly tropical, at least subtropical, with the interior covered by great forests of oak, laurel, and cinnamon, with magnolia and figs joining pine trees in the highlands. Along the coasts, the hot, damp, climate encouraged the growth of mangrove swamps and palm trees as warm sea currents flowed in from the Indian Ocean - still connected to the Mediterranean at this time. With no ice caps at the North Pole, and relatively few at the South, sea levels were much higher, and parts of continental Europe may, in those days, have still been islands. Certainly, Aqutaine in south-western France and the lower Rhône valley in the south-east were shallow bays stretching some way inland, as was what is now the Tagus valley in Spain and Portugal.

This rich and verdant landscape was home to a wide range of animals, many of them survivors of even earlier times. Many of these, such as the tapirs, didn't survive long in Europe, but a great many did, with musk deer, pigs, and rhinos dominating the herbivorous fauna, and animals less familiar to modern eyes taking the lead among the large carnivores.

But then, as now, the great majority of mammal species were small. While the sight of Diaceratherium rhinos wallowing in the lush swamps of the Swiss shoreline is the sort of thing that would draw the immediate attention of a time-travelling tourist, there was also plenty going on underfoot. Yet the two most common groups of small non-flying mammals that we have in Europe today - the mice and the voles - did not yet exist. So what was there?

Rain Down on Me: Wild Boar and the Weather

Wild boar (Sus scrofa) are very far from being an endangered species. They are found across continental Europe and Asia, and on a number of nearby islands, from the Mediterranean to Japan. We have no idea how large their global population is, but it's clearly pretty big, and they are common animals in many places. But even if their very existence isn't in danger, that doesn't mean that we have no need to figure out how to properly manage their populations in the wild, so as to cause neither humans, nor the boars themselves, any inconvenience.

This is in part because the influence of wild boars on humans is mixed. On the one hand, they can be quite a nuisance. They cause significant damage to crops, can spread diseases to farm animals (most obviously, pigs), and caused almost a thousand traffic accidents a year in northwestern Spain. Clearly, these are all good reasons to keep their numbers down, at least in places where humans are common - which, let's face it, mean pretty much the whole of Europe. On the other hand, wild boar are generally regarded as quite tasty, which, while it's not a great thing to be from the boar's point of view, does at least mean that hunters don't want to drive them away into really remote and inaccessible areas.