PIGS AND PECCARIES - THE SUPERFAMILY SUOIDEA

The superfamily Suoidea is a lineage of artiodactyl mammals that includes the family Suidae (“Old World Pigs”) and Tayassuidae (“New World  Peccaries”), including their fossil kin, and the extinct Palaeochoeridae ("Old World peccaries"). The oldest fossil suoids date from the late Eocene of China and Thailand.

The first representatives of the family Suidae (pigs and hogs) are known from the earliest Miocene of Europe, reaching the subcontinent of India and Africa during the Miocene. Nowadays, up to sixteen extant species of pigs and hogs grouped in six genera make up the family Suidae. These are Sus, Potamochoerus, Phacochoerus, Babyrousa, Hylochoerus and Porcula (a more conservative taxonomy would include this genus in Sus).

The Palaeochoeridae are primitive Suoidea which appear in the Early Oligocene of Europe and became extinct in the Old World around the end of the Miocene. The Tayassuidae appeared first in North America during the Late Eocene and reached South America between two and three million years ago in the Late Pliocene or Early Pleistocene, during the Great Faunal American Interchange, due to the formation of the Isthmus of Panama. The oldest known fossil attributed to the family Tayassuidae found in South America belongs to the Middle Pliocene. New molecular and fossil evidence partly supports a much earlier dispersal in the Late Miocene, a hypothesis that was already proposed two decades before, but more fossils need to be found to confirm it. There are three extant species of the family, grouped in three genera, Tayassu, Pecari and Catagonus.

The representatives of the superfamily Suoidea are the most generalized of the living, even-toed, hoofed mammals (Artiodactyla). They are medium-sized animals characterized by a large head, short neck, and powerful but agile body, with a coarse, bristly coat. They have a mobile snout, which ends in a disk-like cartilaginous nose perforated by two nostrils. The snout is used for turning up surface soil and it is strengthened by an unusual bone, the prenasal, situated below the tip of the nasal bones of the skull. The most striking feature of the skull is the elevation and backward slope of the occipital crest, formed by the union of the supraoccipital and parietal bones. Some members of the Suidae also have skin growths without a bony support or core on the face, called warts. The structure of the snout, tusks, and facial warts is intimately linked to diet, mode of feeding, and fighting style.

Other key features of wild pigs and peccaries are their large canine teeth and brachyodont (low-crowned) molars with bunodont cusps (blunt-rounded crowns, a tipically omnivore dentition. The dental formula varies among the different genera; a general formula is (i 1-3/3, c 1/1, pm 2-4/2, m 3/3) = 34 to 44. In Potamochoerus, Sus, and Hylochoerus the dental formula is: (i 3/3, c 1/1, pm 4/4, m 3/3) = 44; in Babyrousa it is: (i 2/3, c 1/1, pm 2/2, m 3/3) = 34; and in Phacochoerus it is: (i 1/3, c 1/1, pm 3/2, m 3/3) = 34. The peccaries (Tayassu and Peccari) have a similar dental formula: (i 2/3, c 1/1, pm 3/3, m 3/3) = 38). In general, the upper incisors decrease in size from the first to the third, and the lower incisors are high, narrow, set closely together, and almost horizontal in position. The incisors and the canines have sharp lateral edges. The continuous contact between superior and inferior upper and lower tusks produces sharper edges that constitute an important defense weapon, and are also used actively in male fighting during mating periods and to mark trees.

It is commonly written, as in some of the classic general manuals of zoology, that suoids have a simple nonruminating stomach. However, anatomical, histological and dietary studies give an idea of its real complexity. In spite of the fact that suid stomach is indeed different to that of ruminants, there is also importan variability between species, as a result of dietary diversification and evolutionary history.

General diagram of the skeleton of a wild boar

Pigs live in many kinds of habitat but generally where there is some vegetation for cover, for the most part forests or woodlands, and the majority of the species are active mainly at night (a notable exception is Phacochoerus, which inhabits open savannah and is mainly diurnal). Suids are generally omnivores. They feed on a wide range of plants (fungi, ferns, grasses, leaves, roots, bulbs, and fruits), and they root in litter and moist earth to take insect larvae, small vertebrates (frogs, rodents, reptiles, young birds), eggs, and earthworms. However, it is reasonable to expect significant differences in diet, when considering differences in habitat preferences and foraging methods. For instance, the giant forest hog and the warthog are more specialized herbivores. Interestingly and contrary to popular belief, a wild pig rarely will overeat.

Many of the suoids are key species affecting plant population demographics by influencing the survival of early successional stages when depredating seeds and roots, and modifying soil structure (mixing of layers). Species such as the Wild Hog or the Red River Hog can destroy complete crop fields, dig up buried animals, eat those recently died on the surface or devour all individuals at nesting places of amphibians or birds. Therefore, suids play a pivotal role in the regeneration, colonization and spatial distribution of plants and animals, influencing the ecosystem they inhabit very visibly.


This text has been adapted from the Msc Thesis of Ignacio Aguilar Lazagabaster "Microwear analysis on Suoid incisors: a new method to study faunal adaptive responses to the environmental changes which shaped Human Evolution" directed by Eugénia Cunha (University of Coimbra) and Jan van der Made (MNCN-CSIC). Find a link here:      https://estudogeral.sib.uc.pt/bitstream/10316/24669/1/Tese%20Mestrado%20Final%20Ignacio.pdf