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The pigs are a group of generalist omnivores, and lack many of the extreme
adaptations seen in other ungulates. They are medium-sized mammals
(although some individuals may weigh up to 350 kg), with relatively short
legs, a compact body, and a long, pointed head. This is an Old World
family, with its eighteen living species being found across most of Eurasia
and Africa. The Suidae appeared in the mid-Oligocene, and have survived
to the present day with only minor changes to the basic body plan. The
recent genera are all relatively recent (from the Pliocene and Pleistocene).
Swine are generally drab in coloration, with the notable exception of the
brightly-colored red river hog, Potamochoerus porcus. The skin
is thick, usually covered with sparse, bristly hairs, and has the most diverse
assemblage of scent glands of all of the ungulates. Many species possess
facial "warts", which are skin growths without a bony core. The canines
are modified into ever-growing tusks which protrude from the mouth and curve
upwards; they are especially large in males, serving as tools, visual status
symbol, and weapon. The dental formula is variable; I 1-3/3, C 1/1,
P 2-4/2-4, M 3/3 x 2 = 34-44.
Most pig species are forest dwellers, although the warthogs
(Phacochoerus sp.) inhabit savannahs. Forested environments
have a wide range of available foods - as omnivores, pigs are able to take
full advantage of this bounty, feeding on both plant and animal matter.
All species have an excellent sense of smell and a cartilaginous nasal
disc; both are used extensively when foraging and rooting through forest
litter. The stomach has two chambers, but pigs do not ruminate.
Swine are highly social: females often live in large groups (called sounders),
while males tend to be solitary or monopolize a group of females as a
harem. The Suidae are the only ungulates which have large litters of
offspring: while litters of 2-6 are normal, some species may have up to 12
infants at a time! Infants of most species (all genera with the exception
of Babyrousa, Hylochoerus, and Phacochoerus) are marked
with bright horizontal stripes, which provide camouflage in forested
environments.
There are four tribes:
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Babyrousini - babirusas
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Phacochoerini - warthogs
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Potamochoerini - African forest pigs
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Suini - Eurasian swine
The tribes Babyrousini and Phacochoerini were formerly considered to be
subfamilies, while the Potamochoerini and Suini used to be united into the
subfamily Suinae; one of the primary distinctions between these three groups
is their dentition.
The domestication of the Eurasian wild pig Sus scrofa first occurred
around 4,900 B.C. in China (although some authors date this as early as 10,000
B.C. in Thailand). While most domestic pigs today are ascribed to Sus
scrofa, several domestic and feral pig populations in Indonesia appear
to be descended from Sus celebensis. Pigs have also been introduced
to many areas, forming feral populations in North America, New Guinea, Australia,
and New Zealand (among others) - Sus scrofa is rated as one of the
worst invasive species on the planet by the IUCN. |
