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Sus scrofa - Domestic Pig

Skull Pictures:       
Anterior mandible     Mandible
Dorsal     Ventral
Lateral 

Geographic Range:

Pioneering pigs, which emigrated from Europe to the Western Hemisphere in the fifteenth and sixteenth centuries quickly, made themselves at home.  The woodlands, hills, swamps, marshes, lowlands, and forests.  Confined to the sty, ranged the woods and grazing lands, or escaped to lead a feral existence Sus scrofa can survive in all conditions  Found Palearctic, Oceanic Islands, Nearctic, Oriental, Ethiopian, Neotropical, Australian; making Sus scrofa the largest ranging Suidae. (Towe 1950, Martin 2001, Hruby 2003)

Physical Description:

The Suidae has 5 genera and 16 species.  Sus scrofa, ordinal name Artiodactyla meaning, and “even-digited ones”.  The fact that artiodactylas are even toed ungulates distinguishes them from the perissodactyls, which are odd-toed ungulates.  There are generally two or four digits and the limbs are paraxonic, with the plane of symmetry passing between the third and fourth digits of each foot.  Sus scrofa has a four pedal digits. Most living artiodactyla are herbivorous, but some of the more generalized forms (hogs) are omnivorous.  Suids have short legs; heavyset bodies; thick skin with short, coarse pelage; small eyes; a relatively large head; and a prominent snout truncated at the end with a round, cartilaginous disk.  Several layers of muscles are associated with the snout, which is used in rooting for food.  Several species have large facial warts, most prominent males.  The sense of smell is its biggest advantage.  Lacking in good eyesight due to eyes being located on the sides of the head. Ears are varying from small and erect to erect and low and flapping.  The maximum body mass range is approximately 200 kg in the wild boar.  Upper incisors present; seven upper cheek teeth on each side; cheek teeth with many rounded cusps; orbit not surrounded by complete, circular, bony ring.  Dental formula 3/3 1/1 4/4 3/3 = 44; 1/3 1/1 3/2 3/3 =34; 2/3 1/1 2/2 3/3 = 34; upper canines curve either outward, upward, or both. (Swine, hogs, pigs)  With simple stomachs, bunodont cheekteeth, and large, ever-growing canines—the upper pair curving up and outward to form tusks.  (Sus scrofa).

Food Habits:

The large head and mobile snout are used to root for food.  Sus scrofa is omnivorous and sometimes indiscriminant diet.  Diet includes shrubs, roots, acorns, nuts, bulbs, tubers, weeds, bird eggs, frogs, snakes, insects, mice, roots, tubers, small weakened or vulnerable animals, carrion, and even manure.  Occasionally cannibalism occurs.  Diet tends to vary with season, climate and availability.  Foraging occurs both during the day and night, but is most intense at night, especially during the summer.  Wild hogs have one stomach and do not chew cud.   Suids are gregarious and often forage in-groups.  The wide array of food sources has allowed Sus scrofa be survive in a wide array of environments from deserts to mountainous terrain.

Reproduction:

Suids are sexually mature by 18 months of age; although male may not have access to females until they are 4 years old. Females have an estrous of about 21 days and are receptive for 3 days.   Gestation is 115 days for domestic pigs.  The litter size ranges from 1to12(peak litter size at 2-3years).  Mating occurs year round in tropical climates and in the spring in temperate climates.  On average only half of litter will survive to maturity in the wild many fall to disease or predators.  The piglets are weaned in three to four months, and may leave the mother prior to the birth of the next litter.  The most aggressive of the males will secure as many as eight sows during one mating season.

Predation:

Humans are the major predators of this species.  Carnivores such as black bears and mountain lions are capable of taking down young adults.   Piglets may be preyed upon my bobcats, foxes, and coyotes.

Behavior:

Foraging occurs both during the day and night, but is most intense at night, especially during the summer.  Near-term females leave the group to give birth and rejoin shortly after as mothers that are extremely protective of their young.  Mating season brings about violent times for males in search of the prize sow.  Sharp tusks are used to fend off other males and a thick tissue is developed around the front of the belly in defense.   Wild hogs are sometimes found in large herds of up to 100.  Typical herds number 20 individuals composed of two families of females and their litters.  Males leave the group at sexual maturity and live on their own.

Pigs are ideal for domestication because of their diverse feeding habits.  Pigs scavenged on discarded food remains in association with early human settlements, before they were eventually confined.  And the piglets are easily tamed and acclimated to humans.

Habitat:

Biomes- temperate forest and rainforest, temperate grassland

Due to domestication feral invasive Sus scrofa have adapted to a wide variety of habitats.  Typically, wild hogs are found in moist forests and shrublands, especially oak forests and areas where reeds are abundant.  Snowfall levels limit the range of the pigs by making travel and finding food relatively difficult.  Severe temperature changes cause difficulties in adaptation.  Wallowing in mud or water help maintain a comfortable temperature while also protecting against sunburn and insect bites.  

Economic Importance for Humans:

Positive-

Pigs play the most important role serving as breakfast, lunch or dinner for humans.   In France, pigs have been used to find truffles (underground fungi) used in French cuisine.  In England the sense of smell was used for hunting.  In ancient Egypt they were used for the planting of seeds in the hoof prints.  Pigs are an important game species in the Gulf states as well as throughout the United States.  Management of the hogs is performed by moving nuisance animals to public hunting areas.   In George on private lands wild pigs are hunted year round for food and sport.   The promise of xenotransplantation is now a reality female pigs have been cloned to have an enzyme that allows for pig to human organ transplantation. Pigs have served as food and as sacrificial animals in many cultures.  Pigs have also contributed to the entertainment business such as starring roles in movies such as Babe and Babe in the Big City, and the world famous Charlotte's Web.

Negative-

Wild pigs have a negative impact on the environment by disturbing the soil and natural vegetation by rooting which leads to the shift in plant community structures.  Pigs also compete with local native animals for food.  Sus scrofa carries transmissible parasitic infections to humans such as trichinosis, cysticercosis, and brudellosis caused by eating undercooked meat. Wild hogs are also reservoirs for several serious diseases.  They carry pseudorabies, which is fatal in panthers, swine brucellosis, which can be fatal in people, African swine fever, cysticercosis, and trichinosis.

Conservation:

Sus scrofa has no special status as far as IUCN, U.S. ESA, or CITES.  Overall pigs are not threatened by extinction, though some domesticated breeds have disappeared in recent years.  Pigs are ever increasingly becoming more popular as indoor house pets.

History:

Along with the sheep, goats, cattle, and horses introduce by Columbus came eight porters, who crossed the Atlantic with the Admiral on his second voyage in 1493, and became the reputed progenitors of all the hogs that populated the Spanish Indies.  In Espanola, Jamaica, and Cuba, they soon ran wild through the jungles and canebrakes.  Soldiers hunting rebellious Indian neophytes and escaped Negro slaves were often attacked by these belligerent pigs, especially when the animals were cornered.  By 1850, the Middle West contained 3.7 times as many swine as the Eastern states.  The Napoleonic wars in Europe made the price of corn along the Atlantic seaboard so high that much of it was shipped abroad, causing a meat shortage so high that much of it was shipped abroad, causing a meat shortage that could be relieved only by the cattle, sheep, and swine of the Midwestern drover.

They may have been domesticated first in the Middle East and western Asia, about 7000 to 8000 years ago. Historically, groups of domesticated pigs were allowed to roam loose, watched by a swineherd, or were housed in a “pigsty” or pen.  Numerous breeds of pigs are now recognized.   More than 100 breeds of domestic pigs are recognized throughout the world today.

Swine Industry Developments:

There are many similarities of the swine and the poultry industry, although the swine industry has provided the market’s demand for pork with independent producers some forty years longer than producers in poultry have have.  However, we can distinguish clear parallels between historical phases in the two industries.  Prior to the last decade, essentially all pork was owned and produced independently by farmers who took their pigs to auction.  Corporate swine farms are operating in a number of states now, and the small independent farmer is finding it increasingly difficult to find a market.  The tremendous production by mega-farms also drives the price of pork down over time, contributing to the demise of many independent farms.  The poultry industry development in which the processors have complete control over all aspects of the production process from embryo to the market shelf.  The swine industry has not yet entered this phase, as processors have not established absolute control over producers.  As more independent producers are eliminated from the business and the majority of production is done under contractors, difficulties in production will multiply.  Pork producers will be situated similarly to poultry growers both economically and socially.  Sustainable agriculture may offer smaller, independent hog farmers hope for finding an alternative to large-scale industrial production.

Hogs constitute an important sector of the Midwestern agricultural economy.  What is more important, hogs are the economic backbone of many diversified family farms.  Hogs provide a value-added market for crops, stabilized farm income, recycled nutrients, and scavenged wastes.  Hogs and other livestock provide year-round employment for farm family members who are otherwise underemployment in specialized cropping systems.  Hogs on farms provide a classic example of synergistic productivity.  They are capable of adding far more to farming systems than in apparent from superficial economic examinations of hog enterprises such as the one descried below.

The production environment in large-scale operations is controlled through utilization of buildings and equipment that require large capital investments but greatly reduce labor requirements.  Production technologies associated with large-scale, contract production also change the nature of management.  Mass production technologies that standardize genetic selection, breeding, feeding, herd health, and marketing functions transfer most of the management function from on-site hog producers to corporate production supervisors who travel among production units and to production mangers at corporate

Headquarters. Large-scale, specialized hog production replaces people with capital intensive, mass-production technologies and centralized management.

For family farms, total returns over direct production costs are available for local retail spending.  For most corporate operations, only those costs paid in local wages and salaries are available for retail spending.  Using average income figures tends to underestimates their impacts on employment in manufacturing and wholesaling.  Successful owner-operated family farms tend to be smaller and, in general, employ more people per acre or per dollar of output than do corporate enterprises.  More people in the local community tend to generate more local retail spending.

Literature Cited:

Dougherty, R.  2002.  National Parks. "Making a Pig Sty of Ancient History". v. 76 no. 9/10

Feldhamer, G.A.; L.C. Drickamer, S.H. Vessey, and J.F. Merritt, Mammalogy: Adaptation, Diversity, and Ecology Second Edition, McGraw-Hill 2004, 1999 P.319-454.

Georgia Wildlife Web.  2000.  "The Georgia Museum of Natural History and Georgia Department of Natural Resources". http://museum.nhm.uga.edu/gawildlife/mammals/artiodactyla/suidae/sscrofa.html.

Hruby, J. “Species Account for Sus Scrofa”. http://animaldiversity.ummz.umich.edu/accounts/sus/s._scrofa$narrative.html. Accessed November, 16, 2003.

Kaebnick, G.E.  2002.  The Hastings Center Report "The Cloned Pigs and the "Reality" of Xenotransplantation." v. 32 no. 2

Kurta, A.  Mammals of the Great Lakes Region, The University of Michigan Press, 1995 P. 320.

Martin, R.E.; R.H. Pine, A.F. DeBlase, A Manual of Mammalogy, Mcgraw-Hill, New York, NY 2001 P. 172-175.

Stuart, P.G.  Non-Indigenous Species in the Gulf of Mexico Ecosystem. "Sus scrofa". www.gsmfc.org/nis/nis/sus_scrofa.html . August 30, 1999.

Thu, K.M.; and E.P. Durrenberger. Pigs, Profits, and Rural Communities Published by State University of New York Press, Albany 1998 P. 6-165.

Towe, C.W. and E.N. Wentworth, Pigs from Cave to Corn Belt, Norman University of Oklahoma Press 1950 P. 66-275.


Reference written by Margaret Haas, Biol 378: Edited by Chris Yahnke.
Page last updated 4-29-04.

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