Fact Sheet for Sus scrofa (Linnaeus, 1758).

Sus scrofa (Linnaeus, 1758).
Photo by FWC

Scientific Name: Sus scrofa

Integrated Taxonomic Information System (ITIS): 180772

Other scientific names appearing in the literature of this species:

Common Name: Wild hog, pig, old world swine, razorback

Wild hogs are variable in color, size, coat, and form. The body is rounded and legs are short. The tail may be coiled (Whitaker, 1988). Skulls of wild hogs are recognizable by the steeply elevated cranium, the absence of a bony ring around the eye socket, the presence of well developed incisor teeth in the upper jaw, and the presence of upper canines that project outward and sometimes upward. The dental formula is I3/3, C1/1, P4/4, M3/3 X 2 = 44 (Lowery, 1974).

Wild hogs in the United States are a mixture of pure-bred wild boars, pure feral domestic strains, and hybrids of the two. Modern domestic hogs are a product of selective breeding and originated from wild boars. Domestication is believed to have begun in China around 4900 B.C., and may have begun as early as 10,000 B.C. in Thailand (Nowack, 1991). At present, domestic hogs are morphologically very different form their parent form. However, when they occur together feral domestic hogs and wild boars readily interbreed forming morphologically intermediate hybrids (Whitaker, 1988). In the United States, introduced pure-bred wild boars chiefly occur in North Carolina, Tennessee and California, and have been reported from preserves in New Hampshire, Vermont, and Pennsylvania. Pure-bred wild boars have a coat of long bristly hairs thickening into a mane on the neck and shoulders. They are usually black and sometimes brown or grey in color. The tail is moderately long and hangs straight, never coiled. The upper tusks are typically between 3 and 5 inches long, but may grow to 9 inches in length, and curl out and up along sides of mouth. The lower tusks are smaller, they turn out slightly rising outside mouth and pointing back towards the eyes (Whitaker, 1988). Wild hogs, which are either feral domestic hogs or hybrids of domestic hog and wild boar, have been reported from all five Gulf states, as well Arizona, Arkansas, Georgia, Missouri, Oklahoma, Oregon, and South Carolina (Whitaker, 1988). They have been reported to range from 108,000 to 375,000 square km of the Coastal Plains region of the southeastern United States (Johnson et al., 1982).

Similar Species:

The peccary, Dicotyles tajacu, which is much smaller, more uniformly and thickly coated, usually with light collar over shoulders, and upper tusks pointed down. Peccaries are found in southeastern Arizona, extreme southeast and southwest New Mexico, and south and central Texas (Whitaker, 1988).

Biology:

Wild hogs usually roam in groups of several females and their young. Males are solitary except when associated with breeding groups (Gingerich, 1994). Home ranges vary between males and females, and with climate, population density, and food availability (Baber and Coblentz, 1986). Baber and Coblentz (1986) reported home ranges for wild hogs established on Santa Catalina Island, California to vary between 0.90 and 2.44 square kilometers, with males having larger home ranges than females. Wild hogs occur in a variety of habitats, but tend to prefer wooded areas close to water (Gingerich, 1994). They occur in flat coastal areas, in swamps and marshes, as well as on hills or mountain sides (Golley, 1962). Their sense of sight is rather poor but their senses of hearing and smell are extremely acute (Ingles, 1965). Wild hogs are typically not aggressive and will retreat if approached. However, when cornered, wounded, or defending young, they may charge and are capable of inflicting serious wounds with their razor sharp tusks (Ingles, 1965; Nowack, 1991; Gingerich, 1994).

Temperature Tolerance: Wild hogs do not have sweat glands. They regulate their body temperature by lying in water or mud, and cannot survive in hot climates without a plentiful supply of water (Gingerich, 1994). Their foraging behavior, and the areas in which they forage most intensely, varies seasonally in accordance with fluctuating temperatures (Belden and Pelton, 1975; Van Vuren, 1984).

Reproduction and Fecundity: In areas of tropical climate, wild hogs breed year round. Breeding peaks are typically associated with the rainy season. In areas of temperate climate breeding occurs in the spring (Nowak, 1991). Males fight for control of female groups, and usually win control of 1-3 females, rarely up to 8 (Nowak, 1991). Males return to their solitary lives after breeding (Nowak, 1991; Gingerich, 1994). Females have an estrous cycle of 21 days and are generally receptive for 2-3 days. The gestation period is 100 to 140 days (Ingles, 1965; Nowack, 1991). Near-term females leave the group to give birth, but rejoin it shortly after. Unlike other ungulates the young are born in a nest in which they remain for some time after birth (Nowak, 1991). Nests are generally shallow depressions lined with grass or Spanish moss (Golley, 1962). Females have one or two litters per year, with five to twelve piglets in a litter (Ingles, 1965; Gingerich, 1994). Litter size has been reported to increase with age and peaks when females are between 2-3 years of age (Baber and Coblentz, 1986). Johnson et al. (1982) reported a mean litter size of 3.3 for wild hogs of the Great Smokey Mountains National Park. Baber and Coblentz (1986) reported litter size as 5 for wild hogs established on San Catalina Island, California. The piglets are weaned in three to four months, and may leave the mother prior to the birth of the next litter (Nowack, 1991). Sexual maturity is obtained as early as 5-8 months in females and 7.5-12 months in males (Johnson et al., 1982). Although cases of under yearling females conceiving in the wild have been reported (Conley et al., 1972), females typically do not breed until they are at least 18 months of age (Nowack, 1991). Males do not breed until they reach full size at about 5 years of age (Nowack, 1991).

Trophic Interactions: Wild hogs are omnivorous eating roots, leaves, acorns, nuts, bulbs, and tubers, as well as snails, slugs, earthworms, insect larvae, frogs, reptiles including venomous snakes, bird eggs, rats, mice, small weakened or vulnerable mammals, and carrion (Lowery, 1974; Bratton et al., 1982; Laycock, 1984; Baber and Coblentz, 1987; Gingerich, 1994). Laycock (1984) reported a wild hog attacking, killing and eating a white tailed deer fawn. They are occasionally even cannibalistic (Gingerich, 1994). Subadults consume a greater quantity of animal matter than adults and under yearlings tend to have a more diverse diet than subadults or adults (Dardaillon, 1989). Diet tends to vary seasonally with availability of mast (fallen acorns and nuts) which is a preferred food item, and with climate (Golley, 1962; Belden and Pelton, 1975; Bratton et al., 1982; Van Buren, 1984; Baber and Coblentz, 1987). For animals established in Georgia, roots and tubers constitute the main food items taken in winter, whereas leeches, earthworms, insects and fiddler crabs make up a greater portion of the diet in spring and summer. In uplands acorns, roots, seeds, and pines are preferred items (Golley, 1962). Foraging occurs both during the day and night, but is most intense at night, especially during the summer (Van Buren, 1984; Gingerich, 1994). The tusks which may be used as dangerous weapons, function primarily in finding and harvesting food (Laycock, 1984). Although a hoofed mammal, wild hogs have only one stomach, and do not chew cud (Ingles, 1965).

Young wild hogs are taken by a number of different predators, including, hawks, owls, eagles, foxes, and bobcats (Laycock, 1984; Gingerich, 1994). Adults are rarely taken because of their large size, but panthers occasionally kill and consume wild hogs in southern Florida (Gingerich, 1994).

Maximum Size:

Some domestic hogs may weigh as much as 450 kg (Nowak, 1991).

Distribution:

Wild boars, from which domestic hogs originated, originally occurred from southern Scandinavia and Portugal to southeastern Siberia and the Malay Peninsula, from western Sahara to Egypt, and on Britain, Ireland, Corsica, Sardinia, Sri Lanka, Japan, the Ryukyu Islands, Taiwan, Hainan, Sumatra, Java, and many small islands of the East Indies as far east as Komodo (Nowak, 1991).

Wild hogs occur in all five Gulf states (Whitaker, 1988), including several barrier islands (Baron, 1982).

Interest to Fisheries:

Current Status of this Species in the Gulf of Mexico Ecosystem:

Domestic hogs are believed to have been first introduced into the United States by Polynesians to Hawaii, around 1000 A.D. (Nowack, 1991). They were first introduced into the continental United States on a ship commanded by Fernado De Soto landing on the Gulf Coast in 1539 (Lowery, 1974; Gingerich, 1994). Wild hogs were introduced into the Gulf ecosystem through intentional or accidental releases (Gingerich, 1994). As mentioned above, most wild Sus scrofa in the Gulf states are either feral domestic hogs or hybrids of domestic hogs and wild boars (Johnson et al., 1982; Whitaker, 1988). Florida's wild hogs, for example, are believed to be a mixture of Spanish wild boars, European hunting stock, Russian wild boars, and domestic hogs (Gingerich, 1994). Wild hogs are the most successful exotic big game species in the United States (Baber and Coblentz, 1987). They have been reported as more common than deer in certain parts of Georgia (Golley, 1962). There are an estimated 500,000 wild hogs in Florida alone (Gingerich, 1994). Population densities are highest in forested areas with dense understories and in protected areas on private lands, state parks, wildlife management areas and national refuges (Frankenberger and Belden, 1976). In Florida, the forested areas in which wild hogs thrive are dominated by coastal salt marsh and slash pine flatwoods interspread with cypress swamps, hydric oak hammocks, and bayheads (Frankenberger and Belden, 1976). Areas where population densities are lowest are those of undisturbed but marginal habitat (Frankenberger and Belden, 1976). Wild hogs are an important game species in the Gulf states as well as throughout the United States (Belden and Pelton, 1975; Frankenberger and Belden, 1976; Laylock, 1984). Management of this species has traditionally consisted of relocating wild hogs from areas where they are considered a nuisance such as state parks, to public hunting areas (Frankenberger and Belden, 1976). The primary source of mortality throughout the Gulf states is hunting, with as many as 50,000 individuals taken per year in Florida (Gingerich, 1994). However, populations remain stable in Florida and have been reported as rapidly expanding in Texas (Singer et al., 1984).

Potential Impacts:

Where abundant wild hogs can have devastating effects on the ecosystem. They consume large amounts of food and may reduce the food supply available for animals such as deer, bear, rabbit, squirrel and turkey (Lacock, 1984; Gingerich, 1994). The most serious damage comes from rooting which is their natural feeding behavior (Laycock, 1984; Gingerich, 1994). Wild hogs overturn large areas of turf leaving a considerable area without vegetation. Rooting is most intense in areas and seasons in which mast is scarce (Bratton et al., 1982). Understory vegetation in forests is greatly affected as are ground nesting birds such as grouse and wild turkey, terrestrial salamanders, etc. (Belden and Pelton, 1975; Laylock, 1984). Rooting is also fairly intense in wet areas under forest cover, and concern over species in these areas has been expressed (Bratton et al., 1982). Reports of species imperilled by rooting behavior from other parts of the United States include the southern red-backed vole, Cleithronomys gapperi, the northern short-tailed shrew, Blarina brevicauda, and the red-cheeked salamander (Laylock, 1984; Singer et al., 1984), as well as regionally endangered herbs such as Stachys clingmanii and Woodwardia virginiana (Bratton et al., 1982). Singer et al. (1984) reported wild boars in monitored areas of the Great Smokey Mountains National Park to have reduced plant cover by as much as 80%, increase bare ground by 88%, reduced the depth of the forest litter by 65%, reduced the weight of leaf litter by 59%, exposed 1,400 - 2,800 tree roots/ha, decreased bulk density of soil, accelerated decomposition and loss of nutrients from the forest floor, and altered the nitrogen transformation process in watersheds, with nitrate-nitrogen in stream water double their usual levels (Singer et al., 1984). Wild hogs probably have similar effects on ecosystems of the Gulf states.

In addition, wild hogs are a reservoir for several serious diseases. They carry pseudorabies, which is fatal in panthers, swine brucellosis which can be fatal in people, and trichinosis (Gingerich, 1994), among others.

Recommendations:

References:

Baber, D.W., and B.E. Coblentz. 1986. Density, Home Range, Habitat Use, and Reproduction In Feral Pigs On San Catalina Island. Journal Of Mammology 67(3):512-525.

Baber, D.W., and B.E. Coblentz. 1987. Diet, Nutrition, and Conception In Feral Pigs On Santa Catalina Island. Journal Of Wildlife Management 51(2):306-317.

Baron, J. 1982. Effects Of Feral Hogs (Sus Scrofa) On The Vegetation Of Horn Island. American Midland Naturalist 107(1):202-205.

Belden, R. C., and M. R. Pelton. 1975. European Wild Hog Rooting In The Mountains Of Eastern Tennessee. Proceedings Of The Annual Conference Of The Southeastern Association Of Game And Fish Commissioners 29:665-671.

Bratton, S.P., M.E. Harmon, and P.S. White. 1982. Patterns Of European Wild Boar Rooting In The Western Great Smokey Mountains. Castanea 47(2):230-242.

Conley, R.H., V.G. Henry, and G.H. Matschke. 1972. European Hog Research Project W-34, Final Report. Tennessee Wildlife Resources Agency, Nashville. 259 Pp.

Dardaillon, M. 1989. Age-class Influences On Feeding Choices Of Free-ranging Wild Boars (Sus Scrofa). Canadian Journal Of Zoology 67:2792-2796.

Frankenberger, W. B., and R. C. Belden. 1976. Distribution, relative abundance and management needs of feral hogs in Florida. Proceedings of the Annual Conference of the Southeastern Association of Game and Fish Commissioners Annual Conference 13:641-644.

Gingerich, J.L. 1994. Florida's Fabulous Mammals. World Publications. Tampa Bay. 128 pp.

Golly, F.B. 1962. Mammals Of Georgia. University Of Georgia Press. Athens. 218 Pp.

Ingles, L.G. 1965. Mammals Of The Pacific States. Stanford University Press. Stanford. 506 Pp.

Johnson, K.G., R.W. Duncan, and M.R. Pelton. 1982. Reproductive Biology Of European Wild Hogs In The Great Smokey Mountains National Park. Proceedings Of The Annual Conference Of The Southeastern Fish And Wildlife Agencies 36:552-564.

Laycock, G. 1984. Hogs In The Hills. Audubon 86(5):32-35.

Lowery, G.H. Jr. 1974. The Mammals of Louisiana and its Adjacent Waters. Louisiana State University Press. 565 pp.

Nowak, R.M. 1991. Walker's Mammals of the World. The John Hopkins University Press. Baltimore. 1629 pp.

Singer, F.J., W.T. Swank, and E.E.C. Clebsch. 1984. Effects Of Wild Pig Rooting In A Deciduous Forest. Journal Of Wildlife Management 48(2):464-473.

Van Vuren, D. 1984. Diurnal Activity And Habitat Use By Feral Pigs On Santa Cruz Island, California. California Fish And Game 70(3):140-144.

Whitaker, J.O., Jr. 1988. The Audubon Society Field Guide to North American Mammals. Alfred A. Knopf, Inc. New York. 745 pp.

Other on-line references:

Date Created: 08/30/1999
Last Modified: 03/08/2004

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