Behavior and Ecology of Wild and Feral Swine (Sus Scrofa) H. B. Graves J Anim Sci 1984. 58:482-492. The online version of this article, along with updated information and services, is located on the World Wide Web at: http://jas.fass.org www.asas.org Downloaded from jas.fass.org by on March 4, 2010. BEHAVIOR AND ECOLOGY OF WILD AND FERAL SWINE (SUS SCROFA) 1'2'3 H. B. Graves 4 The Pennsylvania State University, University Park 16802 Summary stomach and paraxonic foot with only the An overview of wild and feral swine behavior forward pairs of toes (the third and fourth) is presented. In spite of their success as a bearing weight. The first digit is absent in living domesticated animal in the New World, swine members. Other ungulates have a mesaxonic are relative newcomers to the Americas. Feral foot with the axis through the third toe. The swine, i.e., domesticated stocks which have astragalus, the most characteristic Artiodactyl reentered the wild habitat, apparently became bone, has rolling pulley surfaces above and established after early 'stocking' by Spanish below, allowing great freedom of motion to explorers, and wild stocks stem from much the ankle for flexion and extension of the limb more recent imports. The function, or adaptive but limiting movement to fore and aft direc- significance, of the behavior of wild and feral tions. Dentition, which was complete in early swine is usually readily apparent when studied types, is reduced in most living Artiodactyls but within an ecological context, and such studies remains complete in the Suids. may provide insight into the behavior, well- Presumed swine ancestors occur in the being and management of domestic stocks. Eocene; true pigs appeared in the Oligocene and (Key Words: Behavior, Ecology, Feral Swine, were highly successful in later epochs. The Wild Swine, Management.) Suidae canine tusks became prominent during the Miocene; the simple bunodont molar teeth General Characteristics became more highly developed, with a multipli- The Artiodactyla, or even-toed ungulates, is cation in the number of cusps, in the late a highly successful, widespread group of verte- Tertiary. Pigs (and peccaries) are characterized by brates that includes cattle, sheep, goats, camels, rooting behavior and associated cranial features, deer and giraffes as well as members of the including an elaborated rhinarium, lengthening suborder Suina, the pigs, peccaries and hippos. of the snout and hypertrophy of the nuchal The Suidae (pigs) is an Old World family, muscles and areas of attachment. although swine have become widespread in the New World since domestic, feral and wild Recent History stocks have been imported into the Americas. Suids have upward curving canines that form Swine were domesticated in Europe and Asia tusks in males; they have a coarse and sparse 5,000 to 10,000 yr ago (Zeuner, 1963). Domes- hair coat, a simple rather than ruminated tic swine were brought to the Southern U.S. in the 1500's by Fernando de Sota; his extensive travels in that region apparently resulted in at least some involuntary stocking. Other adven- 1Presented at the symposium "Ethograms of turers and settlers brought swine to the U.S. Feral Livestock and Their Application to Contempo- and improved domestic stocks as well as Euro- rary Livestock Production and Experimentation," pean wild boar have continued to be imported Joint Can.-Amer. Soc. of Anim. Sci. Annu. Meet., during this century. A herd of about 15 wild Univ. of Guelph: August 8-11, 1982. 2Paper No. 6739 in the Journal Series of the Penn- boars was brought to an enclosure in the sylvania Agr. Exp. Sta. mountains of North Carolina, probably from 3The technical assistance of Nancy Weir Lilburn, the Harz Mountains of Germany, about 1910 to W. D. McCort and Don Rudzinski is gratefully ac- 1912. The Smokey Mountains still harbor a knowledged. 4 Dept. of Biol. and Dept. of Poul. Sci. large population of these animals (Jones, 1972). Received April 21, 1983. Feral swine are distributed widely in tem- Accepted August 8, 1983. perate and tropic regions of the world. They 482 JOURNAL OF ANIMAL SCIENCE, Vol. 58, No. 2, 1984 Downloaded from jas.fass.org by on March 4, 2010. BEHAVIOR AND ECOLOGY OF SWINE 483 occur throughout the Southeastern U.S. and in obtained on over 2,500 sightings. In addition, several Southern states, in California and in 28 males and 34 females were captured, tagged Hawaii. They are also abundant in Australia, and released. The mean number of resightings New Zealand, Indonesia and, sadly, in many of tagged pigs was 3.56. An additional 25 to 30 island habitats where their presence often pigs were individually identified but were not devastates native fauna and flora. The destruc- tagged. Several thousand feral swine currently tive impact of free-roaming domestic, wild or exist on Ossabaw Island, in spite of an intensive feral pigs on the environment stems in part trap and removal management system. The from their catholic, omnivorous dietary habits origin of the feral swine on Ossabaw is uncer- and in part from their methods of obtaining tain, but there is a variety of markings charac- food by rooting. teristic of assorted domesticated breeds in the Swine utilize their muzzle, which is flattened population as well as reports of occasional into a tough, rounded disk, in an unending piglets with "chipmunk stripes" on the back, search for food on and under the substrate; this markings characteristic of wild boar ancestry. muzzle, or "rooter," gets them in a great deal of trouble when its owner is confined. Hartsock (1982) has accurately argued that many man- Social and Feeding Behavior agement problems with domestic swine stem Social behavior is very highly developed in from our inattention to providing occupation swine. Piglets stand within minutes of birth and for the pig's nose, which, trained over evolu- begin to form social dominance relationships tionary time for gainful employment, gets into with littermates within hours. Because several every conceivable sort of difficulty when given females may combine litters, interactions with nothing productive to do. individuals from other litters begin very early in We (Graves et al., 1975; H. B. Graves, M. life; and early associations often persist into Wilson and J. Elicker, unpublished data) adulthood, especially among females. Early initiated studies on behavior and ecology of associations with humans form the basis for feral and domestic swine over a decade ago. strong, persistent relationships also. For exam- Field studies have emphasized a population of ple, hand raised piglets persistently return to animals on Ossabaw Island, located just south Island homes despite repeated attempts to of Savannah, Georgia and 5 km from the reestablish them on remote corners of the mainland. Ossabaw is the Northernmost and Island. Such strong early socialization to third largest (approximately 110 km 2) of the humans has thwarted attempts to establish Georgia Sea Islands. The island was privately pen-reared European hogs in the wild (Lewis, owned until 1978, when the efforts of Eleanor 1966). Torrey West, past owner and long-time protec- The social behavior of European wild hogs tor, led to its purchase by the State of Georgia (Sus scrofa) closely resembles that of its domes- as the first Georgia "Heritage Preserve" for tic relatives. The wild hog is gregarious, though "natural, scientific and cultural study, research not to the point of forming large herds. The and education, and environmentally sound nuclear social unit in swine is based around one preservation, conservation and management." to several females and their offspring. Other Approximately one-third of the island is forest, individuals may be loosely associated with this mostly live oak (Quercus virginiana), pine basic social unit, and adult males associate with (Pinus spp.), palm (Sabal and Serenoa spp.) and the female(s) whenever the female(s) exhibits magnolia (Magnolia grandiflora) and almost sexual receptivity. two-thirds is smooth cordgrass (Spartina Hogs make use of chemical marking and alterniflora) salt marsh. The area has a temperate auditory and visual communication in intra- climate, with average temperatures of 11, 18, specific interactions. The hogs' senses of smell 27 and 19 C in winter, spring, summer and and hearing are quite well developed and they autumn, respectively. Average rainfall is 125.4 rely more on these than on sight (Conley et al., cm annually. 1972; Eisenberg and Lockhart, 1972). Field observations were conducted peri- Eisenberg and Lockhart (1972) did a 12-mo odically during 1970 to 1980, including a hog census on the Wilpattu Game Preserve in systematic survey study from late summer 1972 Sri Lanka. They recorded 184 "groups" of through the summer of 1974 (Graves et al., hogs, all of which contained less than 20 1975; Graves and Graves, 1977). Data were animals. Seventy (38%) were of solitary indi- Downloaded from jas.fass.org by on March 4, 2010. 484 GRAVES 5.0 viduais and 74% of the solitary individuals were 45 adult or subadult males. The next most frequent 40 grouping consisted of four to six individuals. ~35 Conley et al. (1972), in their wild hog research 23o in Tellico Wildlife" Management Area in Tennes- Q: 25 see, recorded comparable group sizes of wild boar. 15 Solitary individuals were commonly sighted ~ rC,- IE on Ossabaw during the summer months but 5 . almost never during January-February (figure 1). The number of individuals per group (ex- MONTH cluding unweaned piglet-mother groups) was Figure 2. The mean number of individuals per usually two to three (figure 2). The peak in group sighted monthly on Ossabaw Island. January-February represents recently weaned pigs that remain in the sibling groups. Groups usually consisted of a sow and her 9piglets.