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Home , Feral pig, Mon (emblem), Wild boar

Behavior and Ecology of Wild and Swine (Sus Scrofa) H. B. Graves

J Anim Sci 1984. 58:482-492.

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H. B. Graves 4

The 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 in the , swine members. Other have a mesaxonic are relative newcomers to the . 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 , 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, 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 appeared in the Oligocene and (Key Words: Behavior, Ecology, Feral Swine, were highly successful in later epochs. The Wild Swine, Management.) 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 ) are characterized by brates that includes , , goats, , rooting behavior and associated cranial features, and giraffes as well as members of the including an elaborated rhinarium, lengthening suborder , the pigs, peccaries and hippos. of the snout and hypertrophy of the nuchal The Suidae (pigs) is an 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 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 and Their Application to Contempo- and improved domestic stocks as well as Euro- rary Livestock Production and Experimentation," pean 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 , probably from 3The technical assistance of Nancy Weir Lilburn, the 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 (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 and in 28 males and 34 females were captured, tagged Hawaii. They are also abundant in , and released. The mean number of resightings , and, sadly, in many of tagged pigs was 3.56. An additional 25 to 30 island 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 and for the '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 form the basis for feral and domestic swine over a decade ago. strong, persistent relationships also. For exam- 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, 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 (Quercus virginiana), 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 . 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 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 Preserve in systematic survey study from late summer 1972 . 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-

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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 -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. Single sow groups contained one to nine most occurring from October through June, piglets, with a mean of 5.1. The largest groups March being the peak month. Mauget (1981) consisted of two to four adult females and their reported that two farrowing distributions collective progenies, occasionally with one or occur, a unimodal type with a peak in April- more subadult male(s) present. The number of May and a bimodal type with a peak in January- piglets in two mother groups ranged from 3 to February and another in August-September. 19, with a mean of 7.0. Most of the noninfant Jones (1972) reported that tracks of young (weaned and older) Ossabaw groups were of European wild hogs in North Carolina are seen two or three pigs. throughout the year. Stegeman (1938) suggested Females greatly reduce their home range that two breeding seasons exist, although this (Kurz and Marchinton, 1972) and may become situation does not coincide with that reported solitary when they are ready to give birth. They for the same species in Germany. On Ossabaw afterwards often reform into small groups. The Island, the crop (, et cetera) has a young in a group are generally at about the large impact on the distribution of the animals same developmental stage, indicating that estrus and on timing of reproduction. The proportion in the females within a group is somewhat of animals seen in wooded areas peaks in synchronized (Eisenberg and Lockhart, 1972). October-December (figure 3). Ossabaw pigs fed Pine and Gerdes (1973) studied wild pigs in in oak, palmetto and hickory woods during the Monterey County, California and found that late fall and winter (figure 4) when acorns, farrowing continued throughout the year, with palmetto , grapes and hickory nuts are available. Food is often scarce during the summer months, and the pigs move onto the salt marsh in search of grass, , and invertebrates. Reproduction is strongly associ- ated with the availability of mast in the fall. IOO Sow-piglet groups are seen most frequently 9o during November-December (55 %) or February- 8o March (27%) and most (74%) such groupings ?0 were seen in wooded rather than nonwooded !6o areas (figure 5). Feral sows often combine litters as described for wild boar, although each sow continues to nurse only her own young. ~ 30 The mean litter size for groups with a single ~ 20 adult female was 5.1; the mean number of young in two-mother groups was 7.0. Sharing o parental duties such as guarding young allows AUG SEP OCT NOV DEC JAN'FEBMAR-APR MAY'dUN MONTH females to alternate at foraging alone, probably Figure 1. Percentage solitary individuals sighted with greater efficiency than in the case with monthly on Ossabaw Island. single mother groups.

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100 WOODS Farrowing typically lasts for a few hours in --- MARSH 90 .'" -- FIELD feral and in domestic swine, with a few minute .... " 80 interval (usually about 15 min, longer for later Z 70 ." born piglets) between each fetus. After expelling CO 60 each fetus, the sow may stand and sniff the 50 ..

Z 40 / 2 ~.- ~ piglet or simply remain still. She does not assist piglets' efforts to clean themselves of birth 30 // "- O-W / "" membranes and stand upright. Blood and other fluids expelled are often eaten by the I0 sow, as is the afterbirth, perhaps to avoid AUG SF-P OCT NOV DEC JAN'-FEBMAR'-ARR MAY~-JUN attracting predators to the area, to obtain MONTH important nutrients or simply to keep the nest , Figure 3. Proportion of animals seen in wooded clean. Sows often exhibit an infertile estrus areas, marsh and fields on Ossabaw Island during each month. after farrowing, but lactating sows can be successfully rebred. A fertile heat occurs after weaning or seasonally. The is in good agreement with domestic swine (about 21 A detailed study of the fall foods of the d). European Wild Boar was conducted by Henry As in domestic swine (Hartsock and Graves, and Conley (1972) on the Tellico Wildlife 1976), newborn feral piglets progress through Management Area in the four phases in the development of a stable of Eastern . Acorns, which are high in nursing . The precocial feral piglets are and fats, were ranked first both very active and stand within seconds or minutes in volume and in frequency of occurrence. after birth. Although their eyes open immedi- Hickory nuts were second in volume and fourth ately after parturition, piglets apparently do in frequency of occurrence. When hickory nuts not identify teats visually. They move about were abundant, they were as important as nosing any surface they contact, including acorns as a food source. Acorns and hickory littermates. Aggressive behavior is absent or rare nuts together comprised 82% of the total 89% during this "teat seeking" phase. of vegetable material found in the diet. Upon contacting and suckling from a teat, Matschke (1964) also reported that Euro- piglets vigorously massage the udder (a require- pean wild sows were in an anestrous condition ment for milk letdown, Signoret et al., 1975) during years of mast failure and in an estrous and then move from teat to teat in a "teat condition in years when mast was available. sampling" process. Contact with a littermate Mauget (1981) similarly reported that mast during this time usually results in mutually availability strongly affected the timing of the aggressive behavior. Piglets display aggression breeding season. by with specialized "needle teeth" or by pushing with the nose or shoulder to dis- Farrowing and Nursing Early mother-young behavior of feral swine parallels that of domestics (W. D. McCort and I00

H. B. Graves, unpublished film). At about 3 to 90 ..""' '. WOODS 9 d prepartum, the sow's vulva swells and the .... MARSH 80 : ...... " ' " -- FIELD I\,

mammary glands enlarge; colostrum fills the 70 /I "\ teat cisterns at about 24 h before parturition. 60 Her temperament also becomes increasingly "" "... I protective and unpredictable. A concave far- rowing nest is usually constructed by rooting a Z 30 shallow depression in the soil or by rooting soil and vegetation into a and then rooting a

central depression in the pile in which to lie i (also see Hafez et al., 1962; Fr~drich, 1965; AUG SEP OCt NOV OeC JAN-FEaMAR-.PR ~Y-0U. MONTH Kurz and Marchinton, 1972). Domestic sows Figure 4. Proportion of animals feeding in wooded are often calmed at farrowing by providing areas, marsh and fields on Ossabaw Island during each them with straw to into a nest. month.

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(Mount, 1960) and with the sow. The evolution of a mechanism for rapid settlement of teat '~ f .~ox,.~,Es,zE cL.ss~,~, uJ 80 ...... 15-55 acquisition and the beginning of a stable O 70 ...... 55-155 sleep-suckling routine emphasizes the impor- ~<~Z60 ..... 135--275 tance of heat conservation to swine. Colostrum-immunoglobulin concentration drops by as much as 50% during the first few hours of nursing. Because farrowing can last as long as 4 h, earlier born piglets probably ingest more of the immunoglobulins during the "teat s~P o~T ~v 0Eci 0*n-FeS,AR-~R, i ,A*-J~ L ~.-~G, sampling" phase and hence obtain more passive MONTH immunity (pigs begin to produce their own Figure 5. Proportion of pigs of different size classes antibodies at about 10 d of age) than later seen on Ossabaw Island during each month. born littermates (see Bourne, 1969a,b, 1974). Earlier born piglets may have lower mortal- ity rates than piglets born later in the birth place other piglets from teats. The suckling order (Hartsock and Graves, 1976), but artificial piglet positions its body such that the teat itself selection and breed differences may occur. is inaccessible to the intruder. If this tactic fails, Factors contributing to the association between the defending piglet uses the same biting and birth order and mortality include the longer pushing tactics as the intruder. exposure and stress of later born piglets to the The "teat sampling" phase, lasting from 2 to prenatal respiratory gas environment and 6 h, is followed by a "teat defense" phase. birth weight. Piglets with greater than average Durirtg teat defense, the piglets limit their birth weights may be more likely to survive in activities to a specific area of the udder and some environments, but, as in most species, develop preferences for suckling from a specific selection may operate against extremes in body teat or pair of teats during the brief (about 30 weight. Heavier piglets tend to be born earlier s) letdown period, which occurs about once an and are often more vigorous, win more fights, hour (Fraser, 1973, 1975, 1978). Agonistic are able to claim (or, by more vigorous stimula- encounters occurring during this phase are tion, to 'create') the more productive teats of li0aited to adjacent littermates or to encounters the sow, suckle more often and gain more between piglets having possession of a teat and weight than other piglets. Piglets suckling those that have not claimed a particular teat. anterior teats are also less likely to be injured or After the "teat defense" phase, the piglets crushed by the sow (Fraser, 1975, 1978). settle into a "teat maintenance" phase. During Dominance continues to play a major role in this period, the piglets have uncontested access settling disputes over access to food, mates and to their specific teat(s) and alternate sleeping other limiting resources in feral, wild and with suckling. domestic swine. McCort and Gr~ves (1982) A number of factors influence the survival of demonstrated that among penned domestic newborn piglets. Such factors include main- pigs, the dominant individual enjoys greater tenance of body temperature, acquisition of freedom of movement and a less restricted passive immunity from immunoglobulin-rich personal space than do subordinant pigs. colostrum and high birth weight. A brief Subordinant feral pigs are often displaced from consideration of the relationship between such choice feeding sites by dominant animals. factors and neonatal behavior follows. According to Eisenberg and Lockhart Thermo-insulative ability is poor during the (1972), sows participate in some cooperative first week of a piglet's life. When ambient nursing within mother-offspring groups, but ! temperatures drop below 33 to 35 C, piglets have never seen this occur. They noted that must increase metabolic heat production to when a sow lies down, most of the young in the maintain constant body temperature (Curtis et area attempt to suckle. Sows reject (and may al., 1967; Curtis, 1970). With higher metabolic kill) piglets other than their own unless transfer demands, piglets must increase their energy among litters is done (artificially) during or intake to avoid starvation (Morrill, 1952). immediately after farrowing. Piglets reduce exposure of their body surface A primary purpose of the multiple mother- and conserve energy by huddling in groups offspring group appears to be the protection of

Downloaded from jas.fass.org by on March 4, 2010. BEHAVIOR AND ECOLOGY OF SWINE 487 the young. A group surprised by a predator an adult male to female sex ratio of 47:53. may disperse in several directions, perhaps Fights between boars on Ossabaw seem to be confusing the predator, or exhibit cooperative settled rather quickly unless the males are well defense. Eisenberg and Lockhart (1972) sug- matched. gested that such groups travel with sows in the Conley et al. (1972) noted that a boar lead, followed by piglets, with sows or subaduh attracted to an estrous female will chase and males bringing up the rear. Although such front nudge her with his head and snout. The female and rear guard movement may occur, most of responds by urinating. The male smells and the time sows lead and piglets simply follow. tastes the urine, then either ignores her or Ossabaw females frequently left their young to continues nudging. If the sow does not urinate, forage alone while they sought food elsewhere, the boar continues his advances for another 15 although groups with several females and their min, but ceases after that if she is still unrecep- young usually had at least one mother present. tive. According to Eisenberg and Lockhart Such "babysitting" may confer advantages to (1972), an estrous sow may rub her perineal all members of the group, especially if they are region against the ground in an "anogenital kinship groups in which the "cost" of babysit- rub." Ossabaw pigs often rub vigorously but I ting may be offset by the increased advantages have never recognized anogenital marking as

to genetic relatives. Conley et al. (1972) suggest such. that the presence of one sow continuously in the lead might indicate a degree of social Habitat ranking in the multiple mother-offspring group. Pigs are found in forest and scrub brush Eisenberg and Lockhart (1972) found no strict areas surrounding water holes, in riverine leadership in the group, nor have I; although forests or in swamps or . The amount of older sows may take the initiative in moving. cover required is contingent on pres- Family groups do not disperse until either the sures, climate and available habitat, but hogs young are sexually mature (7 to 8 mo old) or are often found in dense brush or near dense the sow is ready to farrow again (Conley et cover. The greatest activity occurs in open areas al., 1972). adjacent to heavy brush pockets and highest Males become relatively solitary by 1 to 2 yr densities of pigs occur where one-third to of age. When a boar is found traveling in a one-half of the area is grassland (Pine and group, it is usually an indication that one or Gerdes, 1973). Pine and Gerdes (1973) noted more sows in the group is in estrus (Conley et that surface water and areas that remain moist al., 1972). Ossabaw males that were in an all throughout the year are essential to good wild male group exhibited a decidedly seasonal hog habitat. Feral hogs on Ossabaw root sandy, distribution (figure 6); males associated strongly grassy, marshy and every other soil and habitat with other males during late summer. type, although their rootings occur most consistently in wet areas unless mast is available Breeding Behavior in the litter of the forest floor. Interestingly, females often exhibit an anestrous period in summer and autumn (Mauget, 1981), and males do not compete with each other for anestrous females. Male ,0o fertility may also be adversely affected by high ~ 90 summer temperature. European wild boar as o 80 well as feral (and domestic) males actively _z r0 compete for access to an estrous sow. Aggressive ~ 60

males stand erect with mane extended. In mild 50 arousal, the small hair tufts in the sacral region ~ ,o may be raised independently of the dorsal ~ 3o (Eisenberg and Lockhart, 1972). Aggressive ~2o males also emit grunts and champ their jaws, ~ ,0 causing tusks to clack and copious amounts of , , i , , ~ L s_ AUG SEP OCT NOV DEC JAN-FEB MAR-APR MAY-JUN

foamy saliva to be generated. Conley et al. MONTH (1972) suggest that male fights over estrous Figure 6. Proportion of males making up groups on females may be a major factor contributing to Ossabaw Island during each month.

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Use of Space : Males have larger home ranges than do females, but the variation in home range size is more a function of food availability than of sex except when females are near parturition. Home range size may be less than 100 ha or over 2,500 ha (Kurz and Marchinton, 1972; Pine and Gerdes, 1973; Martin, 1975; Barrett, 1978; Mauget, 1979). In any case, movement patterns of feral hogs are restricted to a home range that is not defended as is a territory. Typical disperson patterns of marked and released pigs on Ossabaw Island during the course of 1.5 yr are presented in figure 7a,b,c. Resightings of tagged pigs occurred at sites from 50 to 2,400 m from the release site. The "~- ~ '~ ~ mean maximum dispersion from the capture and release sites was only 614 m. The mean of the maximum distance between subsequent resightings of males was 641 m and that of females was 596 m. Considering that resightings < " were occasionally several months apart, it is obvious that the tagged animals exhibited strong site fidelity. Animals displaced from near houses at the North end of the island frequent- ly traveled the length of the island to return. Daily Activity Activity patterns of wild pigs depend in large part on differences in location, season, weather, predator (especially hunting) pressure and food availability. Eisenberg and Lockhart (1972) -~'" -yj/~ty/ " t "I " ~ ; report that in Wilpattu National Park, Sri J"- " .>-, ~.-~f 2 Lanka, activity periods occur during both day Figure 7a, b,c. Typical dispersion patterns of marked and night, but mostly diurnally until about and released pills on Ossabaw Island during the course 2200 h when the pigs become inactive. Activity of 1.5 yr. The figure shows sightings in chronological at midday depends on the extent of cloud cover order along a main road, woods, grassland, salt marsh and season. During the dry season, hogs were and a pond. found at waterholes at midday; they wallowed there and then returned to the shade. During the rainy season, hogs fed intermittently during midday and feeding activity peaked during the Ossabaw. Stegeman (1938) found that adult early evening hours. male hogs have much greater daily and yearly Conley et al. (1972) found that European cruising radii than any other species in the wild boars in Tennessee are nocturnal, feeding forest. The home range becomes stable during at night and resting during the day in beds or the dry season and usually includes several wallows. However, away from civilization they water holes (Eisenberg and Lockhart, 1972). were frequently observed feeding and traveling Flogs are normally found at lower elevations in during the daylight. Stegeman (1938) reported coves and along streams during spring and that when hunted, the hog does most of its summer (Conley et al., 1972). Pine and Gerdes feeding and traveling in the dark, wallow- (1973) also found that during the summer, wild ing or bedding on the sides of ridges during the hogs gather around mud seeps in which they daytime. can wallow; these are particularly desirable if Hogs utilize trails used by other large mam- shaded by an overstory. Because adult wild mals; they often followed cattle trails on hogs are well adapted to cold winter weather,

Downloaded from jas.fass.org by on March 4, 2010. BEHAVIOR AND ECOLOGY OF SWINE 489 their winter movements are mostly governed by gathering may also be practiced by domestic the availbility of food (Conley et al., 1972). swine, which are easily taught to fetch sticks. During the summer, feral pigs are relatively inactive during midday. On especially warm Wallowing days they are active only during early morning Wallowing or rolling by hogs in a muddy and late afternoon. On Butler's and Champney area often results in a depression. The wallowing Islands, in Southeastern Georgia, Hanson an may be brief, just long enough to plaster the Karstad (1959) similarly found weather to be skin with mud as protection against the most important factor in determining (Eisenberg and Lockhart, 1972), to rid the hog activity during the daylight hours. During rainy of ectoparasites (Conley et al., 1972), or for or cloudy summer days, swine were found thermoregulation during the hot dry season feeding at all hours. On the island of Hawaii, (Conley et al., 1972; Eisenberg and Lock- Nichols (1962) also observed feral pigs (espe- hart, 1972; this study). According to local cially the young) feeding during all daylight hunters in the Cherokee National Forest hours. Most of the activity of feral pigs, includ- (Stegeman, 1938), wallowing behavior is ing feeding, is carried on at intervals throughout continued throughout the year. They even the night (Hanson and Karstad, 1959; Nichols, report instances of hogs breaking the ice to 1962, 1963). Under intense hunting pressure, wallow and of pigs wallowing in streams that the swine become even more nocturnal, remain- they crossed while being chased by hunters ing in seclusion for most of the day (Hanson during the winter; such instances likely involve and Karstad, 1959). Barrett (1978) reported thermoregulation. that feral hogs were nocturnal during the Chemical marking may occur in the vicinity summer months but diurnal during winter. of a wallow. A pig may rub its perineal region Nichols (1962, 1963) studied feral pigs in a against the ground in an anogenital rub. During variety of habitats on Hawaii. He noted that brief wallows, traces of body secretions are pigs living in dry areas centered their diurnal often left by means of a "side rub" in which activity around watering places except during the pig lies down and extends and flexes itself the early morning hours when the heavy dew on alternate sides (Eisenberg and Lockhart, filled their water needs. In forested habitats, 1972). Rubs may also be marked by glands pigs obtained water by feeding on moist vegeta- of the antorbital head region. tion.

Bedding Rubbing and Tusking Conley et al. (1972) found that wild hogs Rubbing, like wallowing, probably serves in spend most of their inactive daylight hours in part to remove ectoparasites (Conley et al., characteristic day beds. Bedding spots are 1972), but also seems to be comfort behavior. almost always on the sides or near the top of a Pitch less than 15 cm in diameter are the ridge, usually in thickets and invariably under trees most commonly used fur rubbing, although good cover (Stegeman, 1938). The beds are other tree species and even telephone and often made at the base of a tree, beside a log or electric poles are used (Conley et al., 1972). in other protected areas on an exposure where Tusking, or the honing of tusks on trees by the hogs can warm in the morning sun, especial- boars, is a practice that injures trees by loss of ly during cold weather (Conley et al., 1972). and sometimes of wood. Conley et al. The beds may be only a depression in the (1972) suggest that this behavior may be on the forest floor or with the earth beneath performed as an energy release or as simulation them bare and loosened. Materials such as of a battle with other males. They also believe leaves, evergreen needles or twigs from the that males show some sort of territorial behavior immediate vicinity are sometimes added (Stege- and that tusking may be a way of marking man, 1938; Conley et al., 1972; this study). the territorial boundaries. Boundaries of Dens are not used, even during winter, but in movement patterns of feral hogs on Ossabaw cold weather more elaborate beds are made Island did not correlate with tusking marks on (Stegeman, 1938). The natives of Tennessee trees; and trees that were extensively tusked, report that wild boar cut brush during the often to the point of girdling and killing the winter and throw it into a pile under which tree, were infrequent, so feral hogs on Ossabaw they bed (Stegeman, 1938). This method of did not likely use tusking trees as territorial

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boundaries. In fact, I found no evidence of diet. This includes various species of Sagittaria territories per se, but the animals did have and pickerel (Pontederia cordata), both distinct home ranges. found in marshes. In the uplands, hogs eat the Pine and hemlock trees are often used for of many plants, (Pinus tusking. Local hunters and stockmen had varied palustris) roots, and acorns of several types of explanations of tusking. They noted that pine . Feral swine also eat a relatively large trees were often tusked and would exude pitch, number of small , including , which the hogs rubbed against as a deterrent to , turtles, young and of ground-nesting the overly abundant supply of and lice. In and . Feral pigs are also predators any case, tusking often occurred as a random on and other small . slash at a tree and this seemed to occur in Little aggression was seen among hogs during passing rather than as a deliberate act. On the summer feeding on Ossabaw Island. In the other hand, prolonged, very vigorous tusking of marshes, where food is evenly distributed and particular trees also occurred, often to the not readily defendable, the amount of food extent that the churning hooves of the boars obtained per hog is determined by that indi- wore a trench about the base of the tree, and vidual's feeding activity rather than by defense the bark plus a significant belt of wood would of choice sites. By contrast, acorns, grapes and be slashed away. palmetto berries (fall and winter foods) are present in localized, defendable locations Seasonal Changes in the Diet around ripening trees. Thus, during fall and Preferred foods of feral swine on Ossabaw winter, dominant hogs defend such areas of Island include acorns, palmetto berries, grapes food abundance as they encounter them during and hickory nuts, which are found in wooded their wanderings. Apparently the survival of areas during fall and winter. In the summer, Ossabaw pigs is dependent to some degree on when preferred food becomes less available, their ability to store large quantities of fat feral swine move to the salt marshes where they when food is abundant. Seasonal changes in feed on roots, tubers, grasses and invertebrates. body fat content are correlated with changes in Zervanos et al. (1983) report that pigs feed- dietary energy sources and their availability. ing in these salt marshes are physiologically Ossabaw hogs differed in several respects better adapted to high salt intake than are from purebred Yorkshires at our Pennsylania domestic Hampshires. This may represent State laboratories. The backfat thickness of effects of genetic selection in feral hogs in such Ossabaw hogs was approximately three times island habitats for high salt tolerance or the that of Yorkshires (8.0 vs 2.8 cm), adipose development of a mechanism for salt removal tissue lipogenesis enzymes in the Ossabaw hogs due to early or sustained exposure rather than were several times higher than those in York- to genetic differences between and do- shires and gluconeogenic enzymes were higher mestics. in the Ossabaw hogs (Martin et al., 1973). Hanson and Karstad (1959) examined the Wangsness et al. (1980a) determined that the stomach contents of feral swine in the South- Ossabaw pigs were hyperphagic, spent more eastern U.S. They also found dietary differences time feeding and took more time to eat a given between the summer and winter season. During amount of food than did Yorkshires. Wangsness the winter, only plant remains were found, et al. (1980b) also determined that growth including primarily tubers and of the hormone secretory potential was reduced in the wapota (Sagittaria platyphylla). During the Ossabaw pigs relative to Yorkshires. A wealth spring and summer, animal remains made up a of physiological properties, especially as related considerable portion of the stomach contents to nutrition, appear to differentiate the Ossa- of the hogs on Butler's Island. This included baw pig from at least some domestic stocks, (Pheretima diffringens and Lum- and the continued study of these properties bricoides spp.), three hundred of which were may cast further light on hypertrophy and found in one stomach, and free-living leeches. hyperplasia of adipose cells, on the role of Remains of fiddler crabs (Uca spp.) and endocrine and genetic factors influencing such as the lubber grasshopper (Brachystola obesity and on basic mechanisms underlying magna) were also found in stomachs examined efficient conversion of food to protein. during the summer. Vegetable matter comprises In studies of feral pigs on Hawaii, Nichols a considerable portion of the spring and summer (1963) discovered that although grass corn-

Downloaded from jas.fass.org by on March 4, 2010. BEHAVIOR AND ECOLOGY OF SWINE 491 posed a major portion of the overall diet, it was 1952)! This is probably an exaggeration, but insufficient as a maintenance diet for feral pigs in earlier days may have succeeded in when eaten exclusively. During a drought, when keeping feral swine populations lower than pigs in some areas had nothing but grass to eat, they are today. Davis (1955) studied the food many died of starvation; we have observed the habits of bobcats in Alabama. He observed pigs same phenomenon on Ossabaw Island. in the area but found no evidence of predation Feral swine are fond of and will eat on pigs. pig carcasses (Hanson and Karstad, 1959; Nichols, 1962) as well as , crab, sea turtle Further Economic Significance and other carrion. Feral swine also readily The is generally considered by accept garbage, and this is superior to shelled conservationists to be undesirable. The feral pig corn as trap bait (Hanson and Karstad, 1959). is a potential hazard as a reservoir of disease; it is a host to several helminth, arthropod, viral Competition with Native Animal Species and bacterial parasites, some of which can be In the , pigs compete transmitted to humans, livestock and wildlife with deer ( virginianus), black (Hanson and Karstad, 1959). In large numbers, (Ursus americanus), turkeys (Meleagris gallo- they are also so destructive to the habitat pavo) and other species (including, of course, and to a wide array of flora and fauna that their ). Feral swine are destructive to wildlife presence in high densities ensures a bad reputa- food plantings (such as deer and food tion with wildlife management and conserva- plantings.). However, due to pigs' feeding tion groups. Nevertheless, their tenacity and behavior, they sometimes make certain feeds ability to avoid all-out efforts to eradicate them eaten by these species more available (Hanson ensures that future generations of people will and Karstad, 1959). Whether or not competi- experience the heart-stopping thrill of the tion with these animals is serious depends on bristling, hard-eyed glare of a surprised boar, the locality and food supply. On some Georgia the tender ministrations of a sow with young or coastal islands, including Ossabaw, competition the comic antics of playful piglets. for food is intense, and die-offs do occur. Whether these deaths are attributable to an Literature Cited inadequate food supply, overpopulation that causes a crash in the food supply, or to the Barrett, R. 1978. The feral hog on the Dye Creek Ranch, California. Hilgardia 46(9):283. Agr. Sci. onset of an infectious disease is unknown Pub. Univ. California. (Hanson and Karstad, 1959; this study). Bourne, F. J. 1969a. Studies on colostral and milk whey proteins in the sow. 1. The transition of Predation on Feral Swine mammary secretion from colostrum to milk with natural suckling. Anim. Prod. 11:337. Pigs have a habit of moving along with their Bourne, F. J. 1969b. Studies on colostral and milk nostrils close to the ground, keeping their whey proteins in the sow. 2. Effect of delayed snouts below the tops of ground vegetation, a suckling on colostrum and milk whey proteins. Anim. Prod. 11:345. microhabitat into which outside scents do not Bourne, F. J. 1974. Gammaglobulins in precolostral rapidly penetrate. Thus, they are often unable piglet serum. Res. Vet. Sci. 17: 36. to use their good in detecting and Conley, R. H., V. G. Henry and G. H. Matschke. 1972. avoiding danger. The most important predator European Hog Research Project W-34. Tennessee Game and Fish Comm., Nashville. Final Report. on adult swine is man. In many areas there is p 259. severe hunting pressure on feral swine. However, Cordle, C. G. 1952. Activities of Beach Island Farmers' their value as game animals is minimized by the Club 1846-1862. Georgia Hist. Quart. 36:22. fact that male and female are not quickly and Curtis, S. E. 1970. Environment-thermoregulatory easily distinguished from each other and that interactions and neonatal piglet survival. J. Anim. Sci. 31:576. females may be pregnant anytime during the Curtis, S. E., C. J. Heidenreich and R. B. Harrington. year. 1967. Age dependent changes of thermostability Frequent natural predators on the feral pig in neonatal pigs. Amer. J. Vet. Res. 28:1887. probably include only the bear, the and, Davis, J. R. 1955. Food habits of the bobcat in Alabama. M.S. Thesis. Alabama Polytechnic in certain areas, alligators. In 1847, a plantation Institute, Auburn. owner on the Savannah River reported losing Eisenberg, J. F. and M. Lockhart. 1972. An ecological 5,000 young pigs to wildcats in 3 yr (Cordle, reconnaisance of Wilpattu National Park, Ceylon.

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Smithsonian Inst. Press, Washington, DC. Graves and J. H. Ziegler. 1973. Characterization Fr~drich, H. 1965. Zur Biologic und Ethologie des of an obese syndrome in the pig. Proc. Soc. Exp. Warzenschweines (Phocochoerus aethiopiicus Pal- Biol. Med. 143: 198. lus), unter Berucksichtigung des Verhalrens Matschke, G. H. 1964. The influence of oak mast on anderer Suiden. Zeitschrift fur Tierpsychol. European wild hog reproduction. Proc. of the 22:375. 18th Annu. Conf. Southeastern Assoc. of Game Fraser, D. 1973. The nursing and suckling behavior of and Fish Commissions, October 18-21. pp pigs. 1. The importance of stimulation of the 35-39. Clearwater, FL. anterior teats. Brit. Vet. J. 129: 324. Mauget, R. 1979. Mise en evidence, paz captures- Fraser, D. 1975. The nursing and suckling behavior of recaptures et radiotracking, du domaine vital pigs. IV. The effect of interrupting the suckling chez le Sanglier (Sus scrofa L. L.) Biol. Behav. stimulus. Brit. Vet. J. 131:549. 3:331. Fraser, D. 1978. Observations on the behavioral Mauget, R. 1981. Behavioral and reproductive strate- development of suckling and early weaned piglets gies in wild forms of Sus scrofa (European wild during the 1st 6 weeks after birth. Anim. Behav. boar and feral pigs). In: W. Sybesma (Ed.) The 26: 22. Welfare of Pigs. pp 3-13. Martinus Nijhoff, The Graves, H. B. and K. L. Graves. 1977. Some observa- Hague. tions on biobehavioral adaptations of swine. In: McCort, W. D. and H. B. Graves. 1982. Social domi- G. W. Wood (Ed.) Proc. 1st Wild Hog Syrup. pp nance relationships and spacing behavior of 103-110. The Belle W. Baruch Forest Science swine. Behav. Processes 7: 169. Inst., Clemson Univ., Georgetown, SC. Morrill, C. C. 1952. Studies on baby pig mortality. Graves, H. B., M. Wilson and J. Elicker. 1975. Progress VIIi. Chemical observations on the newborn pig, report: Behavior of feral swine on Ossabaw with special reference to hypoglycemia. Amer. J. Island, GA. In: H. Harpster and G. Kean (Ed.) Vet. Res. 13:164. 1975 Pennsylvania Livestock Day, Animal Mount, L. E. 1960. The influence of huddling and Science Research Summary, March 4. pp 149- body size on the metabolic rate of the young pig. 150. College of , The Pennsylvania J. Agr. Sci. (Camb.) 55:101. State Univ., University Park. Nichols, L., Jr. 1962. Job Completion Report, Hawaii. Hafez, E.S.E., L. J. Sumption and J. S. Jakway. 1962. Ecology of the wild pig. July 1, 1961-June 30, The behavior of swine. In: E.S.E. Hafez (Ed.) 1962. Project No.: W-5-R-13. Job No. 46(13). p The Behavior of Domestic Animals pp 334-369. 20. The Williams and Wilkins Co., Baltimore, MD. Nichols, L., Jr. 1963. Job Completion Report. Re- Hanson, R. P. and L. Karstad. 1959. Feral swine in the search Project Segment. Hawaii. Ecology of the southeastern United States. J. Wildl. Manage. wild pig. July 1, 1962-June 30, 1963. Project 23(1):64. No.: W-5-R-14. Job No. 46(14). p 11. Hartsock, T. G. 1982. Behavioral responses to manage- Pine, D. and G. L. Gerdes. 1973. Wild pigs in - ment systems-Swine. In: W. Woods (Ed.) Proc. terey County, California. California Fish and of the Symp. on Management of Food Producing Game 59(2): 126. Animals. pp 185--193. Purdue Univ., West Signoret, J. P., B. A. Baldwin, D. Fraser and E.S.E. Lafayette, IN. Hafez. 1975. The behavior of swine. In: E.S.E. Hartsock, T. G. and H. B. Graves. 1976. Neonatal Hafez (Ed.) The Behavior of Domestic Animals. behavior and nutrition-related mortality in Bailliere Tindall, London. domestic swine. J. Anim. Sci. 42:235. Stegeman, L. C. 1938. The European wild boar in the Henry, V. G. and R. H. Conley. 1972. Fall foods of Cherokee National Forest, Tennessee. J. Mammol. European wild hogs in southern Appalacians. J. 19(3):279. Wildl. Manage. 36:854. Wangsness, P. J., J. L. Gobble and G. W. Sherritt. Jones, P. 1972. The European wild boar in North 1980a. Feeding behavior of lean and obese pigs. Carolina. North Carolina Wildlife Resources Physiol. Behav. 24:407. Commission. Raleigh, NC. p 27. Wangsness, P. J., R. J. Martin and B. B. Gatchel. Kurz, J. C. and R. L. Marchinton. 1972. Radioteleme- 1980b. Insulin induced growth hormone response try studies of feral hogs in . J. in fast-growing, lean and in slow-growing, obese Wildl. Manage. 36:1240. pigs. Growth 44:318. Lewis, J. C. 1966. Observations of pen-reared Euro- Zervanos, S. M., W. D. McCort and H. B. Graves. 1983. pean hogs released for stocking. J. Wildl. Manage. Salt and water balance of feral vs. domestic 30:832. hogs. Physiol. Zool. 56(1):67. Martin, J. T. 1975. Movement of feral pigs in North Zeuner, F. E. 1963. A History of Domesticated Canterbury, New Zealand. J. Mammol. 56:914. Animals. Harper and Row, Publishers, . Martin, R. J., J. L. Gobble, T. H. Hartsock, H. B. p 560.

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