Food Habits of Feral Hogs in Coastal South Carolina Author(s): Gene W. Wood and D. Nick Roark Source: The Journal of Wildlife Management , Apr., 1980 , Vol. 44, No. 2 (Apr., 1980), pp. 506-511 Published by: Wiley on behalf of the Wildlife Society Stable URL: https://www.jstor.org/stable/3807990 REFERENCES Linked references are available on JSTOR for this article: https://www.jstor.org/stable/3807990?seq=1&cid=pdf- reference#references_tab_contents You may need to log in to JSTOR to access the linked references. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at https://about.jstor.org/terms Wiley and Wildlife Society are collaborating with JSTOR to digitize, preserve and extend access to The Journal of Wildlife Management This content downloaded from 128.227.202.213 on Wed, 06 Nov 2024 21:41:40 UTC All use subject to https://about.jstor.org/terms 506 SHORT COMMUNICATIONS SILVER, J. 1935. Eliminating bats from buildings. U.S. Bur. Biol. Sur. Leafl. 9. 5pp. SIMMONS, J. A., M. B. FENTON, W. R. FERGUSON, M. JUTTING, AND J. PALIN. 1979. Apparatus for research on animal ultrasonic signals. R. Ont. Mus. Life Sci. Misc. Publ. 31pp. TRIMARCHI, C. V. 1978. Rabies in insectivorous temperate-zone bats. Bat Res. News. 19:7-12. Robert M. R. Barclay, Donald W. Thomas,1 and M. Brock Fenton, De- partment of Biology, Carleton Universi- ty, Ottawa, Ontario KIS 5B6, Canada. Received 12 January 1979. Accepted 4 August 1979. 1 Present address: Department of Zoology, Uni- versity of Aberdeen, Aberdeen AB9 2TN, Scotland. FOOD HABITS OF FERAL HOGS IN COASTAL SOUTH CAROLINA Feeding activity of wild hogs (Sus scrofa) can have a dramatic influence on some plant systems (Wodzicki 1950, War- ner 1967, Becking 1970, Barrett 1971, Bratton 1974, 1975, Challies 1975, Howe and Bratton 1976, Wood and Brenneman 1977). Studies of the composition of the diet of these animals are important in de- termining the target species, food cate- gories, and seasonal variation in food se- lection, as well as enabling prediction of when and why certain plant communities might be damaged. The objective of our study was to determine the seasonal food habits of feral hogs in a Lower-Coastal Plain forest-marsh ecosystem. STUDY AREA The study area was Hobcaw Barony, a 7,000-ha plantation located on the Wac- camaw Neck, a peninsula between the Atlantic Ocean and Winyah Bay near Georgetown, South Carolina. The vege- tation of Hobcaw was composed of 3,000 ha of forest, 3,000 ha of salt marsh, and 1,000 ha of brackish and freshwater marshes and abandoned rice fields. For- ty-three percent of the forest land was in loblolly pine (Pinus taeda) and longleaf pine (P. palustris) stands, 22% in pine- hardwoods, 13% in mixed hardwoods and the remainder in cypress-gum (Taxo- dium-Nyssa) swamps and forest open- ings. Dominant species of hardwoods were live oak (Quercus virginiana), lau- rel oak (Q. laurifolia), turkey oak (Q. lae- vis), sweetgum (Liquidambar styraci- flua), and white ash (Fraxinus americana) (Barry and Batson 1969). METHODS During a 12-month period in 1975 and 1976, specimens were collected by shoot- ing and with dogs. Stomachs were re- moved, taken to the laboratory, reflected, and all ingesta were washed over a 1.7- mm sieve. Particles passing through this mesh were largely unidentifiable. The portion of the ingesta sample retained on the sieve was dried at 65 C and subsam- pled for identification. From samples weighing 25 g or less, 26-50 g, 51-100 g, or more than 100 g, subsamples of 100, 50, 25, and 16% by weight, respectively, were selected. This 1st-level subsample was spread evenly over a 32-quadrat grid, and 5 grids of the ingesta were selected randomly for sep- aration and identification. The ingesta were identified to species where possible and placed in 1 of 6 categories: fruits, herbage and foliage, roots, mushrooms, invertebrates, and vertebrates. Percent composition was calculated by J. Wildl. Manage. 44(2):1980 This content downloaded from 128.227.202.213 on Wed, 06 Nov 2024 21:41:40 UTC All use subject to https://about.jstor.org/terms SHORT COMMUNICATIONS 507 Table 1. Percent composition (aggregate dry weight) of the ingesta in stomachs of 92 feral hogs collected on Hobcaw Barony, Georgetown, South Carolina. Fall Winter Spring Summer Category (N = 18) (N = 25) (N = 23) (N = 26) Fruits 77.6 83.7 26.0 9.2 Acorns 43.8 79.8 24.2 tra Hickory nuts 6.5 3.9 1.8 0.7 Tupelo seeds 27.3 tr 5.2 Muscadines 3.3 Herbage and foliage 15.9 9.5 51.4 35.8 Grass 12.6 7.3 34.5 12.8 Dried leaves/needles 0.4 0.2 0.2 0.9 Unidentified 2.9 2.0 16.7 22.1 Roots 3.0 2.2 20.0 38.0 Mushrooms 2.1 0.8 2.9 11.7 Invertebrates 0.6 2.5 2.8 2.7 Vertebrates 0.7 1.2 2.8 2.5 Mammals 0.4 0.7 1.2 1.0 Birds 0.1 Snakes 0.1 0.8 0.2 Lizards 0.4 0.8 0.2 Frogs 0.2 1.1 a Indicates trace (less than 0.1%). the aggregate dry weight method simi- lar to the aggregate volume method de- scribed by Martin et al. (1946) and used by several others studying food habits of wild hogs (Barrett 1971, Henry and Con- ley 1972, Pine and Gerdes 1973, Scott and Pelton 1975, Springer 1977). Weight rather than volume was recorded in order to develop energy and nutrient flow rates for feral hogs under an associated study. Percent frequency of occurrence was cal- culated as the percentage of the stom- achs in which a species or ingesta cate- gory occurred. No animals smaller than 10 kg in weight were collected. All specimens were aged according to Matschke (1967). Seasons of collection were: fall (Sep- Nov), winter (Dec-Feb), spring (Mar- May), and summer (Jun-Aug). The per- cent composition of each major food cate- gory was transformed (arcsin), and the data were treated as a factorial experi- ment using a completely randomized de- sign to test the influence of age (5 levels), season (4 levels), and sex (2 levels). In- dividual animals were counted as repli- cates. The least significant difference test was used to separate means. RESULTS Ninety-two feral hogs were collected during the study period: 18 in fall, 25 in winter, 23 in spring, and 26 in summer. There were no differences (P > 0.05) be- tween age or sex classes in the percent composition of any of the ingesta cate- gories. Fruits, herbage, and roots were the most important types of food, although the relative importance of these cate- gories varied seasonally (Tables 1, 2). Fruits, principally acorns, composed the bulk of the diet in fall and winter. Wa- ter tupelo (Nyssa aquatica) seeds were important only in fall and muscadines (Vitis spp.) only in summer. The percent composition accounted for by the fruit J. Wildl. Manage. 44(2):1980 This content downloaded from 128.227.202.213 on Wed, 06 Nov 2024 21:41:40 UTC All use subject to https://about.jstor.org/terms 508 SHORT COMMUNICATIONS Table 2. Percent frequency of occurrence of categories of ingesta in 92 feral hog stomachs collected in Hobcaw Barony, Georgetown, South Carolina. Fall Winter Spring Summer Category (N = 18) (N = 25) (N = 23) (N = 26) Fruit 94 91 62 54 Acorns 78 88 65 8 Hickory nuts 33 2 1 6 Tupelo seeds 56 8 12 Muscadines 8 Herbage and foliage 100 100 100 100 Grass 78 88 87 73 Dried leaves/needles 68 68 70 88 Unidentified 39 32 56 77 Roots 44 83 86 95 Mushrooms 67 78 57 76 Invertebrates 83 96 62 95 Vertebrates 33 16 24 23 Mammals 28 16 15 23 Birds 4 Snakes 6 4 11 Lizards 4 8 4 Frogs 6 4 category was not different (P > 0.05) be- tween fall and winter, but more fruit was eaten in these seasons (P < 0.05) than in spring or summer. Herbage and foliage were most impor- tant in the spring months when new shoots of herbs were most luxuriant. There were no differences (P > 0.05) in percent composition accounted for by this category among summer, fall, and winter, but the spring percentage was higher (P < 0.01) than the rest. Grasses, including wild rice (Zizania aquatica), southern wild rice (Zizaniopsis mali- acea), and panic grasses (Panicum spp.) were consumed more than any other type of herbage. Sedges (Cyperus spp.) also were important, as was the foliage of this- tle (Carduus spp.). Roots comprised a greater percentage (P < 0.01) of the diet in summer than in any other season. Roots of plants on hy- dric sites were of particular importance. Species with roots in greatest abundance in the ingesta were: sedges, wild rice, southern wild rice, Johnson grass (Sor- ghum halepense), big cordgrass (Spartina cynosuroides), crabgrass (Digitaria spp.), nut grass (Cyperus esculentus), Bermuda grass (Cynodon dactylon), jewelweed (Impatiens capensis), lizard's tail (Sau- rurus cernuus), and blackberry (Rubus spp.). Mushrooms were a minor component in the diet in terms of percent compo- sition. They were found in the ingesta in all seasons and at a relatively high frequency of occurrence. The percent composition accounted for by mush- rooms was larger (P < 0.05) in summer than in any other season. Invertebrates also occurred frequently in the ingesta throughout the year. They accounted for less than 3% of the aggre- gate dry weight. There were no differ- ences (P > 0.05) among seasons, al- though ingestion of invertebrates appeared higher in winter. Types of in- vertebrates included centipedes (Geo- philidae, Scolopendridae), earthworms J. Wildl. Manage. 44(2):1980 This content downloaded from 128.227.202.213 on Wed, 06 Nov 2024 21:41:40 UTC All use subject to https://about.jstor.org/terms SHORT COMMUNICATIONS 509 (Lumbricidae), grubs (Scarabaeidae), clams and mussels (Pelecypoda), fiddler crabs (Uca spp.), and Coleoptera adults and larvae. Vertebrates were of minor importance in the diet, both on a frequency-of-oc- currence and percent-composition basis. There were no differences (P > 0.05) among seasons in the percent composi- tion accounted for by total vertebrate tissue. Mice (Peromyscus spp.) were eat- en more commonly than any other ver- tebrate. Other ingested vertebrates in- cluded snakes (Thomnophis sirtalis, Seminatrix pygaea), lizards (Anolis car- olinensis, Ophisaurus ventralis), and frogs (Rana pipiens sphenocephala). DISCUSSION AND CONCLUSIONS Barrett (1971:122), studying food hab- its of feral hogs in California, felt that stomach analyses gave more accurate data than either scat analyses or exten- sive field observations. Scott and Pelton (1975) made the same point in a study of European wild boar in the Great Smoky Mountains, even though they did not de- tect the presence of pitch pine (P. rigida) roots that field observations indicated were being eaten. We believe that the extent of use of woody plant roots by wild swine is underestimated by stomach analyses, at least in the South Carolina Coastal Plain. Wahlenberg (1946:178- 179) and Wakely (1954:151) described extensive damage that range hogs did to longleaf pine regeneration. Wood and Brenneman (1977) found considerable damage being done to longleaf seedlings in spring on Hobcaw Barony during the time of our study, but no material iden- tifiable as longleaf roots appeared in the ingesta samples. It appeared that feral hogs chew the root, swallow the sap and starches, and reject the woody tissue. Balls of chewed woody tissue were found commonly in areas where feral hogs had been rooting woody plants. In addition, mechanical damage to cy- press (Taxodium spp.) regeneration, the roots of which are not eaten, would not be revealed by stomach analysis. Hog rooting on hydric sites in the forest may destroy many cypress seedlings and could be a major deterrent to regenera- tion (R. M. Allen, pers. commun.). Practically all reported studies have shown that wild hogs are highly seasonal in their forage selection and that their seasonality is largely determined by food availability. There is a high preference for mast, both hard and soft. The avail- ability of fresh shoots of herbs apparently can divert hogs to grazing if mast is scarce. Roots seem to be taken as a 3rd choice, but are a staple in some seasons. Giffin (1978:83), working in rain forest habitat in Hawaii, reported a change in the normal heavy use of roots and shoots of hapuu (Cibotium spp.) when the fruit of banana poka (Passiflora spp.) became available. Barrett (1971:122-126) showed that the extent to which wild hogs were grazers during the fall rains in California depended upon the abundance of the acorn crop. Henry and Conley (1972) found the diet of European wild boar in October and November to be 75-95% acorns and hickory nuts (Carya spp.) over a 7-year period. Scott and Pelton (1975), on the other hand, studied a sim- ilar area in a year of mast failure and found that 62% of the fall diet was roots. During the fall months of our study, the acorn crop was particularly abundant and acorns remained available through most of the winter. It is possible that in years of mast failure the feral hogs of the Coast- al Plain would turn to roots for the bulk of the fall and winter diet. Competition with native wildlife for J. Wildl. Manage. 44(2):1980 This content downloaded from 128.227.202.213 on Wed, 06 Nov 2024 21:41:40 UTC All use subject to https://about.jstor.org/terms 510 SHORT COMMUNICATIONS the acorn crop may be serious, particu- larly in years when mast availability is low. White-tailed deer (Odocoileus vir- ginianus), for instance, are adapted to store energy when it is most available in the late-summer and fall months (French et al. 1955). Competition with feral hogs, which are highly efficient feeders, for the high energy content mast crop could ad- versely affect the nutritional regime of deer. Most workers have reported that the ingestion of animal matter by feral hogs is frequent, but that it composes a minor portion of the diet. In general, our data are in agreement. Earthworms, reported by Hafez et al. (1962:339) and Giffin (1978:83) to be relished by hogs, were abundant in some of our samples. The predation on invertebrate populations, however, seems to be negligible in view of the apparent abundance of the re- source. Fiddler crabs, for instance, were taken as food by the feral hogs, but the crabs apparently were abundant in marshes where hogs also were abundant. Predation on vertebrates may occur, but cannot be verified from our data be- cause it was impossible to know whether an animal had been killed by hogs or in- gested as carrion. Carrion is known to be fed upon frequently (Hanson and Karstad 1959, Pine and Gerdes 1973). Springer (1977) found parts of fawns in some sam- ples in Texas, but had no proof of wheth- er the animals had been preyed upon or taken as carrion. Hobcaw Barony sup- ports an estimated density of 1 deer per 10 ha of forest land, but we found no evi- dence of hogs feeding on deer in this or companion studies. Matschke (1965) and Henry (1969) re- ported that European wild boar prey on nests of ground-nesting birds, but none of 3 stomach analysis studies done in the southern Appalachians has revealed shell fragments in the ingesta. Similarly, we found no evidence of hogs having preyed on bird nests. This does not contradict the evidence that hogs prey on nests, but rather suggests either that this is not a common event in forests or that shell fragments are quickly dissolved by stom- ach acids. Rooting for food potentially could ad- versely affect the plant system at any time of the year. Intensive rooting in fall and winter for mast might adversely af- fect the forest floor litter. Spring rooting of longleaf pine seedlings may lower re- generation stocking. Digging for plant roots, which occurred mainly in summer and on hydric sites, may have some local effect on plant growth, but the species concerned are abundant and resilient, and the sites are nutrient rich so that rap- id recovery could be supported. The potential effect on the fauna of this ecosystem seemed to be primarily in the form of competition for the mast crop. Predation on the invertebrate as well as the vertebrate populations in terms of the biomass ingested seemed to be of little importance with respect to potential ad- verse impact. LITERATURE CITED BARRETT, R. H. 1971. Ecology of the feral hog in Tehema County, California. Ph.D. Diss. Univ. California, Berkeley. 368pp. BARRY, J. M., AND W. T. BATSON. 1969. The vege- tation of the Baruch Plantation, Georgetown, South Carolina, in relation to soil types. Cas- tanea 34:71-77. BECKING, R. W. 1970. Report of the Kipahulu Val- ley Trip. Haleakala Natl. Park, Maui. 15pp. (Mimeogr.) BRATTON, S. P. 1974. The effect of the European wild boar (Sus scrofa) on the high elevation vernal flora in Great Smoky Mountains Nation- al Park. Bull. Torrey Bot. Club 101:198-206. . 1975. The effect of the European wild boar, Sus scrofa, on gray beech forest in the Great Smoky Mountains. Ecology 56: 1356-1366. CHALLIES, C. N. 1975. Feral pigs (Sus-scrofa) on Auckland Island: status, and effects on vege- J. Wildl. Manage. 44(2):1980 This content downloaded from 128.227.202.213 on Wed, 06 Nov 2024 21:41:40 UTC All use subject to https://about.jstor.org/terms SHORT COMMUNICATIONS 511 tation and nesting sea birds. N.Z. J. Zool. 2:479-490. FRENCH, C. E., L. C. MCEWEN, N. D. MAGRUDER, R. H. INGRAM, AND R. W. SWIFT. 1955. Nutri- tional requirements of white-tailed deer for growth and antler development. Pa. State Univ. Agric. Exp. Stn. Bull. 600. 50pp. GIFFIN, J. 1978. Ecology of the feral pig on the island of Hawaii. Hawaii Dep. Land and Nat. Resour., Div. Fish and Game, Final Rep. Pitt- man-Robertson Proj. W-15-3, Study 11. 122pp. HAFEZ, E. S. E., L. J. SUPTION, AND J. S. JAKWAY. 1962. The behavior of swine. Pages 334-369 in E. S. E. Hafez, ed. Behavior of domestic ani- mals. Williams and Williams, Baltimore. 619pp. HANSON, R. P., AND L. KARSTAD. 1959. Feral swine in the southeastern United States. J. Wildl. Manage. 23:64-74. HENRY, V. G. 1969. Predation on dummy nests of ground-nesting birds in the southern Appala- chians. J. Wildl. Manage. 33:169-172. - , AND R. H. CONLEY. 1972. Fall food habits of European wild hogs in the southern Appa- lachians. J. Wildl. Manage. 36:854-860. HOWE, T. D., AND S. P. BRATTON. 1976. Winter rooting activity of the European wild boar in the Great Smoky Mountains National Park. Castanea 41:256-264. MARTIN, A. C., R. H. GENSCH, AND C. P. BROWN. 1946. Alternative methods in upland gamebird food analysis. J. Wildl. Manage. 10:8-12. MATSCHKE, G. H. 1965. Predation by European wild hogs on dummy nests of ground dwelling birds. Proc. Annu. Conf. Southeast. Assoc. Game and Fish Comm. 19:154-156. 1967. Aging European wild hogs by den- tition. J. Wildl. Manage. 31:109-113. PINE, D. S., AND G. L. GERDES. 1973. Wild pigs in Monterey County, California. Calif. Fish and Game 59:126-137. SCOTT, C. D., AND M. R. PELTON. 1975. Seasonal food habits of the European wild hog in the Great Smoky Mountains National Park. Proc. Annu. Conf. Southeast. Assoc. Game and Fish Comm. 29:585-593. SPRINGER, M. D. 1977. Ecologic and economic as- pects of wild hogs in Texas. Pages 37-46 in G. W. Wood, ed. Research and management of wild hog populations. The Belle W. Baruch For. Sci. Inst. of Clemson Univ., Georgetown, S.C. 113pp. WAHLENBERG, W. G. 1946. Longleaf pine. Charles Lathrop Pack For. Found., Washington, D.C. 429pp. WAKELY, P. C. 1954. Planting the southern pines. U.S. Dep. Agric. For. Serv. Agric. Monogr. 18. 233pp. WARNER, R. E. 1967. Scientific report of the Ki- pahulu Valley Expedition. The Nature Conser- vancy, Honolulu. 184pp. WODZICKI, K. A. 1950. Introduced mammals in New Zealand, an ecological and economic sur- vey. Bull. Dep. Sci. and Indust. Res., Welling- ton, 98. 255pp. WOOD, G. W., AND R. E. BRENNEMAN. 1977. Re- search and management of wild hogs on Hob- caw Barony. Pages 23-36 in G. W. Wood, ed. Research and management of wild hog popu- lations. The Belle W. Baruch For. Sci. Inst. of Clemson University, Georgetown, S.C. 113pp. Gene W. Wood and D. Nick Roark,1 The Belle W. Baruch Forest Science In- stitute of Clemson University, George- town, SC 29440. Received 2 November 1978. Accepted 23 May 1979. 'Present address: P.O. Box 12559, Charleston, SC 29412. AVOIDANCE RESPONSE OF MALLARDS TO COLORED AND BLACK WATER Recently, much attention has been fo- cused on problems arising during marine oil spills. One of the most visible events associated with an oil spill is mass mor- tality of birds. Casualties may run into the millions each year (Zeldin 1971). Al- though methods have been developed to remove oil from birds (J. Myers, pers. commun.), survival rates of oiled, re- covered birds are on the order of 10% (Zeldin 1971). Furthermore, it has been estimated that 8 to 11 times as many birds are lost at sea as show up on land and become available for cleaning (Brown et al. 1973). Thus, only about 1% of all birds affected by an oil spill are successfully de-oiled. Obviously a need exists to pre- vent the initial oiling of seabirds. We now report the results of experiments de- signed to test the hypothesis that birds J. Wildl. Manage. 44(2):1980 This content downloaded from 128.227.202.213 on Wed, 06 Nov 2024 21:41:40 UTC All use subject to https://about.jstor.org/terms