University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Wildlife Damage Management, Internet Center Sheep & Goat Research Journal for 10-16-2004 Feral Swine Impacts on Agriculture and the Environment Nathan W. Seward USDA-APHIS-Wildlife Services Kurt C. VerCauteren USDA-APHIS-Wildlife Services, [email protected] Gary W. Witmer USDA-APHIS-Wildlife Services, [email protected] Richard M. Engeman USDA-APHIS-Wildlife Services, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/icwdmsheepgoat Part of the Environmental Sciences Commons Seward, Nathan W.; VerCauteren, Kurt C.; Witmer, Gary W.; and Engeman, Richard M., "Feral Swine Impacts on Agriculture and the Environment" (2004). Sheep & Goat Research Journal. 12. https://digitalcommons.unl.edu/icwdmsheepgoat/12 This Article is brought to you for free and open access by the Wildlife Damage Management, Internet Center for at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Sheep & Goat Research Journal by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Feral Swine Impacts on Agriculture and the Environment Nathan W. Seward, Kurt C. VerCauteren, Gary W. Witmer, and Richard M. Engeman USDA/Wildlife Services, National Wildlife Research Center, 4101 LaPorte Ave., Fort Collins, CO. 80521-2154 Key Words: Depredation, Disease, including: 1) translocation to establish because of the absence of large native Eurasian Wild Boar, Feral Swine, Sus populations for hunting, 2) escapees predators (e.g., mountain lion (Felis con- scrofa, Wildlife Damage Management from shooting preserves or confinement color) and wolves (Canis lupus) over operations, 3) avoidance of capture by much of the area occupied by feral swine. Introduction domestic pigs in free-ranging livestock In southwest Florida where feral swine operations, 4) abandonment by their and a large predator coexist, feral swine More than 30 species of exotic free- owners, and 5) dispersal from established is the most common food item (42%) in ranging mammals have become estab- feral populations (Gipson et al., 1997; Florida panther (F. c. coryi) scats (Maehr lished in the United States since Euro- Witmer et al., 2004). et al., 1990), which may suggest that the pean colonization (De Vos et al., 1956; Feral swine are the most abundant presence of a large predator helps regu- McKnight, 1964; Roots, 1976). These free-ranging, exotic ungulate in the late feral swine density and associated species often become serious economic United States (McKnight, 1964; Decker, damage. pests and can have grave consequences 1978) and have become widespread on their host environments (Cottam, because of their reproductive potential Environmental Damage and 1956; De Vos et al., 1956; Mayer and and adaptability to a wide range of habi- Brisbin, 1991). True wild pigs (Suidae) tats. Like domestic swine, litter size Wildlife Depredation are not native to the United States. depends on the sow’s age, nutrition, and Only the collared peccary (Tayassu time of year. Feral swine are capable of Environmental Damage tajacu; Tayassuidae) that inhabits the producing two litters per year with aver- Feral swine are generalists. Their southwestern and south-central parts of age litter size varying from 4.2 to 7.5 omnivorous diet allows them to utilize a the United States is native (Mayer and piglets (Taylor et al., 1998), but up to 10 variety of food sources and to thrive in a Brandt, 1982; Mayer and Wetzel, 1986). piglets can be born during ideal condi- wide range of environments. The major- Feral swine (Sus scrofa) in the United tions (Conquenot et al., 1996). Mayer ity of their diet consists of grasses, forbs, States have originated from varieties of and Brisbin (1991) and Mackey (1992) and soft and hard mast such as shoots, domestic swine, Eurasian wild boar, and report feral swine populations in 23 roots, tubers, fruit, and seeds. Acorn their hybrids (Jones, 1959; Wood and states. A Southeastern Cooperative Dis- (Quercus spp.) and hickory (Carya spp.) Lynn, 1977; Rary et al., 1968; Mayer and ease Study (1994) and Nettles (1997) nuts are two important food items that Brisbin, 1991). Domestic swine were point out an additional 16 states with feral swine use seasonally (Mungall introduced to the United States as early feral swine populations. An estimated 2001) and may lead to competition with as 750-1000 A.D. during the settlement population of 4 million feral swine cur- other wildlife (Yarrow and Kroll, 1989). of the Hawaiian Islands (Towne and rently occur in the United States Feral swine also eat a variety of inverte- Wentworth, 1950; Joesting, 1972; Smith (Pimentel et al., 2000) with the largest brates including earthworms, leeches, and Diong, 1977). Christopher Colum- populations inhabiting Texas (1 to 1.5 grasshoppers, centipedes, beetles, and bus introduced domestic swine to the million; Pimentel et al., 2000), Florida other arthropods. As a predator, feral West Indies during the 1400s, where (>500,000; Layne, 1997), Hawaii swine eat salamanders, frogs, fish, crabs, they proliferated and became pests. In (80,000; Mayer and Brisbin, 1991), and snakes, turtles, rodents, muskrats (Onda- the 1500s, Spanish explorers, such as California (70,000; Barrett, 1993). Since tra zibethicus), eggs and chicks of ground- DeSoto and Cortez, were the first to 1965, feral swine have expanded their nesting birds, white-tailed deer fawns bring domestic swine to the United range from 15 (26%) to 45 (78%) of the (Odocoileus virginianus) (Hellgren, States mainland (Towne and Went- 58 California counties (Frederick, 1998). 1993), and livestock. Feral swine must worth, 1950; Beldon and Frankenberger, Feral swine populations continue to forage almost continuously because their 1977). By the 1960s, domestic swine and increase (Gipson et al., 1997) because simple stomach is not as efficient as a Eurasian wild boar were established in they possess the greatest reproductive ruminant’s multi-chambered digestive >20 states (McKnight, 1964). Swine potential of all free-ranging, large mam- system — hence the expressions “as introductions have intentionally or acci- mals in the United States (Wood and greedy as a pig” and “eats like a pig.” dentally occurred by a variety of means, Barrett, 1979; Hellgren, 1999) and Feral swine negatively impact natu- 34 Sheep & Goat Research Journal, Volume 19, 2004 ral plant communities (Bratton, 1975; dation may negatively affect bobwhite to increase as feral swine flourish and Wood and Barrett, 1979; Stone and quail (Colinus virginianus) and wild humans encroach wildlife habitat. Keith, 1987) and may seriously impact turkey (Meleagris gallopavo) nest success agricultural ecosystems (Singer et al., (Synatzske, 1979). Tolleson et al. (1993) Livestock Depredation 1982). Feral swine rooting activity, dig- constructed 192 simulated quail nests in ging for food with their snout, loosens Texas and reported that feral swine was Feral swine are well documented as the soil and accelerates erosion, sets the most common predator (28%) of significant predators of lambs (Ovis aries) back plant succession, reduces earth- simulated nests. They concluded feral in Australia (Moule, 1954; Rowley, worm activity, and exacerbates exotic swine could have detrimental effects on 1970, Pavlov et al., 1981, Choquenot et plant invasion (Mungall, 2001). Damage bobwhite quail populations depending al., 1997) where 4 to 20 million feral from rooting, trampling, and compaction upon the density of quail and feral swine, swine exist (Emmerson and McCulloch, directly and indirectly impacts plant quail nesting cover, and quantity and 1994; Pimentel et al., 2000). Feral swine regeneration, plant community structure diversity of other swine food sources. prey on a variety of other livestock (Bratton, 1975), soil properties (Lacki On some southeastern U.S. beaches, including goats (Capra hircus), newborn and Lancia, 1983), nutrient cycling feral swine have become significant cattle (Bos taurus), and exotic game. (Tate, 1984), and water infiltration predators of marine turtle nests by exca- Animal matter typically makes up only a (Mungall, 2001). Rooting and inciden- vating and feeding on the eggs (Stancyk, small percentage of their diet, but con- tal damage may give exotic plants an 1982; Lewis et al., 1996). Feral swine siderable economic loss can occur from ecological advantage over native plants seriously threaten the nesting success of livestock depredation. In Australia, the (Howe and Bratton, 1976) because several threatened and endangered greatest losses occur in sheep (wool and exotic plants are typically better adapted marine turtles including: the loggerhead meat loss) and cattle production (Tis- at colonizing disturbed areas. Addition- (Caretta caretta) (federal; threatened); dell, 1991). In the semi-arid rangelands ally, feral swine may help spread root-rot green (Chelonia mydas) (federal; endan- of Australia, losses of newborn lambs fungus (Phytophthora cinnamomi), which gered); leatherback (Dermochelys cori- from feral swine predation have been as causes disease in native vegetation acea) (federal; endangered); hawksbill high as 32% (Plant et al., 1978), with a (Kliejunas and Ko, 1976). (Eretmochelys imbricata) (federal; endan- multiple-year average loss of 19% Habitat damage by feral swine is gered); and the Kemp’s ridley (Lepi- (Pavlov et al., 1981). Choquenot et al. most pronounced in wet environments dochelys kempii) (federal; endangered),