A comparison and evaluation of feral pig management in two national parks.

Abstract

Pigs (Sus scrofa) are feral in parts of Australia and United States (Bratton 1977, Tisdell 1982). In both countries, feral pigs occur on agricultural land and in nature conservation areas such as national parks (Wood and Barrett 1979, Singer 1981, Tisdell 1982). In Namadgi National Park (NNP) in Australia, Alexiou (1983) reported that pig rooting led to an increase in shrubs such as Leptospermum spp. in Eucalyptus forests and a decrease in some herbaceous species, especially vanilla lily (Arthropodium milleflorum). The population of feral pigs in NNP originated from domestic pigs that escaped near southern boundary of Park in 1959 and subsequently spread north at approximately 4 km/year. Pig activity in Hawaii Volcanoes National Park (HAVO) in U.S. affects plant species composition and density, nutrient cycling, plant succession, and diversity and numbers of native birds and insects (Spatz and Mueller-Dombois 1975, Cooray and Mueller-Dombois 1981, Loope and Scoweroft 1985, Stone 1985, Mountainspring 1987, Vitousek et al. 1987, Stone et al. In Press). Pigs are known to disperse some of most aggressive plant species, such as Psidium cattleianum, P. guajava, Passiflora mollissima, and Myrica faya (Smith 1985, Stone 1985). Pigs were first introduced to Hawaii about 1,000 years ago by Polynesians and were supplemented (circa 1778) by European settlers (Stone 1985, Tomich 1986:120). The goal of pig management in NNP, as stated in Plan of Management (Anon. 1986: 26), is to protect park and adjacent areas from damaging effects of ... pest plants and animals.... Specific objectives are to achieve effective over feral pigs, to reduce their on vegetation, to restrict further introductions, and to minimize susceptibility of park environments to invasion by alien species. Effective control is not defined in plan, nor is magnitude of reduction of the impact specified. The goal of pig management in HAVO is eradication and eventual restoration of ecosystems to natural conditions. Feral pigs in both parks are considered overpopulated, depressing populations of native vegetation and native animals. Pig management is therefore manipulative culling (Caughley 1983) to conserve native vegetation. We compare management programs directed toward reducing or eliminating feral pigs and their effects in these 2 national parks. Changes in management are proposed on basis of comparison.