WETLANDS, Vol. 19, No. 3, September 1999, pp. 535-544 © 1999, The Society of Wetland Scientists EFFECTS OF ROOTING BY FERAL HOGS SUS SCROFA L. ON THE STRUCTURE OF A FLOODPLAIN VEGETATION ASSEMBLAGE D. Albrey Arrington Department of Wildlife and Fisheries Sciences Texas A &M University College Station, Texas, USA 77843 Louis A. Toth and Joseph W Koebel, Jr. Kissimmee River Restoration Division South Florida Water Management District West Palm Beach, Florida. USA 33416 Abstract: We evaluated effects of rooting by feral hogs (Sus scrofa) on total emergent vegetation cover, vegetation species richness, and diversity of plant-defined microhabitat types in an impounded floodplain marsh in central Florida. Data were collected in 6 split-plots (rooted and control) over 10 post-rooting, monthly sampling periods. Hog rooting led to reduced plant cover in broadleaf marsh habitats and to sig- nificantly higher microhabitat diversity and species richness. Although feral hogs can have detrimental effects on native biota and community structure, our data suggest that hog rooting is a disturbance that can enhance plant species richness and associated microhabitat diversity in wetland habitats. Key Words: ecosystem engineer, hog rooting, Sus scrofa, feral hogs, wetlands, disturbance, species richness, percent cover, habitat diversity INTRODUCTION The structure and dynamics of wetland systems are greatly influenced by natural disturbances such as wa- ter-level fluctuations (van der Valk and Davis 1978, Weller 1981, Junk el al. 1989, Wilcox 1995), which can be accompanied by encroachment of terrestrial or- ganisms during dry periods (Kirkman and Sharitz 1994). Cattle, for example, typically graze along flood- plain margins but may alter interior marsh plant as- semblages by grazing and trampling during dry peri- ods (Reimold et al. 1975). Like cattle grazing, feral hogs (Sus scrofa L.) can be a source of significant wetland disturbance during dry portions of the hydro- logic cycle. European wild boars, native to Eurasia and North Africa, were introduced into the Americas for food by early colonists and subsequently by state agencies as a trophy game animal (Belden and Frankenberger 1977). Their current range extends throughout much of southeastern North America and includes almost ev- ery county in Florida and Texas (Wood and Barrett 1979, Taylor 1991). The Florida Game and Freshwater Fish Commission manages feral hogs as game animals on Florida state lands, including our study site, and characterizes the feral hog resource as abundant in this area (Belden and Frankenberger 1977, Dwight Myers, Florida Game and Fresh Water Fish Commission, per- sonal communication). Feral hogs are true omnivores and consume a large quantity of underground fiwage (i.e., roots, tubers, in- vertebrates), which is obtained by "rooting" (d'Huart 1991). Rooting is the procedure by which hogs search for below-ground forage using their snout to turn over soil, mounding it up in places, and creating depres- sions in others. Hog rooting can result in destruction of timber and agricultural crops (Wahlenberg 1946, Barrett 1978, Lipscomb 1989), competition for mast crops with native deer and turkey (Barrett 1978, Wood and Roark 1980), decreased plant ground cover (up to 80-100%), reduction in litter-layer mass, and de- creased food sources fi~r macroinvertebrates (Bratton 1975, Wood and Barrett 1979, Singer et al. 1984). Fe- ral hogs typically feed in oak (Quercus spp.) stands during fall and winter when mast crops are produced but move to swamp and marsh margins to teed on grasses, sedges, tubers, and roots when acorns are no longer available (Wood and Roark 1980). Although feral hogs show preferential use of hydric and mesic sites during hot, dry summer months when they must compensate behaviorally for high daytime tempera- tures (Wood and Brenneman 1980, Winchester et al. 1985, Baber and Coblentz 1986, Bowman and Me- 535