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Temporal Variation of a Small-mammal Community at a Wetland Restoration Site in Arkansas
Tiffany A. Whitsitt and Philip A. Tappe

Southeastern Naturalist, Volume 8, Number 3 (2009): 381–386

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2009 SOUTHEASTERN NATURALIST 8(3):381–386 Temporal Variation of a Small-mammal Community at a Wetland Restoration Site in Arkansas Tiffany A. Whitsitt1 and Philip A. Tappe1,* Abstract - Small mammals serve many ecological roles and contribute to wildlife diversity in wetlands. We investigated a small-mammal community on a southeastern Arkansas wetland-restoration site by trapping monthly from February through October 2007. During 8675 trap nights, 886 captures of six species and 615 individuals were recorded. The numbers and proportions of individuals captured varied monthly by species. Documentation of monthly fl uctuations in the composition and numbers of this small-mammal community provides a basis by which to evaluate future restoration activities. Introduction Small mammals serve ecological roles in terrestrial ecosystems, including as a primary prey base for several mammalian, avian, and reptilian predators (Carey and Johnson 1995, Preston 1990, Soutiere 1979) and as facilitators for the dispersal of fungal spores that form root-inhabiting ectomycorrhizae required by many plants for nutrient procurement (Carey and Johnson 1995, Maser et al. 1978). Small mammals can also impact the regeneration of plants through consumption and dispersal of seeds (Chambers and MacMahon 1994). Hydrological processes control the life processes of animals that live in wetland habitats. Historically, the Lower Mississippi Alluvial Valley in Arkansas was composed of wetlands containing bottomland hardwoods. Approximately 85,000 ha of forested wetlands were converted for agriculture in Arkansas from the mid-1970s to the mid-1980s (Hefner et al. 1994). Many farmers are now trying to convert these areas back to their original condition because of declines in their agricultural value (Smith 2001). Restoration practices in the Arkansas Delta include the creation of wildlife habitat mounds and basins, water-control structures, asymmetrical meandering mounds, meander scrolls, and vernal pools (Smith 2001). These techniques aim to diversify the habitats available for the regional fl ora and fauna. The Bob White Memorial Wetlands Research and Teaching Station (BWMW) allowed us to study small-mammal communities within a wetland system. Baseline inventory data and a greater understanding of the current small-mammal community at this site are needed to understand the impact of current and future management practices. Our objectives were to inventory small mammals and assess temporal variation in numbers of individuals captured and species richness. 1110 University Court, Monticello, AR 71656. *Corresponding author - tappe@ 382 Southeastern Naturalist Vol. 8, No. 3 Study Site Owned by the University of Arkansas at Monticello (UAM), the BWMW is a 148-ha tract of land located in southwestern Chicot County, the southeastern- most county in Arkansas. This property was used for agricultural purposes (wheat, milo, rice) until enrolled as a permanent Wetland Reserve Program (WRP) easement in 2001. Restoration practices were implemented in 2002 and 2003 through the Natural Resources Conservation Service (NRCS). Primary vegetation at the site was Typha spp. L. (cattails), Baccharis halimifolia L. (Eastern Baccharis), Lythrum alatum Pursh (Winged Loosestrife), and hardwood seedlings including: Quercus nuttallii Palmer (Nuttall Oak), Fraxinus pennsylvanica Marsh (Green Ash), Carya illinoinensis (Wangenh.) K. Koch (Pecan), Quercus nigra L. (Water Oak), Quercus shumardii Buckl. (Shumard Oak), Taxodium distichum (L.) L.C. Rich (Bald Cypress), and Quercus lyrata Walt. (Overcup Oak). Located within the Lower Mississippi Alluvial Valley, this property is inundated with water during the winter, with small pools persisting most of the year. Restoration of the site included planting hardwood seedlings throughout the property in 2002 and 2003, with the intention of restoring this site to bottomland hardwoods. Microtopography was introduced to the site by creating basin and mound complexes throughout the central portion of the tract. Basins were designed with irregular profiles to increase the habitat available for waterfowl. Excavated fill from these basins were contoured into mounds adjacent to the basins. Mounds at this site typically ranged from 300–800 m2, with the difference in elevation from the basins to mounds ranging from 1–1.5 m. Methods We captured small mammals using a total of 196 collapsible aluminum Sherman live traps (7.5 x 9 x 23 cm; H.B. Sherman Traps, Inc., Tallahassee, FL) baited with dry rolled oats and spaced at 15 m within four, 0.8-ha, 7 x 7 grids. We placed grids to include basin and mound complexes; grids were >100 m apart. We placed traps no further than 1 m from grid points and along natural habitat features (e.g., runways, trees, burrows; Jones et al. 1996) when available. At times, trap sites were located in standing water due to inundation. If vegetation was present (e.g., cattails), we tied plants together using twine and wedged the Sherman live trap among the plants as close to the water as possible. This provided enough stability for small mammals to safely enter the trap. In the rare case (i.e., 1–5 sites) that this could not be accomplished, a trap was not set at that location. Trapping sessions were five days in length and took place monthly from February to October 2007. We baited traps using rolled oats because peanut butter lures other organisms including Solenopsis invicta Buren (Red Imported Fire Ant) (Dueser and Shugart 1978). We re-baited the traps as needed. Two researchers checked the grids early every morning to prevent 2009 T.A. Whitsitt and P.A. Tappe 383 captured small mammals from being exposed to excessive environmental stresses. We documented sprung traps that contained no specimen or nontarget captures. We identified captured rodents to species level, with the exception of Peromyscus spp. We recorded relevant data including trap site, gender, weight, and recapture status. Individuals were released at the capture site. Capture and release followed American Society of Mammalogist guidelines (Animal Care and Use Committee 1998) and were approved by the UAM Institutional Animal Care and Use Committee (#200601). We combined data from all of the grids and calculated numbers of individuals captured by species and richness (number of species) for each month. Results and Discussion During 8675 trap nights, we recorded 886 captures of 615 individuals. We captured six species, including Sigmodon hispidus Say and Ord (Hispid Cotton Rat; 69.1% of individuals captured), Oryzomys palustris Harlan (Marsh Rice Rat; 18.9%), Mus musculus L. (House Mouse; 4.2%), Peromyscus spp. (deer mice; 2.9%), Reithrodontomys fulvescens J.A. Allen (Fulvous Harvest Mouse; 4.1%), and Cryptotis parva Say (Least Shrew; 0.8%). Species richness varied by month, with March and April having the greatest richness and August having the least (Fig. 1). The numbers of individuals Figure 1. Numbers of small-mammal species recorded by month on a wetland restoration site in southeastern Arkansas, 2007. 384 Southeastern Naturalist Vol. 8, No. 3 captured differed among months, with July having the greatest number of captures and March having the least (Fig. 2). The numbers and proportions of individuals captured varied monthly by species (Fig. 2). Marsh Rice Rat represented the greatest proportion of total captures in February–April; however, during May–October, Hispid Cotton Rat comprised the greatest proportion of captures. Most House Mice were Figure 2. Numbers of small-mammal captures (at top of columns) and percent of captures by species on a wetland restoration site in southeastern Arkansas, February– October, 2007. 2009 T.A. Whitsitt and P.A. Tappe 385 captured during February–April, whereas the greatest numbers of Fulvous Harvest Mouse were captured in April–May, and Peromyscus spp. in February. Least Shrew were captured in June only. Community characteristics of small mammals varied temporally at this site. Peaks in relative abundance of small-mammal species did not occur simultaneously; Marsh Rice Rat captures were greatest in February and Hispid Cotton Rat captures peaked in July. Increased captures of Marsh Rice Rat in February were likely due to the amount of water on the site during this period, and because this species is semi aquatic (Esher et al. 1978) and can utilize areas with standing water more efficiently than other small mammals (Abuzeineh et al. 2007, Wolfe 1982). The subsequent decline in captures of Marsh Rice Rat may be attributable to the decline in water and the proliferation of Hispid Cotton Rat. Hispid Cotton Rat captures were comparatively low in February–April, likely due to mortalities during winter (Fleharty et al. 1972). Species richness was greatest in March and April. This peak in richness coincided with lower relative abundances of Hispid Cotton Rat, which is known to be aggressive toward other small-mammal species living in the same area (Schwartz and Schwartz 2001). Hispid Cotton Rat may have excluded Marsh Rice Rat, House Mice, Peromyscus spp., and potentially other small rodents from this area during summer months. Greater captures per unit effort and species richness were recorded in our study compared to a similar study in Mississippi (Chamberlain and Leopold 2003). The Mississippi study site had fl at topography and contained little vegetation during the fl ooding period. Greater relative abundance and richness of small mammals could be due to the microtopography created by the basin and mound complexes at our study site. Similar to our study, Martin et al. (1991) captured Marsh Rice Rat, Fulvous Harvest Mouse, House Mice, and Least Shrew among different marsh types and adjacent levees during the winter and spring months of a single year in southwestern Louisiana. Monthly variations in the small-mammal community at our study site were likely due to changes in amount of water coupled with species interactions. Species richness was possibly infl uenced by microtopography created by the basin and mound complexes. Our inventory and documentation of smallmammal community changes at this site provide a baseline with which to examine future management practices. Management practices that infl uence water levels and duration will likely infl uence small-mammal community characteristics. Additional investigations of small-mammal communities are warranted at other wetland sites and additional spatial scales to supplement and expand our investigation. Acknowledgments We are grateful for the funding and support provided by the Bob White Memorial Foundation, University of Arkansas at Monticello, and Arkansas Forest Resources Center (AFRC). Additional appreciation is extended to C. Watt, L. Criswell, C. 386 Southeastern Naturalist Vol. 8, No. 3 Barton, A. Schenk, and S. Breedlove for assisting with data collection. We would also like to thank the numerous AFRC faculty for their assistance. Literature Cited Abuzeineh, A.A., R.D. Owen, N.E. McIntyre, C.W. Dick, R.E. Strauss, and T. Holsomback. 2007. Response of the Marsh Rice Rat (Oryzomys palustris) to inundation of habitat. Southwestern Naturalist 52:75–78. Animal Care and Use Committee. 1998. Guidelines for the capture, handling, and care of mammals as approved by the American Society of Mammalogists. Journal of Mammalogy 79:1416–1431. Carey, A.B., and M.L. Johnson. 1995. Small mammals in managed, naturally young, and old-growth forests. Ecological Applications 5:336–352. Chamberlain, M.J., and B.D. Leopold. 2003. Effects of a fl ood on relative abundance and diversity of small mammals in a regenerating bottomland hardwood forest. Southwestern Naturalist 48:306–309. Chambers, J.C., and J.A. MacMahon. 1994. A day in the life of a seed: Movements and fates of seeds and their implications for natural and managed systems. Annual Review of Ecology and Systematics 25:263–292. Dueser, R.D., and H.H. Shugart, Jr. 1978. Microhabitats in a forest-fl oor smallmammal fauna. Ecology 59:89–98 Esher, R.J., J.L. Wolfe, and J.N. Layne. 1978. Swimming behavior of Rice Rats (Oryzomys palustris) and Cotton Rats (Sigmodon hispidus). Journal of Mammalogy 59:551–558. Fleharty, E.D., J.R. Choate, and M.A. Mares. 1972. Fluctuatuions in population density of the Hispid Cotton Rat: Factors infl uencing a “crash.” Bulletin of the Southern California Academy of Sciences 71:132–138. Hefner, J.M., B.O. Wilen, T.E. Dahl, and W.E. Frayer. 1994. Southeast wetlands status and trends, mid-1970s to mid-1980s. Available online at nwi/Pubs_Reports/Sewet/index.html. Accessed 3 March 2007. Jones, C.W., J. McShea, M.J. Conroy, and T.H. Kunz. 1996. Capturing mammals. Pp. 115–155, In D.E. Wilson, F.R. Cole, J.D. Nichols, R. Rudran, and M.S. Foster (Eds.). Measuring and Monitoring Biological Diversity: Standard Methods for Mammals. Smithsonian Institution Press, Washington DC. Martin, R.P., R.B. Hamilton, P.M. McKenzie, R.H. Chabreck, and D.A. Dell. 1991. Habitat use by small mammals in coastal marshes of southwestern Louisiana. Estuaries 14:107–110. Maser C., J.M. Trappe, and R.A. Nussbaum. 1978. Fungal-small mammal interrelationships with emphasis on Oregon coniferous forests. Ecology 59:799–809. Preston, C.R. 1990. Distribution of raptor foraging in relation to prey biomass and habitat structure. Condor 92:107–112. Schwartz, C.W., and E.R. Schwartz. 2001. The Wild Mammals of Missouri, Second Revised Edition. University of Missouri Press, Columbia, MO. Smith, R.M. 2001. Wetland hydrology restoration techniques utilized in the northeast Arkansas delta; 2001 July 29–August 1; Sacramento, CA. ASAE Meeting Paper No. 01-2063. ASAE, St. Joseph, MI: 10 pp. Soutiere, E.C. 1979. Effects of timber harvesting on marten in Maine. Journal of Wildlife Management 43:850–860. Wolfe, J.L. 1982. Oryzomys palustris. Mammalian Species 176:1–5.