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Survival and Habitat Use of Feral Hogs in Mississippi
Robert Hayes, Sam Riffell, Richard Minnis, and Brad Holder

Southeastern Naturalist, Volume 8, Number 3 (2009): 411–426

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2009 SOUTHEASTERN NATURALIST 8(3):411–426 Survival and Habitat Use of Feral Hogs in Mississippi Robert Hayes1, Sam Riffell1,*, Richard Minnis1, and Brad Holder2 Abstract - Sus scrofa (Feral Hog) can cause extensive damage to agricultural crops and native vegetation, is a potential disease vector, and competes with other wildlife for food resources. Without site-specific information about survival and habitat use, habitat management and control efforts may not be effective. We examined home-range size, habitat use, and survival of 29 Feral Hogs in central Mississippi using radio telemetry. Dry-and wet-season survival rates were 80.8% and 41.4%, respectively. Hunting (primarily during the wet season) was the major cause of mortality. Dry-season home ranges were larger (6.4 km2) than wet-season home ranges (3.0 km2). During the dry-season, Feral Hog home ranges (2nd-order selection) were associated with dense vegetation types (seasonally flooded old fields, old fields, and managed openings). During the wet season, old fields and agricultural fields were selected, but seasonally flooded old fields and managed openings were not. Within home ranges (3rd-order selection), hogs selected old fields and managed openings during the dry season. All habitats were used randomly within home ranges during the wet season. Flooding of preferred habitats, changes in food availability, and hunting pressure likely caused these changes in habitat use and home-range placement. Introduction Since first being introduced to North America in the 1500s, Sus scrofa L. (Feral Hog) has steadily spread over much of the United States (Gipson et al. 1998). Feral Hogs disturb the soil by rooting in search of tubers and larval and adult insects. They can cause extensive damage to native plant communities (Engeman et al. 2007), destroy agricultural crops (Beach 1993), and increase the potential for soil erosion, which can, in turn, impact water quality and aquatic fauna (Kaller and Kelso 2006). Foraging behavior of Feral Hogs may impact native wildlife by reducing nesting cover and available forage. In times of low mast availability, competition for resources may limit both Odocoileus virginianus Zimmerman (Whitetailed Deer) and Feral Hog populations (Yarrow 1987). Feral Hogs may prey on eggs of ground-nesting birds (Henry 1969, Matschke 1965), reptiles and amphibians (Ditchkoff and West 2007), and White-tailed Deer fawns (Springer 1977). Although concern about effects of Feral Hogs is growing (Ditchkoff and West 2007), basic life-history information is lacking for many parts of 1Department of Wildlife and Fisheries, Box 9690, Mississippi State, MS 39762. 2Mississippi Department of Wildlife, Fisheries and Parks, 1505 Eastover Drive, Jackson, MS 39211. *Corresponding author - 412 Southeastern Naturalist Vol. 8, No. 3 the southeastern United States. Our objectives were to gather life-history data to better inform population management in Mississippi and to better understand how Feral Hogs select and use habitats. We gathered basic information about survival, home-range size and habitat use of Feral Hogs in an agriculture-dominated region of central Mississippi. Understanding basic life-history of Feral Hog populations is critical for controlling Feral Hogs, reducing negative impacts on native wildlife and agriculture, and minimizing human-wildlife confl icts. Field-site Description We worked in the southwestern corner of Grenada County, MS on the 3837-ha Malmaison Wildlife Management Area (MWMA) and surrounding lands located within the alluvial fl oodplain of the Yalobusha River. Available habitats at MWMA included agricultural fields, bottomland hardwoods, old fields, managed wildlife openings, seasonally fl ooded bottomlands, and seasonally fl ooded old fields. Bottomland hardwood habitat was dominated by Platanus occidentalis L. (Sycamore), Ulmus spp. (elms), Celtis laevigata Willd. (Sugarberry), Liquidambar styraciflua L. (Sweetgum), Quercus nigra L. (Water Oak), Q. phellos L. (Willow Oak), Q. lyrata Walt. (Overcup Oak), Q. michauxii Nutt. (Swamp Chestnut Oak), Q. pagoda Raf. (Cherrybark Oak), and Q. buckleyi Nixon and Dorr (Nuttall Oak). Seasonally flooded bottomlands were similar to bottomland with the addition of some Taxodium spp. (cypress) and Nyssa spp. (black gum). Old field was characterized by very thick vegetation comprised mainly of Rubus spp. (blackberry), Lonicera japonica Thung. (Honeysuckle), and a variety of grasses, forbs, and woody species. Vegetation in old-field habitat was often dense enough to reduce vision to ≤1 m. Areas that were characterized by dense ground cover, including hardwood regeneration areas, clear-cuts, and fallow fields 2–8 years old, were classified as old field. Bottomland hardwoods and old fields that were flooded ≥3 months of the year were considered seasonally flooded. Seasonally flooded old-field habitat was similar to old field in vegetative structure, except for the presence of some aquatic plants such as Polygonum sp. (smartweed) and Lotus spp. (water lilies). Ground cover in seasonally flooded bottomlands was sparse. Managed openings included small openings (<3 ha) that were planted and managed specifically as wildlife food plots. These openings were planted with Zea mays L. (Corn), Echenechloa spp. (millet), Sorghum spp. (sorghum), or Trifolium spp. (clover) to benefit waterfowl, Meleagris gallopavo L. (Wild Turkey), and White-tailed Deer. Agricultural fields were planted in Corn, Gossypium spp. (cotton), and Glycine spp. (soybean). More detailed description of these habitats is in Hayes (2007). 2009 R. Hayes, S. Riffell, R. Minnis, and B. Holder 413 Methods Trapping techniques We began trapping animals throughout the study area on 1 April 2005 and ended with the onset of hunting season in early October 2005. Once a suitable area with abundant hog sign was discovered, we baited the area with corn. If the hogs returned to the area, a trap was placed at the site and baited again. We set the traps after the hogs became accustomed to the trap (usually <2 nights). We used box-style panel live traps with roottype gates (Littauer 1993). We anesthetized hogs with a mixture of 3.2 mg/kg Telazol® and 1.6 mg/kg Xylezine (Sweitzer et al. 1997). We weighed each individual, determined sex, and marked it with a unique eartag. We fitted animals >23 kg in mass with collar transmitters from Lotec® Lotec Wireless (Newmarket, ON). Hogs were processed and released on site as quickly as possible to minimize handling stress. Handling and marking procedures were approved by the Institutional Animal Care and Use Committee (IACUC), Mississippi State University (IACUC Protocol # 04-090). Telemetry procedures We located collared hogs using a 3-element Yagi antenna and a multifrequency receiver (Advanced Telemetry Systems, Isanti, MN) using a rotational schedule to evenly distribute sampling over a complete 24-hr period (night and day). Each sampling period was divided into 6-hr sampling shifts (0600–1200 CST, 1200–1800 CST, etc.). On each successive collection period, we progressed to the next sampling shift. We attempted to locate each radio-collared hog on ≥3 days each week from the time of capture until the animal’s death or the end of the study period (31 March 2006). To triangulate hog locations, we took 3–4 bearings from spatially referenced telemetry stations in the direction of the strongest signal. Occasionally, hogs were visually located in open habitats. In these cases, we recorded UTM coordinates of observer location, one bearing toward the animal, and a distance estimate. Because hogs did not stop foraging or move in response to observation in these instances, collection of occasional locations by visual observation had minimal effects on hog locations. Bearing data were entered into LOAS software (Ecological Software Solutions, Urnäsch, Switzerland) to generate UTM coordinates (MLE estimator) of hog locations. We estimated telemetry error for both winter (leaf-off) and summer (leaf-on) conditions encountered during our study period using 2 methods. First, a technician held dummy transmitters in a habitat similar to, but separate from, our study area while 3 bearings toward the strongest signal were collected. Second, we used radio-collared hogs sending mortality signals as test transmitters (Withey et al. 2001). Mean distance error was 50 m (SE = 6, n = 30). This is a reasonable error considering the 414 Southeastern Naturalist Vol. 8, No. 3 dense vegetation where hogs were often located. To minimize telemetry error due to hog movements, we kept the time between the first and last bearing under 12 minutes (Holder 2006). Any locations with an error ellipse that was greater than 3 times the interquartile range above the 75th percentile was rejected (Phillips et al. 2004). Estimating available habitat We used a combination of aerial photo interpretation and ground-truthing to delineate habitat types and create a digital habitat coverage map in ArcGIS (ESRI 2004). We delineated the following habitat types: agricultural fields (AG), bottomland hardwood forests (BLHD), seasonally fl ooded bottomland hardwoods (FLHD), old fields (OF), seasonally fl ooded old fields (FLOF), and managed openings (MGDO). We conducted analyses for two separate time periods because seasonal flooding and hunting season co-occurred and created a distinct change in habitats. We defined the dry season as 1 April 2005–31 October 2005 and the wet season as 1 November 2005–31 March 2006. Most of the seasonal flooding occurred—either naturally or mechanically to provide winter waterfowl habitat (M. Cooper, Backwater Brake Hunting Club, MS, pers. comm.)—after 1 November. Additionally, general gun hunting season began on 18 November, and agricultural crops such as corn were maturing in November. These events had the potential to profoundly influence habitat use and/or Feral Hog distributions within a few days of 1 November. The beginning date (April 1) for the dry season was when most of the water had receded from the flooded areas, and general gun hunting season had closed. Survival We used the nest-survival model within program MARK (Dinsmore et al. 2002, White and Burnham 1999) to determine effects of a priori selected factors on daily survival rates (DSR) of Feral Hogs. We modeled effects of season, sex, and initial weight on DSR. We selected the model with the lowest adjusted Akaike’s information criterion (AICc: Burnham and Anderson 2002) as the best approximating model (White and Burnham 1999) to estimate survival rates. To calculate seasonal survival estimates, we raised the DSR to the power of the days included in the season (DSR# days in season). Calculating home ranges Seasonal home ranges for each hog were generated using a 95% adaptive kernel estimator within the Animal Movement Extension (Hooge and Eichenlaub 1997) in ArcView 3.2 (ESRI 2002). Because hogs formed groups during the course of our study, some home ranges were not truly independent. To avoid pseudoreplication, we dropped all but one animal in each group of closely associated animals, retaining the animal with the largest 2009 R. Hayes, S. Riffell, R. Minnis, and B. Holder 415 number of locations. We estimated annual home ranges (i.e., across both wet and dry seasons) for hogs monitored ≥8 months (n = 7). We estimated seasonal home ranges for hogs with ≥30 locations (Seaman et al. 1999) in either season (dry n = 10, wet n = 4). To allow comparison with other studies (Saunders and McLeod 1999), we also calculated seasonal home ranges using minimum convex polygons. We used unequal variance t-tests to test the hypotheses that mean home-range size did not differ between sexes and seasons. We used linear regression to determine the effects of mid-point weight (estimated wt. at mid-point of the observation period for each individual) on home-range size. We were able to obtain multiple weights for 12 hogs (5 boars and 7 sows) through recapture or hunter cooperation after harvest. Including quadratic and cubic terms did not improve model fit over the simple linear model (ΔAICc > 16.0), so we used the simple linear model to calculate a simple estimate of weight gain: 0.115 kg/day for boars (n = 5) and 0.049 for sows (n = 7). We used these rates of gain to estimate weight at the mid-point of the observation period for each animal. Although this assumes that weight gain was linear during the observation period, it does represent a better estimate of the size of the animal across the observation period than would initial weight. Habitat use We restricted our analysis to independent animals with ≥30 locations during either season (dry n = 10; wet n = 4). To estimate 2nd-order habitat use (comparing habitat within the home range to habitat available in the study area; Johnson 1980), we generated 10,000 random points in the study area and calculated distances between random points and the nearest polygon representative of each habitat type using ArcView Calculate Distance command (ESRI 2002). We calculated distances from animal locations to each habitat type (Conner and Plowman 2001). We compared the mean of these distances for each animal to the mean distances of random points to each habitat type. All habitats within the study area were considered available. To define the extent of the study area, we created a 100% minimum convex polygon of all hog locations and then created a 500-m buffer around that polygon (Harveson et al. 2004). We used the same distance methods to describe 3rd-order habitat use (use of habitat types within a home range; Johnson 1980), except that we generated 1000 random points within each animal’s home range rather than for the entire study area. Typically, MANOVA is used to control Type I error rate before using univariate t-tests to test the hypotheses that use of each specific habitat type did not differ from random (Conner and Plowman 2001:278). However, we modified this approach because small sample sizes precluded using MANOVA for the wet season. Instead of using MANOVA to control Type 416 Southeastern Naturalist Vol. 8, No. 3 I error rate, we used a sequential Bonferroni correction (which provides stricter control than a MANOVA) on the t-tests for the individual habitat types (Holm 1979, Westfall et al. 1999). To minimize high rates of Type II error (low power) associated with small sample sizes, we used α = 0.10 for all analyses. Results Survival We observed 29 hogs for periods ranging from 15–346 days. Twelve of the 15 mortalities (6 boars and 6 sows) were from hunting or trapping. The other mortalities appeared to be related to reproductive stress, collar mortality, and unknown factors, but we could not rule out disease, hunting, or aggressive encounters as potential causes. A reduced 2-season model was the best approximating model (ΔAICc = 0.00, wi = 0.92; Table 1), indicating that hogs had lower daily survival in the wet season (0.9946, 95% CI = 0.9906–0.9970) than in the dry season (0.9990, 95% CI = 0.9970–0.9997; Fig. 1). This approximation translated into seasonal survival rates of 80.8% over the 204-day dry season and 41.4% over the 164-day wet season. There was little evidence to suggest that sex or initial weight had any effect on DSR. Home range Annual home ranges (Table 2) averaged 10.0 (± 2.6) km2 for all hogs, 8.1 (± 3.2) km2 for 5 boars;, and 15.0 (± 1.9) km2 for 2 sows (mean # locations/ hog = 83). Home-range sizes were larger in the dry season (6.4 ± 1.3 km2) than in the wet season (3.0 ± 0.7 km2; t11.8 = 2.23, P = 0.046). We did not observe any significant effect of sex (t12 = 0.80, P = 0.437) or weight (t12 = -0.66, P = 0.522) on home-range sizes. Home-range estimates are listed with other published estimates in Table 2. 2nd-order habitat use Available habitat in the study area was 24% agricultural fields (AG), 40% bottomland hardwoods (BLHD), 10% seasonally fl ooded hardwoods (FLHD), 4% seasonally fl ooded old fields (FLOF), 2% managed openings (MGDO), and 20% old field (OF). In the dry season, hogs were found closer to seasonally fl ooded old fields, old fields, and managed openings than at random (Table 3). There were no Table 1. Model selection for daily survival of Feral Hogs at Malmaison WMA, MS and surrounding lands, 1 April 2005–31 March 2006. Model AICc ΔAICc AICc wi k Deviance Seasonal survival 194.27 0.00 0.92 2 190.27 Constant survival 200.56 6.29 0.04 1 198.56 Initial mass 200.56 6.29 0.02 2 198.56 Sex 201.97 7.70 0.02 2 197.97 2009 R. Hayes, S. Riffell, R. Minnis, and B. Holder 417 Table 2. Feral Hog body mass estimates (kg) and home-range estimates (km2) in the southeastern US from published sources. Other Body mass Time/ MCPB methods StateA Boar Sow Season Boar (n) Sow (n) MethodC Boar Sow Source MS 67 50 ≈6 mo/wet 2.1 (3) 3.8 (1) 95% AK 2.9 3.2 This study MS 62 53 ≈6 mo/dry 7.6 (6) 4.1 (4) 95% AK 7.5 4.6 This study MS 59 46 >8 mo 8.1 (5) 15.1 (2) 95% AK 8.1 15.0 This study SC 58 57 3–10 mo 5.3 (4) 4.4 (1) MMA 10.2 8.1 Kurz and Marchinton 1972 SC - - <1 yr 1.1 (6) 1.2 (3) - - - Wood and Brenneman 1980 SC - - >1 yr 2.3 (3) 1.8 (3) - - - Wood and Brenneman 1980 TN - - Summer 3.8 (9) 3.5 (4) - - - Singer et al. 1981 TN - - Winter 3.9 (9) 2.7 (4) - - - Singer et al. 1981 TX - - ≤24 mo - (18) - (27) MOU 19.6 16.2 Yarrow 1987 TX - - Annual 15.8 (6) 6.5 (10) - - - Mersinger and Silvy 2007 TX - - 10 mo 35.0 (7) 28.3 (6) 95% AK 58.7 43.4 Adkins and Harveson 2007 TX - - 2 yrs - - - 5.95 (18) Gabor et al. 1999 AMS = Mississippi, SC = South Carolina, TN = Tennessee, and TX = Texas. BMinimum convex polygon technique. CAbbreviations for methods as follows: AK = adaptive kernel, HM = harmonic mean, MMA = modified minimum area, MOU = multivariate Ornstein-Uhlenbeck. Figure 1. Daily survival rates and 95% CI for Feral Hogs at Malmaison WMA, and surrounding lands, 1 April–31 March 2006. 418 Southeastern Naturalist Vol. 8, No. 3 differences in distances to hog locations compared to distances to random points for bottomland hardwood, agricultural fields, and seasonally fl ooded hardwood habitats (Table 3). Thus, 2nd-order habitat use of Feral Hogs during the dry season can be ranked as follows: the greatest preference was for seasonally fl ooded old field; followed by old field and managed openings. No preference for bottomland hardwood, agricultural fields, or seasonally fl ooded hardwoods was detected. During the wet season, hog locations were closer to old-field habitat at random. Agricultural fields, managed openings, seasonally fl ooded old field, seasonally fl ooded hardwoods, and bottomland hardwoods were used no differently than expected by chance (Table 3). Wet season 2nd-order habitat- use analysis indicated that the greatest preference was for old field followed by agricultural fields, managed openings, seasonally fl ooded hardwoods, seasonally fl ooded old fields, and bottomland hardwoods. 3rd-order habitat use The mean composition for hog home ranges for the dry season was 29% agricultural fields, 32% bottomland hardwood, 5% seasonally fl ooded hardwoods, 3% seasonally fl ooded old fields, 6% managed openings, and 25% old fields. Mean composition for wet-season home ranges were 28% agricultural fields, 34% bottomland hardwood, 4% seasonally fl ooded hardwoods, 2% seasonally fl ooded old fields, 6% managed openings, and 26% old fields. During the dry season, hog locations were closer to old fields and managed openings compared to random points within each home range. Hog Table 3. Ranking and associated P and t values for 2nd- and 3rd-order habitat selection by Feral Hogs at Malmaison WMA, MS and surrounding lands, 1 April 2005–31 March 2006. Dry Wet Habitat ρ T P Habitat ρ T P 2nd-order FLOF 0.402 -4.81 <0.001* OF 0.380 -5.54 0.012* OF 0.623 -6.58 <0.001* AG 0.422 -3.84 0.031 MGDO 0.663 -3.33 0.007* MGDO 0.906 -0.33 0.763 BLHD 0.932 -0.52 0.612 FLOF 1.223 0.36 0.740 AG 1.067 0.49 0.637 FLHD 1.042 0.11 0.919 FLHD 1.321 1.99 0.075 BLHD 1.813 3.67 0.035 3rd-order OF 0.807 -4.56 0.001* OF 0.691 -1.17 0.327 FLOF 0.850 -2.38 0.039 MGDO 0.818 -2.18 0.118 MGDO 0.884 -2.82 0.018* FLHD 0.871 -2.06 0.131 BLHD 0.918 -1.83 0.097 FLOF 0.985 -0.35 0.751 AG 0.976 -0.59 0.567 AG 1.097 0.73 0.520 FLHD 1.065 1.36 0.204 BLHD 1.114 0.73 0.520 *Significant using a sequential Bonferroni correction (experiment-wise α = 0.10). 2009 R. Hayes, S. Riffell, R. Minnis, and B. Holder 419 locations were also closer to seasonally fl ooded old fields, but not significantly after a Bonferroni sequential adjustment (P = 0.039). Bottomland hardwoods, agricultural fields, and seasonally fl ooded hardwoods were used randomly (Table 3). The ranking of dry-season habitat use was: old fields were most preferred, followed by seasonally fl ooded old fields and managed openings, with no preference for bottomland hardwoods, agricultural fields, or seasonally fl ooded hardwoods. None of the habitats were used disproportionately to their availability within the home ranges during the wet season (Table 3). Discussion Survival Although others have documented greater Feral Hog mortality during dry weather (Massei et al. 1997, Woodall 1983), we observed the opposite pattern in our study area. Feral Hogs often experience food shortages during periods of low rainfall because of hardening ground which makes rooting more difficult (Massei et al. 1997, Woodall 1983). But even the dry season in Mississippi can have substantial rainfall, and coupled with the abundant wetland habitats in our study area, conditions at our study area likely did not mirror the arid environments in the studies cited above. In contrast, we observed lower survival during the wet season, and we are confident this was not related to food availability for two reasons. First, natural food resources (i.e., hard mast), maturing agricultural crops, and wildlife food plots were plentiful at this time (R.C. Hayes, pers. observ.). Second, general gun hunting season was open during most of the wet season, and hunting was the major cause of mortality among the animals that died during the study. Neither initial weight nor sex affected hog survival in our study. Weight can be an indicator of overall health. Conversely, larger animals are often targeted by hunters (thus, larger hogs could have had a greater likelihood of being shot). However, hogs in our study area often traveled in mixed groups of males and females of varying mass, and hunters tended to shoot the first hog that presented itself (J.R. Lee, Delta Wings Hunt Club, MS, pers. comm.). Jezierski (1977) and Massei et al. (1997) found that for European Wild Boar, juvenile males tend to experience higher mortality than juvenile females. However, adult females had higher mortality than adult males (Jezierski 1977, Massei et al. 1997), a result which was attributed to costs of reproduction and caring of young incurred by females during summer (Massei et al. 1997). Feral Hogs in our study area suffered very little mortality from causes other than hunting. This result suggests that hunting may be one way to control Feral Hog populations. Evidence supports the potential of hunting as a measure for reducing Feral Hog populations in some areas, thus reducing 420 Southeastern Naturalist Vol. 8, No. 3 damage and confl ict (Waithman et al. 1999). In California, hog densities were lower in areas that received high hunting pressure compared to areas where hunting was restricted (Pine and Gerdes 1973, Sweitzer et al. 2000). Damage to sensitive wetlands in hunted areas can be less than half that of unhunted areas, and supplemental removal of hogs in those unhunted areas reduced damage substantially (Engeman et al. 2007). An important caveat, however, is that a large portion of the total population may have to be removed each year to maintain stable hog numbers (Caley 1993, Dzieciolowski et al. 1992, Sweitzer et al. 2000). Home range Home-range sizes of Feral Hogs in our study area were generally comparable to elsewhere in the southeastern US (i.e., South Carolina [Kurz and Marchinton 1972, Wood and Brenneman 1980] and Tennessee [Singer et al. 1981]) except markedly smaller than in Texas (Adkins and Harveson 2007, Gabor et al. 1999, Mersinger and Silvy 2007, Yarrow 1987). Home-range size may be inversely related to precipitation (and hence food resources). Adkins and Harveson (2007) described a similar relationship between precipitation and Feral Hog densities across an east–west gradient within Texas. In South Carolina, hog home ranges were larger during the winter–spring season (which overlapped our wet season) than either summer or fall (Kurz and Marchinton 1972), but Feral Hogs in our study area occupied smaller home ranges during winter. Several factors may have contributed to this difference. First, food sources were more available during winter (our wet season) compared to summer (our dry season), the opposite of of Kurz and Marchinton (1972). Early in the wet season, waste grain was abundant in agricultural fields, acorns were available in bottomlands, and crops planted in managed openings were maturing. Increased food resources may allow animals to meet their energetic requirements in a smaller area (Saunders 1966), resulting in smaller home ranges. This increased food availability may partially account for the smaller home ranges observed in our wet season. Second, many areas were fl ooded during the wet season, both naturally and mechanically (to create winter waterfowl habitat). Thus, home ranges may have been restricted during the wet season simply because hogs were excluded from part of their home range (i.e., these habitats may have been unavailable). However, the water levels (and hence, true availability) varied over both time and space, and hogs could have potentially accessed (waded in or through) much of the seasonally fl ooded habitat. Additionally, fl ooded habitats represented a maximum of 13% and 8% of the total habitat for 2nd and 3rd-order selection, respectively. Thus, fl ooding of habitats cannot entirely account for the large difference in home-range size between the wet and dry seasons. Third, hunting activity (either direct hunting of hogs or activities related to waterfowl hunting) may have caused hogs to avoid portions of 2009 R. Hayes, S. Riffell, R. Minnis, and B. Holder 421 their dry-season home range during this period as well. Beyers and Labisky (2005) documented a similar phenomenon with White-tailed Deer. Although several studies have suggested that boars tend to have larger home ranges than sows (Baber and Coblentz 1986; Saunders and Kay 1991, 1996), Saunders and McLeod (1999) pooled data from several home-range studies and found that there were no differences in home-range size after accounting for body mass. We found no evidence of effects of either body mass or sex on home-range size. This finding suggests that home-range size in the southeastern US may be driven by availability of suitable habitat and/ or food resources. Habitat use During the dry season, ranking of habitats based on animal locations were very similar for both 2nd- and 3rd-order selection. Animal locations were closer than expected to seasonally fl ooded old fields (2nd-order only), old fields, and managed openings (Table 3). Old-field habitats in our study area were comprised of dense vegetation that hogs prefer (Baber and Coblentz 1986, Barrett 1982, Mersinger and Silvy 2007). Additionally, the seasonally fl ooded old fields may have provided cool areas for wallowing and available food sources during the dry season (Wood and Brenneman 1980). Hogs were observed feeding on smartweed (a common moist soil plant in these areas) in seasonally fl ooded old fields after the water had receded early in the dry season (R.C. Hayes, pers. observ.). Hogs also were associated with managed openings (at both the 2nd and 3rd order) during the dry season. These wildlife food plots may have provided another important food source for hogs. Baber and Coblentz (1986) reported that cultivated areas, similar to managed openings, composed only 1% of their study area, yet were heavily exploited. Our results suggest that hogs preferentially selected habitats that permitted access to these potential food sources. Land managers around MWMA often reported hog damage to these openings (D. Adams, Malmaison Wildlife Management Area, MS, pers. comm.). Considering the time and money invested in creating managed openings by landowners, this points to a potential conflict with Feral Hog populations. The remaining 3 habitats—bottomland hardwoods, agricultural fields, and seasonally fl ooded hardwoods—were not used differently from random. It was surprising that bottomland hardwoods did not infl uence home-range placement because bottomland is traditionally considered a key habitat for Feral Hogs in the southeastern US (Kurz and Marchinton 1972). One possible explanation is that bottomland hardwood habitat may not have been limiting in our study area. Hogs had access to ample bottomland hardwood habitat wherever their home range was positioned. It was not surprising, however, that seasonally flooded hardwoods were not preferred. Flooded hardwood stands may produce fewer acorns 422 Southeastern Naturalist Vol. 8, No. 3 than adjacent, unflooded hardwoods (Francis 1983). Our observations suggest this was the case in our study area (R.C. Hayes, pers. observ.). Aside from poor mast production, these areas offered little groundcover vegetation. Neither was it surprising that agricultural fields were not preferred by hogs during the dry season because there was little food or cover available in agricultural habitat until crops matured towards the end of the dry season. We observed changes in both 2nd- and 3rd-order habitat selection during the wet season. Although home-range placement continued to be associated with old fields, they were no longer associated with fl ooded old fields or managed openings (Table 4). These changes may be explained by the onset of hunting season and changes in management. Specifically, fl ooding of the seasonally fl ooded bottomland and old-field habitats may have excluded the hogs from using these habitats during this part of the year. The dense cover provided by old-field habitat may have been more important when hunting pressure began. Old-field habitat was rarely disturbed by humans (R.C. Hayes, pers. observ.) and may have provided safe loafing and feeding areas when hogs were being hunted and excluded from seasonally fl ooded habitats. Similarly, Swenson (1982) found that Odocoileus hermionus Rafinesque (Mule Deer) selected habitats with more cover during hunting season, presumably in response to hunting pressure (see also Kilgo et al. 1998). Old-field habitat was frequently adjacent to agricultural habitat where crops such as corn and cotton were maturing. Thus, old-field habitat may have provided excellent escape cover immediately adjacent to a viable food source during a time of high hunting pressure. A second important change in 3rd-order selection was that all habitat types appeared to be used randomly within the home range during the wet season. Flooding of previously used habitats and hunting pressure may have caused hogs to shift their habitat-use patterns to find necessary cover and alternate food sources. Such shifts could cause habitat selection to appear random. Furthermore, our small sample size for wet season may have resulted in low power to detect non-random habitat use. Our results suggest that hunting may infl uence small-scale patterns of habitat use. Thus, hunting might be effective at reducing hog damage to localized resources such as wildlife food plots, even though it may not reduce hog numbers over large areas. Hunting, trapping, and general harassment of hogs near sensitive areas may cause hogs to relocate to areas where they may not cause as much damage (Barrett and Birmingham 1995, Maillard and Fournier 1995). Engeman et al. (2007) found that although sport hunting removed only a small number of animals, hog damage in areas open to hunting was less than half that in unhunted areas. Hunting in areas and during times when specific resources are most susceptible to damage may help reduce damage and confl icts at a local scale. 2009 R. Hayes, S. Riffell, R. Minnis, and B. Holder 423 Acknowledgments D. Adams, M. Cooper, and J. Lee provided logistical support in the field. S. Demarais provided input at several stages of this project. Anonymous reviewers provided helpful comments on an earlier version of this manuscript. We thank the Mississippi Department of Wildlife, Fisheries, and Parks (Study #63, Project # W–84–53) and the Mississippi Agricultural and Forestry Experiment Station for financial support. This manuscript is publication #WF260 of the Forest and Wildlife Research Center, Mississippi State University. Literature Cited Adkins, R.H., and L.A. Harveson. 2007. Demographic and spatial characteristics of Feral Hogs in the Chihuahuan Desert, Texas. Human-Wildlife Confl icts 1:152–160. Baber, D.W., and B.E. Coblentz. 1986. Density, home range, habitat use, and reproduction in Feral Hogs on Santa Catalina Island. Journal of Mammalogy 67:512–525. Barrett, R.H. 1982. Habitat preference of Feral Hogs, deer, and cattle on a Sierra foothill range. 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