Eagle Hill Masthead

Southeastern Naturalist
    SENA Home
    Range and Scope
    Board of Editors
    Editorial Workflow
    Publication Charges

Other EH Journals
    Northeastern Naturalist
    Caribbean Naturalist
    Urban Naturalist
    Eastern Paleontologist
    Eastern Biologist
    Journal of the North Atlantic

EH Natural History Home


About Southeastern Naturalist


Wet-season Food Habits and Intersexual Dietary Overlap of Florida Box Turtles (Terrapene carolina bauri) on National Key Deer Wildlife Refuge, Florida
Steven G. Platt, Clint Hall, Hong Liu, and Christopher K. Borg

Southeastern Naturalist, Volume 8, Number 2 (2009): 335–346

Full-text pdf (Accessible only to subscribers.To subscribe click here.)


Site by Bennett Web & Design Co.
2009 SOUTHEASTERN NATURALIST 8(2):335–346 Wet-season Food Habits and Intersexual Dietary Overlap of Florida Box Turtles (Terrapene carolina bauri) on National Key Deer Wildlife Refuge, Florida Steven G. Platt1,*, Clint Hall1, Hong Liu2, and Christopher K. Borg3,4 Abstract - We studied the wet-season food habits of adult Terrapene carolina bauri (Florida Box Turtles) on National Key Deer Wildlife Refuge, Big Pine Key, FL. Feces were collected from 112 Box Turtles (64 females, 48 males) and analyzed to determine diet. Based on percent occurrence (number of samples in which a particular dietary item occurs divided by the sample size), terrestrial gastropods and fl eshy fruits were the principal foods consumed. Lesser amounts of leafy vegetation were recovered, whereas insects and other invertebrates, vertebrates (most likely consumed as carrion), and fungi composed a minor portion of the diet. The occurrence of deer feces in a single scat constitutes the first report of coprophagy by box turtles. Our fecal analysis provided little evidence of dietary specialization by either sex, which is consistent with earlier descriptions of box turtles as generalist omnivores. Male Florida Box Turtles were significantly larger than females, but there was no indication that larger body size in males provides access to an expanded resource base; the near-complete dietary overlap between the sexes suggests they consume the same foods. Introduction Terrapene carolina bauri Taylor (Florida Box Turtle), one of six extant subspecies of T. carolina in North America, occurs from extreme southeastern Georgia, southward throughout peninsular Florida, and into the Florida Keys (Dodd 2001). Within this distribution, Florida Box Turtles occupy a variety of habitats (Carr 1952), often at high densities (to 16.3 adults/ha) (Dodd 2001, Langtimm et al. 1996, Pilgrim et al. 1997, Verdon and Donnelly 2005). Surprisingly few studies have been conducted on the ecology of Florida Box Turtles (Dodd 1997a, Dodd et al. 1994, Pilgrim et al. 1997, Verdon and Donnelly 2005) despite its widespread distribution and high abundance in many areas, and in particular, little is known regarding its diet. Anecdotal observations on foraging have been reported (Carr 1952, Dodd et al. 1994), but otherwise there is a notable paucity of dietary information in the literature (Dodd 2001). Studies of diet are fundamental to understanding the ecology of an organism (Rosenberg and Cooper 1990), and among turtles, diet directly affects energy allocation, which in turn determines survival, growth, and 1Sul Ross State University, Department of Biology, Box C-64, Alpine, TX 79832. 2Department of Earth and Environment, ECS 343, Florida International University, 11200 SW 8th Street, Miami, FL 33199. 3Department of Biological Sciences, Florida International University, 11200 SW 8th Street, Miami, FL 33199. 4Current address - Tall Timbers Research Station, 13093 Henry Beadel Drive, Tallahassee, FL 32312. *Corresponding author - splatt@sulross.edu. 336 Southeastern Naturalist Vol. 8, No. 2 reproductive rates (Ford and Moll 2004, Sloan et al. 1996). Indeed, annual variation in the availability of food resources may limit clutch size and reproductive frequency of Florida Box Turtles (Dodd 1997b). Information on diet is also a necessary prerequisite for the study of complex ecological relationships such as seed-dispersal mutualisms between plants and animals (Liu et al. 2004). Moreover, dietary studies can provide information on potential pathways of exposure to environmental contaminants, which may be responsible for a high incidence of aural abscesses observed among box turtles (Brown et al. 2003, Holladay et al. 2001). From the standpoint of conservation, knowledge of diet is essential for assessing the potential impacts of urbanization and land-management practices on box turtle populations (Budischak et al. 2006). This need for greater understanding of dietary habits is especially relevant in south Florida, where Florida Box Turtle populations are thought to be declining (Dodd and Franz 1993), and habitat is being modified or destroyed by human activities at an increasingly rapid rate (Pilgrim et al. 1997, Snyder et al. 1990, Verdon and Donnelly 2005). When the sexes differ in body size, they often exploit different food resources, possibly as a means of reducing the potential for intraspecific competition (Slatkin 1984). Florida Box Turtles exhibit pronounced sexual size dimorphism, with males attaining a larger average body size and growing to greater maximum sizes than females (Dodd 1997a, Ernst et al. 1998, Verdon and Donnelly 2005). However, with the exception of Stuart and Miller (1987), intersexual dietary differences among Box Turtles have received little attention. Here we present the results of a dietary study of Florida Box Turtles in pine rockland forests on Big Pine Key, FL. In this study, we characterize the wet-season diet, estimate dietary specialization, quantify sexual size dimorphism, and measure dietary overlap between the sexes. Study Area and Methods This study was conducted on National Key Deer Wildlife Refuge (NKDWR; 24°42'N, 81°22'W), Big Pine Key, Monroe County, FL. NKDWR (3110 ha) was established for the protection of Odocoileus virginianus clavium Barbour and Allen (Key Deer), an endangered subspecies of Whitetailed Deer endemic to the Lower Florida Keys. The refuge is characterized by extensive pine rockland forest with smaller areas of hardwood hammocks and coastal mangrove forests. Pine rockland forest is a fire-dependent ecosystem that occurs on limestone outcrops in extreme southern Florida (Snyder et al. 1990). This ecosystem is dominated by a relatively open canopy of Pinus elliottii Engelm. (Slash Pine) with a diverse and often dense understory of shrubs, vines, herbs, and several species of palms (Snyder et al. 1990). The climate of the region is considered tropical with pronounced wet (May to October) and dry (November to April) seasons. Wet- and dryseason rainfall averages 743 and 265 mm, respectively, while the average dry-season temperature (22 °C) is considerably less than that of the wet season (29 °C) (Verdon and Donnelly 2005). 2009 S.G. Platt, C. Hall, H. Liu, and C.K. Borg 337 Florida Box Turtles were collected from June through October 1999 and July through November 2000 as part of a larger study on seed dispersal (Liu et al. 2004). We searched for turtles in the morning (0730–1000 h) and late afternoon (1700–1930 h). During both years, we found Florida Box Turtles by visually searching suitable microhabitats and through opportunistic encounters. A trained dog augmented our search efforts in 1999. Additionally, we searched for dead turtles in the wake of prescribed burns on NKDWR, conducted as part of a study to assess the effects of fire on pine rockland vegetation (Snyder et al. 2005). Straight-line carapace and plastron lengths (CL and PL, respectively) of each turtle were measured with calipers (± 0.1 cm). Following Dodd et al. (1994), only turtles with a CL >11.0 cm were considered adults. The sex of adult turtles was determined based on plastral morphology; males exhibit a deep concavity that is absent in females (Dodd 2001). Each captured turtle was permanently marked by notching a unique series of marginal scutes (Cagle 1939) and released at the capture site within 24–48 hours. We used a one-tailed Student’s t-test (Zar 1996) to test the hypothesis that the CL of adult male Box Turtles was greater than that of adult females. The degree of size dimorphism (defined as a statistically significant difference in mean length of sexually mature organisms) among the sexes was quantified with a compressed sexual size dimorphism index (SDI; Lovich and Gibbons 1992). SDI is a dimensionless number that is calculated by dividing the mean size of the larger sex by the mean size of the smaller sex, then adding or subtracting one from this value depending on whether males or females, respectively, are the larger sex (Lovich and Gibbons 1992). Although SDI may be based on mass or some measure of body length (CL or PL), we selected CL as the appropriate variable because body mass can exhibit considerable variation among turtles of similar length due to the presence of eggs in gravid females, recent ingestion of large meals, and overall body condition (Lovich and Gibbons 1992). Mean values are presented as ± 1 SE, and results considered significant at P ≤ 0.05. In 1999, we collected feces from captured Florida Box Turtles and analyzed the contents to determine diet. Feces were obtained by retaining turtles overnight (12–18 hours) in plastic buckets containing about 5 cm of water to stimulate defecation (Platt et al. 2001). The contents of each bucket were then passed over a sieve (2-mm mesh) and food items recovered, dried, and later identified to the lowest possible taxonomic level. We calculated the percent occurrence of each food item recovered from the feces following Rosenberg and Cooper (1990), who defined percent occurrence as the number of samples in which a particular item occurs divided by the sample size. Although often considered synonymous with frequency of occurrence, percent occurrence differs slightly and is a more appropriate metric when the number of individual food items cannot be quantified (Rosenberg and Cooper 1990). 338 Southeastern Naturalist Vol. 8, No. 2 We used the Shannon-Wiener diversity index (H') to estimate dietary niche breadth and determine the degree of dietary specialization of each sex (Schoener 1968). The Shannon-Wiener index is calculated as: H' = – Σ pj log pj, where pj is the proportion of individuals using resource j (category of food items). Because H' may range from 0 to ∞, we standardized the index on a scale of 0 to 1 using the evenness measure J' calculated as J' = H' (log n) –1, where n is the number of categories of dietary items (Krebs 1989). The lower the value of J', the more specialized the feeding habits of a particular sex, i.e., low J' values indicate little diversity in the resources consumed, and hence a greater degree of dietary specialization (Krebs 1989, Schoener 1968). Dietary niche overlap between the sexes was determined using percent overlap (P), which measures the area of overlap of the resource utilization curves of males (m) and females (f) (Krebs 1989). P is estimated by Σ (minimum pim, pif) x 100, where pim and pif are the proportion of food item (i) used by males and females, respectively, and ranges from 0 (no overlap) to 1 (complete overlap) (Krebs 1989). Results We found 207 adult Florida Box Turtles on NKDWR, including 194 living turtles and 13 (7 females, 6 males) killed by prescribed burns. Our sample consisted of 120 females and 87 males. Mean CL values for adult male and female Box Turtles were 15.3 ± 0.09 cm (range = 12.8 to 17.3 cm), and 14.1 ± 0.07 cm (range = 12.1 to 15.8 cm), respectively. Male CL was significantly greater than female CL (t = 10.4, df = 205; P < 0.001), and we calculated a SDI of 2.08 for the NKDWR sample. We obtained feces from 112 adult (64 female and 48 male) Florida Box Turtles from which we identified 24 dietary items (Table 1). Gastropod remains and seeds of plants producing fl eshy fruits were the items most frequently recovered from turtle feces. We identified several intact and partially intact gastropod shells as Chondropoma dentatum Say (Crenulate Horn) and Helicina clappi Pilsbry (Rainbow Drop), but most remains consisted of little more than small pieces of unidentifiable crushed shells. The most frequently recovered seeds were Byrsonima lucida (Mill.) DC. (Long Key Locustberry), Mosiera longipes (O. Berg) Small (Mangroveberry), and Thrinax morrisii H. Wendel (Key Thatch Palm). Seven other species of fl eshy fruits were recovered, but occurred in <10% of fecal samples. Seeds were from the dominant components of the shrub (Long Key Locustberry, Key Thatch Palm, and Coccothrinax argentata (Jacq.) L.H. Bailey [Florida Silver Palm]) and herbaceous (Morinda royoc L. [Redgal]) layers of pine rockland forest (Snyder et al. 1990). Leafy vegetation was recovered from the feces of 30 (26.7%) Florida Box Turtles, whereas insects, crustaceans, vertebrate remains, fecal pellets of Key Deer, and fungi each occurred in the 2009 S.G. Platt, C. Hall, H. Liu, and C.K. Borg 339 feces of nine (8.0%) or fewer turtles. Dietary diversity (H') and evenness (J') values were similar for males and females, and evenness values approached 1 for both sexes, indicating little dietary specialization (Table 1). We calculated an 88.3% overlap in the diet between the sexes. Discussion Florida Box Turtles on NKDWR are generalist omnivores that consume a variety of animal and plant foods, a profile similar to other studies of box turtles (Klimstra and Newsome 1960, Stuart and Miller 1987). Terrestrial Table 1. Dietary items recovered from the feces of adult Terrapene carolina bauri (Florida Box Turtle) collected on National Key Deer Wildlife Refuge, Big Pine Key, FL from June through October 1999. Number of turtles from which a specific dietary item was recovered is followed by percent occurrence (%) in parentheses. Percentages do not sum to 100 because multiple items were often found in the feces of a single turtle. Dietary item Females (n = 64) Males (n = 48) All turtles (n = 112) Fruits Annona glabra L. (Pond Apple)A 2 (3.1) 0 2 (1.7) Brysonima lucidaA 44 (68.7) 31 (64.5) 75 (67.0) Coccoloba uviferaA 0 3 (6.2) 3 (2.6) Coccothrinax argentataA 6 (9.3) 2 (4.1) 8 (7.1) Ficus sp.A 0 1 (2.0) 1 (0.9) Fabaceae (unidentified) 2 (3.1) 0 2 (1.7) Morinda royocA 4 (6.2) 6 (12.5) 10 (9.0) Mosiera longipesA 23 (36.0) 15 (31.2) 38 (34.0) Smilax havanensis Jacq.A 2 (3.1) 0 2 (1.7) (Everglades Greenbrier) Thrinax morrisiiA 14 (21.8) 9 (18.7) 23 (20.5) Foliage Foliage (unidentified) 15 (23.4) 7 (14.5) 22 (19.6) Mosiera longipes 4 (6.2) 3 (6.2) 7 (6.2) Tillandsia sp. 0 1 (2.0) 1 (0.9) Animal remains Bone 1 (1.5) 0 1 (0.9) Crustacean 1 (1.5) 0 1 (0.9) Fish 0 1 (2.0) 1 (0.9) Insects 4 (6.2) 5 (10.4) 9 (8.0) Gastropods 60 (93.7) 44 (91.6) 104 (92.8) Snake (shed skin) 2 (3.1) 0 2 (1.7) Terrapene carolina 2 (3.1) 2 (4.1) 4 (3.5) Miscellaneous items Feces (Odocoileus virginianus) 0 1 (2.0) 1 (0.9) Fungus 1 (1.5) 1 (2.0) 2 (1.7) PaperB 2 (3.1) 0 2 (1.7) StonesB 0 1 (2.0) 1 (0.9) Diversity (H') 1.21 1.17 1.16 Evenness (J') 0.91 0.90 0.89 ASpecies with fl eshy fruits. BDietary categories not included in calculations of H'. 340 Southeastern Naturalist Vol. 8, No. 2 gastropods were the most frequently occurring food item that we observed. Gastropods (snails and slugs) are common prey for other subspecies of box turtles, occurring in the diet at frequencies as high as 72% (Barbour 1950, Bush 1959, Klimstra and Newsome 1960, Stuart and Miller 1987). However, the percent occurrence (92.8%) we observed for NKDWR is the highest yet reported anywhere. In addition to being consumed as food, snails could be an important source of calcium for eggshell formation in reproductive female box turtles (Beasom and Pattee 1978, Esque and Peters 1994). In contrast to studies in which insects and invertebrates other than gastropods comprise much of the diet (Klimstra and Newsome 1960, Stickel 1950, Strang 1983, Stuart and Miller 1987), these prey appear relatively unimportant for Florida Box Turtles on NKDWR. The diet of Florida Box Turtles on Egmont Key is thought to be composed primarily of cockroaches (Dodd et al. 1994), a prey item that we did not detect among the feces of turtles from NKDWR. Little is known about prey selection in box turtles (Dodd 2001), but the occurrence of gastropods, insects, and other invertebrates in the diet probably refl ects their relative availability to foraging turtles. The vertebrate remains we recovered in turtle feces were most likely consumed as carrion. Scavenging of vertebrate carrion by Box Turtles is well documented (Carr 1952, Dodd 2001, Klimstra and Newsome 1960), and when available, carrion provides an energetically rich food source that can be safely obtained without the cost of capturing and subduing prey (DeVault and Krochmal 2002). Similar to carrion, shed snake skins represent a protein source for Box Turtles (Weldon et al. 1993). Interestingly, the most common vertebrate remains we observed were carapacial bones of other box turtles. Osteophagy is widespread among terrestrial chelonians (Walde et al. 2007), and bones are an excellent source of calcium and phosphorus (Esque and Peters 1994)—nutrients that are poorly represented in the shallow, leached sandy soils typical of pine rockland forest (Snyder et al. 1990). The large size of most carapacial bones indicated they were from adult turtles and almost certainly consumed as carrion; however, one scat contained costal bones from a hatchling or small juvenile. Although there is no way to determine if this juvenile was scavenged as carrion, our observation raises the possibility that Florida Box Turtles may occasionally engage in cannibalism. Seeds from fleshy-fruited species were the principal plant material that we found in turtle scats. Most fruits consumed by Florida Box Turtles were either those that readily dropped to the ground at maturity (Long Key Locustberry, Key Thatch Palm, and Florida Silver Palm) or occurred on plants with prostrate growth forms (Redgal). The fruits most frequently found in turtle feces were drupes with a covering of sugar- or lipid-rich mesocarp, but berries and aggregate fruits (e.g., Ficus sp. (figs) and Mangroveberry) were also represented. Most species of fruit found in scats were dark colored (blue/purple/black), although there was no significant difference between the color of fruits available on NKDWR and those consumed by 2009 S.G. Platt, C. Hall, H. Liu, and C.K. Borg 341 turtles (Liu et al. 2004). Other studies of box turtles have likewise noted an abundance of fleshy fruits in the diet (Braun and Brooks 1983, Dodd et al. 1994, Klimstra and Newsome 1960). Fleshy fruits are high in calories, offer a rich energetic reward (Golley 1961), and may also be an important source of moisture in xeric pine rockland habitats, especially during the dry season (Dodd et al. 1994). The seeds of non-fleshy fruits rarely occurred among turtle feces from NKDWR. Dodd et al. (1994) observed Florida Box Turtles on Egmont Key consuming the fruits of Coccoloba uvifera L. (Seagrape), Opuntia sp. (cactus), Scaevola plumieri (L.) Vahl. (Half-Flower), and Sabal palmetto (Walter) Lodd. Ex Schult & Schult f. (Cabbage Palm), and found Schinus terebinthifolius Raddi. (Brazilian Pepper) seeds in turtle feces. With the exception of Seagrape, which is a minor component of the diet on NKDWR, seeds of these plants were absent from our samples. Such differences are not unexpected, as most of these species are rare or absent in our study area, or produce fruit primarily during the dry season (e.g., Brazilian Pepper), a period in which we did not sample. Nor did we observe large (30–40) aggregations of Florida Box Turtles foraging beneath fruiting trees as described by Dodd et al. (1994) on Egmont Key. The largest group of feeding Florida Box Turtles that we encountered was three individuals beneath a single Long Key Locustberry shrub. In contrast to Egmont Key, where box turtles from throughout the island converge on clumps of fruiting trees (Dodd et al. 1994), the principal fruiting species used on NKDWR are widespread and abundant; consequently it is unnecessary for turtles to congregate in large groups to exploit this food resource. Studies of box turtles in temperate regions of North America have found that shoots, buds, and leaves compose a significant portion of the diet (Dodd 2001, Stuart and Miller 1987); however, leafy vegetation was relatively uncommon in the diet of turtles on NKDWR. Moreover, some of this material may have been incidentally ingested while turtles were consuming fruits (e.g., Mangroveberry). The relative paucity of leafy vegetation in the diet is not unexpected given the high lignin and cellulose content and low caloric value of leaves in comparison to the high caloric content and widespread availability of fruit (Golley 1961). Leafy vegetation may assume greater dietary importance during the dry season, when most fruits are unavailable (S. Koptur et al., Florida International University, Miami, FL, unpubl. data). Box turtles elsewhere in North America reportedly consume large amounts of fungi (Strang 1983, Stuart and Miller 1987, Surface 1908), an item that we recovered from only two turtles. These differences may be due to the bias inherent in different sampling methodologies; two of the studies that noted a high frequency of fungi were based on an examination of stomach contents (Stuart and Miller 1987, Surface 1908). In our study, fungi may have been completely digested and thus would likely have gone undetected in the feces. We consider the latter unlikely, however, as Moskovits and Bjorndal (1990) noted that fungi were resistant to digestion and often 342 Southeastern Naturalist Vol. 8, No. 2 defecated intact by Geochelone carbonaria Spix (Red-footed Tortoise) and G. denticulata (L.) (South American Yellow-footed Tortoise). Likewise, we have recovered undigested fungi from the feces of Rhinoclemmys areolata Duméril, Bibron, and Duméril (Furrowed Wood Turtle) in Belize and T. carolina major Agassiz (Gulf Coast Box Turtles) in Louisiana (S.G. Platt et al., unpubl. data). More importantly, it is our subjective impression that fungi are rare in the xeric soils of pine rockland forest and therefore less available to foraging turtles. The large number of seeds found in individual fecal samples (Liu et al. 2004), coupled with the high population density (10.2 box turtles/ha; Verdon and Donnelly 2005), suggests that Florida Box Turtles are significant dispersers of fl eshy-fruited plant species on NKDWR. In an earlier study, we planted the seeds of nine fl eshy-fruited species recovered from turtle feces and all successfully germinated at rates ranging from 10 to 80% (Liu et al. 2004). However, the effects of digestion on the germination performance of seeds is complex and varied among species; larger-seeded species were more likely than smaller-seeded species to exhibit a positive response (greater germination percentage of ingested vs. control seeds) to digestion (Liu et al. 2004). Furthermore, digestion appears to initiate long-term seed dormancy in Key Thatch Palm, possibly allowing seeds to disperse through time as well as space (Liu et al. 2004). Similar to our results, Braun and Brooks (1983) found that passage of seeds through the digestive tract of Terrapene carolina carolina L. (Eastern Box Turtles) enhanced the germination percentage in 5 of 15 species tested. Although saurochory (dispersal of seeds by reptiles) has received comparatively little attention from researchers (Traveset 1998) and previous studies suffer from several serious limitations (reviewed by Liu et al. 2004), our investigation and others (Braun and Brooks 1983, Carlson et al. 2003, De Lima et al. 1997, Ford and Moll 2004, Iverson 1987, Milton 1992, Moll and Jansen 1995, Moskovits and Bjorndal 1990, Varela and Bucher 2002) are part of a growing body of literature that strongly suggests turtles are important seed-dispersal agents in both terrestrial and aquatic ecosystems. Notably, the consumption of Cabbage Palm (Dodd et al. 1994), Serenoa repens (Bartr.) Small (Saw Palmetto; Liu et al. 2004), Key Thatch Palm, and Florida Silver Palm fruits and probable dispersal of their seeds by Florida Box Turtles are among the few documented cases of palm seed dispersal by a reptile (see also De Lima et al. 1997, Moskovits and Bjorndal 1990). An earlier review concluded that reptile-mediated dispersal of palm seeds is rare and identified only one species of lizard as an important dispersal agent (Zona 2006, Zona and Henderson 1989). To our knowledge, the occurrence of deer fecal pellets in a single scat sample constitutes the first report of coprophagy by box turtles. Coprophagy has occasionally been observed among other terrestrial and aquatic turtles (Goodman and Stuart 1998, Mares 1971), which probably derive nutritional benefits from partially digested food items in the feces (Robbins 2001). Although it is possible that box turtles secondarily ingest some seeds when consuming deer 2009 S.G. Platt, C. Hall, H. Liu, and C.K. Borg 343 feces (e.g., Gervais et al. 1998), it is unlikely that coprophagy contributes significantly to the number of seeds we found in scats for two reasons. First, coprophagy appears rare among box turtles, and second, while Key Deer are known to consume many of the same fruits as box turtles, their principal dietary components are forbs and woody browse (Klimstra and Dooley 1990). Our results on sexual size dimorphism are consistent with Verdon and Donnelly (2005), who found that the CL of male Florida Box Turtles (14.7 ± 0.2 cm; n = 27) was significantly greater than that of females (13.4 ± 0.1 cm; n = 47) on Big Pine Key. Using the mean CL for male and female turtles reported by Verdon and Donnelly (2005), we calculated a SDI of 2.09, a value very similar to our sample. Although Verdon and Donnelly (2005) did not find any females with a CL >15.0 cm, 18 females (15%) in our sample had a CL exceeding this value. The CL of the largest males (to 17.3 cm) found on Big Pine Key (Verdon and Donnelly 2005, this study) exceeds the maximum of 16.6 cm reported for other populations of Florida Box Turtles (Dodd 1997a, Ernst et al. 1998). Large body size in male box turtles is thought to confer a mechanical advantage during copulation; the larger plastron of the male permits the development of a deeper plastral concavity that meshes with the relatively smaller carapace of the female, enabling the male to better grasp the front of the female’s carapace with his claws (Dodd 1997a). Although male Florida Box Turtles are significantly larger than females, we saw no indication that larger body size in males provides access to an expanded resource base. The near-complete overlap in diet suggests that male and female turtles consume essentially the same foods on NKDWR. Similarly, Stuart and Miller (1987) found no dietary differences between male and female Eastern Box Turtles in North Carolina. Dodd (2001) suggested that intersexual dietary differences are unlikely because both sexes use the same habitats concurrently, thereby encountering the same food resources. Diversity values that indicate little dietary specialization by either sex on NKDWR are consistent with the characterization of box turtles as generalist omnivores (Allard 1948, Dodd 2001, Stuart and Miller 1987). Finally, because this dietary study only spanned a single wet season, we were unable to investigate seasonal patterns of food consumption among Florida Box Turtles on NKDWR. Given the pronounced wet–dry seasonality of southern Florida, variation in the diet is expected owing to the seasonal availability of food resources (Dodd 1997b). Not only do few plants bear fruit during the dry season (S. Koptur et al., unpubl. data), but drought conditions probably reduce the availability of snails and insects (Dodd 1997b). Moreover, annual variation in dietary composition probably also exists, particularly with regards to mast-fruiting species such as Long Key Locustberry. For example, in 1999, Long Key Locustberry fruit was abundant, which was refl ected in fecal samples, but during two subsequent fruiting seasons (2000 and 2001), we were unable to locate a sufficient number of fruits for germination trials (Liu et al. 2004). Other food resources likely exhibit similar annual fl uctuations in availability. Future multi-season studies conducted over several years will be necessary to address questions of seasonal and annual variation in Florida Box Turtle diets. 344 Southeastern Naturalist Vol. 8, No. 2 Acknowledgments Support for S.G. Platt was provided by Wildlife Conservation Society and Sul Ross State University. Hong Liu and Chris Borg were supported by Florida International University. We are grateful for the assistance of Joanne Springfield Globe, Elizabeth Birgh, and Trouble (dog) with turtle collections, and Timothy Collins for snail identifi- cations. Suzanne Koptur kindly provided lab space and logistic assistance. Early drafts of this manuscript benefited from the comments of Thomas Rainwater, Lewis Medlock, Trip Lamb, and two anonymous reviewers. Literature Cited Allard, H.A. 1948. The Eastern Box Turtle and its behavior. Journal Tennessee Academy of Science 23:307–321. Barbour, R.W. 1950. The reptiles of Big Black Mountain, Harlan County, Kentucky. Copeia 1950:100–107. Beasom, S.L., and O.H. Pattee. 1978. Utilization of snails by Rio Grande Turkey hens. Journal of Wildlife Management 42:916–919. Braun, J., and G.R. Brooks, Jr. 1983. Box Turtles (Terrapene carolina) as potential agents for seed dispersal. American Midland Naturalist 117:312–318. Brown, J.D., J.M. Sleeman, and F. Elvinger. 2003. Epidemiologic determinants of aural abscessation in free-living Eastern Box Turtles (Terrapene carolina) in Virginia. Journal of Wildlife Diseases 39:918–921. Budischak, S.A., J.M. Hester, S.J. Price, and M.E. Dorcas. 2006. Natural history of Terrapene carolina (Box Turtles) in an urbanized landscape. Southeastern Naturalist 5:191–204. Bush, F.M. 1959. Foods of some Kentucky herptiles. Herpetologica 15:73–77. Cagle, F.R. 1939. A system of marking turtles for future recognition. Copeia 1939:170–173. Carlson, J.E., E.S. Menges, and P. Marks. 2003. Seed dispersal by Gopherus polyphemus at Archbold Biological Station, Florida. Florida Scientist 66:147–154. Carr, A. 1952. Handbook of Turtles. Cornell University Press, Ithaca, NY. 542 pp. De Lima, A.C., W.E. Magnusson, and V.L. da Costa. 1997. Diet of the turtle Phrynops rufipes in Central Amazonia. Copeia 1997:216–219. DeVault, T.L. and A.R. Krochmal. 2002. Scavenging by snakes: An examination of the literature. Herpetologica 58:429–436. Dodd, C.K., Jr. 1997a. Population structure and evolution of sexual size dimorphism and sex ratios in an insular population of Florida Box Turtles (Terrapene carolina bauri). Canadian Journal Zoology 75:1495–1507. Dodd, C.K., Jr. 1997b. Clutch size and frequency in Florida Box Turtles (Terrapene carolina bauri): Implications for conservation. Chelonian Conservation and Biology 2:370–377. Dodd, C.K., Jr. 2001. North American Box Turtles: A Natural History. University of Oklahoma Press, Norman, OK. 231 pp. Dodd, C.K., Jr., and R. Franz. 1993. The need for status information on common herpetofaunal species. Herpetological Review 24:47–49. Dodd, C.K., Jr., R. Franz, and L.L. Smith. 1994. Activity patterns and habitat use of Box Turtles (Terrapene carolina bauri) on a Florida island, with recommendations for management. Chelonian Conservation and Biology 1:97–106. Ernst, C.H., J.C. Wilgenbusch, T.P. Boucher, and S.W. Sekscienski. 1998. Growth, allometry, and sexual dimorphism in the Florida Box Turtle, Terrapene carolina bauri. Herpetological Journal 8:72–78. 2009 S.G. Platt, C. Hall, H. Liu, and C.K. Borg 345 Esque, T.C. and E.L. Peters. 1994. Ingestion of bones, stones, and soil by Desert Tortoises. Pp. 105–111, In R.B. Bury D.J. Germano (Eds.). Biology of North American Tortoises. US Department of Interior, National Biological Survey, Washington, DC. Fish and Wildlife Research Report 13. 204 pp. Ford, D.K., and D. Moll. 2004. Sexual and seasonal variation in foraging patterns in the Stinkpot, Sternotherus odoratus, in southwestern Missouri. Journal of Herpetology 38:296–301. Gervais, J.A., A. Traveset, and M.F. Willson. 1998. The potential for seed dispersal by the Banana Slug (Ariolimax columbianus). American Midland Naturalist 140:103–110. Golley, F.B. 1961. Energy values of ecological materials. Ecology 42:581–584. Goodman, R.H., Jr., and G.R. Stewart. 1998. Clemmys marmorata pallida (Southwestern Pond Turtle). Coprophagy. Herpetological Review 29:98. Holladay, S.D., J.C. Wolf, S.A. Smith, D.E. Jones, and J.L. Robertson. 2001. Aural abscesses in wild-caught Box Turtles (Terrapene carolina): Possible role of organochlorine-induced hypovitaminosis A. Ecotoxicology and Environmental Safety 48:99–106. Iverson, J.B. 1987. Tortoises not dodos, and the tambalacoque tree. Journal of Herpetology 21:229–230. Krebs, C.J. 1989. Ecological Methodology. Harper Collins, NY. 654 pp. Klimstra, W.D., and A.L. Dooley. 1990. Foods of the Key Deer. Florida Scientist 53:264–273. Klimstra, W.D., and F. Newsome. 1960. Some observations on the food coactions of the Common Box Turtle, Terrapene c. carolina. Ecology 41:639–647. Langtimm, C.A., C.K. Dodd, Jr., and R. Franz. 1996. Estimates of abundance of Box Turtles (Terrapene carolina bauri) on a Florida island. Herpetologica 52:496–504. Liu, H., S.G. Platt, and C.K. Borg. 2004. Seed dispersal by the Florida Box Turtle (Terrapene carolina bauri) in pine rockland forests of the lower Florida Keys, United States. Oecologia 138:539–546. Lovich, J.E., and J.W. Gibbons. 1992. A review of techniques for quantifying sexual size dimorphism. Growth, Development, and Aging 56:269–281. Mares, M.A. 1971. Coprophagy in the Texas Tortoise, Gopherus berlandieri. Texas Journal of Science 23:300–301. Milton, S.J. 1992. Plants eaten and dispersed by adult Leopard Tortoises Geochelone paradalis (Reptilia:Chelonii) in the southern Karoo. South African Journal of Zoology 27:45–49. Moll, D., and K.P. Jansen. 1995. Evidence for a role in seed dispersal by two tropical herbivorous turtles. Biotropica 27:121–127. Moskovits, D.K., and K.A. Bjorndal. 1990. Diet and food preferences of the tortoises Geochelone carbonaria and G. denticulata in northwestern Brazil. Herpetologica 46:207–218. Pilgrim, M.A., T.M. Farrell, and P.G. May. 1997. Population structure, activity, and sexual dimorphism in a central Florida population of Box Turtles, Terrapene carolina bauri. Chelonian Conservation and Biology 2:483–488. Platt, S.G., S.T. Khaing, W.K. Ko, and Kalyar. 2001. A tortoise survey of Shwe Settaw Wildlife Sanctuary, Myanmar, with notes on the ecology of Geochelone platynota and Indotestudo elongata. Chelonian Conservation and Biology 4:172–177. Robbins, C.T. 2001. Wildlife Feeding and Nutrition. Academic Press, Inc., NY. 352 pp. Rosenberg, K.V., and R.J. Cooper. 1990. Approaches to avian diet analysis. Studies in Avian Biology 13:80–90. 346 Southeastern Naturalist Vol. 8, No. 2 Schoener, T.W. 1968. The Anolis lizards of Bimini: Resource partitioning in a complex fauna. Ecology 49:704–726. Slatkin, M. 1984. Ecological causes of sexual dimorphism. Evolution 38:622–630. Sloan, K.N., K.A. Buhlmann, and J.E. Lovich. 1996. Stomach contents of commercially harvested adult Alligator Snapping Turtles, Macroclemys temminckii. Chelonian Conservation and Biology 2:96–99. Snyder, J.R., A. Herndon, and W.B. Robertson. 1990. South Florida rockland. Pp. 230–277, In R.L. Myers and J.J. Ewel (Eds.). Ecosystems of Florida. University of Central Florida Press, Orlando, FL. 840 pp. Snyder, J.R., M.S. Ross, S. Koptur, and J.P. Sah. 2005. Developing ecological criteria for prescribed fire in south Florida pine rockland ecosystems. Open File Report: OF 2006–1062. US Geological Survey, Washington, DC. 109 pp. Stickel, L.F. 1950. Populations and home range relationships of the Box Turtle, Terrapene c. carolina (Linnaeus). Ecological Monographs 20:351–378. Strang, C.A. 1983. Spatial and temporal activity patterns in two terrestrial turtles. Journal of Herpetology 17:43–47. Stuart, M.D., and G.C. Miller. 1987. The Eastern Box Turtle, Terrapene c. carolina (Testudines:Emydidae) in North Carolina. Brimleyana 13:123–131. Surface, H.A. 1908. First report on the economic features of the turtles of Pennsylvania. Zoological Bulletin of Pennsylvania Department of Agriculture 6:105–196. Traveset, A. 1998. Effect of seed passage through vertebrate frugivores’ guts on germination: A review. Perspectives of Plant Ecology, Evolution, and Systematics 1:151–190. Varela, R.O., and E.H. Bucher. 2002. Seed dispersal by Chelonoidis chilensis in the Chaco dry woodland of Argentina. Journal of Herpetology 36:137–140. Verdon, E., and M.A. Donnelly. 2005. Population structure of Florida Box Turtles (Terrapene carolina bauri) at the southernmost limit of their range. Journal of Herpetology 39:572–577. Walde, A.D., D.K. Delaney, M.L. Harless, and L.L. Pater. 2007. Osteophagy by the Desert Tortoise. Southwestern Naturalist 52:147–149. Weldon, P.J., B.L. Demeter, and R. Rosscoe. 1993. A survey of shed skin-eating (dermatophagy) in amphibians and reptiles. Journal of Herpetology 27:219–228. Zar, J.H. 1996. Biostatistical Analysis. Prentice Hall, Saddle River, NJ. 662 pp. Zona, S. 2006. Addition to “A review of animal-mediated seed dispersal of palms.” http://www.virtualherbarium.org/palms/psdispersal. Accessed 30 October 2007. Zona, S., and A. Henderson. 1989. A review of animal-mediated seed dispersal of palms. Selbyana 11:6–21.