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Status and Distribution of the Alligator Snapping Turtle (Macrochelys temminckii) in Southeastern Missouri
Paul A. Shipman and J. Daren Riedle

Southeastern Naturalist, Volume 7, Number 2 (2008): 331–338

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2008 SOUTHEASTERN NATURALIST 7(2):331–338 Status and Distribution of the Alligator Snapping Turtle (Macrochelys temminckii) in Southeastern Missouri Paul A. Shipman1 and J. Daren Riedle2,* Abstract - Macrochelys temminckii Harlan (Alligator Snapping Turtle) is a large aquatic turtle species that has been experiencing population declines throughout its range. Unfortunately, little is known about the species’ basic biology or historic status throughout the majority of its range. In order to better understand the status and distribution of M. temminckii in southeastern Missouri, we visited 50 sites with suitable habitat and trapped at 19 of them in Dunklin, Mississippi, New Madrid, and Pemiscot counties, MO in 1994. We captured 37 M. temminckii at four sites in Pemiscot and Dunklin counties. The Dunklin County site was resampled in 1997, and radio transmitters were attached to 11 Alligator Snapping Turtles (6 males: 4 females: 1 unknown sex). Telemetered turtles were found at microhabitats consisting of more cover, high-density canopy, and lower gradient banks than random locations. We noted a significant difference in turtle size between sites that have and those that have not experienced historical take of Alligator Snapping Turtles. Introduction Macrochelys temminckii Harlan (Alligator Snapping Turtle), the largest freshwater turtle in North America, is known to occur from the Florida panhandle to eastern Texas and Oklahoma (Ernst et al. 1994) and as far north as Kansas and Illinois (Clarke 1981, Galbreath 1961). In Missouri, the Alligator Snapping Turtle is historically known to occur in the Mississippi River and southern Ozarkian drainages (Anderson 1965, Johnson 2000). Pritchard (1989) lists more specific Missouri localities along the White, Black, St. Francis, and Mississippi rivers and records in Ozark and Taney counties, particularly near Bull Shoals Lake. Little is known about their distribution within the Missouri River, as only one specimen has been documented in that stream, near St. Charles. The majority of records of the Alligator Snapping Turtle in Missouri occur along slow-moving rivers associated with the Mississippi Lowlands of southeastern Missouri. The region was historically typified by Taxodium distichum (L.) L.C. Rich. (bald cypress), Nyssa spp. (tupelo) swamps, and bottomland hardwood forest. Lumbering and drainage programs have converted most of the region to agriculture (Johnson 2000). The stream systems originating on the Ozark Plateau are typically stream-fed, clear, and fairly swift (Robison and Buchanan 1988), and Alligator Snapping Turtles occasionally occur in these swift, upland streams (Phelps 2004). 1Department of Biological Sciences, Rochester Institute of Technology, 85 Lomb Memorial Drive, Rochester, NY 14623. 2Department of Life, Earth and Environmental Sciences, West Texas A&M University, Canyon, TX 79016. *Corresponding author - 332 Southeastern Naturalist Vol.7, No. 2 The Alligator Snapping Turtle is thought to be declining throughout its range, with overharvesting and habitat alteration listed as primary causes (Reed et al. 2002). The United States Fish and Wildlife Service proposed listing the Alligator Snapping Turtle as a threatened species in 1984, but listing was precluded due to a lack of ecological information about the species (United States Fish and Wildlife Service 1991). The Alligator Snapping Turtle is currently listed as a species of conservation concern in Missouri (Johnson 2000). Our objectives were to survey the southeastern corner of Missouri, augmenting work done previously by Santhuff (1993), and to determine current distribution and habitat requirements for Alligator Snapping Turtles. Materials and Methods Oxbows, lakes, streams, and rivers were surveyed in Dunklin, New Madrid, Mississippi, and Pemiscot counties, MO, from 6 June to 11 August 1994. The St. Francis River in Dunklin County was re-sampled between April and August 1997. Turtles were trapped using commercial hoop nets that were 2.1 m in length and constructed of 4 hoops (1.05 m in diameter) covered in 2.5-cm square mesh. Nets were set upstream from submerged structures (i.e., logs and log jams) or overhanging trees. Nets were baited with fresh fish suspended by a piece of twine on the hoop furthest from the opening of the trap. We set nets in the late afternoon or evening and checked them the following morning. Sex and mass were recorded for all Alligator Snapping Turtles captured. Turtles were marked by drilling a unique series of holes in the rear marginal scute. Tarred nylon twine was tied through each hole to prevent the hole from growing back during the course of the study. A numbered livestock tag was also attached through one of the holes with nylon straps, to serve as an additional means of identification. Eleven Alligator Snapping Turtles (6 males: 4 females: 1 unknown sex) were outfitted with radio transmitters between 29 April 1997 and 29 October 1997. Turtles were captured and tracked along a disjunct stretch of the St. Francis River adjacent to Wilhelmina Conservation Area, Dunklin County. This “old channel” is a remnant from earlier channelization efforts on the St. Francis River. The 55-g radio transmitters (Wildlife Materials Inc.) were attached by drilling holes in the rear marginal scutes of the carapace and securing them with plastic cable ties. All turtle locations were marked with a GPS unit, and TNTlite v5.8 (MicroImages, Inc.) was used to plot turtle location and movement data. The average distance moved between location fixes and the minimum linear home range (farthest location upstream to the farthest location downstream for each turtle) was calculated. Habitat data were recorded at all turtle locations and at sites representing habitat available to the turtles in the St. Francis River. To represent available habitat, transects were located evenly along the length of the channel used by telemetered turtles. At each transect location, habitat variables were recorded at six points evenly spaced across the width of the stream. A total of 102 transects were surveyed along a 10.7-km stretch of stream. 2008 P.A. Shipman and J.D. Riedle 333 At each turtle location and all transect points, we measured water depth (meters), and percent canopy cover using a concave forest densiometer (Lemmon 1957). The number of tributaries present 25 m up and downstream were also recorded. Amount of cover present was categorized as follows: area cover ranked as none = 0, overhanging tree (not submerged) = 1, overhanging bank = 2, brush pile = 3, single log = 4, or log jam = 5; relative number of fl oating or submerged logs 25 m upstream and downstream ranked as none = 0, one to two = 1, three to five = 2, greater than five = 3; and gradient of nearest bank ranked as 0 to 15 degrees = 0, 15 to 45 degrees = 1, 45 to 90 degrees = 2. Wilks’ lambda multivariate test for overall differences and univariate F-tests to contrast independent variables were used to test for differences between habitat use by Alligator Snapping Turtles and available habitat. To control Type I error, the standard Bonferroni correction was used to determine significance of P-values. Results We visited 50 sites with potential Alligator Snapping Turtle habitat, and trapped at 19 sites in Dunklin, Pemiscot, and Mississippi counties. The remaining sites were either unsuitable for trapping (too shallow), or inaccessible (private property). No sites in New Madrid County were suitable for sampling. Our survey efforts consisted of 275 net nights at nineteen sites in 1994 and 121 additional net nights on the St. Francis River in 1997 (Fig. 1). We captured 37 Alligator Snapping Turtles at four sites, within two general Fig 1. Sites sampled for Alligator Snapping Turtles in Dunklin, Pemiscot, and Mississippi counties, MO in 1994. 334 Southeastern Naturalist Vol.7, No. 2 localities: Wolf Bayou, Pemiscot County, and the St. Francis River, Dunklin County. Eleven Alligator Snapping Turtles were captured in 1997, including one recapture from the 1994 surveys. We obtained 131 locations on ten individuals between 29 April 1997 and 29 October 1997. A field assistant released the 1 unknown sexed animal before obtaining size measurements. Only two locations were obtained for one individual due to either transmitter failure, or the turtle leaving the study site. That individual was removed from subsequent analysis. The mean linear home range for all turtles was 1793.5 m ± 857.1 m (range = 549.7–3322.7 m). There was no significant difference in homerange size between sexes (t = -1.734, df = 8, P = 0.126) nor did the distances moved between core sites differ significantly (t = -1.931, df = 7, P = 0.094), although females made longer movements in both cases (Table 1). Turtles prefered specific microhabitats that contained submerged cover and differed from the available habitat at transect sites (Wilks’ lambda F6, 182 = 15.5, P < 0.001) by having significantly more cover, lower gradient banks, and higher percentage canopy cover (Table 2). We noticed a marked size difference between individuals of Alligator Snapping Turtles at Wolf Bayou and the St. Francis River. These data were pooled with earlier survey data collected by Santhuff (1993) on the Black River System in Missouri to test for size differences between populations (Table 3). A one-way analysis of variance (ANOVA) was used to test for differences in mass between populations. Pooling weights from all individuals at all sites, there was no significant difference in mass between populations (F2,51 = 0.801, P = 0.465). Several individuals that could not be sexed due to their small size were dropped from the analysis (five from the Black River drainage and three from the St. Francis River). Among adult turtles, there was a significant difference in mass between populations (ANOVA: F2, 43 Table 2. Means (± 1 SD) and univariate F-test P-values for comparison of microhabitat variables of core sites with available habitat in the old channel of the St. Francis River (P to reject H0 = 0.006) Variable Core sites mean (SD) Available habitat mean (SD) P-value Cover 2.18 ± 2.02 0.94 ± 1.66 <0.0001 Canopy (%) 45.63 ± 38.89 26.38 ± 35.88 <0.0001 Bank rise 1.34 ± 0.94 2.03 ± 0.86 <0.0001 Area cover 1.57 ± 0.96 1.47 ± 0.61 0.8411 Depth (m) 2.52 ± 0.70 2.40 ± 1.05 0.3777 # of tributaries 0.06 ± 0.23 0.12 ± 0.32 0.1511 Table 1. Mean home-range size (± 1 SD) and mean distance moved between core sites (± 1 SD) by male and female Alligator Snapping Turtles. Sex n Mean home range (m) Mean distance moved between core sites (m) Male 5 1309.5 ± 566.8 232.2 ± 108.4 Female 4 2207.4 ± 980.5 361.7 ± 87.5 2008 P.A. Shipman and J.D. Riedle 335 = 11.979, P < 0.001). The Wolf Bayou and Black River turtles were larger than those in the St. Francis River. However, there was no difference in mass between turtles in Wolf Bayou and the Black River. Discussion The Alligator Snapping Turtle has been impacted heavily in southeastern Missouri, largely due to habitat alteration. We were only able to sample 38% of the 50 sites visited. Most sites had been manipulated for channelization or drained and converted to agriculture fields. Riedle et al. (2005) noted a drastic decline of Alligator Snapping Turtles in Oklahoma, due in part to habitat degradation because of stream channelization and thermal alteration by hypolimnetic releases from impoundments. Alteration of stream channels turns a low energy meandering system with high habitat diversity into a high-energy system with low habitat diversity (Moll and Moll 2000). Straightening a stream channel decreases availability of cover sites and potentially reduces foraging opportunities for Alligator Snapping Turtles. Draining of backwater habitats along the Mississippi River fl oodplain has probably had a major detrimental effect on not only Alligator Snapping Turtles, but other turtle species as well. Conversion of these areas to agriculture has the obvious effect of removing any available aquatic habitat. In addition to habitat conversion, chemical runoff and erosion associated with agricultural fields may have affected turtle populations. Heck (1998) and Riedle et al. (2005) noted that these same factors may have contributed to the decline of Alligator Snapping Turtles in eastern Oklahoma. Results from radio-telemetry efforts were very similar to those conducted on this species in Kansas (Shipman 1993), Oklahoma (Riedle et al. 2006), and Louisiana (Harrel et al. 1996, Sloan and Taylor 1987), including the species’ relationship to submerged cover sites as resting and/or foraging sites. Although there were no significant differences in distances moved, or homerange size between sexes, females did make longer movements than males. Riedle et al. (2006) noted that females also made longer movements and had significantly larger home ranges during the course of their Oklahoma study. We did lose one individual to either transmitter failure or movement out of the study site. A long-distance movement is a likely scenario, and has been reported in several other instances. Wickham (1922) reported on an individual in Oklahoma that moved between 27–30 km in 3 years. Shipman et Table 3. Mean mass, standard deviation, and range of adult and sub-adult Alligator Snapping Turtles from three populations. Population n Mean mass (kg) Range SD Wolf Bayou 20 15.9 6.2–24.0 5.4 St. Francis River 14 7.4 3.3–11.7 2.7 Black River* 15 15.1 7.3–33.6 6.8 Pooled Statistics 49 13.2 3.3–33.6 6.4 *Data taken from Santhuff (1993). 336 Southeastern Naturalist Vol.7, No. 2 al. (1991) noted a 7-km movement in 5 years by an individual in Kansas. A shorter-term movement of 16 km in a 2-month time period was documented in Oklahoma (Riedle et al. 2006). Commercial harvest of Alligator Snapping Turtles may have contributed to local declines of the species in Missouri. There is evidence for historical harvest of Alligator Snapping Turtles on the St. Francis River in both Missouri and Arkansas. Until 1993, Arkansas allowed the commercial harvest of Alligator Snapping Turtles (Santhuff 1993). The old channel of the St. Francis River is 4.8 km from the Arkansas/Missouri border, where the main channel becomes the political boundary separating the two states. Legally, harvest could take place along the Arkansas side of the river pior to 1993. Lacking data on the number of turtles harvested, and in the absence of preharvest population data, there is no direct evidence that commercial harvest of Alligator Snapping Turtles had a detrimental effect on their populations. Several observations during the course of both Santhuff’s (1993) study and ours have led us to the conclusion that harvest did impact Alligator Snapping Turtle numbers on the St. Francis River. First, individuals of Alligator Snapping Turtles captured on the St. Francis River were smaller than at other sites, suggesting recent removal of larger adults. As we moved south along the river, particularly where it bordered Arkansas, no Alligator Snapping Turtles were captured despite the presence of seemingly suitable habitat. Santhuff captured one small individual (160 mm midline carapace length [MCL]) on the Ben Cash Wildlife Area (BCWA) during his 1993 survey. We resampled this site in 1994, but captured no Alligator Snapping Turtles. Large individuals have been reported on the St. Francis River; a 58-kg male was captured near BCWA prior to the initiation of our 1994 survey (Tom Johnson, Missouri Department of Conservation, Jefferson City, MO, pers. comm.). Similar trends in size disparity between harvested and unharvested sites have also been documented in Arkansas (Trauth et al. 1998), Georgia (Jensen and Birkhead 2003), and Oklahoma (Riedle et al., in press). Incidental mortality of Alligator Snapping Turtles due to trotlines and setlines has been reported in Kansas by Shipman (1993). Moll and Moll (2004) describe the use of baited setlines for commercial turtle harvest. During the course of this study, we observed several hundred setlines and trotlines in the old channel of the St. Francis River. On one occasion, we removed a live Apalone spinifera LeSueur (Spiny Softshell Turtle) that was snagged on a setline. Santhuff (1993) found one dead and one living Alligator Snapping Turtle snagged on setlines during his survey. Unattended fishing gear is not allowed in Wolf Bayou, possibly reducing direct take of Alligator Snapping Turtles at that site. Habitat loss has greatly reduced the number of sites where Alligator Snapping Turtles might occur in southeast Missouri, but reducing the threat of take will allow the species to recover at sites where suitable habitat still occurs. There is still habitat available along stretches of the St. Francis River in Dunklin County, although the only turtles captured during our surveys 2008 P.A. Shipman and J.D. Riedle 337 were in stream segments not shared with Arkansas. Congdon et al. (1993, 1994) demonstrated that any harvest of turtles is not viable. Riedle et al. (in press) provided evidence that with the removal of harvest, Alligator Snapping Turtles will recover over time. Continued protection of habitat and possible reintroductions to former parts of the turtles range should secure their future in unaltered segments of their range in southeastern Missouri. Acknowledgments We would like to thank the Natural History Division of the Missouri Department of Conservation (MDC) for funding this project. The staff at the MDC Southeast Regional Office in Cape Girardeau, the New Madrid Forestry Office, the Duck Creek Conservation Area, and the Otter Slough Conservation Area provided logistical support. We also want to thank K. Cole and A. Neeley for assistance in the field. Literature Cited Anderson, P. 1965. The Reptiles of Missouri. University of Missouri Press, Columbia, MO. 330 pp. Clarke, R.F. 1981. A record of the Alligator Snapping Turtle, Macroclemys temminckii (Testudines: Chelydridae), in Kansas. Transactions of the Kansas Academy of Science 84:59–60. Congdon, J.D., A.E. Dunham, and R.C. van Loben Sels. 1993. Delayed sexual maturity and demographics of Blanding’s Turtles (Emydoidea blandingii): Implications for conservation and management of long-lived organisms. Conservation Biology 7:826–833. Congdon, J.D., A.E. Dunham, and R.C. van Loben Sels. 1994. Demographics of Common Snapping Turtles (Chelydra serpentina): Implications for conservation and management of long-lived organisms. American Zoologist 34:397–408. Ernst, C.H., J.E. Lovich, and R.W. Barbour. 1994. Turtles of the United States and Canada. Smithsonian Institution Press, Washington, DC. 313 pp. Galbreath, E.C. 1961. Two Alligator Snappers, Macroclemys temminckii, from southern Illinois. Transactions of the Illinois State Academy of Science 54:134–135. Harrel, J.B., C.M. Allen, and S.J. Herbert. 1996. Movements and habitat use of subadult Alligator Snapping Turtles, Macroclemys temminckii, in Louisiana. American Midland Naturalist 135:60–67. Heck, B.A. 1998. The Alligator Snapping Turtle (Macroclemys temminckii) in southeast Oklahoma. Proceedings of the Oklahoma Academy of Science 78:53–58. Jensen, J.B., and W.S. Birkhead. 2003. Distribution and status of the Alligator Snapping Turtle (Macrochelys temminckii) in Georgia. Southeastern Naturalist 2: 25–34. Johnson, T.R. 2000. The Amphibians and Reptiles of Missouri. 2nd Edition. Missouri Department of Conservation, Jefferson City, MO. 400 pp. Lemmon, P.E. 1957. A new instrument for measuring forest overstory density. Journal of Forestry 55:667–668. Moll, E.O., and D. Moll. 2000. Conservation of river turtles. Pp 126–155, In M.W. Klemens (Ed.). Turtle Conservation. Smithsonian Institution Press, Washington DC. 334 pp. 338 Southeastern Naturalist Vol.7, No. 2 Moll, D., and E.O. Moll. 2004. The Ecology, Exploitation, and Conservation of River Turtles. Oxford University Press, Oxford, UK. 393 pp. Phelps, J.P. 2004. Aquatic turtles of diversely managed watersheds in the Ouachita Mountains, Arkansas. Pages 183–186, In J.M. Guldin (Ed.). Ouachita and Ozark Mountains Symposium: Ecosystem Management Research. General Technical Report SRS-74. Department of Agriculture, Forest Service, Southern Research Station, Asheville, NC. Pritchard, P.C.H. 1989. The Alligator Snapping Turtle: Biology and Conservation. Milwaukee Public Museum, Milwaukee, WI. 104 pp. Reed, R.N., J. Congdon, and J.W. Gibbons. 2002. The Alligator Snapping Turtle [Macrochelys (Macroclemys) temminckii]: A review of ecology, life history, and conservation, with demographic analyses of the sustainability of take from wild populations. Report, Division of Scientific Authority, United States Fish and Wildlife Service, Arlington, VA. 17 pp. Riedle, J.D., P.A. Shipman, S.F. Fox, and D.M. Leslie, Jr. 2005. Status and distribution of the Alligator Snapping Turtle Macrochelys temminckii in Oklahoma. The Southwestern Naturalist 50:79–84. Riedle, J.D., P.A. Shipman, S.F. Fox, D.M. Leslie, Jr. 2006. Microhabitat use, home range, and movements of the Alligator Snapping Turtle Macrochelys temminckii in Oklahoma. The Southwestern Naturalist 51:35–40. Riedle, J.D., P.A. Shipman, S.F. Fox, J.C. Hackler, and D.M. Leslie, Jr. In press. Population structure of the Alligator Snapping Turtle, Macrochelys temminckii, on the western edge of its distribution. Chelonian Conservation and Biology. Robison, H.W., and T.M. Buchanan. 1988. Fishes of Arkansas. The University of Arkansas Press, Fayetteville, AR. 536 pp. Santhuff, S.D. 1993. Alligator Snapping Turtle, Macroclemys temminckii, trap, mark, and release project 1993. Final Report to the Missouri Department of Conservation, Jefferson City, MO. 17 pp. Shipman, P.A. 1993. Alligator Snapping Turtle: Habitat selection, movements, and natural history in southeast Kansas. M.Sc. Thesis. Emporia State University, Emporia, KS. 90 pp. Shipman, P.A., D.R. Edds, and D. Blex. 1991. Report on the recapture of an Alligator Snapping Turtle (Macroclemys temminckii) in Kansas. Kansas Herpetological Society Newsletter 85:8–9. Sloan, K.N., and D. Taylor. 1987. Habitats and movements of adult Alligator Snapping Turtles in northeast Louisiana. Proceedings of the annual conference of Southeastern Association of Fish and Wildlife Agencies 41:343–348. Trauth, S.E., J.D. Wilhide, and A. Holt. 1998. Population structure and movement patterns of Alligator Snapping Turtles (Macroclemys temminckii) in northeastern Arkansas. Chelonian Conservation and Biology 3:64–70. United States Fish and Wildlife Service (USFWS). 1991. 1991 status review of the Alligator Snapping Turtle (Macroclemmys temminckii). Endangered Species Office, Jackson, MS. 26 pp. Wickham, M.M. 1922. Notes on the migration of Macrochelys lacertina. Proceedings of the Oklahoma Academy of Science 2:20–22.