Alligator Snapping Turtle Research Articles

Characteristics of a Historically Harvested Alligator Snapping Turtle (Macrochelys temminckii) Population

Following perturbations like commercial harvests, turtles are susceptible to population declines because of life history characteristics such as long generation times, low recruitment rates, delayed maturity, and slow growth rates. Prior to gaining state-wide protection in 1993, the Alligator Snapping Turtle (Macrochelys temminckii) was commercially harvested in Arkansas. We conducted a mark–recapture study from 2005–2007 on a population of M. temminckii known to have been harvested in the East Fork Cadron Creek, a slow-moving stream in central Arkansas and part of the Mississippi River drainage. Captured turtles were marked, measured, weighed, and sexed. We compared observed characteristics to what would be expected if this population did not exhibit any evidence of past commercial harvest. We caught few large adults and approximately one adult for every juvenile. The adult sex ratio was highly female biased (6 F∶1 M). Population density (18 turtles/km stream reach) was slightly lower than expected. The ...

Habitat Use by the Alligator Snapping Turtle (Macrochelys temminckii) and Eastern Snapping Turtle (Chelydra serpentina) in Southeastern Missouri

This study addresses habitat differences of two sympatric turtle species, alligator snapping turtles (Macrochelys temminckii) and eastern snapping turtles (Chelydra serpentina) in six watersheds in southeastern Missouri. We found that alligator snapping turtle presence corresponded with higher abundance of submerged physical structures in the stream, deeper water, relatively higher levels of detritus, and warmer water temperatures. Greater amount of aquatic vegetation was important in characterizing eastern snapping turtle presence in traps. Eastern snapping turtles and alligator snapping turtles did not use the same areas spatially at either a microhabitat or macrohabitat scale, and were only trapped at the same location once in 282 trap locations. Future conservation plans for the alligator snapping turtle and eastern snapping turtle should consider the microhabitat characteristics of sites used by these turtles.

Temporal changes in an alligator snapping turtle (Macrochelys temminckii) population

Context Monitoring populations of long-lived species requires continuous long-term efforts. This is especially applicable for species that have experienced declines range-wide. Aims Our study assessed the current status of a population of wild Macrochelys temminckii and compared the present results to those from a survey conducted nearly a decade ago. Methods Trapping in 2010–2011 was conducted on two creeks within the refuge, during the months of May–July. Capture data were compared with data collected by similar methods in 1997–2001. Key results The population structure of M. temminckii was dominated by juveniles, with few large adults or small juveniles detected and a missing size class was evident. Retrospective analysis of 1997–2001 data revealed that the population was likely to be in decline even then, despite high capture rates. Conclusions The M. temminckii population showed significant declines that indicated that the population had experienced stressors of unknown origin. The status of M. temminckii at the refuge is concerning, given the protection afforded this remnant population. Implications Short-term data from 1997–2001 indicated a healthy M. temminckii population, whereas longer-term data showed that the population has declined, resulting in significant demographic changes. Continued monitoring will be necessary to develop management recommendations and track the impact of implemented management practices. Longer-term monitoring of long-lived vertebrates is required to identify population trends.

Anatomy of the fully formed chondrocranium of Emydura subglobosa (Chelidae): A pleurodiran turtle

The chondrocranium is a cartilaginous structure that forms around and protects the brain and sensory organs of the head. Through ontogeny, this skeletal structure may become more elaborate, remodeled and reabsorbed, and/or ossified. Though considerable attention has been given to the formation of the chondrocranium and a great amount of data has been gathered on the development of this structure among many craniates, the anatomy of this structure in turtles often is neglected. We describe the mature chondrocranium of the pleurodiran turtle, Emydura subglobosa (Chelidae) based on hatchling specimens. Though formation and ossification of bony elements has been studied previously in this species, a detailed description of the chondrocranium of this pleurodiran turtle has not been presented. Anatomy of the chondrocranium was described for E. subglobosa by examination of cleared and double-stained specimens. The orbitotemporal region of E. subglobosa is dramatically different from that of other described turtles (e.g., Apalone spinifera, Pelodiscus sinensis, Chelydra serpentina, Macrochelys temminckii, Trachemys scripta, Chrysemys picta, and Eretmochelys imbricata) in that a prominent taenia marginalis spans the space between the planum supraseptale and otic capsules, and the pila antotica (which becomes modified and ossified through ontogeny to form the processus clinoideus) is greatly reduced and essentially absent in hatchling specimens. The morphology seen in E. subglobosa is similar to that of Caretta caretta, particularly as it relates to the taenia marginalis. Variation in the orbitotemporal region is briefly discussed in the context of the taenia marginalis, taenia medialis, pila metoptica, and pila antotica.

Population ecology of the snapping turtle (Chelydra serpentina osceola) in a northern Florida river

Snapping turtles (Chelydra serpentina) occur in nearly every type of freshwater habitat in North America east of the Rocky Mountains, but little is known about the ecology of populations in the southern part of their range, as well as those in lotic habitats. We conducted a mark-recapture study of the Florida snapping turtle (C. s. osceola) in the Santa Fe River in northern Florida between August 2005 and November 2010. Ninety-six percent of all captures occurred within a 9 km section of the river that receives direct input from 21 artesian springs. Within this “high density spring area,” population density and biomass of adults were 2.7 turtles/ha and 24.9 kg/ha, respectively. The total sample (n = 113 turtles) consisted of 14.2% immature individuals, 45.1% adult females, and 40.7% adult males. Adult sex ratio was 1:1. Juveniles occupied spring and spring run habitats disproportionally to the river habitat. Adult males (straight midline carapace length [CL] 243–439 mm, mean = 360 mm) are the largest known in Florida, and adult females (CL 257–380 mm, mean = 325 mm) are similar in size to the largest known conspecifics in Nebraska and South Dakota. The large body sizes in our population are inconsistent with previous studies that indicate a positive relationship between body size and latitude in this species, emphasizing the importance of habitat type in influencing demography. Large body sizes in the Santa Fe River may be related to the thermal/food resources provided by artesian springs, the physical environment of the riverine habitat, or coexistence with alligator snapping turtles (Macrochelys temminckii).

Cutaneous Fibroma in a Captive Common Snapping Turtle (Chelydra serpentina)

An adult female common snapping turtle (Chelydra serpentina) had a mass on the plantar surface of the right forelimb that was removed surgically. Microscopical examination revealed many spindle cells with mild anisocytosis and anisokaryosis and a surrounding collagenous stroma. There were no mitoses. Immunohistochemistry showed that the spindle cells expressed vimentin, but not desmin. A diagnosis of cutaneous fibroma was made. Tumours are reported uncommonly in chelonian species. Cutaneous fibroma has been diagnosed in an alligator snapping turtle (Macrochelys temminckii), but not previously in a common snapping turtle.

Interspecific Variation in Temperature Effects on Embryonic Metabolism and Development in Turtles

We measured temperature-induced differences in metabolic rates and growth by embryos of three turtle species,Macrochelys temminckii, Trachemys scripta, andApalone spinifera, at different, constant, temperatures. Oxygen consumption rate (VO2) was measured during development and used to characterize changes in metabolism and calculate total O2consumption. Results from eggs incubated at different temperatures were used to calculate Q10s at different stages of development and to look for evidence of metabolic compensation. Total O2consumption over the course of incubation was lowest at high incubation temperatures, and late-term metabolic rate Q10s were <2 in all three species. Both results were consistent with positive metabolic compensation. However, incubation temperature effects on egg mass-corrected hatchling size varied among species.Apalone spiniferahatchling mass was unaffected by temperature, whereasT. scriptamass was greatest at high temperatures andM. temminckiimass was lowest at high temperatures. Hatchling mass : length relationships tended to correlate negatively with temperature in all three species. Although we cannot reject positive metabolic compensation as a contributor to the observed VO2patterns, there is precedence for drawing the more parsimonious conclusion that differences in yolk-free size alone produced the observed incubation temperature differences without energetic canalization by temperature acclimation during incubation.

Characterization of 10 novel microsatellite loci and cross-amplification of two loci in the snapping turtle (Chelydra serpentina)

We use 454 (“shotgun”) sequencing to obtain a partial genomic library for the snapping turtle (Chelydra serpentina). We characterize ten microsatellite loci from these sequences and test cross-amplification of loci originally developed for the alligator snapping turtle (Macrochelys temminckii). We genotype 127 individuals from Ontario at twelve loci. The number of alleles per locus ranges from 1 to 14; heterozygosity ranges from 0.157 to 0.850. These loci will be used to study population genetic structure in this long-lived reptile and may cross-amplify in two closely related species.

Hatchling Emergence From Naturally Incubated Alligator Snapping Turtle (Macrochelys temminckii) Nests in Northern Louisiana

Abstract We report emergence dates for 38 alligator snapping turtle (Macrochelys temminckii) hatchlings from 6 naturally incubated nests laid during the 2008 and 2009 nesting seasons in northeastern Louisiana. Per capita emergence success for 2008 and 2009 combined was 19.5%. Hatchling emergence occurred from 28 August to 25 September and was asynchronous for 80% of nests that had multiple hatchlings emerge, with emergence duration as long as 12 days. We found no evidence of delayed emergence; some hatchlings may remain in the nest for up to 3 weeks before successfully emerging.

Infestation of a Naturally Incubated Nest of the Alligator Snapping Turtle (Macrochelys temminckii) by the Phorid Fly Megaselia scalaris

Larvae of the phorid fly Megaselia scalaris were in eggs in a naturally incubated nest of an alligator snapping turtle (Macrochelys temminckii). It appears that these larvae contributed to failure of this nest. Infestation by phorid larvae has been reported previously for eggs and nests of multiple species of turtles, but has not been reported from M. temminckii.

Ingestion by a Freshwater Turtle Alters Germination of Bottomland Hardwood Seeds

Seed dispersal by animals is well documented in many habitats; however, this knowledge is depauperate in bottomland hardwood forests. The alligator snapping turtle (Macrochelys temminckii) is a large freshwater turtle of the southeastern United States that consumes primarily fish but also eats vegetation, including seeds of trees. To evaluate the role this species may play as a seed disperser in bottomland hardwood systems, we investigated the effect of ingestion by M. temminckii on germination of seeds of the following trees: common persimmon (Diospyros virginiana), water tupelo (Nyssa aquatica), and willow oak (Quercus phellos). Captive turtles were presented seeds of these three species in a series of feeding trials. Ingestion reduced the proportion of seeds that germinated compared to uneaten controls for D. virginiana and N. aquatica but had the opposite effect on Q. phellos. Ingested D. virginiana and N. aquatica seeds also germinated more slowly than uneaten controls; however, ingested Q. phellos seeds germinated faster than uneaten controls. This study suggests M. temminckii may have a role as a disperser of Q. phellos, N. aquatica, and D. virginiana; however, information on post-dispersal seed fate is needed to completely assess this species and other freshwater turtles as dispersers of wetland vegetation.

Thermal biology and temperature-based habitat selection in a large aquatic ectotherm, the alligator snapping turtle, Macroclemys temminckii

Ectotherms in water experience rates of heat transfer at least two orders of magnitude greater than in air, seriously constraining their thermoregulatory capabilities. Yet, even in water, individuals may exert control over body temperature ( T b ) via behaviors such as selecting thermally favorable microhabitats. The interactions among body size, physiology, and behavior on the thermal biology of large, entirely aquatic, ectotherms is poorly understood. We tested the hypothesis that alligator snapping turtles ( Macroclemmys temminckii) selected microhabitats based on temperature by comparing temperatures at sites used by turtles to temperatures at randomly selected sites. These large turtles selected a narrow range of microhabitats that were significantly warmer and less variable in temperature than random sites. Cooling trials in the laboratory indicated larger turtles equilibrated more slowly to ambient temperature ( T a ) than smaller turtles. We recorded T a and body temperature ( T b ) of turtles in the field continuously throughout the year. The T b generally conformed to T a but there were periods when T b − T a differences were great. These results suggest that while physiology and size of aquatic turtles can affect T b transiently, microhabitat selection may be the only meaningful mechanism for large, entirely aquatic, turtles to control T b .

Natural History of Resident and Translocated Alligator Snapping Turtles (Macrochelys temminckii) in Louisiana

Abstract Translocation is often considered a viable conservation strategy, despite the absence of species-specific post-translocation data. Macrochelys temminckii (Alligator Snapping Turtle) populations have declined across their range and they may be considered candidates for translocation, but few studies have examined the response of individuals to movement events. I monitored M. temminckii with radiotelemetry in northwest Louisiana to provide baseline data regarding the species' response to translocation. I calculated average distances moved per day, measured water depths, and recorded growth of translocated and resident turtles. There was no observed mortality during the study, and translocated turtles gained mass and increased shell dimensions, indicating they effectively located resources after translocation. Resident individual shell dimensions increased, but some residents lost mass, possibly due to early recapture and reweighing dates. Movement distances were within the ranges reported by previo...

Luring in the Neonate Alligator Snapping Turtle (Macroclemys temminckii): Description and Experimental Analysis

Observations were made on the feeding behavior of 8 newborn Macroclemys temminckii, a species known to lure fish prey with a vermiform appendage situated on the floor of the oral cavity. Each turtle was observed on 3 occasions, including its first feeding experience, over a 7-week period. 4 phases of predation on live fish are described: waiting, luring, attack, and prey-handling. Experiments involving 14 ingestively naive turtles from a second litter investigated the role of visual, chemical, and mechanical cues in eliciting the luring and attack responses.

Habitat Selection of the Alligator Snapping Turtle (Macrochelys temminckii) in Arkansas

Habitat selection in adult Alligator Snapping Turtles (Macrochelys temminckii) is known for only a few populations. Given that habitat availability can vary in different geographical locations, we used radiotelemetry to study habitat selection in a riverine habitat in central Arkansas by attaching radio transmitters to 14 female and four male Alligator Snapping Turtles. We tested the hypothesis that males and females select different habitats throughout the year because of differences in reproductive cycles and higher thermoregulatory requirements for females prior to nesting. Our results indicated that males and females selected similar habitats with similar thermal properties, but both sexes selected submerged structure. The tendency for Alligator Snapping Turtles to select sites with structure may be caused by higher prey densities (e.g., fish and crayfish) in these areas, protection from predators (e.g., American Alligators), or as an aid in surfacing to breathe rather than for thermoregulatory purposes.

Conservation genetics of the alligator snapping turtle: cytonuclear evidence of range-wide bottleneck effects and unusually pronounced geographic structure

A previous mtDNA study indicated that female-mediated gene flow was extremely rare among alligator snapping turtle populations in different drainages of the Gulf of Mexico. In this study, we used variation at seven microsatellite DNA loci to assess the possibility of male-mediated gene flow, we augmented the mtDNA survey with additional sampling of the large Mississippi River System, and we evaluated the hypothesis that the consistently low within-population mtDNA diversity reflects past population bottlenecks. The results show that dispersal between drainages of the Gulf of Mexico is rare (F STmsat = 0.43, ΦSTmtDNA = 0.98). Past range-wide bottlenecks are indicated by several genetic signals, including low diversity for microsatellites (1.1–3.9 alleles/locus; H e = 0.06–0.53) and mtDNA (h = 0.00 for most drainages; π = 0.000–0.001). Microsatellite data reinforce the conclusion from mtDNA that the Suwannee River population might eventually be recognized as a distinct taxonomic unit. It was the only population showing fixation or near fixation for otherwise rare microsatellite alleles. Six evolutionarily significant units are recommended on the basis of reciprocal mtDNA monophyly and high levels of microsatellite DNA divergence.

Temperature Effects During Early Life Stages of the Alligator Snapping Turtle (Macrochelys temminckii)

Alligator snapping turtle (Macrochelys temminckii) populations have declined across much of the southeastern United States in recent decades, due at least in part to overcollection. Recently, however, legal protection from large-scale harvesting has been granted to the species in all states where it is native, thereby drastically reducing one of the greatest threats to its survival. There is growing interest in captive propagation of alligator snapping turtles for reintroduction where populations have been decimated. In conjunction with one such effort, we analyzed the physiological effects of temperature on embryonic and posthatching development. Results indicate that extreme high and low incubation temperatures negatively affected embryo survival, and high incubation temperatures corresponded with shorter incubation time but also produced smaller hatchlings. The effects of temperature on gonadal differentiation indicated that the upper pivotal temperature was approximately 27.58C. Posthatching growth was faster at warmer water temperatures, and there was little to no acclimation of metabolic rate to exposure to either incubation or water temperature. We conclude that intermediate (27.58-28.58C) incubation temperatures produce a female-biased mixed sex ratio and maximize hatching success and hatchling size while increasing incubation duration only slightly over that at the higher temperatures. In addition, posthatching growth was positively influenced by hatchling body temperature; therefore, warmer water temperatures (;308C) decreased the time required to rear turtles to a size suitable for reintroduction.

A New Haemogregarina Species of the Alligator Snapping Turtle, Macrochelys temminckii (Testudines: Chelydridae), in Georgia and Florida that Produces Macromeronts in Circulating Erythrocytes

Haemogregarina macrochelysi n. sp. (Apicomplexa: Haemogregarinidae) of the alligator snapping turtle, Macrochelys temminckii, is characterized by slender, recurved gamonts 29-35 x 3-4.5 microm, in which the anterior limb comprises 48-54% of the total length. The gamont nucleus, 5-7.5 x 2-5 microm, is situated at approximately midbody of the gamont. Meronts typical of Haemogregarina occupying erythrocytes have 3-8 small, compact nuclei and are 13-17 x 4.5-9 microm. Erythrocytic meronts that contain larger, nearly square or rectangular nuclei become rounded, and then undergo 7 or more nuclear divisions, which produce very large, usually ovoid to rounded meronts that may contain up to 150 nuclei or more within the thinly stretched host erythrocyte membrane. In tissues of the Placobdella spp. leech vectors, merogony occurs directly from sporozoites, forming merozoites that presumably are infective for the turtle host.

Cross-reactivity of a Polyclonal Antibody Against Chinemys reevesii Vitellogenin with the Vitellogenins of Other Turtle Species: Chelydra serpentina, Macrochelys temminckii, and Pelodiscus sinensis

Vitellogenin (VTG), a yolk-precursor protein in oviparous vertebrates, is a useful biomarker for reproductive physiology and environmental estrogenic pollution. To examine interspecific applicability of an enzyme-linked immunosorbent assay (ELISA) for quantifying Chinemys reevesii VTG, we observed cross-reactivity between a polyclonal antibody against Chinemys reevesii VTG and the VTGs from other turtle species: Chelydra serpentina (Chelydridae), Macrochelys temminckii (Chelydridae), and Pelodiscus sinensis (Trionychidae), which are phylogenetically distant from Chinemys reevesii (Geoemydidae). The VTGs of the three species were induced by injecting estradiol 17beta into the turtles and purified by using the EDTA-MgCl(2) precipitation method. The purified VTG appeared as a 200-kDa protein in sodium dodecylsulfate polyacrylamide gel electrophoresis, indicating that the molecular mass of the VTGs of the three species was similar to that of Chinemys reevesii VTG. The purified VTGs were serially diluted (0.004-2 mug/ml) and applied to the ELISA. Although the VTGs of the two chelydrid turtles showed cross-reactivity in a concentration-dependent manner, the degree of cross-reactivity was only 22.8-41.2% (mean=30.0%) and 19.7-53.0% (mean=33.2%) for Chelydra serpentina VTG and Macrochelys temminckii VTG, respectively. The ELISA may therefore be theoretically applicable to measure relative levels of the VTGs of these two species, but the absolute concentration values may be inaccurate. Pelodiscus sinensis VTG showed almost no cross-reactivity (8.0-9.7%, mean=8.9%) at any concentration tested, thus indicating the inapplicability of the ELISA to quantify Pelodiscus sinensis VTG. There are thus limitations in extending the applicability of the ELISA across species, even within the order Testudines.

Population Structure of the Alligator Snapping Turtle, Macrochelys temminckii, on the Western Edge of its Distribution

A mark-recapture project on Macrochelys temminckii was conducted between 1997 and 2000 at Sequoyah National Wildlife Refuge, Muskogee and Sequoyah counties, in eastern Oklahoma. Turtles were captured in all streams and exhibited equal sex ratios, marked sexual-size dimorphism, and population densities between 28 and 34 animals per km stretch of stream. There was evidence of past population perturbations, with very few large adults captured, and a cohort of subadults highly underrepresented.