Many of the early taxonomic studies of fossil sea turtles relied heavily on postcranial evidence. Both the Cheloniidae and Dermochelyidae were erected on detail of the shell and limbs. ‘Desmatochelys’ was originally described in part using cranial evidence, but later workers (Zangerl and Sloan, 1960) suppressed the family on evidence from the shell. Little in the way of comparative work has been undertaken using the cranial morphology of fossil or living forms. This is thought long overdue. The first bone by bone description of the living cheloniids has revealed a large number of taxonomically useful characters and a close relationship between the genera. However, a great deal of interspecific variation was noted. ‘Chelonia mydas’ is considered to format least three subspecies on cranial evidence. The newly described ‘Natator (Chelonia) depressa’ is thought distinct from other living forms. The Dermochelyidae are seen to be a very conservative group and a large number of cranial characters link fossil and living forms. The arterial circulation of Dermochelys is redescribed and the importance of the blood flow to the head for use by the salt secreting glands in electrolyte balance is shown to be important. The Desmatochelyidae is shown to be a family in its own right, and a number of other genera, notably ‘Rhinochelys’ and ‘Notochelone’, are thought members of the group. Many of the basicranial features identified by Gaffney in the 70s for other fossil groups have been shown to be of use in the taxonomic study of the families under review.

Sea turtles are large migratory animal stay in the water most of their life time. In the east coast of Taiwan, there is a strong northward Kuroshio current. It is hypothesis that ocean current might play an important role to the migration tracks of sea turtles in the region. To test the hypothesis, two turtle tracks based on Argos records were analyzed. The first turtle moved from Lanyu in the NE direction to Ishigaki Island. The second one moved southward from Dong-Auo, along the east coast of Taiwan, to the southern tip of Taiwan, and then detoured westward across the Taiwan Strait, swum southward along coastal China to Leizhou Peninsula finally. In this study, we analyze data of EASNFS model, drifter tracks, weather buoy records and MODIS sea surface temperature, to explore the relationship between the ocean currents and the migration tracks of sea turtles. The Lanyu turtle seems follow very well with Kuroshio current in the early stage of its migration. The migration matches well with many Argos drifter tracks, and Lagragian drifter of EASNFS model. The probability of this turtle arriving Ishigaki Island is 26% if without other help. There is a turning point, as indicated by the comparison of model and real track. The Lanyu turtle swam hard to correct the migration route in order to reach the final destination. The Dong-Auo turtle track is analyzed together with data of winds, waves and drifters. This turtle migrated southward along the east coast of Taiwan seemly agree with the northeast monsoon wind driven coastal current. The migration route turned west at the southern tip of Taiwan. The turn matches well with the currents indicate by Argos drifters, as well as EASNFS modeling. In additional to the guidance of currents, this migration route also followed the sea surface temperature of 21¢J. In conclusion, this study suggests that turtles migration, in additional to the efforts of swimming and temperature guidance, will take advantage of prevailing currents to reach their final destinations.

An estimated 250,000 loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles are taken each year as incidental catch by the pelagic long-line fishing industry. Various gear and bait modifications as well as time/area closures to fishing, enacted to reduce anthropogenic impacts on sea turtles, have been ineffective or incompatible with regional fishery interests. Chemosensory and auditory deterrents have yielded little benefit thus far in repelling sea turtles from long-lines. The fact that sea turtles are highly visual animals has precipitated studies of the efficacy of using shark shapes to repulse them from long-lines. Previous shark-shape studies yielded promising results, but their design lacked statistical rigor. The present study examined the response of 42 captive-reared loggerhead sea turtles (Caretta caretta) to a shark-shape model at the NOAA Sea Turtle Facility in Galveston, TX. To measure repulsive effect, time taken to consume squid bait beneath the shark model was compared to that for controls in which loggerheads were offered squid beneath a spherical object or a bare squid (i.e., no object control) in a captive setting. Additional responses compared among these three treatments were time spent near treatment, number of breaths taken, approaches to the treatment, and avoidance behaviors displayed (e.g., turning carapace toward treatment). Loggerheads exhibited anti-predator behavior toward the shark model, taking significantly more time to consume squid bait beneath the shark model than for the other two treatments. Turtles also spent significantly more time opposite the tank from the shark model, approached it less often, and exhibited more carapace turns to the model. Some avoidance of the spherical control object also was observed, but was not as pronounced as that displayed toward the shark model. While a repulsive effect of the shark model was resolved during the aforementioned trials, application of such models to reducing long-line fishery bycatch would require further research to identify a plausible application; numerous shapes attached to long-line hooks would be very cumbersome. However, it may be plausible to develop a “boy’s day kite” shark model that would unfurl and “fly” underwater, and could possibly be clipped to buoy float lines.

Loggerhead sea turtles (Caretta caretta) are listed as threatened under the Endangered Species Act and are protected both on nesting beaches and in United States waters. Loggerhead sea turtles are long-lived species and are most easily studied on the beaches during the nesting season. Bald Head Island, North Carolina has one of the highest density nesting beaches of loggerhead sea turtles in the turtle's northern range on the East Coast of the United States. Key life history parameters were estimated and applied to a population model using 16 years of data from a mark-recapture study on the loggerhead sea turtle nesting population on Bald Head Island, North Carolina. The beach survey conducted on the island only allowed for the capture of adult female sea turtles during the breeding state even though females may spend multiple years in the unobservable non-breeding state. The majority of females captured over the last 16 years have never been recaptured at the original capture site. These transients in the data coupled with unobservable states violate the assumption of equal catchability in the available single state mark-recapture models. Therefore, a multistate mark- recapture model originally developed for leatherback sea turtles was applied to the Bald Head Island loggerhead population. Multistate modeling provides a new technique to estimate sea turtle demographic parameters in which all model assumptions can be met. The multistate model outputs female survival rates, capture probability, and transition probabilities between breeding and non-breeding states. A correction factor for trap-dependence and transients was included given that both factors tested significant in the global model goodness-of-fit tests. The estimates of annual adult survival rate and breeding transitions were then used to project population size for the northern subpopulation. For the first time, estimation error around estimates of benthic juvenile and adult survival rates was included in a loggerhead sea turtle model. I explored the effects of estimation error, three levels of clutch frequency, and larger TED openings on population growth rate and on the probability of reaching a nesting recovery threshold. The nesting recovery threshold was based upon recovery criteria from the Federal Recovery Plan and set as the probability of reaching 12,800 nests/season in the states of North Carolina, South Carolina, and Georgia within a 50 year time period. The results of this study provide important information to guide future management and research. / Master of Science

A twenty year mark-recapture dataset from the loggerhead nesting beach on Keewaydin Island, off the southwest coast of Florida, was analyzed using a two-state open robust design model in Program MARK to provide insight into recent nesting declines in the state. A total of 2,292 encounters representing 841 individual tag IDs were used for this analysis. Survival was estimated at 0.73 (95% CI 0.69-0.76), and there was no evidence from remigration rate or clutch frequency to suggest the composition of the nesting assemblage had changed over time. The mark-recapture analysis was supplemented with a satellite tracking component to identify the offshore foraging areas utilized by Keewaydin nesters. Eleven nesting females were outfitted with platform terminal transmitters, which transmitted for 42 to 300+ days including inter-nesting intervals and subsequent migration to foraging grounds. Site fidelity tests and kernel density home range analyses were used to describe foraging habitats. Females foraging in the eastern Gulf of Mexico were within the recent 64 m bottom longline fishery restriction. Areas identified as important habitats during the remigration interval should be used to inform managers in creating targeted management strategies to aid population recovery without the use of broad fishery closures.

The global population of leatherback sea turtles is decreasing worldwide, with extinction predicted for some populations within 15 years. The population of leatherbacks nesting at Sandy Point National Wildlife Refuge (SPNWR), St. Croix, USVI, displayed a significant population increase from 1982 2001 but has experienced a slowed recovery since then. To better understand the causes of this decline, a historical database of SPNWR nesting female data was utilized to investigate trends in reproductive indices. Since 2001, average remigration interval (RI) has increased significantly, while average number of clutches laid, hatch success, hatchling production, and the percentage of neophytes recruited annually have decreased. Annual remigrant numbers have been stable to increasing, suggesting that adult survivorship remains high. To assess whether maternallyderived factors may be influencing clutch production and low hatch success, blood samples were collected by saturation sampling during nesting. Circulating estradiol, testosterone, and progesterone were evaluated in conjunction with reproductive data. All hormones were highest at deposition of the first clutch and declined progressively with each consecutive clutch, as previously observed in other sea turtle species. Increased clutch production in remigrants was associated with higher estradiol levels compared to neophytes, presumably due to ovarian size and maturity. Contrary to observations in Pacific leatherbacks, progesterone decreased significantly with successive nests and total levels of estrogen were significantly lower, suggesting Atlantic leatherbacks may undergo a longer migration or spend more time in the feeding grounds prior to migrating. Linear Mixed Effect (LME) modeling was employed to determine whether hormone levels at nesting might serve as indicators of reproductive variables. Because models for all hormones were individual specific, a population model could not be developed that effectively utilized hormone levels at nesting to predict clutch size, hatch success, age or RI. However, number of clutches laid may potentially be predicted based on individually tailored estrogen models. Decreased recruitment (due to increased mortality of early life stages, altered sex ratios, or delayed age to sexual maturity), decreased productivity, and increased RI (possibly due to diminished foraging ground productivity) appear primarily responsible for current population trends which threaten the population's future.

The aims of this work are:1. To provide the normal cervical and coelomic radiographic appearance of the Loggerhead sea turtle, in the dorso-ventral view, as well as other useful landmarks, to allow for correlation of shell scutes with internal anatomic structures. 2. To provide the normal radiographic anatomy of the limbs of the Loggerhead sea turtle in combination with data obtained from computed tomography - osteological, gross anatomical and histological data.3. To describe the normal ultrasonographic appearance of cervical structures and coelomic organs of the Loggerhead sea turtle, and to provide the respective images of frozen cross-sections for anatomical reference.4. To provide normal computed tomographic images of the vertebral column and coelomic structures of the Loggerhead sea turtle, by establishing reference standards for organ size and position in this species; to provide images of virtual tracheo-bronchoscopy and 3D reconstructions of the respiratory tract and bone structures.5. To provide the normal magnetic resonance imaging (MRI) appearance of coelomic structures of Loggerhead sea turtles in T1 and T2-weighted scans via comparison with cross-sectional anatomic sections of this species.

In oviparous animals, maternal traits such as the investment of resources in eggs and oviposition site selection are often important determinants of offspring phenotypic quality, and may have an adaptive role in tailoring offspring phenotypes to local environmental conditions. This thesis examines the adaptive significance of two specific maternal traits in the green turtle (Chelonia mydas); namely the deposition of fat-soluble antioxidants in egg yolk, and the selection of nest sites via natal homing. (Please view 'front matter' file for full abstract)

Traditional views of food web dynamics have characterized species interactions as linear and direct. However, modern food web theory suggests that interactions can also be nonlinear and indirect, so that disturbance at one trophic level is transmitted throughout the community. Many previous studies have demonstrated that the removal of top predators from terrestrial ecosystems can have broad-scale impacts on community ecology. I examined the direct and indirect effects of raccoon removal from sea turtle nesting beaches in east-central Florida during the summers of 2003 and 2004. Raccoon and ghost crab predation are among the highest causes of egg mortality for sea turtles in Florida and raccoons are intraguild predators of ghost crabs. Because of the damage done to sea turtle nests, raccoons have been removed from some beaches during the sea turtle nesting season. I compared the diet and demography of a raccoon population that had experienced two decades of raccoon removal to a population that had previously been unmanipulated. I found that long-term raccoon removal had created a significantly male-biased sex ratio in that population. I also examined the indirect effects of raccoon removal by comparing the abundances of raccoons and ghost crabs at four study sites using passive tracking plots. My data suggest intraguild predation by raccoons limits ghost crab abundance and that reduced raccoon abundance allowed ghost crab abundance to increase, resulting in a net increase in sea turtle egg predation. These results support my hypothesis that intraguild predation of ghost crabs by raccoons is an influential interaction on sea turtle nesting beach community dynamics.

Ectotherms (including marine turtles) being especially sensitive to climate, are at risk to the accelerated rate of human-driven climate change. This study addresses two concerns associated with marine turtles and climate change – the relationship between the timing of marine turtle nesting and sea surface temperature; and the concern over the feminization of marine turtle populations due to rising sand temperatures. Previous studies of loggerhead sea turtles (Caretta caretta) and green sea turtles (Chelonia mydas) have documented the relationship between sea surface temperatures and nesting phenology. Earlier nesting behaviors in both species have been associated with warmer sea surface temperatures. Also, sex determination for marine turtles is temperature-dependent. Due to current sand temperatures, it is estimated that loggerhead (Caretta caretta) nests along the Atlantic coast of Florida already produce over 89% female hatchlings. Using shade to reduce nest temperature and increase the proportion of male hatchlings is one option for mitigating the impacts of climate change on marine turtle sex ratios. In this study, a 21- year (1988-2008) dataset of hawksbill sea turtle (Eretmochelys imbricata) nesting at Buck Island Reef National Monument, St. Croix, U. S. Virgin Islands was analyzed in a similar manner to previous studies. It was found that warmer sea surface temperatures were associated with longer nesting seasons and later median nesting dates. Additionally, a preliminary sand shading study was conducted in the first field season (2011) with a subsequent loggerhead nest shading study in the following field season (2012). Although hatching success was not significantly impacted, temperatures were significantly reduced in the majority of shaded nests. This practice may not be immediately applicable as a means of managing sex ratios, but it could be used to reverse the temperature effects of nest relocation