Many marine organisms are highly mobile, which presents a variety of research and conservation management challenges. Sea turtles are a particularly paradigmatic group of long distant migrants whose movements as adults have been detailed by satellite tracking technology. However, small hatchlings are not amenable to this approach. This thesis used Lagrangian oceanography approaches to study the cryptic lives of juvenile turtles, since ocean currents drive their dispersion from natal beaches. Through increasingly sophisticated and novel uses of Lagrangian surface drifter buoys, state-of- the-art global ocean models and emerging animal life history datasets, my PhD thesis details significant findings of the key life history attributes of these enigmatic migrants. Initially, 1 modelled the dispersal of hatchlings from their nesting beaches to derive the first robust estimates of hatchling growth rates and by so doing, highlighted the long maturation times of turtle species. Then, I programmed hatchling swimming behaviour into ocean model simulations to reveal how these small drifters could improve their survival chances in strong current flows. More interdisciplinary research also highlighted aberrant routes of dispersal that can arise through storm displacements. Subsequent meta-analysis on the movements of flying, swimming and walking migrants highlighted key biological determinants of sea turtle migrations. Spatio-temporal analysis of sea turtle marine protected area (MPA) use highlighted minor (tractable) legislative revisions that would significantly improve MPA effectiveness. Finally, research culminated in a global synthesis of the movement patterns of adult and hatchling sea turtles which provided global support for a new migration paradigm, that whilst adult turtles travel independently of ocean currents, ocean currents still indirectly drive the ontogeny of adult sea turtle migrations and foraging habitat selections due to their past experiences as drifting hatchlings. This new understanding into the biological and physical determinants of sea turtle migration strategies is thus hoped to have broad conservation utility.

Recent studies show that sea turtles use both magnetic and visual cues to successfully orient. Juvenile green sea turtles from the near shore reefs of Palm Beach County, Florida were brought to the lab to determine whether the sun could serve as a visual orientation cue. When tethered during the day in a large outdoor tank west of the ocean, the turtles oriented east to northeast. To determine whether the sun's position was used to maintain their heading, I altered the turtles' perception of time by entraining them to a light cycle advanced by 7 h relative to the natural cycle. When tested afterward in the same outdoor tank the turtles oriented northwest, the predicted direction after compensating for the sun's movement over 7 h across the sky. Orientation was unchanged when the turtles bore magnets that negated the use of magnetic cues. These results are consistent with the hypothesis that the turtles used the sun for orientation. / by Cody Robert Mott. / Thesis (M.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Loggerhead sea turtles nest on either the Atlantic or Gulf coast of Florida. The hatchlings from these nests migrate offshore in opposite directions. The purpose of my study was to determine if Gulf coast hatchlings use magnetic maps, as Atlantic coast hatchlings do, both to locate areas favorable for survival in the Gulf of Mexico and to orient appropriately within surface currents that could transport them into the Atlantic Ocean. To find out, I presented Gulf coast hatchlings with magnetic fields corresponding to different locations inside the Gulf, and within currents leading into (Florida Straits) and within (Gulf Stream) the western portion of the Atlantic Ocean. I conclude that Gulf coast hatchlings (i) use a high resolution magnetic map for navigation within the Gulf of Mexico, (ii) initially remain within the eastern Gulf, but later may (iii) gain entry into currents that transport them into Atlantic waters. / by Maria W. Merrill. / Thesis (M.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

During the summers of 1988 and 1989, nests of 528 loggerhead sea turtles (Caretta caretta), 27 green sea turtles (Chelonia mydas), and 1 leatherback sea turtle (Dermochelys coriacea) were monitored on Wabasso Beach in Indian River County, Florida. Two hundred and forty four of the loggerhead and 2 of the green sea turtle nests were marked during night surveys as the females laid their clutches, permitting exact clutch counts and carapace measurements on the nesting females. Each marked nest was inspected daily for signs of disturbance and hatching. After incubation (70 days), study nests were excavated and inventoried to determine hatchling emergence success. Parametric multiple regressions, nonparametric multiple regressions, and logistic regressions were used to determine the effects of several measured variables on clutch sizes and incubation times; and nesting, hatchling emergence success, and predation. Excluding the last 2 weeks of the nesting season, nesting was positively correlated with ocean temperatures (P< 0.05), but not with human beach-side development (P> 0.05). Nesting loggerheads on the study area had an average carapace length of 89.8 cm (S.E.=0.31), and a mean clutch size of 112 eggs (S.E.=1.07). Clutches required an average of 53.9 days (S.E.=0.21) to incubate during 1988, with a hatchling emergence success of 57%. During 1989, the mean incubation time and hatchling emergence success was 51.5 days (S.E.=0.21) and 44%, respectively. Over the 2 study years, the average green turtle nest had 118 eggs, took 54.6 days to incubate, and had a hatchling emergence success of 40%. During 1988, 4.6% of the loggerhead nests were lost to beach erosion or alteration (deposition of sand on nests by the surf). This loss was 22% during 1989 for loggerheads, and 30% over both years for green turtles. The difference in loggerhead losses over the 2 years was due to 2 late-season hurricanes which affected the area during 1989. Predation on loggerhead nests was 16% and 8% during 1988 and 1989, respectively. In both years, predation was positively correlated with human beach-side development (P<0.05); during 1989, predation also was positively correlated with distance of the nest from the beach dune (P< 0.05). Clutch size and carapace size of nesting females were positively correlated (P< 0.05). Incubation time was negatively correlated with egg laying date, and hatchling emergence success was strongly affected by the late summer storms of 1989. The study area produced an estimated 70,469 loggerhead sea turtle hatchlings per year (8,808 hatchlings/km), and 535 green sea turtle hatchlings per year (66 hatchlings/km). The number of loggerhead sea turtle hatchlings produced per nest was adversely affected by beach-side development. / Master of Science

There are four distinct subpopulations of loggerhead sea turtles (Caretta caretta) in Florida as determined behaviorally by geographic fidelity, and genetically by mitochondrial haplotypes. The South Florida subpopulation consists of females nesting on the southeastern and southwestern coasts of Florida and their offspring. Previous research shows that west coast hatchlings exhibit higher levels of nocturnal swimming during the postfrenzy period than east coast hatchlings. This study attempted to determine how these differences in migratory behavior develop. A reciprocal translocation experiment was conducted to distinguish between environmental and genetic factors. No consistent differences in hatchling swimming behavior were seen based on geography. Movement of nests resulted in lower levels of nocturnal swimming behavior in hatchlings compared to hatchlings that emerged from natural nests, suggesting that the relocation of nests may not provide a natural incubation environment for developing hatchlings. / by Jeffrey Guertin. / Thesis (M.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.