Animals use their senses for everything on an immediate, and day to day fashion – detecting danger, finding food, finding mates among other activities. In sea turtles and other migratory species senses are used for long-distance migrations. Senses such as smell, vision and hearing, have been studied experimentally under laboratory conditions but seldom have been investigated in the field. This thesis takes a combination of field and laboratory experiments and investigates some of the hypotheses involved in natal homing and nest site selection. The loggerhead’s nesting distribution in Maputaland is distinct with characteristic high and low density nesting areas which are consistent from year to year. Investigations by earlier researchers on these beaches suggested that beach characteristics, such as beach morphodynamic type and beach width, do not appear to influence the beaches at which loggerheads emerge to nest. The high density nesting area (with approximately 440 loggerhead emergences/km) have similar beach characteristics as the low density nesting area (with <50 loggerhead emergences/km). It is therefore suggested that there is another cue that drives nest site selection. It can either be related to a physical characteristic not yet realised, or is a non-physical (but chemical or biological) cue. This dissertation aims to identify the sensory inputs received during the nest selection process, as well as sea-finding ability after nesting. To investigate the mechanism causing the high-density as opposed to the low-density nesting area, three potential drivers were investigated namely: chemical imprinting (as a natal beach cue), ambient and artificial light (as deterrents) and social facilitation (as a learned behaviour). It was also attempted to identify the strength of the most common senses – vision, hearing and smell. As animal ethics restricts interfering with emerging or nesting turtles, the strengths of these senses were tested during sea-finding by adult loggerheads. The results indicate that sulfide concentrations appear to be used as chemical cues for nesting as these concentrations are elevated (>150 percent) in the high density nesting beaches compared to the low density nesting beaches within and among seasons however further investigations are required. Artificial light (range: 0.045–0.5 lux) is an active deterrent of female emergences while ambient light, even under extreme conditions such as lightning during electric storms (up to 8.2 lux), appears to have no observable influence on the spatial or temporal distributions of emergences. Social facilitation appears unlikely as a primary nest site selection factor for loggerheads. It may however, play a minor secondary role to preferred areas or hotspots. Sea-finding in post-nesting female loggerheads appears to be driven exclusively by visual cues such as the light horizon, with minimal to no influence from other cues (the sound of the breakers, slope or smell of the ocean) which solidify the visual system’s use in sea-finding. This research on the nest site selection of loggerheads and the sensory systems involved in this process has added valuable information to the limited pool of knowledge already present and has created a solid framework on which further investigations can be based. Future work in this field should focus on integrating a suite of sensory stimuli and cues to receive a greater understanding of the sensory systems used in nest site selection.

Catalytic and regulatory properties of phosphofructokinase (PFK) (EC 2.7.1.11), pyruvate kinase (PK) (EC 2.7.1.40), and creatine kinase (CK) (EC 2.7.3.2) from the heart of the red-eared turtle (Pseudemys scripta elegans) were studied. Particular attention was given to those properties of the enzymes which could help to explain the high glycolytic efficiency in this tissue and so provide insights into the selective forces involved in the evolutionary development of an extreme tolerance to anoxia. The control of glycolytic flux in turtle ventrical muscle has been vested primarily in phosphofructokinase and pyruvate kinase. Creatine phosphate and fructose diphosphate play pivotal roles in the channelling of carbon through the pathway and in the production of metabolic energy as ATP. The levels of these key metabolites are in turn tightly regulated. One of the enzymes studied (phosphofructokinase) controls the levels of fructose diphosphate produced and creatine kinase (itself modulated by the cell's redox balance) controls creatine phosphate levels. When oxygen levels are reduced, NADH accumulates because of a decrease in electron transport chain regeneration of NAD (129). This leads to an effective activation of creatine kinase by lowering the Kм for creatine phosphate. This activation causes a drop in creatine phosphate levels without the decline in ATP levels that are seen at the onset of hypoxia in other tissues ( 4 ). Since the high levels of creatine phosphate present in aerobic heart are responsible for the inhibition of phosphofructokinase by greatly increasing the for its substrate, fructose-6-phosphate, this drop in concentration deinhibits the enzyme and leads to a flush of its product, fructose diphosphate. The increase in fructose diphosphate (1) serves to activate phosphorructokinase by itself, and (2) further reduces the effect of creatine phosphate by a deinhibition of the enzyme. These two effects cause an autocatalytic increase in flux through this locus* Fructose diphosphate also feed-forward activates pyruvate kinase by decreasing the Km for its substrate, phosphoenolpyruvate, and serves to deinhibit this enzyme which is normally inactive due to alanine and ATP inhibition. The most important feature of such a regulatory system is that it is a kind of autocatalytic cascade. Once the activation of creatine kinase is initiated by the redox imbalance inherent in anaerobiosis, all the various regulatory interactions potentiate one another. Drops in inhibitor levels lead to increases in activator levels and these activators serve to further deinhibit. These interacting effects serve to potentiate anoxic production of energy to compensate for the temporary depletion of oxygen in diving stress and in long periods of hibernation in this turtle, Nature's premier vertebrate anaerobe. / Science, Faculty of / Zoology, Department of / Graduate

Human activities, such as urban expansion, have led to an increase in contacts between humans and wildlife and have resulted in the loss and isolation of suitable habitats for animal populations. These human-induced pressures threaten the persistence of animal populations and understanding how animals respond to them is crucial for conservation. A multidisciplinary approach that includes different biological components of a species, such as behaviour, physiology, and population genetic structure, is necessary to obtain a comprehensive insight into the impact of human activities on wildlife. Turtle populations are particularly vulnerable to human disturbance due to their life-histories, but there is limited information available on how human-induced perturbations affect different components of their biology. In this context, my thesis aims to evaluate the impact of human disturbance and human-made barriers on the behaviour, physiology, and genetic structure of painted turtles (Chrysemys picta) in the Rideau Canal, Ontario, Canada. In chapter one, I evaluate the relationship between risk-taking behaviours and human disturbance levels. In chapter two, I assess the impact of human disturbance on the relationships between risk-taking behaviours, physiological response, and colouration. Finally, in chapter three I characterize the genetic structure of painted turtles in the Rideau Canal and assess the impact of human-made barriers, such as locks, on the genetic substructuring occurring in the system. Overall, I show that human activities and human-made barriers have several impacts on painted turtle biology, from influencing their risk-taking behaviours to inducing physiological changes and causing genetic discontinuities among groups. More specifically, in chapter one, I show that painted turtles are consistent in their risk-taking behaviour and that turtles located in areas with more boat activities are more prone to take risks, suggesting that being risk-prone may be associated with a greater tolerance to human disturbance. I also show that painted turtles exhibit a lower physiological response when human activity is limited, indicating that human activities may induce physiological costs on wildlife. In addition, I report variations in physiological responsiveness according to the propensity of turtles to take risks, where risk-prone males have higher physiological responses than risk-averse males, highlighting the importance to use different disciplines to better understand the consequences of human activities and how the different biological components interact together under human-induced pressures. Finally, I found genetic substructuring among groups of turtles within the Rideau Canal, which seems to be partly caused by locks, especially when they are numerous and clustered in space. My results provide a better understanding of the impact of human disturbance on animal populations as well as information that could be used to better guide management decisions that are relevant to species vulnerable to human activities, such as turtles. Monitoring animal behaviour alongside physiological biomarkers and genetic populational trends can aid in the development of better adapted conservation strategies.

No description available.

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Thesis (M.S.)--Ohio University, August, 2008. / Title from PDF t.p. Includes bibliographical references.

Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (January 13, 2010) Includes bibliographical references (p. 89-97)

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 86-91). Also available via the Internet.

Resource subsidies are flows of nutrients from one ecosystem to another. Sandy beach ecosystems are at the interface between land and sea and thus receive nutrients from both land/seascapes. The seasonal nesting of sea turtles introduces large inputs of eggs, and so nutrients, onto sandy beach ecosystems, but little is known about the effects of these spatially and temporally variable nutrient input pulses on the dynamics of consumers in the recipient system. In this study, I examined the ecological role of sea turtles as vectors of nutrients that introduce large amounts of nutrients (in the form of eggs) from distant foraging grounds into nutrient-poor beach ecosystems. Although some of the nutrients return to the sea in the form of hatchlings, nutrients from unhatched and depredated eggs, dead and predated hatchlings, as well as chorioallantoic fluid and egg shells remain on the beach and presumably enter sandy beach food webs. I hypothesized that turtle nutrients significantly increase the availability of nutrients to sandy beach ecosystems and that those nutrients are incorporated by both terrestrial and marine food webs. These hypotheses were tested by comparing isotopic signatures of 13C and 15N of consumers on beaches with high and low turtle nest densities. The response of meiofauna to the decomposition of turtle eggs was also investigated. I predicted that meiofaunal abundance is positively affected by turtle nutrients and that higher meiofaunal abundances will be obtained in decomposing, depredated nests. I tested this hypothesis by comparing meiofaunal abundance in naturally predated nests to densities away from turtle nests (as a control). An in situ experiment that mimics conditions of naturally predated sea turtle nest, was set up to test meiofaunal community responses to turtle nutrients over time. The study indicates that sea turtle eggs represent a short pulsed resource subsidy that increases the nutrient and energy budget of sandy beach ecosystems. The results show that of the five potential nutrient pathways tested, ghost crabs appear to consume egg nutrients in measurable quantities, altering their diet and feeding behaviour according to food availability. The study also showed that there was a strong, but short-lived positive response of meiofauna to the introduction of nutrients, with increased abundance of all taxa in predated nests and experimental treatments. This response was particularly strong for nematodes which peaked in abundance after seven days. I conclude that turtle-derived nutrients represent a pulsed resource subsidy that makes significant contribution to the energy budget of sandy beach/dune ecosystems.