Thesis (M.S.)--University of Florida, 1999. / Includes bibliographical references (p. 68-72).

In tropical wetlands, breeding wading birds rely on concentrations of aquatic fauna during the dry season to meet increased energetic demands. Wetland microtopography increases aquatic fauna concentration levels. Crocodilians modify the landscape creating deep-water refugia but their role as a mechanism for aquatic fauna concentration is unknown. I sampled alligator (Alligator mississippiensis) abundance and slough microtopography to examine correlation between the two measures. Despite increased microtopography in high alligator use sloughs, the differences were not significant. Using an in situ experimental approach, I quantified the magnitude, timing, and spatial extent of aquatic fauna concentrations within simulated alligator depressions and the surrounding marsh. Aquatic fauna density and biomass were greater within simulated depressions, thus enhancing wading bird foraging habitat. Further understanding the mechanisms creating microtopography, thus enhancing wading bird habitat, is critical to facilitate restoration and prevent declines of wading bird populations in seasonally pulsed wetlands worldwide. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

The objective of this study was to determine the dietary protein requirements of the Nile crocodile (Crocodylus niloticus) between the ages of 5 – 8 months, and to compare the results with documented protein requirements of the American alligator (Alligator mississippiensis). This was achieved by feeding the crocodiles 4 diets with varying amounts of crude protein (CP), including 62%, 56.6%, 51.6% and 46%. All four diets were iso-energetic with a metabolisable energy to protein ratio of 25.85KJ/g. The highest protein diet contained 44% raw minced chicken and 46.9% fish meal with minimal contribution (of 6.4%) made from vegetable protein sources (full fat soya). The lowest protein diet was made up of a majority of vegetable protein (30% soya bean oilcake, 9.8% full fat soya and 17.2% maize meal) and some contribution from protein of animal origin (4.3% carcass meal and 35% fish meal). This study was carried out for 12 weeks during the crocodiles first year of life. Body mass, total body length, head length and snout to vent length were measured five times at 3 weekly intervals. Twenty representative crocodiles in a pen of 200 were individually tagged for the duration of the trial. As there were 3 replicates for each of the 4 treatment diets, 240 crocodiles in 12 pens were tagged. During the early phase of the study, it was observed that crocodiles on the 46% CP treatment diet were not performing well, and that most of the crocodiles on this diet were losing mass. This treatment diet was discontinued at 9 weeks into the trial for both financial and ethical reasons. The remaining three diets were tested for the full 12 weeks. Chromium oxide was mixed into the diets at two time periods during the trial to determine the protein, energy and dry matter digestibility. It was determined that the 46%, the 51.6%, the 56.6% and the 62% CP diets had a digestible protein (DP) content of 246.44 g/kg, 294.80 g/kg, 381.32 g/kg and 468.65 g/kg and a digestibility coefficient of 53.50%, 57.00%, 69.15% and 75.65% respectively. Performance of crocodiles on the 46% CP treatment diet was found to be lower in all measurement categories than crocodiles on the three higher protein diets. However, crocodiles on the 62% CP treatment diet outperformed all the crocodiles (on all measurement criteria) on the lower protein diets. The poor performance of crocodiles on the lowest protein diet correlates with previous research indicating that crocodilians are unable to perform optimally when the majority of the diet’s protein is made up of vegetable protein sources. It was determined that juvenile American alligators would grow at optimal levels when the diet contained a DP content of 450 g/kg. As the Nile crocodiles in this study performed the best when the diet contained a DP value of 468.65 g/kg, it was concluded that juvenile Nile crocodiles have the same range of protein requirements as that determined for juvenile American alligators. / Dissertation (MSc(Agric))--University of Pretoria, 2011. / Animal and Wildlife Sciences / unrestricted

Par Pond is a man-made 1120 ha cooling reservoir located on the Savannah River Site near Aiken, South Carolina. From 1972-1978 a detailed study on the status of the alligator in Par Pond was conducted by Tom Murphy (unpub. MS thesis Univ. of GA, 1977). Murphy estimated that approximately 110 alligators inhabited Par Pond with an adult (> 1.8 m) to juvenile (< 1.8 m) ratio of (1.8:1), an overall sex ratio of 3.2:1, and an average of only 2.3 nests/yr. The purpose of this study (1986-1989) was to determine the current population size and structure, determine how the population has changed in the last 15 years and to examine growth and survival of juvenile alligators. Data were collected by monthly night-time eyeshine counts aerial surveys, capturing animals, and locating and following the fate of nests. There was a strong positive correlation between water temperature and the number of alligators observed during eyeshine counts. Both eyeshine counts and aerial surveys were highest in spring and varied seasonally. A total of 184 different non-hatchling and 157 hatchling alligators were captured between May 1986 and November 1988. Population estimates and size distributions based on capture data indicate that over the last 15 years the population has increased from approximately 110 to 200 alligators, and the size distribution has shifted from one dominated by large adults to one that has a higher proportion of juveniles. The current sex ratio (2.6:1) is not significantly different from that reported by Murphy (1977, 3.2:1). However, the average number of nests/yr has increased from 2.3 to 4.0. Data on juvenile growth and survival show that the growth rate of hatchlings (32.9 cm/yr total length) is greater than that of animals age 1-3 (21.6 cm/yr total length) and survival of all ages is variable between years and between clutches. Results from this study indicate that from 1972-988 the population has increased ac an average exponential rate of 6 % per year. If conditions in Par Pond do not change, the population size should continue to increase.

Wildlife management and conservation frequently rely on understanding mechanisms that influence distribution and abundance of animals. I quantified space use for a population of inland riverine adult male alligators in Mississippi. Results indicated habitat selection is a scale-dependent process and aquatic vegetation, water depth, and water temperature may be important factors influencing alligator foraging and thermoregulation. Apparent habitat suitability and low alligator density did not manifest in an observed body size-based dominance hierarchy. I also analyzed long-term Mississippi alligator spotlight survey data for trends and effects of environmental covariates on counts. Model results indicated alligator counts have increased over time. This response likely reflects benefits accrued from decades of protection and wetland conservation. Distance sampling does not appear to be a feasible monitoring technique for riverine alligator populations. Nevertheless, it is important that survey protocols and monitoring programs account for imperfect detection and model important covariates.

Crocodilians and birds comprise sister taxa of archosaurs, the development of these vertebrates occurs within an egg case that leaves developing embryos susceptible to fluctuations in the nesting environment. Studies suggest that sub-optimal conditions alter morphological growth and cardiovascular physiology. Regulation of the cardiovascular system is immature in the subjects studied, and embryos may rely on humoral rather than neural control of the cardiovascular system. The primary focus of this dissertation was to assess regulatory mechanisms responsible for maintenance of arterial pressure and heart rate. Dehydration stress had marked effects on embryo growth, and altered baseline cardiovascular parameters, while leaving the response to humoral regulator, angiotensin II (Ang II), unaffected. However, dehydrated alligator embryos developed cholinergic tone on heart rate. Hypoxic incubated chicken embryos were reduced in embryo mass, and altered response to humoral regulatory components Ang I and adenosine in addition identifying a novel regulatory component of the cardiovascular response to acute hypoxia. Collectively, these studies add to the existing knowledge of cardiovascular physiology in embryonic archosaurs and suggest that some components of cardiovascular regulation are plastic following developmental stress.

The American alligator (Alligator mississippiensis) has been frequently studied in large reservoirs and coastal marshes. Large ontogenetic shifts in their diet and morphology have been linked with changes in habitat use, with adult males using deep, open water and juveniles and nesting females relying on vegetated marsh. In certain regions of the inland portion of the alligator’s range, these different aquatic habitats are represented by seasonal wetlands and riverine systems that are separated by a terrestrial matrix. Ontogenetic habitat shifts, therefore, would require overland movements between systems, which has important implications for conservation of the species. I tested several commonly used methods of surveying alligator populations to determine the most effective method of studying alligators in seasonal wetlands. I then used systematic trapping, nest surveys and radio telemetry to determine habitat use and overland movement rates by different sex and size classes. I found that seasonal wetlands provided nesting and nursery sites for these inland alligator populations, but that both juveniles undergoing an ontogenetic shift and nesting females move between the wetlands and riverine systems. Overland movements by alligators between the wetland and riverine habitats establish a level of functional connectivity between these aquatic ecosystems. I constructed a habitat suitability index of both the wetlands and the surrounding landscape to determine which patch and landscape characteristics were important to wetland use by alligators. I found that both descriptive wetland characteristics and the spatial relationships between wetlands were important predictors of alligator use. Overland movement was related to upland landuse as well as distance between aquatic habitats. Conserving a variety of wetland sizes and types within an intact upland matrix is critical to maintaining connectivity across the landscape. Furthermore, understanding how species may act as mobile links between ecosystems, particularly those with ontogenetic niche shifts, illustrates the importance of approaching conservation from a landscape perspective.

The American alligator (Alligator mississippiensis) has been frequently studied in large reservoirs and coastal marshes. Large ontogenetic shifts in their diet and morphology have been linked with changes in habitat use, with adult males using deep, open water and juveniles and nesting females relying on vegetated marsh. In certain regions of the inland portion of the alligator’s range, these different aquatic habitats are represented by seasonal wetlands and riverine systems that are separated by a terrestrial matrix. Ontogenetic habitat shifts, therefore, would require overland movements between systems, which has important implications for conservation of the species. I tested several commonly used methods of surveying alligator populations to determine the most effective method of studying alligators in seasonal wetlands. I then used systematic trapping, nest surveys and radio telemetry to determine habitat use and overland movement rates by different sex and size classes. I found that seasonal wetlands provided nesting and nursery sites for these inland alligator populations, but that both juveniles undergoing an ontogenetic shift and nesting females move between the wetlands and riverine systems. Overland movements by alligators between the wetland and riverine habitats establish a level of functional connectivity between these aquatic ecosystems. I constructed a habitat suitability index of both the wetlands and the surrounding landscape to determine which patch and landscape characteristics were important to wetland use by alligators. I found that both descriptive wetland characteristics and the spatial relationships between wetlands were important predictors of alligator use. Overland movement was related to upland landuse as well as distance between aquatic habitats. Conserving a variety of wetland sizes and types within an intact upland matrix is critical to maintaining connectivity across the landscape. Furthermore, understanding how species may act as mobile links between ecosystems, particularly those with ontogenetic niche shifts, illustrates the importance of approaching conservation from a landscape perspective.