• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 187
  • 17
  • 14
  • 8
  • 8
  • 8
  • 8
  • 8
  • 8
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 252
  • 252
  • 58
  • 45
  • 33
  • 32
  • 20
  • 20
  • 17
  • 17
  • 17
  • 17
  • 16
  • 16
  • 15
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Quantifying the energetic cost of disorientation in loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtle hatchlings

Unknown Date (has links)
The photopollution of beaches caused by artificial light sources can interfere with sea turtle hatchlings' ability to orient properly towards the sea. Exhaustion due to extended disorientation crawling may then increase hatchling mortality. This study evaluated the energetic consequences of long-distance crawls in green and loggerhead sea turtle hatchlings. Turtles crawled for 200 m or 500 m on a treadmill, followed by a 30 minute evaluation of swim performance. Metabolic activity was quantified via measures of blood glucose, blood lactate, and oxygen consumption. No significant changes in metabolism resulted from long-distance crawling activity in loggerheads ; however, loggerheads rested for extended periods of time during the crawl trials, often unresponsive to stimuli. This behavior implies that loggerhead hatchlings would be vulnerable to predation or temperature stress due to exhaustion from extended periods of crawling. Further data is required to draw any significant conclusions about long-term disorientatin crawling in green hatchlings. / by Sean Williams. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
142

Foraging ecology of wading birds in a sub-tropical intertidal zone

Unknown Date (has links)
The first of five chapters describe the study area and study species, including a short description about the impetus for this research. The second chapter describes a unique hydrologic model for application in tidal ecosystems. The second chapter represents new information on the effects of various abiotic and biotic factors on foraging wading birds in this highly dynamic environment. The third chapter identifies important factors affecting the abundance of foraging wading birds in intertidal environments. The fourth chapter presents a study of the foraging habitat preferences of two wading bird species in intertidal environments. The fifth chapter describes a conceptual model of wading bird foraging ecology and a predictive model of foraging habitat in intertidal zones. The conceptual model captures the major drivers and linkages between the abiotic and biotic variables thought to affect wading bird foraging abundance in intertidal habitats. The conceptual model also identifies major knowledge gaps in our understanding of foraging ecology of wading birds in coastal intertidal areas. The predictive model of foraging habitat is meant to be used by resource managers, but its framework may be useful for ecological studies in general. The final and sixth chapter provides a summary of all the major findings. Each chapter has been written so as to be independent of the other chapters. As such, a full background, along with a discussion of the relevance of the chapter's findings is provided for each chapter. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
143

Predatory Impacts of Crayfish on Apple Snails (Pomacea paludosa and P. maculata)

Unknown Date (has links)
Theory predicts that when prey can reach a size refuge from predation, prey vulnerability to predation is a function of hatchling size, growth rate, and the handling limitations of its predator, which collectively influence the amount of time prey spend vulnerable. I examined the mechanistic role of prey size for the predator-prey interaction between predatory crayfish (Procambarus fallax) and apple snail prey (Pomacea paludosa and P. maculata) and found that crayfish feeding rates decreased with snail size, such that smaller hatchling P. maculata were more than twenty times more vulnerable than hatchling P. paludosa. Experimental manipulations of productivity increased apple snail growth rates, reducing the effects of predatory crayfish on P. maculata survivorship, but not P. paludosa survivorship. My results indicate that when prey can reach a size refuge from predation, increased system productivity decreases predator limitation of that prey. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
144

The Role of Chemical Cues in Locating Pelagic Sargassum by the Associated Fish Stephanolepis hispidus

Unknown Date (has links)
The ecosystem created by pelagic Sargassum is important in the life histories of a number of economically and ecologically important associated organisms. Fishes play a vital role in this food web and nutrient flow within these systems, but it is unknown how they locate these floating habitats. This study examined the role of natural chemical cues from Sargassum patches and the synthetic chemical Dimethylsulfonionpropionate (DMSP) for an associated fish, the planehead filefish (Stephanolepis hispidus) and a control fish species not associated with Sargassum, the masked goby (Coryphopterus personatus). Choice trials with a Y-maze apparatus determined that S. hispidus responded significantly to chemical cues from Sargassum while C. personatus did not. DMSP cues did not result in any significant behavioral responses for either fish. Demonstrating that S. hispidus can respond to chemical cues from Sargassum helps further our understanding of this unique floating algal reef and how fishes may locate it. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
145

Origins, movements, and foraging behavior of Hawksbill Sea Turtles (Eretmochelys imbricata) in Palm Beach County waters, Florida, USA

Unknown Date (has links)
This dissertation examined the natal origins, home-range, and in-situ foraging behavior of an aggregation of sub-adult hawksbill turtles (Eretmochelys imbricata) found off the coast of Palm Beach County, Florida. Surveys were conducted on approximately 30 linear km of reef between 15 and 30 m in depth. Tissue samples were retrieved from 112 turtles for mtDNA haplotype determination. GPS-linked satellite transmitters were deployed on six resident sub-adults, resulting in both minimum convex polygon (MCP) and 95%, 50%, and 25% kernel density estimates (KDE) of home-range size. A foraging ethogram was developed, and sequential analysis performed on thirty videos (141 total minutes) of in-situ foraging behavior. Seventeen total haplotypes were identified in this aggregation, the majority (75%) of which represented rookeries on Mexico’s Yucatan Peninsula. Other sources, from most to least important, include Barbados, Costa Rica, Puerto Rico, Antigua, and the U.S. Virgin Islands. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
146

Physiological Effects of Disorientation in Loggerhead (Caretta caretta) and Green (Chelonia mydas) Sea Turtle Hatchlings

Unknown Date (has links)
Following nest emergence, sea turtle hatchling dispersal can be disrupted by artificial light or skyglow from urban areas. Mis- or disorientation increases exposure to predation, thermal stress, and dehydration, could consume valuable energy, and thus influence the likelihood of survival. This study utilized laboratory simulations of extended crawl distances and field observations to investigate the energy cost of disorientation crawling on loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtle hatchlings and the impact on the subsequent swim frenzy. Extended crawls increased oxygen consumption, decreased plasma glucose, and reduced green hatchling swim performance following a 200m crawl. Surprisingly, plasma lactate concentrations did not increase with crawl distance, likely due to frequent rest periods that would, however, increase time on the beach and thus exposure to predators. This research may provide managers with physiological data to determine best practices for sea turtle conservation and adds to the biological knowledge of these animals. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection
147

A comparison of body proportions in juvenile sea turtles: how shape may optimize survival in a vulnerable life stage

Unknown Date (has links)
Marine turtles produce many offspring which offsets the high mortality experienced by turtles during early development. Juvenile mortality might be reduced by evolving effective behavioral as well as morphological anti-predator defenses. Body proportions of three species (Caretta caretta, Chelonia mydas, Dermochelys coriacea) of turtles were measured in the first fourteen weeks of development to examine how growth may mitigate predation by gape-limited predators. Growth was categorized as isometric if shape did not change during development or allometric if body shape did change. All three species showed allometric growth in carapace width; however it was less pronounced in the larger D. coriacea turtles. Allometric growth in carapace width decreased as all three species grew in size. When high predation occurs in early development, many species will favor rapid growth into a size refuge. Juvenile sea turtles may optimize their survival by growing allometrically when predation risk is the greatest. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection
148

Investigating maternal health and hatchling mortality in leatherback sea turtles (Dermochelys coriacea v.)

Unknown Date (has links)
The reproductive success of leatherback turtles (Dermochelys coriacea) is typically the lowest of the seven sea turtle species. Why this vital rate is decreased has remained unanswered for nearly a century. Recently, detailed postmortem examination of leatherback hatchlings identified muscular pathologies that suggested possible selenium deficiency. High bodily burdens of mercury compounds are associated with selenium depletion. Selenium is a necessary detoxifying nutrient that itself can be toxic at elevated concentrations. Mercury compounds are toxicants with no known biological function. High bodily concentrations of mercury can be detrimental to marine organismal health, reproduction and survival, both directly and indirectly through inducing selenium depletion. The goals of this dissertation are to evaluate several related hypotheses to explain low leatherback nest success. ... Because leatherbacks take in high volumes of prey, high tissue concentrations of mercury and selenium can result. This study provides the first evidence that chemical contaminants may explain low reproductive success in leatherback sea turtles. / by Justin R. Perrault. / Thesis (Ph.D.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
149

Mechanisms that generate resource pulses and drive wading bird nesting in a fluctuating wetland

Unknown Date (has links)
Variation in the seasonal water level fluctuations of tropical and subtropical wetlands controls the production and concentration of aquatic fauna that support breeding wading birds. However, little is known about how particular components of the annual hydrologic cycle affect processes that control food availability and reproduction. This thesis identifies specific mechanisms responsible for transforming wet season prey standing stock into dry season prey concentrations, links landscape hydrological patterns to wading bird nesting, and presents a predictive model of Wood Stork nesting. I examined the supoort for several a priori hypotheses of factors affecting wading bird prey concentrations and wading bird nest effort. Factors affecting the concentration and vulnerability of prey were important for transferring secondary production to higher trophic levels. Receding water levels, microtopographic variation, and high standing stocks of prey were critical for generating pulses of food availabiltiy to meet the high energy requirements of breeding predatory birds. / by Bryan A. Botson. / Thesis (M.S.)--Florida Atlantic University, 2012 / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.
150

Jaws of significance: the conservationist's perception of the shark in South Florida

Unknown Date (has links)
In examining the intentional relationship between the conservationist and the shark in South Florida, this thesis considers the latter as both a scarce natural resource - caught up in what Clifford Geertz citing Weber referred to as "webs of significance" (Geertz 1973:5) - and as a reflection of dynamic human conceptions of nature : a meta shark. This complex relationship is described by interpretations of conservation discourse recorded through ethnographic interviews that demonstrate how these perceptions have been influenced by factors such as personal experiences, film and text, and broad changes in the relationship between humans and nature since the early days of the environmental movement. By linking these perceptual changes with changes in American shark conservation policy, this work not only explains a relationship between culture, perception, and policy, but also celebrates the emergence of a multispecies marine community. / by Patrick Nason. / Thesis (M.A.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Page generated in 0.0989 seconds