Thesis (Ph. D.)--University of Wisconsin--Madison, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Knowledge of the structuring of natural populations is important for understanding both evolutionary processes and population ecology, and for supporting management decisions. Conventional methods of direct observation often suffer from a lack of resolution, particularly when studying mobile animals in a marine environment. In this study, I combined direct observation with indirect molecular genetic approaches to infer the social and population structure of coastal (inshore) bottlenose dolphins, Tursiops truncatus. Genetic diversity and structure of bottlenose dolphins around the UK and Ireland was examined using tissue samples from stranded dolphins and incidental fisheries by-catch. Mitochondrial DNA (mtDNA) sequence data indicated significant subdivision among four main sample regions (NE Scotland, Wales, NW Scotland and Ireland). Genetic divergence between NE and NW Scotland populations, and low genetic diversity within the NE Scotland population, provide further support for the precautionary approach currently applied to the management of this population. Inference from both mtDNA and nuclear microsatellite genetic markers, and direct observational data were used to examine the social and population structure of bottlenose dolphins in the NE Bahamas. Novel strategies for collecting genetic samples (remote biopsy and faecal sampling) from free-ranging dolphins were developed and validated, enabling an individual-based analysis of population subdivision. Patterns of individual associations in two contrasting habitats indicated that environmental pressures affect dolphin grouping patterns; with a genetic basis for social affiliations occurring only where predation pressures are low. Nonetheless, a particularly notable feature of the social structure in both habitats was the persistence of stable alliances among maternally related males. At the population level, the significant degree of genetic structuring revealed among three sampled regions on Little Bahama Bank, supported the high degree of site fidelity suggested by individual-based photo-identification data. Contrary to the patterns of male dispersal and female philopatry common among both mammals and bottlenose dolphins, sex-specific patterns of genetic differentiation inferred from both mtDNA and microsatellite markers were indicative of female-mediated gene flow. This study provides novel insight into the factors governing the patterns of structuring within populations of highly mobile small cetaceans, and demonstrates the value of integrating both direct (field-based) and indirect (molecular genetic) data in the study of free-ranging animals.

A number of field studies on small mammals have suggested that aggressive behavior may limit breeding density. To investigate how the presence of one individual affects another's chances for survival, reproduction, and growth, I carried out a series of experimental studies on Microtus townsendii near Vancouver, Canada. In the first experiments, population density was reduced by removing voles before or during the spring decline. Drastic artifical reduction during a spring decline improved female survival but not male survival; similar reduction in the fall prior to a decline improved both male and female survival. Survival was not density-dependent in males, but was in females during one decline. To explain these results, a behavioral model is proposed in which females compete for nest sites and males compete for females. In a second experiment, a population predicted to experience a decline was enclosed. I wanted to see if preventing emigration would stop the decline. Unfortunately the control area remained at peak densities and neither area suffered a spring decline. The enclosed population had higher rates of increase, reached higher densities, and had higher survival rates than those on the control area. This resulted in severe overgrazing and a sharp population decline within the enclosure. These results indicate that movements play a necessary role in population regulation when voles are at peak, densities. In a third experiment, the role of predation in causing population changes was measured. Predation was not necessary to initiate a decline or to maintain it. Of the tagged voles known to have been eaten, there was no consistent selection by predators for either of the saxes, for any weight class, or for voles with any other characteristic that could be measured by live-trapping. Of the total number of voles known to have been eaten, avian predators consistently chose animals that were smaller than those in the tagged population. This indicates that either the live-traps selectively caught large animals, or avian predators selectively caught small animals, or that both biases were present. In the fourth experiment, the role of resident adults in determining juvenile survival was tested by removal of adults and by adding juveniles to experimental populations. Survival of young was improved in the absence of all adults, but not in either intact populations, in reduced populations, or in female populations. Survival of young was better in periods of reduced adult breeding. Height at sexual maturity tended to be higher in the presence of adults of the same sex. Growth in young males tended to be reduced in the presence of adult males. These results indicate that females reduce survival of young, and suggest that emphasis be placed on the study of female behavior as a factor affecting microtine numbers. In the final experiment, the survival and dispersal rates of very young voles were examined to determine where the enormous loss between birth and recruitment occurred. A high density vole population was trapped concurrently with live-traps and pitfall traps. Capture of a large number of young in pitfalls indicated that mortality was higher among post-weanlings than among any other age group. The pitfall traps enumerated up to twice as many animals as the live-traps, and over half of the 1100 animals caught first in pitfalls were never caught in live-traps. Trapping solely with live-traps may severely underestimate numbers (at least when densities are high) and give inaccurate population statistics. Populations of J. townsendii fluctuate in size and Chitty's behavior hypothesis predicts that spacing behavior underlies these density changes. My experimental results are consistent with this general view and add specific details to the mechanism by which density is regulated. My experiments pinpoint post weaning survival as a critical phase determining population changes in this vole and focus attention on two critical areas: adult female - postweanling interactions and adult female-adult female interactions. / Science, Faculty of / Zoology, Department of / Graduate

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Call number: LD2668 .T4 1961 R65

Call number: LD2668 .T4 1966 H671 / Master of Science

Thesis (M.S.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Nov. 19, 2009). Includes bibliographical references.

Matrix difference equations have been used to model the discrete time dynamics of a variety of populations whose individual members have been categorized into a finite number of classes based on, for example, age, size, or stage. Examples of such models include Leslie's age-structured model and the Usher model, a size-classified model which has been applied to trees, corals, sea turtles, copepods, and fish. These matrix difference equations can incorporate virtually any type of nonlinearity arising from the density dependence of fertility and survival rates and transition probabilities between classes. Under a fairly general set of assumptions, it can be shown that the normalized class distribution vector equilibrates, and thus an asymptotic or limiting equation for total population size can be derived. In this research we assume the existence of a dynamically modeled resource in limited supply for which the members of the species compete, either exploitatively or through interference. The existence and stability of population size equlibria or cycles is then studied by means of bifurcation theory. Several biological considerations are addressed, including the Size-Efficiency Hypothesis of Brooks and Dodson, the effects of changes in individual physiological parameters on the size and competitive success of a species, and the effects of delays on the viability of a species.

No description available.

Thesis (Ph. D.)--University of California, Davis, 2003. / Includes bibliographical references. Also issued online.