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  • 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.
1

Ecological Implications of Flavor Generalization by Sheep: Role of Flavor Intensity and Variation in Toxin Dose

Launchbaugh, Karen L. 01 May 1992 (has links)
Researchers studying diet selection of ungulate herbivores have generally considered plant palatability independent of animals' dietary history. However, more recent studies demonstrate that experiences within the life of an animal strongly influence plant selection. We are beginning to understand how food preferences and aversions are formed through gastro-intestinal feedback. My research specifically examines factors that influence the formation of conditioned flavor aversions in the generalist herbivore, sheep. I first examined how variability of food toxicity affects the intake of those foods. I determined that sheep apparently have several mechanisms for regulating intake of toxic foods regardless of whether or not toxic variation can be detected through flavor changes. When changes in flavor correspond to changes in toxicity, animals adjusted intake based on an increase or decrease in toxin concentration. When toxic variation was not detectable through flavor, animals adopted a conservative strategy of eating an amount based on the maximum toxin dose they had experienced.' I was also interested in how illness following the consumption of one food influences the selection of other foods. In diet selection, animals may generalize selection responses among foods with similar flavors. Generalization may be particularly important in the selection of novel foods, i.e., a new food may look, smell, or taste like a familiar food that is preferred or avoided. In several experiments on the generalization of flavor aversions I found that: 1) sheep generalize aversions from familiar to novel foods when both foods had a flavor in common; 2) the more sick an animal got after eating a food the greater the aversion formed to the food and the greater the generalization of that aversion to new foods; 3) the salience or intensity of flavor did not affect the strength of conditioned flavor aversions in sheep on the generalization of the aversion, but this may not always be the case; 4) flavor intensity strongly influenced the acceptance of a novel food. A novel food (wheat) with a strong flavor (3% added ground oregano) was more avoided than a novel food (wheat) with a mild flavor (1% oregano added).
2

The Asian Tiger Mosquito (Aedes albopictus): Spatial, Ecological, and Human Implications in Southeast Virginia

Ratigan, Christopher William 26 May 2000 (has links)
The overall theme that drove my research was the concern for public health and its possible compromise due to the colonization of large areas of the United States by the disease-vectoring Aedes albopictus. The main objective is to determine the elements that make an environment conducive to Aedes albopictus populations. Specifically, the objective of this research is to identify the socio-economic impact of Aedes albopictus on residents in the Hampton Roads area in southeast Virginia and determine if there is an identifiable environment in which A. albopictus could be found. Data were collected at the Census block group level (demographic variables) and at the single household level (survey and physical-cultural variables). The variables were then correlated (Pearson) and the results were analyzed. Only variables that were less than (.1) significance were examined. The following physical-cultural variables were found to be associated with the reduction of A. albopictus activity: having a sea breeze, being near an oceanfront, cutting the grass frequently, and keeping the overall neatness of a property high. Secondary variables that are related to the decrease in A. albopictus populations are sunny yards, yards with no containers that can hold water, and yards that contain coniferous trees versus deciduous trees. The primary socio-economic variables that can signify an environment with high A. albopictus activity are: lower house value and median rent value, lower levels of education, and a lower median income level. Other demographic variables that help determine the size of an A. albopictus population are (in order of significance): ethnicity (white or black), poverty/unemployed, owner/renter occupied, and the year a house was built. These secondary variables increase A. albopictus numbers if the following trends exist: high percent of persons in poverty and unemployed, higher percent of renter occupied homes, and older houses. / Master of Science

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