• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 201
  • 114
  • 49
  • 34
  • 11
  • 10
  • 9
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 623
  • 157
  • 123
  • 89
  • 79
  • 64
  • 60
  • 60
  • 59
  • 51
  • 48
  • 39
  • 38
  • 37
  • 35
  • 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.
121

Fat-Pad Specific Effects of Lipectomy on Appetitive and Consummatory Ingestive Behaviors in Siberian Hamsters (Phodopus sungorus)

Johnson, Kelly Deshon 09 June 2006 (has links)
The aim of this experiment was to test whether LIPX-induced decreases in body fat affect appetitive (foraging effort and food hoarding) or consummatory (food intake) ingestive behaviors and whether the effects of LIPX on these behaviors is in turn affected by changes in energy expenditure produced by varying the amount of work required to obtain food. This was accomplished by housing male Siberian hamsters (Phodopus sungorus) in a foraging/hoarding apparatus where food pellets (75 mg) could be earned by completing various wheel running requirements. Requiring a foraging effort (10 revolutions/pellet) abolished the normal compensation of WAT mass by the non-excised WAT pads that typically follows IWATx or EWATx. After foraging, food hoarding was increased more than food intake when hamsters were required to forage for food (10 revolutions/pellet). The magnitude of the LIPX-induced lipid deficit (IWATx > EWATx) did not correspond to a proportional change in either appetitive or consummatory ingestive behaviors.
122

Designing A Better Internet Search Engine Based On Information Foraging Theory

Lee, Szeyin 01 January 2014 (has links)
The first part of the thesis focuses on Information Foraging Theory which was developed by Peter Pirolli, a cognitive scientist from Intelligent Systems Lab at Palo Alto Research Center, to understand how human search in an information environment (Pirolli 1995). The theory builds upon the optimal foraging theory in behavioral ecology, which assumes that people adapt and optimize their information seeking behavior to maximize the success of accomplishing the task goals by selectively choosing paths based on the expected utility from the information cues. The expected utility in Information Foraging Theory is called Information Scent. The second part is to design and build a new way to visualize search engine results in a graphical way that incorporates the concept of information scent to make search experience more efficient for users. The end result of the project will be an improved visualization of search results, obtained by using Google’s Application programming interface (API), latent semantic analysis, and data visualization methods to present a semantics-based visualization of the search results. The proposed design is developed to increase information scent for relevant results and shorten the foraging path to reach the search goal by presenting users with fewer but more valuable proximal cues, thus making search a more human-centered experience.
123

Narwhal (Monodon monoceros) diet and dive behaviour as an assessment of foraging adaptability with changing climate

Watt, Cortney January 2014 (has links)
Narwhals (Monodon monoceros) are sentinel species in the Arctic environment and are a vital component for Inuit culture and subsistence. The Arctic is undergoing rapid changes in temperature and sea ice cover and relatively little is known about how this has and will change narwhal foraging behaviour. There are three narwhal populations in the world, the Baffin Bay (BB), Northern Hudson Bay (NHB), and East Greenland (EG) populations; however, foraging behaviour, in terms of dive behaviour and primary dietary components, has really only been investigated in the BB population. Using a combination of stable isotopes, fatty acids, genetic techniques, and satellite tracking technologies I evaluated foraging behaviour in all three of the world’s narwhal populations. I also investigated social structure in the BB population to determine how adaptable narwhals are to a changing and dynamic Arctic environment. Stable isotopes (δ13C and δ15N) and fatty acids are chemical signatures in the tissues of an organism that can provide long-term information on their diet over varying temporal scales depending upon the tissue. Stable isotope analysis in the three narwhal populations found they forage on different primary prey, suggesting narwhal are adaptable in their preferred prey and that there is potential for them to adjust foraging behavior in the face of changing climate. Dietary changes were also assessed over three decades to determine how sea ice changes have affected narwhal foraging for the NHB and BB populations. Dietary changes were evident and can be attributed to changes in sea ice patterns and an altered migratory pathway for narwhals. An understanding of narwhal social structure is also needed to determine how behaviourally flexible narwhal are in diet and site fidelity. Genetic relatedness and dietary signatures from fatty acids were assessed for an entrapped group to determine if individuals that are closely related forage together, which would support a matrilineally driven social structure where females teach their young foraging strategies, and/or travel and forage together. I found no evidence that narwhals form a matrilineal social group, but they may display a fission-fusion structure, which may be an adaptation to patchy prey distribution in the Arctic. Finally, narwhal dive behaviour in all three populations was investigated to determine if dive behaviour could be used to predict diet. Dive differences among populations did correspond with differences in diet, suggesting that narwhals employ specialized foraging strategies. This has repercussions for their ability to adapt to ecosystem changes. Overall, narwhals may be more flexible in terms of their foraging behaviour than previously believed. However, an increased resilience to changing food webs will not be the only predictor of how narwhals will fare in the face of a changing climate; how they respond to increased industrial activities in their preferred habitats, increased predation from southern predators, and increased competition from southern cetaceans and humans alike, will play an equally large role in how they cope with the future.
124

Home range size and resource selection by the swamp wallaby, Wallabia bicolor, in a landscape modified by timber harvesting

Di Stefano, Julian January 2007 (has links) (PDF)
Timber harvesting results in patches of regenerating forest that are substantially different from surrounding unharvested stands, and provides an opportunity to investigate the effect of habitat change on forest fauna. In this thesis I used timber harvesting as an experimental treatment to investigate the effect of a changed resource base on the home range and resource selection of the swamp wallaby, Wallabia bicolor. I recorded habitat attributes at unharvested control, recently harvested (<12 months old), 5 year old and 10 year old sites. Initially, harvesting removed almost all above-ground plant biomass, although the nitrogen and water content of grass on recently harvested sites was relatively high. Five years after harvesting, sites were dominated by densely regenerating 1-3 m tall Eucalyptus seedlings. Relative to unharvested sites, there was substantial lateral cover and values of a forage quality index were high. In contrast, 10 year old sites supported dense, closed stands of 3-6 m tall eucalypt regeneration, had a moderate amount of lateral cover and had low values of the forage quality index. (For complete abstract open document)
125

Sběr plodů: (ne)tradiční strategie získávání potravin ve městě? / Urban foraging: a (non)traditional strategy of food privisioning in the city?

Růžičková, Lucie January 2018 (has links)
A research of foraging represents a relatively new phenomenon abroad. In Czechia, on the other hand, this is an ordinary issue with a long-time tradition, but until recently it has not received much attention by the scientific community. For this reason the following diploma thesis deals with this activity. It consists of two main units. The first part aims to create the theoretical framework necessary for the introduction into the foraging study. There is a familiarization with the trend of the self-provisioning in general both in Czechia and abroad. A substantial part of the theoretical framework deals with the quantity and the typology of harvested products, the reasons for foraging, the characteristics of the harvesters, etc. It also outlines the problem of western academics' interpretation of foraging in post-communist conditions as a survival strategy. In the second part, using the mixed research methods, the thesis seeks to find out what is the tradition of foraging in Czech conditions during recent decades, who are the harvesters and what are the reasons and motivations to harvest. By statistical data analysis and by interviewing method, it is confirmed that people across a variety of demographic and socio-economic characteristics are harvesting and motivation is certainly not a bad...
126

USING MADAGASCAR HISSING COCKROACHES AS RESEARCH SUBJECTS IN BEHAVIOR ANALYSIS

Gunnarsson, Karl Fannar 01 August 2013 (has links)
The current study investigated the effects of environmental cues on foraging behavior of Madagascar hissing cockroaches using a maze. By placing the subjects in the maze and have them freely roam around; familiarizing themselves with the maze they gradually spent more time where reinforcement was available. As a mean of measurement, the reinforcers were then removed and the maze was flipped 180 degrees. The results were that the subjects allocated majority of their time in the area of the maze where reinforcers were previously available, and when reinforcers had a different spatial location they went to the location where it had been previously. Implications and limitations are discussed.
127

DETERMINING FOOD RESOURCES FOR AMERICAN BLACK DUCKS WINTERING AND SPRING STAGING ON THE EASTERN SHORE OF VIRGINIA

Lewis, Ben Lewis 01 August 2016 (has links)
AN ABSTRACT OF THE THESIS OF Benjamin S. Lewis Jr., for the Master of Science degree in ZOOLOGY, presented on December, 2, 2015 at Southern Illinois University Carbondale. TITLE: DETERMINING FOOD RESOURCES FOR AMERICAN BLACK DUCKS WINTERING AND SPRING STAGING ON THE EASTERN SHORE OF VIRGINIA MAJOR PROFESSOR: Dr. Michael W. Eichholz I evaluated food availability and food preference for American black ducks (Anas rubripes) wintering and spring staging on the Eastern Shore of Virginia during 2006–2007 and 2007–2008. I estimated food availability by taking core and sweep net sample at 78 sites selected by a stratified random sample throughout our study area, representing 4 dominant wetland habitat types. Seed and invertebrate biomass found in each of these samples were converted to measurements of kilograms per hectare. I found that salt marsh and mudflat habitats contained the highest amount of invertebrate biomass, while freshwater habitats contained the highest amount of seed biomass. I estimated food preference by collecting crop samples from 76 foraging black ducks. Animal matter made up 73% of the aggregate percent biomass of all foods eaten by black ducks. Foods found in black duck crops were compared to their availability in the environment and classified as either selected for, avoided or consumed relative to their availability. Although they were not found to be the most abundant foods, amphipods (Gammarus spp), salt marsh snails (Melampus bidentatus) and ribbed mussels (Geukensia demissa) were foods selected for in black duck wintering habitats. These food items are found most predominantly in salt marsh and mudflat habitats. As may be expected these areas are identified as the most important habitats for black ducks wintering on the Eastern Shore of Virginia. Results from this study provide energetic supply data for bioenergetically based habitat conservation for black ducks in Virginia and in the Atlantic Flyway. I found that the density of food items available for wintering black ducks were lower than densities found in in the more northern wintering range of the black duck and considerably lower than estimates from the wintering regions of other species of dabbling ducks. By concurrently measuring food selection and availability I was also able to reliably determine food preference. Removing avoided food items from food availability estimates provides more accurate estimates of preferred food biomass and it is important for bioenergetically based habitat models to use estimates of preferred food biomass in determining habitat objectives. I found that when avoided food items are removed, estimates of available food biomass decrease substantially, (up to 97%) further emphasizing discrepancies in estimates of food availability between coastal black duck wintering areas and estimates from the wintering regions of other species of dabbling ducks.
128

Uso de abelhas sem ferrão (Meliponinae:Apidae) em casa de vegetação para polinização e produção de frutos com e sem semente de minimelancia [Citrullus lanatus (Thunb.) Matsum. &Nakai] / Use of stingless bees (Meliponinae: Apidae) in greenhouse For pollination and fruit production of seeded and Seedless mini watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai]

Bomfim, Isac Gabriel Abrahão January 2013 (has links)
BOMFIM, Isac Gabriel Abrahão. Uso de abelhas sem ferrão (Meliponinae:Apidae) em casa de vegetação para polinização e produção de frutos com e sem semente de minimelancia [Citrullus lanatus (Thunb.) Matsum. &Nakai]. 2013. 140 f. Tese (doutorado em zootecnia)- Universidade Federal do Ceará, Fortaleza-CE, 2013. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-04-08T17:25:53Z No. of bitstreams: 1 2013_tese_igabomfim.pdf: 1449717 bytes, checksum: 5c363ee9760d3cfcfebb1aed8f8f70f2 (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-05-25T19:54:36Z (GMT) No. of bitstreams: 1 2013_tese_igabomfim.pdf: 1449717 bytes, checksum: 5c363ee9760d3cfcfebb1aed8f8f70f2 (MD5) / Made available in DSpace on 2016-05-25T19:54:36Z (GMT). No. of bitstreams: 1 2013_tese_igabomfim.pdf: 1449717 bytes, checksum: 5c363ee9760d3cfcfebb1aed8f8f70f2 (MD5) Previous issue date: 2013 / The aim of this thesis was to investigate the viability of using the stingless bees, Melipona subnitida and Scaptotrigona sp. nov. for pollination and fruit production of seeded and seedless mini watermelon (Citrullus lanatus) under greenhouse conditions. To this end, the floral biology and pollination requirements of seeded and seedless mini watermelon varieties were investigated, as well as the adaptive and foraging behavior of both meliponines. The experiment was carried out in a greenhouse situated in the city of Fortaleza-CE. The results revealed that the varieties studied were monoecious plants with diclinous flowers, and that the stigma of its pistillate flowers remained receptive throughout the anthesis, which was from 05:25 h to 14:20 h. The seeded varieties set fruits by geitonogamous and xenogamous pollination, within the same variety and between different diploid genotypes. In contrast, the seedless genotypes set fruits only by cross-pollination with pollen from seeded varieties. M. subnitida did not show any interest in the crop, under the experimental conditions. On the other hand, Scaptotrigona sp. nov. adapted well to the confinement and collected floral resources since the second day after its introduction. Scaptotrigona sp. nov. showed an essential behavior for the pollination of mini watermelon, as they visited, for direct collection of nectar, staminate and pistillate flowers of both diploid and triploid genotypes. The quantity and the quality of fruits resulting from the pollination of this bee did not differ significantly (P > 0.05) from the hand pollination. It was concluded that M. subnitida did not adapt to the mini watermelon cultivation in protected environment with cooling system, and the introduction of Scaptotrigona sp. nov. colonies, for pollination purposes, is viable in the commercial exploitation of seeded and seedless mini watermelon under greenhouse conditions. / O objetivo desta tese foi investigar a viabilidade da utilização dos meliponíneos, jandaíra (Melipona subnitida) e Scaptotrigona sp. nov. na polinização e produção de frutos de minimelancia (Citrullus lanatus) com e sem semente, sob cultivo protegido. Para tanto, foram investigados a biologia floral, os requerimentos de polinização das variedades de minimelancia, bem como o comportamento de adaptação e forrageamento, e a eficiência de polinização desses meliponíneos sob ambiente protegido. O experimento foi conduzido em uma casa de vegetação localizada no município de Fortaleza-CE. Os resultados revelaram que as variedades estudadas eram plantas monóicas com flores díclinas, e que o estigma de suas flores pistiladas permaneceu receptivo durante toda antese, a qual foi de 05:25 h às 14:20 h. As variedades com semente produziram frutos por meio da geitonogamia e da xenogamia, dentro da mesma variedade e entre diferentes genótipos diplóides. Diferentemente, os genótipos sem semente apenas formaram frutos por meio da polinização cruzada com pólen proveniente de variedades com semente. A abelha jandaíra não demonstrou nenhum interesse pela cultura diante das condições experimentais. Por outro lado, a abelha Scaptotrigona sp. nov. se adaptou bem ao confinamento e coletou recursos florais desde o segundo dia após sua introdução. Scaptotrigona sp. nov. mostrou comportamento essencial para a polinização da minimelancia, pois visitou, para coleta direta de néctar, flores estaminadas e pistiladas tanto dos genótipos diplóides quanto dos genótipos triplóides. A quantidade e qualidade dos frutos resultantes da polinização por essa abelha não diferiram significativamente da obtida pela polinização manual (P > 0,05). Conclui-se que a espécie de abelha M. subnitida não se adaptou ao cultivo de minimelancia em ambiente protegido com sistema de arrefecimento, e que a introdução de colônias Scaptotrigona sp. nov., para fins de polinização, é viável na exploração comercial da minimelancia com e sem semente em ambiente protegido.
129

Sensory abilities in food localization in four species of African mole-rats with diverse social organization

VITÁMVÁS, Miloš January 2013 (has links)
Until recently, it was assumed that African mole-rats search for food randomly, as it is in concordance with Aridity food distribution hypothesis. However, recent studies indicate that some subterranean rodent species including mole-rats could be able to use plant chemicals (kairomones) for food localization. In my master thesis I conducted a battery of experiments on four mole-rat species to prove, that these species also posses the ability of kairomone guided foraging independently of their social organization.
130

Ecologie sensorielle des rapaces : vision et olfaction / Sensory ecology of raptors : vision and olfaction

Potier, Simon 18 October 2016 (has links)
La vision est certainement le sens le plus développé chez les rapaces, souvent cités comme les vertébrés possédant la plus grande acuité visuelle. Pourtant, les rapaces figurent parmi les victimes les plus fréquentes des collisions avec des éoliennes et autres dispositifs anthropiques. Etant donné les enjeux de conservation et le coût des opérations de conservation, il est indispensable de mieux comprendre comment les capacités sensorielles des rapaces affectent leur technique de recherche alimentaire et les interactions avec les dispositifs anthropiques (par exemple jusqu’à quelle altitude/distance les vautours peuvent-ils être détecter les charniers et les obstacles potentiels et comment optimiser les mesures de gestion des habitats ?). En ce qui concerne l'olfaction, le postulat ancien que les oiseaux en général ont une olfaction quasi nulle est réfuté grâce à la publication récente d’expériences qui montrent le contraire chez plusieurs espèces d’oiseaux, des passereaux aux oiseaux marins. L’olfaction est-elle vraiment un sens « manquant » chez les rapaces? Pourquoi seuls les vautours américains auraient-ils développé un sens aigu de l’olfaction ? Notre projet d’étude de l’écologie sensorielle des rapaces repose principalement sur de test de conditionnement avec renforcement, conduits sur des oiseaux issus de plusieurs parcs zoologiques de France. L’originalité de notre projet serait de combiner des expériences de vision et d’olfaction, sur une grande diversité d’espèces (Vautours, Buses, Milans), d’origine phylogénétique, de régimes alimentaires et de technique de recherche alimentaire différents, à la fois au sol et en vol. La première étape aura lieu en conditions contrôlées en volières, avec des expériences de conditionnement opérant après dressage : réponses des oiseaux à différents stimuli visuels et odeur. Dans un deuxième temps des expériences en vol pourront être menées, sur des oiseaux dressés à effectuer des vols libres, dont les mouvements précis peuvent être suivis en 3 dimensions par des balises GPS couplées à des accéléromètres et des caméras vidéos. Il serait alors possible de connaître précisément les capacités sensorielles utilisées pour la recherche alimentaires de chaque espèce et d’analyser les comportements de vol en lien avec l'aérologie. / The vision is certainly the most developed sense in raptors, and these birds are cosidered as the vertebrates with the greatest visual acuity. However, raptors are among the most frequent victims of collisions with wind turbines and other human features. Given the conservation issues and the cost of conservation operations , it is essential to understand how sensory abilities of raptor affect their foraging ecology and interactions with human features (eg at which altitude / distance vultures can detected graves and potential obstacles and how optimize the measure of habitats management). But vision is not the only sense that raptor may have. Olfaction in birds was historically neglected, but recent evidence suggests that many bird species, from passerines to seabirds, use olfaction. Consequently, it make sense that olfaction may lead some behaviours in raptor too. To date however olfaction has been searched and shown only in the American vultures. Our project aims to study the sensory ecology of raptors based primarily on captive animals and condition protocols. The originality of our project is to combine the experience of vision and olfaction, on a wide variety of raptor species present in French zoos, with different phylogenetic origin, diets, and different foraging ecologies. The first step will takes place under controlled aviaries conditions, with operant conditioning experiments: responses of birds to different visual and odor stimuli. In a second phase, flight experiments will be conducted on birds trained to perform free flights, whose precise movements can be tracked in three dimensions by GPS tags coupled with accelerometers and cameras videos. It would then be possible to determine precisely the sensory capabilities used for food research for each species, and analyze the flight behaviour with respect to aerology

Page generated in 0.0352 seconds