Graduate Theses & Dissertations

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Maya Exploitation of Animal Resources during the Middle Preclassic Period
This study examines the foraging strategies of animal resource exploitation during the Middle Preclassic period (900-300 BC) at the ancient Maya site of Pacbitun, Belize. The faunal remains analyzed in this study were recovered from various domestic structures associated with the production of shell artifacts. Detailed taphonomic analyses have revealed that the Pacbitun faunal remains were particularly affected by weathering and density-mediated attrition. White-tailed deer was the prey most frequently acquired by the Middle Preclassic Maya of Pacbitun, followed by other lower-ranked artiodactyls. A variety of less profitable prey were sometimes included in the diet breadth. Using the central place forager prey choice model as a framework, the analysis of diet breadth, habitat use, and carcass transport patterns suggests that most animal resources were acquired from terrestrial habitats, at short distances from the site. Complete carcasses of large game appear to have been frequently transported to the site, where they were exploited for their meat and marrow. Comparisons with other Middle Preclassic faunal assemblages indicate significant differences in terms of taxonomic composition, with an emphasis on the procurement of fish and turtles. It is suggested that the Middle Preclassic Maya adopted foraging strategies focusing on the exploitation of local habitats, with occasional use of exotic resources. Author Keywords: Animal, Belize, Foraging, Maya, Subsistence, Zooarchaeology
Effects of Silver Nanoparticles on Lake Bacterioplankton
Silver nanoparticles (AgNP) released into aquatic environments could threaten natural bacterial communities and ecosystem services they provide. We examined natural lake bacterioplankton communities' responses to different exposures (pulse vs chronic) and types (citrate and PVP) of AgNPs at realistic environmental conditions using a mesocosm study at the Experimental Lakes Area. An in situ bioassay examined interactions between AgNPs and phosphorus loading. Bacterial communities exposed to high AgNP concentrations regardless of exposure or capping agent type accumulated silver. We observed increases in community production during additions of polyvinylpyrrolidone (PVP) -capped AgNPs and that site and nutrient-specific conditions are important to AgNPs toxicology in aquatic systems. Toxicological effects of AgNP are attenuated in natural conditions and differ from results from laboratory studies of AgNP toxicity. Our results demonstrate more studies are needed to fully assess the risk posed by these novel chemicals to the environment. This work could be useful in forming risk assessment policies which are largely based on lab studies and typically demonstrate strong toxic effects. Author Keywords: bacterial production, bacterioplankton communities, ecological stoichiometry, Experimental Lakes Area, mesocosms, silver nanoparticles
EXAMINING DREAMS, DREAM CONTENT, AND MEANING OF DREAMS IN BEREAVEMENT
Dreams that occur in bereavement have been mainly overlooked in the psychological literature. This study focuses on the most memorable dreams of the bereaved that contain imagery of the deceased. There were 52 participants who completed the study via email. The main goal of the study was to investigate the occurrence of common themes in the dreams that have the deceased as a character. It was hypothesized that the most memorable dreams are memorable because they positively influenced the dreamers waking life grief process, which was partially supported. Furthermore, it was expected that that the most memorable dreams will have a greater frequency of positive elements and a lower frequency of negative elements than the normative data on dreams, which was partially supported. These findings support past research on dreaming of the deceased and expand the impact that these types of dreams can have on the grief process. Author Keywords: bereavement, deceased imagery, dream content, dreams, grief
Hybridization Dynamics between Wolves and Coyotes in Central Ontario
Eastern wolves (Canis lycaon) have hybridized extensively with coyotes (C. latrans) and gray wolves (C. lupus) and are listed as a `species of special concern' in Canada. Previous studies have not linked genetic analysis with field data to investigate the mechanisms underlying Canis hybridization. Accordingly, I studied genetics, morphology, mortality, and behavior of wolves, coyotes, and hybrids in and adjacent to Algonquin Provincial Park (APP), Ontario. I documented 3 genetically distinct Canis types within the APP region that also differed morphologically, corresponding to putative gray wolves, eastern wolves, and coyotes. I also documented a substantial number of hybrids (36%) that exhibited intermediate morphology relative to parental types. I found that individuals with greater wolf ancestry occupied areas of higher moose density and fewer roads. Next, I studied intrinsic and extrinsic factors influencing survival and cause-specific mortality of canids in the hybrid zone. I found that survival was poor and harvest mortality was high for eastern wolves in areas adjacent to APP compared with other sympatric Canis types outside of APP and eastern wolves within APP. Contrary to previous studies of wolves and coyotes elsewhere, I hypothesized that all Canis types exhibit a high degree of spatial segregation in the Ontario hybrid zone. My hypothesis was supported as home range overlap and shared space use between neighboring Canis packs of all ancestry classes were low. Territoriality among Canis may increase the likelihood of eastern wolves joining coyote and hybrid packs and exacerbate hybridization. Canids outside APP modified their use of roads between night and day strongly at high road densities (selecting roads more at night), whereas they responded weakly at lower road densities (generally no selection). Individuals that survived exhibited a highly significant relationship between the difference in their night and day selection of roads and availability of roads, whereas those that died showed a weaker, non-significant response. My results suggest that canids in the unprotected landscape outside APP must balance trade-offs between exploiting benefits associated with secondary roads while mitigating risk of human-caused mortality. Overall, my results suggest that the distinct eastern wolf population of APP is unlikely to expand numerically and/or geographically under current environmental conditions and management regulations. If expansion of the APP eastern wolf population (numerically and in terms of its geographic distribution) is a conservation priority for Canada and Ontario, additional harvest protection in areas outside of APP may be required. If additional harvest protection is enacted, a detailed study within the new areas of protection would be important to document specific effects on eastern wolf population growth. Author Keywords: Canis, coyotes, eastern wolves, hybridization, resource selection, survival
Constraints on phenotypic plasticity in response to predation risk
Inducible defenses are plastic responses by an organism to the perception of predation risk. This dissertation focuses on three experiments designed to test the hypothesis that plastic ability is limited by energetic constraints. Chapter 1 provides a general introduction to phenotypic plasticity research and the theoretical costs and limitations affecting the expression of plastic traits. In Chapter 2, I tested the hypothesis that costs of early plasticity may be manifested by a reduced response to risk in later life stages. I found that amphibian embryos are able to detect and respond to larval predators, but that the energetic cost of those plastic responses are not equivalent among behavioural, growth, and morphological traits, and their expression differs between closely-related species. Chapter 3 explicitly examines the relationship between food resource availability and plasticity in response to perceived predation risk during larval development. Food-restricted tadpoles showed limited responses to predation risk; larvae at food saturation altered behaviour, development, and growth in response to predation risk. Responses to risk varied through time, suggesting ontogeny may affect the deployment of particular defensive traits. Chapter 4 examines the influence of maternal investment into propagule size on the magnitude of the plastic responses to predation risk in resulting offspring. I found that females in better body condition laid larger eggs and that these eggs, in turn, hatched into larvae that showed greater morphological plasticity in response to predation risk. Maternal investment can therefore affect the ability of offspring to mount morphological defenses to predation risk. Last, Chapter 5 provides a synthesis of my research findings, identifying specific factors constraining the plastic responses of prey to perceived predation risk. Overall, I found constraints on plastic responses imposed by the current environment experienced by the organism (resource availability), the prior experience of the organism (predator cues in the embryonic environment), and even the condition of the previous generation (maternal body condition and reproductive investment). Together, these findings both provide new knowledge and create novel research questions regarding constraints limiting phenotypic variation in natural populations. Author Keywords: behaviour, inducible defense, Lithobates pipiens, morphometrics, phenotypic plasticity, predation risk
Self-Organizing Maps and Galaxy Evolution
Artificial Neural Networks (ANN) have been applied to many areas of research. These techniques use a series of object attributes and can be trained to recognize different classes of objects. The Self-Organizing Map (SOM) is an unsupervised machine learning technique which has been shown to be successful in the mapping of high-dimensional data into a 2D representation referred to as a map. These maps are easier to interpret and aid in the classification of data. In this work, the existing algorithms for the SOM have been extended to generate 3D maps. The higher dimensionality of the map provides for more information to be made available to the interpretation of classifications. The effectiveness of the implementation was verified using three separate standard datasets. Results from these investigations supported the expectation that a 3D SOM would result in a more effective classifier. The 3D SOM algorithm was then applied to an analysis of galaxy morphology classifications. It is postulated that the morphology of a galaxy relates directly to how it will evolve over time. In this work, the Spectral Energy Distribution (SED) will be used as a source for galaxy attributes. The SED data was extracted from the NASA Extragalactic Database (NED). The data was grouped into sample sets of matching frequencies and the 3D SOM application was applied as a morphological classifier. It was shown that the SOMs created were effective as an unsupervised machine learning technique to classify galaxies based solely on their SED. Morphological predictions for a number of galaxies were shown to be in agreement with classifications obtained from new observations in NED. Author Keywords: Galaxy Morphology, Multi-wavelength, parallel, Self-Organizing Maps
Aeolian Impact Ripples in Sand Beds of Varied Texture
A wind tunnel study was conducted to investigate aeolian impact ripples in sand beds of varied texture from coarsely skewed to bimodal. Experimental data is lacking for aeolian megaripples, particularly in considering the influence of wind speed on ripple morphometrics. Additionally, the modelling community requires experimental data for model validation and calibration. Eighteen combinations of wind speed and proportion of coarse mode particles by mass were analysed for both morphometrics and optical indices of spatial segregation. Wind tunnel conditions emulated those found at aeolian megaripple field sites, specifically a unimodal wind regime and particle transport mode segregation. Remote sensing style image classification was applied to investigate the spatial segregation of the two differently coloured size populations. Ripple morphometrics show strong dependency on wind speed. Conversely, morphometric indices are inversely correlated to the proportion of the distribution that was comprised of coarse mode particles. Spatial segregation is highly correlated to wind speed in a positive manner and negatively correlated to the proportion of the distribution that was comprised of coarse mode particles. Results reveal that the degree of spatial segregation within an impact ripple bedform can be higher than previously reported in the literature. Author Keywords: Aeolian, Impact Ripples, Megaripple, Self-organization, Wind Tunnel
TESTING THE ROLE OF BIMODAL CELLS IN NEAR-HAND EFFECTS
We investigated whether hand-proximity effects arise from the recruitment of visual-tactile bimodal cells. In Experiment 1, we executed right-hand open-loop reaching movements to targets, presented either near or far from the resting left-hand, and after applying repetitive transcranial magnetic stimulation (rTMS) to suppress neuronal activity in the PMd and AIP, in Experiment 2. Results from Experiment 1, indicated that near-hand targets improved accuracy and reduced variability. In Experiment 2, suppressing PMd showed similar near-hand effects as above. In contrast, applying rTMS to AIP disrupted the representation of target location, indicating less accuracy and greater error. Near-hand proximity effects possibly arise from the recruitment of visual-tactile bimodal cells within the human AIP. Author Keywords: anterior intraparietal sulcus, peripersonal space, repetitive transcranial magnetic stimulation (rTMS), , rTMS, anterior intraparietal sulcus, AIP., visual-tactile bimodal neurons
Critical Analysis of the Adoption of Maize in Southern Ontario and its Spatial, Demographic, and Ecological Signatures
This thesis centers on analyzing the spatial, temporal, and ecological patterns associated with the introduction of maize horticulture into Southern Ontario - contextualized against social and demographic models of agricultural transition. Two separate analyses are undertaken: a regional analysis of the spread of maize across the Northeast using linear regression of radiocarbon data and a standard Wave of Advance model; and a local analysis of village locational trends in Southern Ontario using a landscape ecological framework, environmental data and known village sites. Through the integration of these two spatial and temporal scales of analysis, this research finds strong support for both migration and local development. A third model of competition and coalescence is presented to describe the patterning in the data. Author Keywords: Demographic Modeling, Environmental Modeling, Geostastical Analysis, Maize, Ontario Archaeology, Spread of Agriculture
Investigating the sources and fate of monomethylmercury and dimethylmercury in the Arctic marine boundary layer and waters
Monomethylmercury (MMHg), the most bioavailable form of mercury (Hg) and a potent neurotoxin, is present at elevated concentrations in Arctic marine mammals posing serious health threats to the local populations relying on marine food for their subsistence living. The sources of MMHg in the Arctic Ocean surface water and the role of dimethylmercury (DMHg) as a source of MMHg remain unclear. The objective of this research was to determine the sources and fate of methylated Hg species (MMHg and DMHg) in the marine ecosystem by investigating processes controlling the presence of methylated Hg species in the Arctic Ocean marine boundary layer (MBL) and surface waters. A method based on solid phase adsorption on Bond Elut ENV was developed and successfully used for unprecedented measurement of methylated Hg species in the MBL in Hudson Bay (HB) and the Canadian Arctic Archipelago (CAA). MMHg and DMHg concentrations averaged 2.9 ± 3.6 (mean ± SD) and 3.8 ± 3.1 pg m-3, respectively, and varied significantly among sampling sites. MMHg in the MBL is suspected to be the product of marine DMHg degradation in the atmosphere. MMHg summer (June to September) atmospheric wet deposition rates were estimated to be 188 ± 117.5 ng m-2 and 37 ± 21.7 ng m-2 for HB and CAA, respectively, sustaining MMHg concentrations available for bio-magnification in the pelagic food web. The production and loss of methylated Hg species in surface waters was assessed using enriched stable isotope tracers. MMHg production in surface water was observed from methylation of inorganic Hg (Hg(II)) and, for the first time, from DMHg demethylation with experimentally derived rate constants of 0.92 ± 0.82 x 10-3 d-1 and 0.04 ± 0.02 d-1 respectively. DMHg demethyation rate constant (0.98 ± 0.51 d-1) was higher than that of MMHg (0.35 ± 0.25 d-1). Furthermore, relationships with environmental parameters suggest that methylated Hg species transformations in surface water are mainly biologically driven. We propose that in addition to Hg(II) methylation, the main processes controlling MMHg production in the Arctic Ocean surface waters are DMHg demethylation and deposition of atmospheric MMHg. These results are valuable for a better understanding of the cycle of methylated Hg in the Arctic marine environment. Author Keywords: Arctic Ocean, Atmosphere, Demethylation, Dimethylmercury, Methylation, Monomethylmercury
Demography and habitat selection of Newfoundland caribou
The objective of this thesis is to better understand the demography and habitat selection of Newfoundland caribou. Chapter 1 provides a general introduction of elements of population ecology and behavioural ecology discussed in the thesis. In Chapter 2, I examine the causes of long-term fluctuations among caribou herds. My findings indicate that winter severity and density-dependent degradation of summer range quality offer partial explanations for the observed patterns of population change. In Chapter 3, I investigate the influence of climate, predation and density-dependence on cause-specific neonate survival. I found that when caribou populations are in a period of increase, predation from coyotes and bears is most strongly influenced by the abiotic conditions that precede calving. However, when populations begin to decline, weather conditions during calving also influenced survival. I build on this analysis in Chapter 4 by determining the influence of climate change on the interplay between predation risk and neonate survival. I found that the relative equilibrium between bears and coyotes may not persist in the future as risk from coyotes could increase due to climate change. In Chapter 5, I investigate the relationships in niche overlap between caribou and their predators and how this may influence differential predation risk by affecting encounter rates. For coyotes, seasonal changes in niche overlap mirrored variation in caribou calf risk, but had less association with the rate of encounter with calves. In contrast, changes in niche overlap during the calving season for black bears had little association with these parameters. In Chapter 6, I examine broad-level habitat selection of caribou to study trade-offs between predator avoidance and foraging during the calving season. The results suggest that caribou movements are oriented towards increased access to foraging and the reduction of encounter risk with bears, and to a lesser extent, coyotes. Finally, I synthesize the major findings from this thesis and their relevance to caribou conservation in Chapter 7, to infer that Newfoundland caribou decline is ultimately driven by extrinsic and intrinsic elements related to density-dependence. Reduction in neonate survival emerged from nutritionally-stressed caribou females producing calves with lower survival. Author Keywords: Behavioural ecology, Black bear (Ursus americanus), Coyote (Canis latrans), Population ecology, Predator-prey interactions, Woodland caribou (Rangifer tarandus)
GIS-based Spatial Analysis of Visibility and Movement Using the Ancient Maya Center of Minanha, Belize
It has long been hypothesized the location of the ancient Maya center of Minanha was a strategic one based on its ability to control the flow of communication and key resources between major geopolitical zones. Situated in the Vaca Plateau, at the nexus of the Belize River Valley, the Petén District of Guatemala, and the Maya Mountains, Minanha became a Late Classic polity capital that was tapped into a regional economy as well as long-distance trade networks. In this thesis I present a GIS-based spatial analysis that includes viewshed and cost surface analysis (CSA) to model visibility and movement within the north Vaca Plateau and neighboring regions to address specific questions concerning Minanha's strategic value. The results indicate that Minanha occupied a visually prominent location in proximity to major corridors of movement that suggest it was strategically, and in fact ideally located, as a polity capital with the ability to monitor the movement of people and resources. Author Keywords: Belize, GIS, Least Cost Path, Maya, Minanha, Viewshed

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Graduate student theses produced at Trent University. You may also browse theses and dissertations by year, program, or author.

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