<p>Increased pressure has been placed on researchers to focus on processes at an ecosystem level. However, ecological processes operate at multiple scales from an individual predator up to ocean basin migrations, and research across these scales is extremely difficult. More accurate and detailed understanding of prey distributions relative to physical and biological features can greatly aid in understanding top predator distributions and ultimately ecosystem functioning. High resolution acoustic data is a critical tool that can be used to investigate food web linkages at many spatial scales. At a broad scale, migratory top predators are often modeled relative to oceanographic structure as a proxy for the distribution of their prey. At a fine scale, combining novel technologies including fisheries acoustics, real time oceanographic sensors, and digital tags allows examination of decisions made by an individual foraging whale. In the Gulf of Mexico, fish distributions at fine scales (both horizontal and vertical) were examined relative to hypoxic bottom waters to understand potential ecosystem effects. Forage fish distribution (sand lance, Ammodytes spp.) were measured relative to physical features and oceanographic processes up to the decision making of a top predator, the humpback whale (Megaptera novaeangliae). The effect of geostrophic currents and environmental regimes on the deep scattering layers of the central tropical pacific were examined relative to sightings of marine mammals in the area. Analyses across trophic levels and at multiple scales is an important step towards understanding community ecology and ecosystem processes in pelagic systems.</p> / Dissertation

This dissertation examines some important physiological and pheromonal factors regulating foraging and colony growth in honey bee colonies. The first study analyzed effects of soybean trypsin inhibitor (SBTI) on the development of hypopharyngeal gland, midgut enzyme activity and survival of the honey bee. In this study newly emerged caged bees were fed pollen diets containing three different concentrations of SBTI. Bees fed 1% SBTI had significantly reduced hypopharyngeal gland protein content. This study indicated that nurse bees fed a pollen diet containing at least 1% SBTI would be poor producers of larval food. In the second study nurse bee biosynthesis of brood food was manipulated using SBTI, and the resulting effects on pollen foraging were measured. Experimental colonies were given equal amounts of SBTI treated and untreated pollen. SBTI treatments had significantly lower hypopharyngeal gland protein content than controls. There was no significant difference in the ratio of pollen to non-pollen foragers and pollen load weights collected between the treatments. These results supported the pollen foraging effort predictions generated from the direct independent effects hypothesis. In the third study we tested whether brood pheromone (BP) regulated queen egg laying via modulation of worker-queen interactions and nurse bee rearing behaviors. This experiment had BP and control treatments. Queens in the BP treatment laid greater number of eggs, were fed for a greater amount of time and were less idle. Significantly more time was spent in cell cleaning by the bees in BP treatments. The results suggest that brood pheromone regulated queen egg-laying rate by modulating worker-queen interactions and nurse bee rearing behavior. The final study of this dissertation focused on how dose-dependent BP-mediated division of labor affected the partitioning of non-foraging and foraging work forces and the amount of brood reared. Triple cohort colonies were used and there were three treatments, Low BP, High BP and Control. Low BP treatments had significantly higher ratio of pollen to non-pollen foragers and greater pollen load weights. Low BP treatment bees foraged at a significantly younger age. This study has shown that BP elicits dose-dependent modulation of foraging and brood rearing behaviors.

Brood pheromone of the honey bee, (Apis mellifera) has been shown to elicit a wide array of primer and releaser effects on non‐foragers and foragers leading to the regulation of nursing, pollen foraging, and behavioral development such that the behavior of the colony may be regulated by the amount and condition of the larvae. To date, all studies into the effects of brood pheromone have either used uncharacterized whole extracts or a single blend of brood pheromone characterized from a population of honey bees in France. The variation in the relative proportions of the ten fatty‐acid ester components that characterize brood pheromone and some effects of this variation on pollen foraging and sucrose response thresholds were therefore observed. The objectives met in this dissertation were to determine whether changes in brood pheromone component proportions (blend) or amount communicates larval nutritional status and reports the results of observations of nurses and foragers in response to blends of brood pheromone from deprived and‐non deprived larvae, to measure how changes in brood pheromone blend changed pollen foraging behavior and if such changes could account for the pollen foraging differences between Africanized and European bees, and finally to observe the effects of exposure time on brood pheromone blend and to observe whether non‐foragers made contact with the pheromone. Brood pheromone was found to vary by larval rearing environment, but did not elicit the expected behaviors that would support a cue of nutritional status. Brood pheromone also varied significantly by mitochondrial lineage/population source and responses to brood pheromone appeared to be coadapted to blend, suggesting that brood pheromone may be important in race recognition. Finally, brood pheromone varied significantly over time and was found to be removed from sources by bees, suggesting possible mechanisms for loss of effect. Combined the results of this research indicate that brood pheromone blend differences lead to profound changes in colony behavior related to pollen foraging and food provisioning, providing novel tools for colony manipulation and mechanisms for understanding brood rearing division of labor and chemical communication.

The green turtle, Chelonia mydas, is a circumglobal species that exhibits several important developmental or ontogenetic shifts throughout its life history. The first major shift occurs when juvenile turtles migrate from pelagic habitat, where they forage as omnivores, to coastal neritic habitat, where they become primarily herbivores, foraging on algae and seagrass. Anecdotal evidence and gut-content analyses suggest that juvenile green turtles in south Texas bays, such as the lower Laguna Madre and Aransas Bay, undergo an additional ontogenetic shift during this important life history stage. Evidence from stable isotope analysis (SIA) of scute tissues of green turtles from Texas' lower Laguna Madre and Aransas Bay supports an intermediate stage between this species' shift from pelagic waters to seagrass beds in neritic waters; this additional shift comprises an initial recruitment of post-pelagic juveniles to jetty habitat located on the channel passes Gulf-ward of adjacent bays before subsequently recruiting to seagrass beds in these bays. Examination of stable carbon ([delta]¹³C) and nitrogen ([delta]¹⁵N) isotopes in microlayers of scute tissue from several size classes of green turtles from the lower Laguna Madre and Aransas Bay was used to confirm the occurrence of two ontogenetic shifts. Smaller green turtles (< 35 cm SCL) exhibited more depleted [delta]¹³C signatures and more enriched [delta]¹⁵N signatures, consistent with jetty habitat, compared to those of larger counterparts (> 45 cm SCL) that displayed enriched [delta]¹³C signatures and depleted ¹⁵N signatures, consistent with seagrass habitat. Changes in the isotopic composition between these size classes indicate distinct shifts in diet. Post-pelagic juveniles first recruit to jetty habitat and forage primarily on algae, before subsequently shifting to seagrass beds and foraging primarily on seagrass. These findings indicate the use of a characteristic sequence of distinct habitats by multiple life history stages of green turtles in Texas bays, a conclusion with broad management implications for this endangered species.

Honey bees (Apis mellifera) are the most economically important insect pollinator of agricultural crops in the United States. Honey bee colonies are required for pollination of approximately one-third of the nation’s fruit, vegetable, nut, and forage crops, with an estimated annual value in the billions of dollars. The economic value of a honey bee colony comes from its population size, as large colonies provide the necessary foraging force required for large-scale crop pollination services. A major component of colony strength is its genetic diversity, a consequence of the reproductive mating strategy of the queen known as polyandry. Despite some inherent risks of multiple mating, several studies have demonstrated significant advantages of intracolonial genetic diversity for honey bee colony productivity. Colony-level benefits include better disease resistance, more stable brood nest thermoregulation, and greater colony growth. Instrumental insemination of honey bee queens is a technique to precisely control queen mating, and thereby creates the opportunity to investigate the effects of intracolonial genetic diversity on colony performance. In this dissertation, I first consider the effects of intracolonial genetic diversity on pollen foraging using colonies headed by queens which were instrumentally inseminated with either one or twenty drones to generate colonies of very high or very low intracolonial genetic diversity, respectively. I found that colonies with high intracolonial genetic diversity amass significantly more pollen and rear more brood than colonies with low intracolonial genetic diversity. Of particular interest, colonies with low intracolonial genetic diversity collected a significantly greater variety of pollen types. I discuss these results in the context of scouting and recruiting, and suggest a more efficient foraging strategy exists among genetically diverse colonies. While intracolonial genetic diversity is positively correlated with collected pollen, its effect on the colony’s ability to process and distribute inbound protein resources is unknown. Again using colonies headed by queens instrumentally inseminated with either one or twenty drones, I studied the effects of intracolonial genetic diversity on pollen consumption and digestion by nurse bees, as well as protein allocation among nestmates by assessing total soluble protein concentration of late instar larvae, and total soluble hemolymph protein concentration in both nurses and pollen foragers. I found that nurse bees from colonies with high intracolonial genetic diversity consume and process more protein than nurses from colonies with low intracolonial genetic diversity, even when given equal access to protein resources. Further, both forager hemolymph protein concentrations and larval total protein concentrations were higher among the colonies with high intracolonial genetic diversity. My findings suggest that protein processing and distribution within a honey bee colony is affected by the social context of the hive. I discuss “worker policing”, and the role of nurse bees in modulating the foraging effort. Finally, I assess the standing genetic variability among several colonies sourced from different genetic and geographic locations. Using microsatellite DNA from workers sampled from each colony, I determined allelic richness, gene diversity, and effective mating frequency for each genetic line. I found differences in all three metrics between lines, and for one line in particular, there was no correlation with genetic variation and effective mating frequency, suggesting non-random mating. My results showed very different levels of intracolonial genetic diversity among naturally mated queens. Because of its impact on colony performance, the importance of maintaining genetic diversity in breeding populations is discussed.

Ant colonies are often considered to be a superorganism, exhibiting complex collective behaviors, reproducing at the colony level, and dividing functional roles among groups of workers. For this reason, it is often appropriate to study ant behavior at the colony, rather than the individual, level. In this study, I investigated decision-making and foraging behavior in colonies of several species belonging to the ant community of Sonoran Desert scrub habitat. First, I used laboratory experiments to examine how the spatial structure of Crematogaster torosa colonies changes in response to the availability of temporally stable food sources. I found that in this polydomous species the formation of nests is associated with foraging, but that colonies will build broodless structures called “oustations” regardless of food presence. Next, I examined colony spatial structure of a related polydomous species, Crematogaster opuntiae, in the field. I found that colonies used large foraging territories up to three hectares in size, containing up to twenty nest entrances interconnected by a network of trails. Nest location appeared to be related to foraging, with nests located close to extrafloral nectar-secreting cacti (Ferocactus wislizeni) and a negative relationship between cactus density and territory size. Within colonies, forager behavior on neighboring cacti was not independent at short distances, suggesting that separate plants in this system cannot be treated as independent replicates. In the third chapter, I used an individual-based simulation model to investigate the effects of individual worker behavior on the ability of pheromone-recruiting ant colonies to maintain trails to multiple food sources simultaneously. Interestingly, small changes in the behavior rules used by individuals led to large-scale changes in emergent behaviors at the colony level. Lastly, I used field experiments to relate the ability of colonies of three ant species to maintain multiple trails to their ranking in the community competitive dominance hierarchy. I found that the most dominant species tended to forage asymmetrically, whereas the least dominant species exhibited more symmetrical patterns of foraging. The ability of ant colonies to collectively maintain multiple trails may therefore be an adaptive trait linked to the foraging ecology of species.

Formal models, those which explicitly specify the postulates on which they are based, the development of their 'predictions' from those postulates, and the boundary conditions under which they apply, have the potential to be useful tools in archaeological inference and explanation. Detailed examination of one such model, the mathematical model commonly referred to as the diet breadth or prey choice model, shows that its archaeological application is severely complicated by two factors that are difficult or impossible to specify for prehistoric cases: 1) limits on the amount of meat consumable by a food-sharing group before spoilage or loss to scavengers and 2) hunting failure rates. The former introduce significant uncertainties into the food yield or energetic return term of resource rankings, while the latter affect both resource rankings and the resouce encounter rates leading to prey inclusion or exclusion from the diet. Together, these factors make rigorous diet breadth / prey choice model-based inferences from ungulate archaeofaunas impractical, especially in Paleolithic cases. Following success in recent years in making diet breadth model-based inferences about Paleolithic demography from small game analyses that involved computer simulation modeling of prey species' resilience to hunting pressure, the development and employment of a similar model applied to ungulate species reveals that, in general, the differences in the abilty of populations of different ungulate species to sustain harvest rates are not sufficient to allow the relative representation of ungulate remains in archaeological sites to be a viable basis for human demographic inferences. However, in cases where ungulate remains allow the determination of both prey age structure and sex ratio, it is possible to distinguish low exploitation rates, high exploitation rates, and overhunting. In some cases, the sex ratio data may also alter relative hunting resilience levels in such a way that it may be possible to infer that one species was capable of supporting a larger human population than another.

Behavioural choices of animals as they acquire resources in the wild are well characterized by foraging theory; however, the neural mechanisms underlying these behaviours are not well understood. The goal of this thesis is to understand the brain mechanisms involved in selecting and executing such foraging behaviours. To do so, rhesus monkeys performed a novel visuosaccadic foraging task while we recorded the activity of single neurons in the intermediate layers of the superior colliculus (SCi). An important innovation of this task is that both target profitability – the measure of value in the simplest case of foraging theory – and saccade choice are measured separately. We hypothesized that target profitability is represented in the SCi in addition to its well characterized role in saccade planning and preparation. Visual Foraging Task: Monkeys harvested coloured dots representing prey items by fixating them for a pre-specified handling time. On each trial, multiple prey are presented, sharing identical physical attributes except that each was one of three colours. All prey of the same colour shared the same profitability [Profitability = reward magnitude (ml)/handling time (s)]. According to foraging theory, intake of reward is maximized if prey are selected in descending order of their profitability. Indeed, we found subjects gradually approached optimal efficiency. We computed an index of the relative subjective profitability of each prey colour, which compared the rank order with which monkeys chose prey of each colour. This subjective index of profitability was then compared to concomitant SC activity attributed to the prey item in the neuron’s response field (RF). First, we found that the amount of SC activity reflected the subjective profitability of the RF targets, and established that this effect was not simply a result of saccade goal planning. Second, profitability information remains dominant throughout the handling period until reward delivery, after which activity also became selective for upcoming saccades. Together, our results highlight the prominent role of target profitability in shaping SCi activity. We propose that profitability information in the SCi may play an important role in resolving competition between numerous target representations to choose the next saccade goal. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2011-02-21 15:37:43.468

In tropical forest systems, attine ants are the dominant herbivores. They construct large nest structures that include foraging trails that extend to multiple plant sources throughout the forest. These foraging areas vary from nest to nest and they are highly dynamic over time and season changes. It was expected that characteristics of both the nest structure and the surrounding environment would affect the size of nest foraging areas. In this study, COMPASS survey software and ArcGIS were used to map the foraging trails and calculate the foraging areas of 12 attine ant nests located on the Firestone Reserve, over the course of 6 weeks. Data collected at the ant nest sites on nest area, flow rate, trail number and neighboring nest proximity were combined with data collected from previous studies on soil pH and light fractions in order to test correlation hypotheses between these factors and foraging area. The mean foraging areas differed significantly from each other and significant correlations were found between foraging area and trail number, flow rate, neighbor distance and soil pH. Understanding foraging behavior of attine ants is important in the field of restoration ecology because these ants are important in determining overall structure and nutrient distribution in tropical forests.

Albatross populations are currently in decline around the world. Survival and reproduction of these large pelagic birds depends mostly on the conditions they encounter in their marine environment. Their ability to range far across ocean basins exposes them to a variety of anthropogenic threats. It is thus crucial to understand spatial and temporal patterns in the distribution and habitat use of each albatross species during different stages of their annual cycle in the context of seasonally changing demands as well as environmental constraints, in order to develop effective conservation measures. Using Global Location Sensing (GLS) loggers I investigated the non-breeding movements and habitat associations of three threatened or near-threatened albatross species breeding in New Zealand’s Chatham Islands, the Chatham Albatross (Thalassarche eremita), Northern Buller’s Albatross (T. bulleri platei) and Northern Royal Albatross (Diomedea epomophora sanfordi), within South American waters. Chatham and Northern Buller’s Albatrosses mainly occupied waters with mean sea surface temperatures (SST) of 17-18ºC along the coasts of Chile and Peru, while Northern Royal Albatrosses were mostly found in 10-12ºC waters off southern Chile and Argentina. Monthly movement patterns were linked to seasonal shifts in temperature range, suggesting SST was an important environmental factor in explaining the observed spatial and temporal patterns. GLS loggers were also applied to study the patterns of movement and habitat use of Chatham Albatrosses when migrating across the South Pacific between breeding and non-breeding grounds. The route and timing of migration were consistent over the three year period of the study, although subject to individual variation. Stopovers on migration were found to be common, lasting between 3 and 26 days. Activity patterns suggested that birds stopped in order to forage en route. Lastly, I used high resolution Global Positioning Sensing (GPS) loggers to address the fine-scale movements and habitat selection of foraging Chatham Albatrosses over three years during early chick rearing. This is a time when their behaviour is expected to respond to increased energetic demands as they are feeding young chicks. Foraging trips lasted between 1 and 6 days and the foraging range rarely exceeded 400 km. The location of potential foraging spots varied between years, but followed non-random patterns in bathymetry, slope, SST and Chlorophyll a. The results presented here suggest that albatrosses rely on predictable habitat features but are flexible to respond to fine scale changes within their marine environment. The dynamic nature of both birds and environment may prove challenging but has to be taken into account in conservation planning.