Strategies animals use to find and consume food in the face of conflicting forces such as competition and predation are central questions in the fields of ecological theory and management. Whereas theoretical models abound, proper empirical tests of these theories are less abundant. In studying the relationship between food abundance, predation risk, and competition there exists an array of confounding factors, which need to be accounted for by manipulating some aspect of the system. I used a guild of spring migratory ducks as a model system and manipulated food abundance in areas differing in presumed risk to assess the relative effects of food abundance, predation risk, competition, and life history characteristics on foraging strategies used by ducks. Using a randomized block design, I established a pair of 0.4 ha plots (block) in emergent, open water, and forested wetlands in the Wabash River Floodplain in eastern Illinois. I randomly selected one plot within each block to supplement with 2000 kg/ha of corn (Zea mays), creating an area of very high duck food abundance next to a control area with no added food. I conducted instantaneous focal animal samples and used video recorders to estimate the proportion of time mallard (Anas platyrhynchos), blue-winged teal (Anas discors), wood duck (Aix sponsa), ring-necked duck (Aythya collaris), and lesser scaup (Aythya affinis) devoted to feeding, identify the specific behaviors used, and estimate feeding stint lengths and frequencies. I used these metrics as an index of risk that ducks were willing to engage in for a known food reward. I predicted that species with a faster life history strategy, factors that increase perceived predation risk (cover, water depth, group size), and increase energetic demand (due to nesting or temperature), would elicit more risk-taking behaviors in ducks. This would be realized by an increase in the proportion of time spent feeding, longer feeding durations, and deeper feeding behaviors in treatment plots compared with control plots. Consistent with my life history prediction, species with a faster life history strategy were willing to engage in more risky behavior (feeding more) for a greater food reward (food treatment). Mallards, lesser scaup, and wood ducks exhibited risk-taking behavior consistent with perceived predation risk. Mallards devoted more time to feeding and used longer feeding stints when in areas with less cover. Alternatively, lesser scaup devoted more time to feeding when in areas of more cover. Wood ducks devoted more time to feeding in treatment plots, when in shallow areas, and larger flocks. When blue-winged teal fed on the surface (eyes above water), they devoted more overall time to feeding indicating that surface feeding is less risky than deeper feeding. Wood ducks and lesser scaup exhibited behavior consistent with an increase in energetic demand as observed by an increase in the proportion of time devoted to feeding later in the spring. I also examined how food abundance influenced aspects of ducks' foraging niches. I found that dabbling ducks used a greater variety of behaviors (behavior niche breadth) when in treatment plots compared to control plots and also shifted to slightly deeper feeding behaviors in treatment plots. This greater breadth when food was more abundant was due to individuals of the same species diverging from one another, rather than each individual using a broader array of behaviors. Overall, I found substantial variability among and within species in how they manage risk while foraging, although this was partially explained by life history theory, and what types of conditions they perceive as risky. I document the importance of taking the state of the forager (life history, perceived risk, energetic demand) into account when examining patterns of risk-taking.

xvii, 141 p. : ill. / Territoriality, defined as an animal or group of animals defending an area, is thought to have evolved as a means to acquire limited resources such as food, nest sites, or mates. Most studies of territoriality have focused on vertebrates, which have large territories and even larger home ranges. While there are many models used to examine territories and territorial interactions, testing the models is limited by the logistics of working with the typical model organisms, vertebrates, and their large territories. An ideal organism for the experimental examination of territoriality would exhibit clear territorial behavior in the field and laboratory, would be easy to maintain in the laboratory, defend a small territory, and have movements and social interactions that were easily followed. Lottia gigantea , the owl limpet, is just such a model animal. With a small territory (< 900 cm 2 ) and slow movements (3 mm/min), the interactions of several L. gigantea can be continuously and simultaneously monitored. Using time-lapse photography, experiments were conducted to observe behaviors of L. gigantea , ranging from how L. gigantea form home ranges to how territorial L. gigantea interact. Lottia gigantea formed home ranges within four weeks, returning to a home scar after each foraging cycle. To determine whether L. gigantea returned to areas with greater food resources, three different algal density treatments were used, and individuals were monitored to see which tiles they frequented the most. Lottia gigantea actually avoided areas with a thick algal covering, potentially due to the loss of suction they experienced while moving across algae. When L. gigantea established territories, home ranges overlapped considerably. Two individuals were placed in one arena, under the assumption that a dominance hierarchy would be established. Dominant status was predetermined, and in four of the seven dyads both individuals were evasive. When subjected to territorial encounters for two weeks, L. gigantea avoided areas where they experienced agonistic losses. Mucus may serve as an olfactory cue to define territorial boundaries. Individuals avoided tiles with conspecific's mucus more often than tiles with self-mucus or no mucus. / Committee in charge: Barbara (“Bitty”) Roy, Chairperson; Alan Shanks, Advisor; Craig Young, Member; Mark Hixon, Member; Frances White, Outside Member

Abstract In this thesis, I examine two important aspects surrounding salmonid reproductive ecology, namely: (i) the problems with passing obstructions during migratory spawning runs and (ii) how the early life stages in boreal streams are influenced by increased levels of fine-grained particulate matter from drained peatlands. These aspects are not only critical to salmonid reproductive success but have grave implications regarding environmental quality and species conservation. Spawning runs can be re-established by constructing fishways at obstructions but the efficiency of fishways depends on several factors. The passage of multi-sea-winter salmon was enhanced in the Isohaara fishway by increasing its water flow and by creating a small waterfall at the entrance. The fishway, which consists of vertical slot and Denil sections, proved to be unsuitable for most freshwater fish, whitefish and river lamprey, whereas salmonids, once they had entered, successfully negotiated the fishway. In fishway design, the migratory behaviour and the demands of the species of interest should be considered. For salmonids, priority should be given to the attractiveness of the fish entrance. When there is a migration corridor, the availability and the quality of spawning and rearing habitats has a major effect on the success of restoration projects. In the humic rivers studied, the survival of incubated brown trout eggs was lower in riffles susceptible to increased levels of fine-grained particulate matter from drained peatlands. Additionally, an increase in the Fe content of high molecular weight dissolved organic matter followed by its precipitation and sedimentation was proposed to be involved. Correspondingly, the recapture rates of stocked yearling salmon were lower in the affected riffles, individual salmon being smaller and thinner and having less food in their stomachs than reference salmon. Based on these results, it seems probable that peatland drainage, by influencing the incubation success of salmonid embryos and the foraging, growth and survival of juveniles, eventually affects the number and quality of smolts produced. In future, such water pollution control measures should be implemented that would enhance the success of natural spawning and help ensure environmental quality.

Fathead minnows (Pimephales promelas) were exposed to mercury (1.69, 6.79, and 13. 57 µg/l HgCl2; 10 d exposure) and afterwards tested using various metrics of foraging ability while feeding in a vegetated habitat. Among the foraging metrics were foraging efficiency, capture speed, and the ability to learn and retain information regarding habitat characteristics. Comparisons with control fish and fish from the two highest exposure groups revealed consistent performance deficits in foraging efficiency and capture speed. However, no treatment effects on learning were detected. In determining the underlying proximate cause of the foraging deficits, it is believed that the greater pause time exhibited by treatment fish while foraging was the main cause of treatment differences. In the future, behavioral studies will continue to allow toxicity testing of environmentally relevant variables such as those used by behavioral ecologists. Such tests, when combined with tests of field collected specimens, could prove powerful in linking laboratory toxicity to toxicity in wild populations. / Master of Science

Locomotion is central to the survival of many animal species; however large variation in performance, for example in speed or endurance, exists between individuals within a species. Using the bumblebee species, Bombus impatiens, I studied the extent of the variation in several flight performance traits and how they are associated. I first addressed how bumblebee workers vary in foraging effort and observed that only around half of the monitored individuals underwent foraging activity. Additionally, significant variation in metabolic rate between foragers and non-foragers was uncovered. I further investigated if such variation could be associated with flight performance capacity, such as an individual’s ability to carry a load, their flight speed and distance traveled, their wing morphology and kinematics, and their flight metabolic rate. These traits are commonly measured to characterize flight capacity in insects, however the links between them have yet to be investigated. Links between morphology, wing kinematics and peak metabolic rate previously uncovered in the literature were observed in my analysis, although variation in their scaling with body mass was detected. Vertical force scaled isometrically with body mass but was not related to it when expressed in on a mass specific basis (VF m-1g-1, where m is gravitation acceleration). In regard to forward flight speed, body mass does have an affect, however it alone does not have a great degree of explanatory power and other factors such as morphology and wing kinematics are likely to play a greater part in its determination. Finally, maximum flight speed had a significant relationship with total flight time. Together, these results demonstrate that some links do exist between flight performance traits, however links are not present between all traits and certain flight performance traits should be treated as independent of each other.

The nutritional ecology of the black carpenter ant, Camponotus pennsylvanicus (De Geer) was investigated by examining macronutrient preference and particle consumption in foraging workers. The crops of foragers collected in the field were analyzed for macronutrient content at two-week intervals through the active season. Choice tests were conducted at similar intervals during the active season to determine preference within and between macronutrient groups. Isolated individuals and small social groups were fed fluorescent microspheres in the laboratory to establish the fate of particles ingested by workers of both castes. Under natural conditions, foragers chiefly collected carbohydrate and nitrogenous material. Carbohydrate predominated in the crop and consisted largely of simple sugars. A small amount of glycogen was present. Carbohydrate levels did not vary with time. Lipid levels in the crop were quite low. The level of nitrogen compounds in the crop was approximately half that of carbohydrate, and exhibited seasonal dependence. Peaks in nitrogen foraging occurred in June and September, months associated with the completion of brood rearing in Camponotus. In choice tests, foragers demonstrated a preference for sucrose, fructose, and glucose, the most common honeydew sugars. Sucrose was preferred over other sugars in laboratory and field tests. Consumption rates peaked at a concentration of 20%. Casein hydrolysate and processed fish products stimulated the most feeding in choice tests of protein foods. Though a variety of lipids of plant and animal origin were offered in both field and laboratory tests, they were generally ignored. No effect of time was observed during choice tests of macronutrient preference. Overall, nitrogenous food was collected four-fold more intensively than carbohydrate, in contrast to the results obtained from examinations of the crop contents. These data suggest that accessible nitrogen is limited in the environment. Workers readily consumed fluorescent microspheres 0.5 - 45 μm diameter. Forty-five μm microspheres were excluded from the crop. Particles 3 - 10 μm reached the crop, but were never seen in the mid- or hindguts of either major or minor workers. They also filled the infrabuccal pocket, where they were compacted into pellets. It is thought that the proventriculus contains such particles in the foregut, where they are eventually filtered from the ingluvium. Microspheres 1 μm or less were difficult to observe in the infrabuccal pocket, suggesting that they are not as effectively sequestered as larger particles. Microspheres smaller than 1 μm were seen in the mid- and hindgut of both worker castes, indicating that particles of this size are immune to the proventricular filter. Caste exerted an effect at one μm diameter, the threshold of filtering efficiency. One μm microspheres consumed by minor workers were detected in the mid- and hindgut, whereas one μm microspheres were never detected beyond the proventriculus in major workers. / Ph. D.

Most studies of foraging behavior in bees have been performed under artificial conditions. One highly neglected area is the daily nectar secretion rhythm in flowers including how nectar properties may vary with time of day. As a first step in understanding the connections between forager behavior and nectar presentation under more natural conditions, we examined nectar secretion patterns in flowers of the squash Cucurbita pepo. Under greenhouse conditions, squash flowers exhibit consistent diel changes in nectar volume and concentration through anthesis. These temporal patterns are robust, persisting under field conditions as well as simulated drought conditions in the greenhouse. In the presence of active pollinators, diel patterns are evident but with highly variable, severely reduced volumes. The potential consequences of these factors for pollinator behavior are discussed.

Foraging behavior has recently become a popular area of research with which ethologists, behavioral ecologists, and experimental psychologists converge their traditionally separate disciplines into a more multidisciplinary framework. Ethologists and behavioral ecologists usually study foraging as it occurs in the natural environment or the "field," while experimental psychologists contrive laboratory simulations of foraging and make the assumption, sometimes incorrectly, that generalization occurs across settings, situations, and species. Scientific advances are now beginning to occur in the ability of laboratory researchers to better simulate foraging as it occurs in the field. Field researchers are also becoming more willing to accept these findings as important. The purpose of this dissertation was to use a laboratory analogue of foraging behavior to examine the effects of prey vulnerability, density, and prey-patch replenishment on the number of prey rejections and switches between patches. This analogue may have more biological validity than previous simulations in the operant laboratory by simulating conditions of replenishing and depleting patches under adjusting (progressive and regressive) random-ratio schedules of reinforcement. Three experiments were conducted. The first examined the effects of response-cost on acceptability of prey items offered. Results indicated that as the cost of obtaining one prey item increased while the cost of another was held constant, subjects consistently pursued the lower-cost prey and rejected higher-cost prey at increasing probability ratios of 1:3, 1:10, and 1:15. The second experiment covaried response cost (vulnerability) with the probability of encounter (density) for two prey types and evaluated their effects on the acceptability of prey. This experiment showed that when the density of the low-cost prey increased (p = .66), the subjects were more selective. Subjects were less selective when the density of the low-cost prey decreased (p = .33). In the third experiment, prey patches were replenished at reinforcer-determined (regressive random ratio) baseline rates and compared to several fixed-time schedules of patch replenishment. Results of Experiment III indicated no major differences in patch use behaviors (number of switches between patches). The validity and utility of this simulation was discussed as a useful model for the experimental analysis of foraging behavior.

Two experiments were conducted to investigate the hypothesis that exotic macrophytes alter littoral zone habitat and impact fish that inhabit these areas. The pond experiment was conducted to explore impacts of exotic invasive plants on growth and condition of juvenile largemouth bass (Micropterus salmoides). The second experiment was conducted at a smaller scale in aquaria to simulate an invasion of hydrilla (Hydrilla verticillata) and its influence on juvenile bass foraging. Fish experienced slower growth in the hydrilla treatment than in the diverse, and the ability of bass to capture prey fish was impeded in hydrilla. Juvenile bass growth decreased in habitats containing hydrilla and is likely a result of increased difficulty in capturing quality prey items such as small fish. Results from the two experiments collectively supported my hypothesis that hydrilla growth altered the littoral zone habitat such that foraging was hindered and resulted in slower growth.

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