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Smiley-Walters, Sarah AnnInteractions between Pigmy Rattlesnakes (Sistrurus miliarius) and a Suite of Prey Species: A Study of Prey Behavior and Variable Venom Toxicity
Doctor of Philosophy, The Ohio State University, 2017, Evolution, Ecology and Organismal Biology
Interactions between predators and prey are widespread in nature but the ecological and evolutionary factors that shape these interactions are poorly understood. In my dissertation, I use pigmy rattlesnakes (Sistrurus miliarius) and their prey as a system in which to examine several aspects of this species interaction where different ecological and evolutionary factors may be shaping variation in adaptive traits. In Chapter 1, I review factors affecting predator-prey interactions and explain why the pigmy rattlesnake system is valuable for addressing important research questions. In Chapter 2, I present research on the behavioral component of this interaction, demonstrating that native cotton mice do not change their foraging behavior in the presence of a sit-and-wait rattlesnake predator. In Chapter 3, I explore the toxicity of venom to native prey versus non-native "models" to determine to what extent non-native species are representative of prey in the same broad taxonomic group. I show that native prey have higher resistance to venom than non-natives and encourage the use of native prey in future toxicity work. In Chapter 4, I use native treefrog prey from two different populations in Florida and venom from snakes in the same populations to see if there is a signal of local adaptation present in these populations. I show that detection of a signal of local adaptation depends on the measure of venom function used: evidence for local adaptation was observed in the time to death measure of mortality but not in the 24 hour mortality measure. In Chapter 5, I look at the function of venom at a smaller scale by exploring the amount of functional variation present across and within populations of snakes using a lizard model prey. I found the individual component of venom toxicity to be larger than the population-level differences that have been the focus of previous research. Overall, this dissertation demonstrates that rattlesnake venom function differs at both the individual and population scale and that toxicity is relative, depending on the specific prey species tested.

Committee:

H. Lisle Gibbs, Ph.D. (Advisor); Ian Hamilton, Ph.D. (Committee Member); Thomas Hetherington, Ph.D. (Committee Member); Stuart Ludsin, Ph.D. (Committee Member)

Subjects:

Animals; Behavioral Sciences; Biology; Ecology; Evolution and Development; Toxicology; Zoology

Keywords:

predator-prey; venomous snakes; LD50; Peromyscus gossypinus; Hyla squirella; Anolis sagrei; adaptive traits; local adaptation; giving-up density; rodent foraging; individual variation

Wyza, Eileen M.Human Impact on Space Use, Activity Patterns, and Prey Abundance of Madagascar's Largest Natural Predator, Cryptoprocta ferox
Master of Science (MS), Ohio University, 2017, Environmental Studies (Voinovich)
Madagascar is home to a broad array of intriguing, endemic, and increasingly endangered species. The fosa (Cryptoprocta ferox) is the largest living (non-introduced) mammalian carnivore on the island and is considered a keystone species for maintaining ecosystem complexity in a broad range of Madagascar’s forested habitats. Sadly, the fosa is threatened, with viable populations remaining in only two protected areas. In this context, complex interactions among fosa, prey, and myriad introduced species, reveal a dynamic that is increasingly sensitive to human pressures (e.g., hunting, deforestation for agriculture and fuel wood). This project assembles detailed geographic information to augment long-term data collection and help inform the fosa conservation effort. Research was conducted in Ankarafantsika National Park, a dry deciduous forest in the northwest region of the country, and one of the two places where viable fosa populations still exist. Species encounters and trap rates, roadkill patterns, and the spatial and activity patterns of GPS-collared fosas were analyzed to gather a comprehensive assessment on habitat pressures experienced by the fosa. Species encounter and trap rates documented a shift in prey item encounters over time. Roadkill surveys, together with the roadkill death of one of the GPS-collared study animals, demonstrated failure of current mitigation efforts in addressing roadkill dangers. Fosa space use and activity patterns clearly reveal that they rely almost exclusively upon forested habitats, and that they avoid human settlements. Interestingly, although fosa do rely heavily on forest habitat, their ability to use forest edges and narrow forested strips suggests that corridors may be a viable method to enhance habitat connectivity and promote positive conservation outcomes.

Committee:

Nancy Stevens (Advisor); Geoffrey Dabelko (Committee Member); Viorel Popescu (Committee Member)

Subjects:

Environmental Studies; Wildlife Conservation

Keywords:

fosa; cryptoprocta ferox; home range; gps; radiotrack; habitat; activity pattern; fossa; space use; Ankarafantsika; Madagascar; prey; roadkill; speed bumps

Malpass, Jennifer SEffects of food and vegetation on breeding birds and nest predators in the suburban matrix
Doctor of Philosophy, The Ohio State University, 2015, Environment and Natural Resources
The expansion of urbanization globally has prompted scientists to examine the effects of human developments on wildlife communities, often using birds as a focal taxa. My research investigates population and community-level consequences of anthropogenic food and vegetation resources in the suburban matrix, focusing on breeding birds and their nest predators. I combine observational and experimental approaches to test how anthropogenic subsidies and habitat modification affect avian population demography and predator-prey interactions, and compare these patterns between developed (i.e. residential yards) versus undeveloped (i.e. forested parks) areas within suburban landscapes. During April- August 2011-2014, I examined resource availability, and nest predators, and nest survival of two common birds (American robin, Turdus migratorius and northern cardinal, Cardinalis cardinalis) in seven suburban neighborhoods in the Columbus, Ohio metropolitan area. For the first component of my work, I evaluated demographic differences of robins and cardinals breeding in riparian forest parks and adjacent residential neighborhoods and tested if nest predation was higher in yards. Both robins and cardinals experienced similar nest survival rates in residential yards and forest parks, but there were clear differences in which species were responsible for depredation events. Specifically, domestic cats (Felis catus) were over 5x as frequently documented depredating cardinal nests in yards versus forest parks. For the second component of my work, I tested the hypothesis that wildlife-friendly gardening programs that promote planting trees and shrubs (i.e. increasing woody cover) have the unintended consequence of attracting predators of avian nests by examined relationships between woody cover and diurnal activity patterns of nest predators. Predator activity varied widely among individual yards, but contrary to my hypothesis, the availability of woody cover at either yard or neighborhood scales was not a strong predictor of diurnal activity of five common nest predators. For the third component of my work, I used observational and experimental approaches to investigate how the most common anthropogenic food subsidy, bird feeders, affected predator-prey dynamics in between birds and nest predators in yards. Bird feeders were positively associated with diurnal activity of two nest predators, but the relationship among birdfeeders, nest predators, and nest survival was complex. Nest survival for robins declined with increasing number of bird feeders but only where American crows (Corvus brachyrhynchos) were most frequently detected. For cardinals, nest survival rates showed no association with either feeder availability or predator activity. For the final component of my work, I examined the extent to which nest sites in the residential matrix may offer protection from predation by testing the ability of vegetation characteristics of nest sites and features unique to the urban environment (i.e. roads, buildings, and anthropogenic foods) to predict nest survival. I found that nest site characteristics failed to predict nest survival for cardinals and height was the only significant predictor of robin nest survival. I suggest that the lack of relationship between nest site characteristics and nest fate stem from a diverse predator community that effectively precludes any nest site from being predictably safe for birds breeding in the suburban matrix.

Committee:

Stephen Matthews (Advisor); Amanda Rodewald (Advisor); Stanley Gehrt (Committee Member); Jeremy Bruskotter (Committee Member)

Subjects:

Ecology; Environmental Science; Wildlife Conservation; Wildlife Management

Keywords:

urban ecology; nesting success; predator-prey dynamics; species interactions; anthropogenic resources; subsidies; suburban; nest predators

Kennedy, Sara IWhite-tailed Deer (Odocoileus virginianus) Fawn Survival and Seasonal Movement Patterns of White-tailed Deer and Coyotes (Canis latrans) in the Cleveland Metropolitan Area
Master of Science, The Ohio State University, 2015, Environment and Natural Resources
White-tailed deer (Odocoileus virginianus) and coyotes (Canis latrans) are challenging wildlife species to manage in urban areas. Deer often reach densities which exceed cultural and ecological carrying capacities. Varied public opinions of both species present additional challenges. Cleveland Metroparks implements a population model to guide management efforts to reduce deer densities. However, two elements of the model lacking reliable estimates are fawn survival and migration across park boundaries. Also, the influence of coyotes on deer dynamics is unknown for urban systems. To develop better estimates of survival and habitat use and to understand the coyote-deer relationship, we conducted a multi-year study to quantify coyote and doe movement and fawn survival. Six coyotes were collared with GPS transmitters. Twenty-nine adult deer were captured; seven pregnant does received a radio collar and vaginal implant transmitter. Fifty-seven neonatal fawns were captured and fitted with expandable radio collars. We recorded 22 fawn mortalities. Vehicle strikes and culling were the most common causes of mortality. Average six month survival was 78%. Factors with the potential to influence fawn survival were modeled using known-fate models in Program Mark in a two-step process, first incorporating intrinsic covariates and then adding spatial and habitat covariates to the best-supported model from the first step. The best supported models varied with the time period of the analysis, but all included age class. Additional covariates included in one or more top models included habitat composition, home range size, and road density. Habitat use and selection were examined on a seasonal basis. For does, location data was divided into pre-parturition and post-parturition. Fawn locations were examined at three age classes: birth to two weeks, two to eight weeks, and older than eight weeks. Coyote locations were classified into three periods of differing levels of fawn vulnerability: pre-fawn (March – April), hiding (May – June), and fleeing (July – August). For coyotes, we calculated overlap indices between seasonal home ranges and core use areas. Both does and fawns used natural habitat out of proportion with availability. Both showed little seasonal change in habitat use or selection, although some does increased their use of open habitat post-parturition. Habitat use by fawns showed more variation between individuals than between seasons. Coyotes showed substantial individual variation in all spatial metrics, but a majority increased their use of forested habitat during the hiding period. Seasonal overlap indices varied from 6.2% to 82.5% for home ranges and from 0.0% to 42.9% for core use areas. Improved estimates of population parameters for urban white-tailed deer can aid in management of this potentially overabundant species. Our work demonstrates that fawn survival can be high in urban areas and reinforces the link between urban parkland and surrounding residential areas for managing urban wildlife.

Committee:

Stanley Gehrt (Advisor); Jeremy Bruskotter (Committee Member); Stephen Matthews (Committee Member); Terry Robison (Committee Member)

Subjects:

Animals; Biology; Ecology; Natural Resource Management; Wildlife Conservation; Wildlife Management

Keywords:

white-tailed deer, Odocoileus virginianus, coyote, Canis latrans, urban ecology, fawn survival, spatial ecology, predator-prey, ecology of fear

Schmidt, Jason M.Adaptive Foraging in a Generalist Predator: Implications of Habitat Structure, Density, Prey Availability and Nutrients
Doctor of Philosophy, Miami University, 2011, Ecology, Evolution and Environmental Biology
Adaptive foraging is a recent theoretical synthesis linking foraging decisions to the structure and functioning of ecological communities. However, empirical research is required to characterize the consequences of different environmental challenges on organisms foraging behavior. The goal of this dissertation was to explore ecological factors that are responsible for variation in the foraging behavior of a common generalist predator, the wolf spider Pardosa milvina. I conducted four studies to investigate aspects of the adaptive foraging framework, space use and prey selection. I first explored the how habitat structure affects density and foraging ability. Spiders preferred areas containing more structural features, but contrary to predictions, they preferred patches low in prey. Foraging rate was reduced by some habitat features, and habitat structure lowered interference levels between spiders. I examined the role of prey abundance and predator abundance on interference determined by changes in patch leaving frequency and in their functional response. While prey abundance had strong effects on the tendency to leave patches, indicating the importance of prey to predator patch use, increasing the abundance of predators led to increased dispersal rates and interference. I used a two-pronged approach to understanding prey selection in this spider. In one set of experiments I measured changes in consumption of a target prey group in the field using a molecular probe. Although there was variation in the proportion of spiders testing positive for prey, the consumption of prey did not follow strict frequency dependence expected for generalist species. In a second set of experiments I tested for one prey characteristic, nutrient quality, to help explain predation rate and prey choice. The functional response of spiders to different prey nutrient compositions was comparable, but when spiders were fed on a prior nutrient enhanced diet, spiders killed a significantly greater number of prey over densities of prey offered. Prior diets also influenced prey choice. Taken together, these results paint this predator as an adaptive forager that makes foraging decisions based on multiple stimuli in the environment.

Committee:

Ann Rypstra (Advisor); A. John Bailer (Committee Member); Alan Cady (Committee Member); Thomas Crist (Committee Member); Michael Vanni (Committee Member)

Subjects:

Ecology

Keywords:

agroecosystem; C:N; density dependent interactions; ELISA; functional response; interference; habitat selection; food-webs; model selection; molecular analysis; prey selection; refuge; space use; spiders

Pavlic, Theodore P.Optimal Foraging Theory Revisited
Master of Science, The Ohio State University, 2007, Electrical Engineering
Optimal foraging theory explains adaptation via natural selection through quantitative models. Behaviors that are most likely to be favored by natural selection can be predicted by maximizing functions representing Darwinian fitness. Optimization has natural applications in engineering, and so this approach can also be used to design behaviors of engineered agents. In this thesis, we generalize ideas from optimal foraging theory to allow for its easy application to engineering design. By extending standard models and suggesting new value functions of interest, we enhance the analytical efficacy of optimal foraging theory and suggest possible optimality reasons for previously unexplained behaviors observed in nature. Finally, we develop a procedure for maximizing a class of optimization functions relevant to our general model. As designing strategies to maximize returns in a stochastic environment is effectively an optimal portfolio problem, our methods are influenced by results from modern and post-modern portfolio theory. We suggest that optimal foraging theory could benefit by injecting updated concepts from these economic areas.

Committee:

Kevin Passino (Advisor)

Keywords:

robotics; automation; autonomous vehicles; behavior; behavioral ecology; intelligent control; portfolio theory; modern portfolio theory; MPT; post-modern portfolio theory; PMPT; optimal foraging theory; OFT; optimal diet selection; predator; prey

Holding, Matthew LandonEvolution of Rattlesnake Venom involves Geographically Structured Coevolution and Local Adaptation to Prey
Doctor of Philosophy, The Ohio State University, 2017, Evolution, Ecology and Organismal Biology
Predators and prey coevolve to produce some of the most fascinating phenotypic characteristics of animals. However, coevolution is not a simple race toward the most extreme traits. The occurrence, strength, and outcomes of coevolution are hypothesized to be determined by multiple factors; some are environmental and others are intrinsic to the species involved. Although this complexity has been recognized and studied in fast-evolving hosts-parasite systems, testing the key predictions of coevolutionary theory in natural populations of predators and prey has remained a difficult task. I evaluated the effects of two key factors that impact coevolving rattlesnake venom and ground squirrel venom resistance–mechanisms of interaction and population demography–and I provide evidence that the broader composition of the small mammal prey community exerts selection on the venom phenotype as well. Toward this end, I collected Northern Pacific rattlesnake (Crotalus oreganus) venom and California ground squirrel (Otospermophilus beecheyi) blood serum (which contains venom inhibitors) from multiple populations in California where California ground squirrels have evolved resistance to the venom. I developed an experiment to test for population-level adaptation of venom metalloproteinases in their interaction with ground squirrel venom inhibitors. I demonstrated local adaptation in a snake-prey relationship for the first time, where venom metalloproteinase enzymes have evolved to overcome ground squirrel resistance. Furthermore, the existence of local adaptation in these biochemical traits suggests that the mechanism of coevolution involving venom is not an escalating arms race as previously thought, but rather a phenotype matching-based interaction involving a molecular lock-and-key mechanism between multiple snake venom proteins and prey inhibitor molecules. The high levels of medically-significant intraspecific venom variation seen in snakes must now be also viewed in terms of a geographic mosaic of molecular coevolution with resistant prey species, and not merely in terms of broad scale variation in the prey species consumed. Yet, the extent that each population of snakes is adapted to local squirrels varied, and two demographic factors, population size and the relative amount of gene flow in each species, are predicted to explain this variation. I generated thousands of DNA-based SNP loci for both rattlesnakes and squirrels using RAD-seq to test the prediction that rattlesnakes, as the locally adapted interacting species, will have higher effective population sizes and less gene flow than ground squirrels, facilitating the adaption of the snakes over squirrels. Using coalescent-based population genetic analysis, I supported the prediction that the difference in effective population sizes between rattlesnakes and ground squirrels is positively associated with the population-specific signals of local adaptation. This work represents the first analysis of theoretically-predicted impacts of demography on coevolution outside of a host-parasite system, and the first quantitative demonstration of a relationship between effective population size and local adaptation in any coevolving system in nature. Finally, ground squirrels are present at every site I sampled, while the broader mammalian prey community differs substantially. To understand the potential importance of prey community variation in venom divergence among populations, I measured quantitative differences in the venom protein expression profiles of each population. Both population genetic differentiation based on RADseq loci and differences in the prey community combine to predict over 70% of the between-population variation in venom, thus supporting a role for the prey community in driving divergence and suggests that isolation by environment in the heterogeneous landscape of California may drive correlated levels of population genetic differentiation and adaptive divergence in venom composition. Overall, my work will help in understanding how diverse evolutionary and ecological factors influence the coevolutionary process to produce the planet’s diversity of species and their traits.

Committee:

H. Lisle Gibbs (Advisor); Marymegan Daly (Committee Member); Bryan Carstens (Committee Member); Stuart Ludsin (Committee Member)

Subjects:

Biology; Evolution and Development; Genetics

Keywords:

Evolution of Rattlesnake Venom; Geographically Structured Coevolution; Local Adaptation to Prey

Jurcak, Ana MDefining the reaction space of predator-prey interactions
Doctor of Philosophy (Ph.D.), Bowling Green State University, 2018, Biological Sciences
This dissertation contributed to the call for a greater comprehension of sensory ecology within predator-prey interactions, particularly in the non-consumptive effects (NCEs) of predators. I investigated how stimulus modality, predator movement, environmental transmission, prey sensory ecology, pollution, and the interaction of these factors modify prey behavioral responses to predators. Specifically, I experimentally tested three research questions: 1) how the reaction space of predators with different hunting modes in different flow environments altered prey behavior, 2) how modulating signal intensity and prey detection thresholds altered the reaction space, and 3) how the exposure to anthropogenic chemicals altered the reaction space of prey. First, I placed prey (crayfish) in two different environments (flow and no flow) in one of three predator treatments (active predator [bass], sit-and-wait predator [catfish], no predator) and monitored the behavior of the crayfish in a resource patchy environment. Predator hunting mode changed prey behavior, but only in flowing water that would enhance the transmission of predator cues. The most significant interaction between predator treatment and flow environment was found with the active predator in flowing habitats, but this same interaction did not alter NCEs from a sit-and-wait predator. Second, I exposed virile and rusty crayfish to low, medium, or high concentration of odor from largemouth bass and to controls without bass odor and monitored crayfish. The results showed that the behavior of virile crayfish was significantly altered across concentrations more than rusty crayfish, indicating that the virile crayfish may have larger reaction space. Finally, I exposed virile and rusty crayfish to a pesticide (carbaryl) then placed the crayfish in a two-choice flume containing predator odor and clean river water to monitor their behavior. I found that the exposure to a carbaryl did not affect the anti-predator behavior of either species. The findings show that each factor of the reaction space is important in understanding and altering NCEs of predators. Additionally, NCEs may be hidden unless the interaction of factors is taken into consideration. Investigating the sensory environment of predator-prey interactions is crucial for better understanding the mechanisms driving the NCEs of predators and their consequences.

Committee:

Paul Moore (Advisor); Emily Freeman Brown (Committee Member); Jeffrey Miner (Committee Member); Shannon Pelini (Committee Member); Delbert Smee (Committee Member)

Subjects:

Biology

Keywords:

reaction space; predator-prey; NCEs;

Clark, JessicaThe Sensory Mechanisms of Crayfish (Orconectes rusticus) Used in Detecting Predatory Threats
Master of Science (MS), Bowling Green State University, 2017, Biological Sciences
Organisms are exposed to numerous environmental stimuli in which they must be able to distinguish threats from food sources. In order to make such distinctions, organisms rely upon sensory mechanisms, including chemoreception, vision, and mechanoreception. With the reception of chemical, visual, and/or mechanical cues prey species can determine the location, size, and movement of a nearby predator. Then, with the information gathered, prey can determine the severity of the threat and respond accordingly, whether to flee or to display a defensive stance. Various studies suggest that several aquatic species, including crayfish, rely on the integration of sensory modalities to accurately assess predatory threats. This study aimed to determine whether a hierarchy in the reliance upon sensory modalities exists in crayfish (Orconectes rusticus) and if this hierarchy is altered across different sensory environments (such as flowing and non-flowing environments). We also sought to determine the significance of sensory multimodality in crayfish. To study the relevance of each of the sensory modalities, as well as the integration of these modalities, in crayfish combinations of lesions/blocks were conducted. Two sensory mechanisms (chemical and mechanical, chemical and visual, or visual and mechanical) were lesioned/blocked at once, leaving one sensory mechanism (vision, mechanoreception, or chemoreception) functional. Each of the crayfish were then exposed to a predatory largemouth bass (Micropterus salmoides) in either a flowing or non-flowing stream where their behavior was recorded for 30 minutes. The behaviors and movements of the crayfish were then analyzed with the use of Ethovison Noldus XT. Linear mixed models were then conducted to determine the impact of the lesions, flowing environments, and the combination of iv the lesions and flowing environments on the ability of crayfish to detect predatory stimulus. Significant Least Squares Means (LSM) test were followed by Type II Wald Chisquare tests. Results from this study support the significance of sensory multimodality in crayfish for accurately detecting and assessing predatory threats. When the sensory multimodality of crayfish was eliminated the animals were challenged to successfully assess the severity of the predator. Crayfish with only the full use of chemoreceptors or mechanoreceptors showed a greater avoidance of the predator, indicating that these individuals could detect the threat but could not accurately locate the source. Results from this study also suggest that a hierarchy in the reliance upon sensory modalities does exist in crayfish, with a bias towards chemoreception, followed by mechanoreception, and finally vision.

Committee:

Paul Moore (Advisor); Jeffrey Miner (Committee Member); Daniel Wiegmann (Committee Member)

Subjects:

Aquatic Sciences; Behavioral Sciences; Biology; Ecology

Keywords:

sensory modalities; multimodality; sensory hierarchy; crayfish;predator-prey interactions; nonconsumptive effects

Shortridge, Megan GDiet Analysis of Maumee River Fishes using Cytochrome C Oxidase (COI) DNA Metabarcoding ― Insights into a Critical Time of Year
Master of Science (MS), Bowling Green State University, 2016, Biological Sciences
In recent years, DNA barcoding, the sequencing of a common marker region for taxonomic identification, has become integrated into U.S. agency protocols and procedures. Chapter 1 provides an overview of areas where DNA barcoding is currently being used by U.S. agencies to address questions of management concern; the benefits and limitations of using barcoding in an agency setting are considered, as well as how the technology may evolve in the near future. A diet metabarcoding study was then conducted in Chapter 2, which addressed a question of fisheries management concern, the diet of Maumee River fishes at an important time of year using cytochrome c oxidase (COI) DNA metabarcoding, with a particular focus on detecting predation on early life stages (ELS) of walleye (Sander vitreus). DNA amplified from the homogenized gut contents of fishes captured in the Maumee River during early spring was analyzed using next generation sequencing. Walleye eggs and larvae were present when predators were collected, although at lower densities than previously reported at peak density in the Maumee River. Despite the presence of walleye ELS in the system, the number of fishes with sequences assigned to walleye was lower than initially expected. One female white perch (Morone americana), one male white bass (Morone chrysops), and two emerald shiners (Notropis atherinoides) that were caught in the spawning grounds (Orleans Park) had gut content sequences assigned to walleye. Relatively low density of walleye in the system, the presence of alternative prey items (e.g., chironomids), lower overall feeding intensity by predator fishes near the onset of spawning, and/or turbidity in the Maumee River acting as a predation refuge may explain the lower than expected predation on walleye ELS, however, this requires further investigation and confirmation. Overall, sequences assigned to 7 phyla of metazoans were detected using DNA metabarcoding, including 9 genera of chironomids. Unexpected diet items were encountered, including potential predation on the bryozoan, Plumatella casmiana, by emerald shiner. This study reinforced the utility of DNA barcoding in providing insight where morphological identification is difficult as described in Chapter 1, but also points to areas where methods need improvement.

Committee:

Jeff Miner (Advisor); Daniel Heath (Committee Member); Michael McKay (Committee Member); Christine Mayer (Committee Member)

Subjects:

Biology; Ecology; Molecular Biology; Zoology

Keywords:

walleye; Maumee River; Lake Erie; DNA barcoding; DNA metabarcoding; predator-prey interaction; predation; fish; emerald shiner; white bass; white perch; sportsfish; recruitment; fisheries management; next generation sequencing;

Crosby, Chelsea HeleneThe role of individual learning and dietary preference in the consumption of the invasive Green Porcelain Crab, Petrolisthes armatus, by Native Crab Predators
Master of Science, The Ohio State University, 2018, Environment and Natural Resources
Although many predators forage adaptively in response to changes in the abundance of their prey, some predators may be slow to adapt to a novel prey that is added through biological invasion. The invasive Green Porcelain Crab (Petrolisthes armatus) is an abundant potential prey resource for native predators within oyster reef communities along the southeastern coast of the U.S. Yet the species’ invasion success suggests that native predators may not readily consume this novel prey. Here I used an individual learning experiment to examine whether evolutionary history, short-term exposure and previously learned handling skills influenced the foraging behavior and consumption of P. armatus by two native predators, the Atlantic Mud Crab (Panopeus herbstii) and the Blue Crab (Callinectes sapidus). Individual predators collected from populations where predators were either naïve or experienced with P. armatus were trained on morphologically similar (e.g. native crab) or dissimilar (e.g. native mussel) prey and then exposed to the invasive P. armatus for five consecutive days. Both species exhibited improvements in aspects of their foraging behavior, which suggests that both species have the ability to learn following short-term exposure to a novel prey. However, naïve P. herbstii did not forage on P. armatus as efficiently as experienced individuals, which suggests that learning occurs over a longer time scale in this species. In contrast, there were few differences in foraging behavior between experienced and naïve populations of C. sapidus, and both populations consumed a high number of the invasive species, which suggests that C. sapidus are relatively neophilic and will readily consume a novel prey species. Finally, naïve C. sapidus trained on similar native prey were quicker to approach the invasive P. armatus, and C. sapidus trained on similar native prey had shorter handling times on the invasive species, suggesting that the predator’s previous diet can influence foraging behavior. I further examined patterns of diet and prey preference in a population of native C. sapidus that has co-occurred with invasive P. armatus for 24 years. Although C. sapidus readily consumes P. armatus when given no-choice of alternative prey, when given a choice between alternative native prey and P. armatus, I found that C. sapidus rarely incorporated P. armatus into its diet. In addition, I found very limited within- population, individual variation in diet of C. sapidus. This is in contrast to previous work demonstrating that native P. herbstii predators exhibit considerable individual variation in diet, with some individual predators beginning to specialize on the invasive P. armatus, but others avoiding the species completely. These findings suggest that both native predators exert limited predation pressure (i.e. partial enemy release) on P. armatus, which likely contributes to its continued invasion success.

Committee:

Lauren Pintor, PhD (Advisor); Suzanne Gray, PhD (Committee Member); Susan Gershman, PhD (Committee Member)

Subjects:

Animals; Aquatic Sciences; Climate Change; Conservation; Environmental Science; Environmental Studies

Keywords:

Individual Learning; Biological Invasions; Dietary Behavior; Predator Prey Interactions; Enemy Release; Biotic Resistance; Skill Transfer; Blue Crab; Callinectes sapidus; Atlantic Mud Crab; Panopeus herbstii; Green Porcelain Crab; Petrolisthes armatus

Kinney, Kaitlin AlyseThe role of biotic resistance through predation on the invasion success of the green porcelain crab (Petrolisthes armatus) into nearshore oyster reef communities.
Master of Science, The Ohio State University, 2017, Environment and Natural Resources
The northward spread of the non-native, invasive filter feeding crab Petrolisthes armatus into oyster reef communities along the Southeastern US is hypothesized to be limited by cold snaps associated with northern winters. However, several native predators in oyster reefs have been shown to consume this abundant and profitable prey item, suggesting that biotic resistance through predation may be an additional factor limiting its northward spread. My objectives were to 1) determine if the per capita predation risk exerted by native predators might be a factor that explains the current distribution of P. armatus, and 2) test whether the relative abundance of alternative native prey affects the consumption and preference of P. armatus by a native predatory crab Panopeus herbstii. I conducted a field study to quantify predation risk across 8 invaded estuary sites from St. Augustine, FL to North Inlet, SC and conducted a lab experiment to quantify the consumption of P. armatus when in low to high abundance relative to alternative native prey. While predation rates were high (68.2 – 98.2%) across sites, there was no relationship between predation and latitude across the 8 invaded estuaries. Furthermore, while P. herbstii increased consumption of P. armatus in response to increased abundance in the tank, P. herbstii always showed a preference for native prey regardless of its relative abundance. Overall, I found no evidence of biotic resistance through predation, suggesting that native predators do not prevent the spread of P. armatus and this species is likely to continue its expansion into northern waters as sea temperatures increase with climate change.

Committee:

Lauren Pintor, Dr. (Advisor); Stuart Ludsin, Dr. (Committee Member); Christopher Tonra, Dr. (Committee Member); James Byers, Dr. (Committee Member)

Subjects:

Ecology; Environmental Studies; Natural Resource Management

Keywords:

biological invasion; biotic resistance; green porcelain crab; Petrolisthes armatus; geographic range; nonnative species; predator-prey; optimal foraging theory

Sitvarin, Michael IanBehavioral and ecological consequences of multiple intraguild predators and connections between predators, prey, and ecosystem function
Doctor of Philosophy, Miami University, 2014, Zoology
Prey species sit at a pivotal point in food webs, serving as a connection between predators and energy sources (e.g., plants or detritus). Most prey face multiple predators and must integrate information about predation risk if they are to avoid being consumed. Meanwhile, predators interact with one another and can increase or decrease their combined pressure on prey. By interacting with their prey, predators can indirectly affect ecosystem functions, even without reducing prey population size. The goal of my dissertation was to understand how prey survive in a world with multiple predators and to uncover linkages between predators and the soil food web. I first tested hypotheses about how the wolf spider Pardosa milvina responds to cues from multiple predators (the larger wolf spider Tigrosa helluo and the ground beetle Scarites quadriceps) and how inaccurate information regarding predation threat affects survival. Pardosa were capable of distinguishing between predators and responding adaptively, though prey responses were not optimized when predators were at elevated hunger levels. As a second step, I allowed multiple predators (the wolf spider Rabidosa rabida along with Tigrosa and Scarites) to freely interact with each other and their prey (Pardosa) to test the influence of predator characteristics and the occurrence of intraguild predation on prey survival. Overall, I found support for a predictive framework of emergent multiple predator effects, though intraguild predation events caused significant deviations from model predictions. I also investigated the consumptive and nonconsumptive effects predators can have on their environment, focusing on the detrital food chain. The presence of either Pardosa or their cues impacted CO2 flux and soil nitrogen content as mediated by the detritivore Sinella curviseta, suggesting indirect top-down control of ecosystem function by predators. Finally, I tested the response of Sinella to cues indicating predation risk to determine if changes in detritivore activity linked predators to ecosystem function. Sinella responded innately to necromones but did not alter activity levels in the presence of Pardosa cues, even after a conditioning period.

Committee:

Ann Rypstra, Ph.D. (Advisor); Nancy Solomon, Ph.D. (Committee Member); Brian Keane, Ph.D. (Committee Member); Tom Crist, Ph.D. (Committee Member); Dave Gorchov, Ph.D. (Committee Member)

Subjects:

Biology; Ecology; Entomology; Organismal Biology; Soil Sciences; Zoology

Keywords:

predation; ecology; behavior; predator; prey; nonconsumptive effects; intraguild predation; emergent multiple predator effects; activity; survival; ecosystem function; soil respiration; soil nitrogen content; trait-mediated interaction; interference

Thieme, Jennifer LeeBehavioral and reproductive consequences of predator activity to grassland birds
Master of Science, The Ohio State University, 2011, Environment and Natural Resources
Grassland birds are declining at greater rates than any other habitat guild in North America, yet conservation remains difficult due to extensive habitat loss and fragmentation throughout the urbanizing Midwest. Human presence is often associated with non-native predators (e.g., cats) and anthropogenic food sources, which collectively can promote high densities of nest predators in urban landscapes. High densities of nest predators are a concern because predation is the leading source of nest failure. Behavioral responses to predators may further diminish the value of urban habitats if birds avoid areas with high levels of predator activity, which could result in lower occupancy rates or densities of birds in urban habitat patches. In my research, I examined how habitat heterogeneity and variation in the predator community influenced the breeding ecology of grassland and early successional birds in urban parks. I asked two broad questions: (1) how do birds respond behaviorally to abundance and activity of predators in urban natural areas? (2) to what extent is avian reproductive success linked to predator communities and/or activity at plot and site scales? I collected data on avian density, nest placement, and reproductive success of eight focal species of grassland birds within 46 2-ha plots at seven urban parks near Chicago, Illinois, during 2009 and 2010. Relative abundance and activity levels of potential nest predator species, including mesopredators, small mammals, snakes, and avian predators, were estimated for each plot during surveys and as part of a collaborative study. As capture rates of small mammals increased, territory densities of Field Sparrow (Spizella pusilla), Common Yellowthroat (Geothlypis trichas), and Savannah Sparrow (Passerculus sandwichensis) declined, but density of Song Sparrow (Melospiza melodia) rose. Mesopredator capture rates were negatively associated with Common Yellowthroat and Savannah Sparrow densities within 2-ha plots, as well as Eastern Meadowlark (Sturnella magna) at the site level. Whereas small mammal and mesopredator capture rates explained some of the observed variation in territory density, daily nest survival of both Field and Song Sparrows was best explained by numbers of snakes observed within plots. Interestingly, snake activity was positively associated with nest survival of Field Sparrows, though negatively associated with that of Song Sparrows. At large scales, vegetation characteristics best predicted nest survival of both species, with nest survival of Field Sparrow improving as density of groundcover increased and nest survival of Song Sparrow improving as structural complexity increased. While the structural complexity of vegetation at nest sites was not explained by predator activity, Song Sparrows selected nest sites with lower groundcover density than available as activity of Brown-headed Cowbird (Molothrus ater) increased. As a whole, these results provide evidence that breeding grassland and early successional birds respond to both habitat structure and activity of potential predators at different scales. I also found that behavioral (e.g., territory selection) and demographic (e.g., nest survival) associations with predators do not necessarily match. For example, snakes had the strongest, though sometimes counterintuitive, relationship with nest success of Field and Song Sparrows, yet appeared to elicit no response during territory or nest site selection. My results are also consistent with other studies demonstrating the importance of vegetation structure to both settlement and reproductive success. Consequently, the best management practices in urban parks will both maintain vegetation structure that promotes successful nesting and discourage activities that promote high abundances of predators.

Committee:

Amanda Rodewald (Advisor); Stanley Gehrt (Other); Jacqueline Augustine (Other)

Subjects:

Ecology

Keywords:

predator; prey; avian; nest success; grassland; bird; reproduction; territory selection; mesopredator; nest site selection; daily survival

Smallwood, John A.Winter territoriality and predation ecology of American Kestrels (Falco sparverius) in southcentral Florida /
Doctor of Philosophy, The Ohio State University, 1987, Graduate School

Committee:

Not Provided (Other)

Subjects:

Biology

Keywords:

American kestrel;Territoriality;Birds of prey--Ecology

Wellington, Colleen G.Effects of turbidity and prey density on the foraging success of age-0 yellow perch (Perca flavescens)
Master of Science, University of Toledo, 2008, Biology (Ecology)
Previous studies on yellow perch (Perca flavescens) foraging indicate that increased turbidity can impair foraging success, and that phytoplankton turbidity can reduce prey consumption more than sediment turbidity. Field data from western Lake Erie suggest that turbidity covaries with prey density. Prey consumption usually increases with prey density, but fish foraging in highly turbid areas may have a modified functional response and therefore not forage at the expected rate. I conducted laboratory experiments to determine how larval and juvenile yellow perch respond to changes in prey density when exposed to different levels and types of turbidity. In all turbidity conditions, consumption increased with increasing prey density. However, the functional response was modified by turbidity type, such that the slope of the consumption-prey density relationship was lower in phytoplankton than sediment turbidity. For larval yellow perch, this effect was dependent on the turbidity level (larger difference at higher turbidity), while for juveniles the difference in consumption with turbidity type was observed across all turbidity levels. Overall, prey density could not compensate for the negative effects of phytoplankton turbidity. These results reinforce the need to control factors leading to excessive phytoplankton blooms in lakes.

Committee:

Christine Mayer, PhD (Advisor); Jonathan Bossenbroek, PhD (Advisor); Stuart Ludsin, PhD (Committee Member); Elliot Tramer, PhD (Committee Member)

Subjects:

Biology; Ecology; Environmental Science; Freshwater Ecology

Keywords:

yellow perch; turbidity; prey density; functional response; foraging

Jones, Jared K.THE ALTERATION OF HABITAT USE BY CRAYFISH (ORCONECTES RUSTICUS) IN RESPONSE TO PREDATOR (ICTALURUS PUNCTATUS) CUES
Master of Science (MS), Bowling Green State University, 2012, Biological Sciences
The use of shelters by crayfish is influenced by the presence or absence of predatory cues. Crayfish are able to detect sensory cues in the environment and use the information gathered to make behavioral changes to reduce the risk of becoming a predator’s next prey item. Factors such as mechanical cues or chemical cues in the water may determine the extent to which the crayfish alter not only the use of shelter, but also other behaviors, such as walking speed and exploratory behaviors. This thesis set out to address which factor elicits the strongest response in behavior alteration and use of shelter. To tease apart the mechanical and chemical cues, five sets of trials were conducted. The first set of trials acted as a control in which a baseline of behavior and shelter use could be determined. The second set of trials exposed the crayfish to the scent of a channel catfish (Ictalurus punctatus), but not to the mechanical cues of the predator. The third set of trials exposed the crayfish to the mechanical cues of a model channel catfish, but not the chemical cues. The fourth set of trials exposed the crayfish to the chemical cues of a channel catfish and mechanical cues of the model channel catfish simultaneously. The fifth and final set of trials exposed the crayfish to the chemical and mechanical cues of a channel catfish. By observing the behaviors under the various experimental designs, the research shows us that the mechanical cues of the model channel catfish had the greatest effects on the behaviors demonstrated by the crayfish. The results from these experiments show us that the crayfish relied more on the mechanical cues in the environment than the chemical cues when considering predator avoidance and behavior modification.

Committee:

Paul Moore (Advisor); Robert McKay (Committee Member); Jeffrey Miner (Committee Member)

Subjects:

Animal Sciences; Aquatic Sciences; Behavioral Sciences; Biology

Keywords:

crayfish; catfish; predator-prey interactions; shelter use; habitat use; chemical cues; mechanical cues

Beattie, Molly C.Diet and familiarity influence on predator recognition by chemical cues in crayfish
Master of Science (MS), Bowling Green State University, 2018, Biological Sciences
Prey often alter their morphology, physiology, and/or behavior when presented with predatory cues. Alteration in behaviors (i.e. habitat use, food consumption) are consequences of non-consumptive effects that can alter the dynamics of prey resources and cause changes in food web structures. One key factor in determining predation threat level by predators is the composition of the diet of the predator. We wanted to test the ability of prey to determine threat level based on cues produced by different predators on various diets. Odors from two different species of fish, bass (Micropterus salmoides), a natural predator of crayfish, and cichlid (Oreochromis aureus x Oreochromis niloticus), a non-natural predator of crayfish that were fed a vegetarian pellet, a protein diet, a heterospecific crayfish, and a conspecific crayfish were collected. Anti-predator behavior was tested by placing the prey, crayfish (Orconectes virilis), in a y-maze and analyzing the side of choice arena the crayfish spent time in, shelter usage of the crayfish, walking speed, walking forward and backward, climbing, and posture when presented with predator odors. Our results show that crayfish spent less time in odors containing conspecific diets, but when in this odor, crayfish spent most of the time hiding in the shelter when odors were emitted from a natural bass predator. However, these results were not present when exposed to non-predatory cichlid odors. Therefore, crayfish can determine different threat levels based off of chemical signals emitted from a potential or real threat, when paired with diet, eliciting predator avoidance behaviors.

Committee:

Paul A. Moore, Dr. (Advisor); Verner P. Bingman, Dr. (Committee Member); Daniel D. Wiegmann, Dr. (Committee Member)

Subjects:

Animals; Behavioral Sciences; Biology; Ecology; Freshwater Ecology

Keywords:

diet; chemical cues; predator-prey; naivety; behavior; crayfish

Bildstein, Keith LouisBehavioral ecology of red-tailed hawks (Buteo jamaicensis), rough-legged hawks (B. lagopus), northern harriers (Circus cyaneus), American kestrels (Falco sparverius) and other raptorial birds wintering in south central Ohio /
Doctor of Philosophy, The Ohio State University, 1978, Graduate School

Committee:

Not Provided (Other)

Subjects:

Biology

Keywords:

Birds of prey

Rincon Rueda, Diego FernandoDelphastus catalinae and the silverleaf whitefly, Bemisia tabaci biotype B, on tomato: modeling predation across spatial scales
Doctor of Philosophy, The Ohio State University, 2015, Entomology
Understanding behavioral traits that determine the ability of predators to suppress pest populations at spatial scales larger than those evaluated in the laboratory may help in selecting the right species and release rates for biological control programs. My thesis is that predation rates within whole plants are driven by the interaction between prey distribution, individual predator patch-to-patch behavior and consumption rates within patch units. I propose that results derived from simple laboratory settings can be useful to predict predation rates within whole plants, if they are combined with spatially explicit descriptions of prey distribution and predator movement patterns. I assume that the leaflet is a spatial scale at which predators and prey behave as in laboratory settings, at least in experiments without replacement of consumed prey. My study extended from the leaflet to the plant scale, encompassing both the relatively homogeneous prey patch unit, leaflet, and the more structurally complex combination of leaflets, leaves, branches and main stem. My study system consisted of the silverleaf whitefly (SWF), Bemisia tabaci biotype B, and the coccinellid predator Delphastus catalinae inhabiting greenhouse tomato plants. To support my thesis, I evaluated key predator behavioral patterns by modeling the interaction between SWF spatial distribution and the search behavior of D. catalinae. First, I developed an algorithm to generate within-plant spatial distributions of the SWF, based on aggregation patterns observed within and among tomato leaves. Second, I described the spatial interaction between the SWF and D. catalinae at the within-plant scale and examined its effects on D. catalinae predation rates and functional response. I found that prey and predator prefer different plant regions and that predation rates and the functional response at the scale of a leaflet are comparable to what have been observed in the laboratory. In contrast, I observed that predation rates are lower and that the functional response changes qualitatively when the scale of observation is increased from the leaflet to the plant. To gain understanding of the processes that drive such a change in predation rates and functional response with scale transition, I developed an individual-based model that incorporates the observed behavioral patterns of D. catalinae individuals when preying on SWF nymphs within tomato plants. I found that the number of leaflets visited per plant by predators and the degree of spatial alignment between predator and prey distributions impact predation rates significantly at the spatial scale of the whole plant. Also, I demonstrated that simple measures of prey distribution and predator foraging patterns can be used to scale up functional responses estimated through laboratory settings. Altogether, my research shows that non-random distributions and movement patterns of prey and predators can be predicted, at least within plant structures, and that simple measures of such patterns can be used to accurately model predation rates within plants using observations from laboratory settings. My thesis can be applied to overcome current limitations in the extrapolation of data collected in the laboratory to the field, which ultimately will help fine-tune release procedures of biological control programs.

Committee:

Luis Canas, Ph.D. (Advisor); Casey Hoy, Ph.D (Advisor); Robin A. J. Taylor, Ph.D. (Committee Member); Laurence Madden, Ph.D. (Committee Member); Larry Phelan, Ph.D (Committee Member)

Subjects:

Ecology; Entomology

Keywords:

Algorithm; Biological control; Functional response; Intra-plant spatial distribution; Predator-prey models; Search behavior; Spatially explicit individual-based model

Koper, MarlenaThe Effect of Hunger and Multiple Chemical Cues on the Foraging Behavior of the Wolf Spider Pardosa Milvina (Araneae, Lycosidae)
Master of Science, Miami University, 2003, Zoology
The decision to obtain food can affect the fitness of an animal. Theory suggests that the present state of an animal may affect whether or not an animal performs a given behavior. I found that hungry wolf spiders (Pardosa milvina) were significantly more active and demonstrated a greater propensity to forage than spiders that were well-fed. This increased activity is predicted to result in higher rates of mortality due to predation. Since P. milvina is known to respond to chemical cues left by other organisms in its environment I also explored the effects of both hunger and environmental cues on activity level and foraging behavior. Across cue treatments, food-limited spiders were significantly more active and demonstrated a greater propensity to forage than well-fed spiders. These results suggest that the effects of hunger may override the presence of environmental cues.

Committee:

Ann Rypstra (Advisor)

Keywords:

SPIDER; prey; PARDOSA; food-limited; well-fed; CUES; FORAGING

Hostert, Lauren ElizabethThe role of individual variation in the consumption of non-native prey: implications for the evolution of diet specialization and biological invasions
Master of Science, The Ohio State University, 2014, Environment and Natural Resources
Abundant non-native species frequently cause changes in natural environments by altering the composition and abundances of native species. One explanation for why non-native species are able to reach higher densities outside of their native range is because they escape their natural enemies (i.e. Enemy Release Hypothesis). Although the release of non-native species from their natural enemies may be due to lower densities or diversity of predators, parasites or pathogens, there are many alternative mechanisms that can reduce the predation pressure that a non-native species may experience following introduction into a new environment. In this study, I examined how individual variation in diet, morphology, competitive ability (i.e. aggression) of a native predator (common mudcrab, Panopeus herbstii), along with the relative energetic value of alternative prey contributes to the consumption of a recently introduced, non-native prey species (green porcelain crab, Petrolisthes armatus). Specifically, I: 1) quantified within-population variation in diet breadth and competitive ability of native P. herbstii predators, 2) evaluated the influence of competitive ability on within-population variation in diet and the consumption of non-native prey, P. armatus , and 3) compared the relative caloric densities of the native prey species of P. herbstii (G. demissa, C. virginica, and E. depressus) with that of the non-native prey P. armatus . AIC model comparisons indicated that predator sex, aggression, and competitor presence were the most important factors influencing diet specialization of P. herbstii predators, wherein predators that exhibited specialist diets were female and more aggressive. Individual P. herbstii predators also tended to exhibit specialist diets in the presence of a competitor. Individuals that specifically specialized on P. armatus were also female and more aggressive, but additionally, larger individuals. Individual P. herbstii predators generally, displayed more specialized diets on P. armatus in the absence of a competitor. The total number of P. armatus consumed was best explained by sex and size, whereby females and larger individuals consumed greater numbers of P. armatus. Also, in the presence of no alternative prey, females and smaller individuals consumed great quantities of P. armatus. Results from the oxygen bomb calorimetry analysis indicated that non-native P. armatus and native ribbed mussels Geukensia demissa have similar specific energies that are significantly greater than native eastern oysters Crassostrea virginica and depressed mud crabs Eurypanopeus depressus (which are not statistically different from one another). Overall, these results demonstrate that there is considerable individual variation in diet (i.e. some individuals are specialists, some generalists) and the consumption of P. armatus among the tested population of P. herbstii predators. P. armatus is a considerably profitable prey type compared to native prey yet only a sub-set of the population including females consumes P. armatus in large proportions. This gives some insight as to why P. armatus has been able to establish and maintain high population densities in this area but it produces more questions regarding why some individuals continue to not consume this abundant, profitable prey item.

Committee:

Lauren Pintor, PhD (Advisor); Elizabeth Marschall, PhD (Committee Member); Mazeika Sullivan, PhD (Committee Member)

Subjects:

Behavioral Sciences; Biology; Ecology; Environmental Science

Keywords:

non -native prey; optimal foraging theory; diet breadth; enemy release hypothesis

Evans, Samuel CStochastic Modeling of Orb-Web Capture Mechanics Supports the Importance of Rare Large Prey for Spider Foraging Success and Suggests How Webs Sample Available Biomass
Master of Science, University of Akron, 2013, Biology
Strong selective pressures can be exerted by events that occur extremely rarely and unpredictably during an organism's lifetime. The importance of such rare events may elude detection if the fitness consequences are not immediately observable, such as in the form of missed foraging opportunities. For orb-weaving spiders, fitness may depend almost exclusively on securing one or a few large, rarely-encountered, difficult-to-capture prey. Here, we present a stochastic individual-based model simulating foraging, growth, and survival of various-sized spiders in environments varying in distribution of biomass among prey sizes. We use this model to assess the degree to which foraging success is determined by the outcome of a small subset of foraging opportunities, and ascertain the architectural and biomechanical properties most crucial to deciding the outcomes of these rare events. Although our deterministic model suggests spiders should, on average, gain the most biomass from small prey sizes, spiders in stochastic simulations grew the most by capturing a single large and difficult-to-capture prey comprising the majority of their diets. The mechanics involved in stopping and retaining flying prey were more important in determining foraging success compared to those involved in encountering and contacting prey. Spiders lost the raw majority of biomass they encountered by failing to stop prey. However, prey retention exhibited the highest rate of biomass loss—spiders lost over 90% of successfully stopped biomass by failing to retain prey, but failed to stop only 40-80% of prey biomass their webs successfully contacted. Our results support the rare large prey hypothesis of Venner and Casas (2005), and reinforce the hypothesis that orb webs are pervasively selected for their potential to arrest large amounts of energy. However, certain factors such as prey availability and the biomechanics of prey retention in webs warrant further investigation, as these may be crucial to the plausibility of alternative foraging strategies.

Committee:

Todd Blackledge, Dr. (Advisor); Randall Mitchell, Dr. (Committee Member); Stephen Weeks, Dr. (Committee Member)

Subjects:

Biology; Biomechanics

Keywords:

foraging; spider; orb web; insect; prey; biomechanics; stochastic; deterministic; model

WRINN, KERRI MARGARETThe Effects of Leg Loss and Regeneration on Prey Capture Growth and Development in Wolf Spiders
MS, University of Cincinnati, 2005, Arts and Sciences : Biological Sciences
I addressed the effects of autotomy and regeneration on foraging success, body condition, growth (size and weight) and development time (molt interval) for Schizocosa ocreata wolf spiders in the laboratory and field. Frequency of autotomy in the field was high (12-19%) and body size, weight and condition were significantly lower in individuals with missing/regenerating legs. Regeneration of a single leg increased development time in laboratory reared spiders but decreased growth in field-caught individuals. Autotomy of multiple legs decreased both growth and development time. Laboratory experiments carried out in artificial conditions showed no effects of autotomy or regeneration on prey capture efficiency or vibration sensory abilities. However, spiders tested in a semi-natural habitat (a leaf litter filled mesocosm) with a missing or regenerating leg had reduced prey capture rates. This suggests that the effects of autotomy and regeneration on foraging may only be apparent in more complex environments encountered in nature.

Committee:

Dr. George Uetz (Advisor)

Keywords:

autotomy; regeneration; wolf spiders; growth and development; prey capture

Sahni, VasavFrom Nano to Micro to Macro: Importance of Structure and Architecture in Spider Silk Adhesives
Doctor of Philosophy, University of Akron, 2012, Polymer Science
Spiders employ clever behavioral strategies combined with almost invisible custom-made adhesives for locomotion and prey-capture. The adhesive produced by modern orb-weaving spiders to capture prey (viscid glue) is laid on a pair of extensible axial silk fibers as micron-size glue droplets that are composed of a mixture of salts and polymeric glycoproteins. Each glue droplet is composed of a dense core surrounded by a sparse shell. We discuss the importance of the structure at nano-, micro-, and macro level in adhesion. At the nano level, we show that the inherent elasticity in the glue enhances adhesion caused by specific adhesive ligand by over two orders of magnitude.Furthermore, we describe how the viscoelastic solid nature of the glue drops help in capturing and retaining prey. We also develop an energy model to separate the axial silk contributions from glue droplet contribution in the force required to separate a whole thread from a surface. We describe the functions of the salts that are present in large quantities in the web, and are nutritionally and physiologically essential for the spider. Previously, it was assumed that the main function of the salts is to sequester water. We show that salts play a major role in adhesion itself and how the core-shell microstructure developed within each drop facilitates reversible usage of this glue. We compare the properties and humidity-responses of orb-weaving glue with the gumfoot glue produced by cob-weavers, the evolutionary descendants of orb-weavers and despite being produced in homologous glands, we find very interesting differences.We mimic the common macro-architecture of these capture threads: Beads-on-a-string (BOAS) architecture, and understand why spiders employ this architecture for capturing prey. Lastly, we discuss the attachment discs produced by spiders, which make it possible for spiders to move, defend, and capture prey. We comment on how the macro architecture of these attachment discs affects their adhesion, thus enabling different functions in a web. This research, thus shows the importance of structure at different length scales in influencing adhesion and shall inspire future efforts directed towards tunable adhesives.

Committee:

Ali Dhinojwala, Dr. (Advisor); Todd A. Blackledge, Dr. (Committee Member); Gary Hamed, Dr. (Committee Member); Toshi Miyoshi, Dr. (Committee Member); Jutta Luettmer -Strathmann, Dr. (Committee Member)

Subjects:

Biology; Biomechanics; Biophysics; Materials Science; Mechanics; Polymers

Keywords:

Spider Silk; Adhesion; Glycoproteins; Viscoelastic Solid; Elasticity; Pyriform Silk; Capture Silk; Prey Capture; Beads on a string