When ovipositing, prey organisms avoid habitat patches containing predator cues because predators consume, and negatively affect the fitness of their prey. Richness of predator species often enhances the strength of consumptive predator effects, but little is known about how multiple predators combined affect prey non-consumptively. We quantified dipteran colonization in aquatic mesocosms in response to varied predator richness. Multiple predator species combined reduced oviposition by Culex mosquitoes, chironomid midges, and the general colonizing dipteran community more than predicted by the effects of the independent predator species. Previous research which quantifies effects of multiple predators on prey as prey abundance, but does not measure consumption by predators, may be underestimating or overestimating the strength of effect by assuming equal colonization. Our findings enhance understanding of the ways predators influence abundances and distributions of their prey, and yields insight into the ways predators may non-consumptively affect prey by changing prey behavior.

Blow fly (Diptera: Calliphoridae) interactions in decomposition ecology are well studied; however, the non-consumptive effects (NCE) of predators on the behavior and development of prey species have yet to be examined. The effects of these interactions and the resulting cascades in the ecosystem dynamics are important for species conservation and community structures. The resulting effects can impact the time of colonization (TOC) of remains for use in minimum post-mortem interval (mPMI) estimations. The development of the predacious blow fly, Chrysomya rufifacies (Macquart) was examined and determined to be sensitive to muscle type reared on, and not temperatures exposed to. Development time is important in forensic investigations utilizing entomological evidence to help establish a mPMI. Validation of the laboratory-based development data was done through blind TOC calculations and comparisons with known TOC times to assess errors. A range of errors was observed, depending on the stage of development of the collected flies, for all methods tested with no one method providing the most accurate estimation. The NCE of the predator blow fly on prey blow fly, Cochliomyia macellaria (Fabricius) behavior and development were observed in the laboratory. Gravid female adult attraction was significantly greater to resources with predatory larvae rather than prey larvae and oviposition occurred on in the presence of heterospecific (predatory) and conspecific larvae equally. However, the life stages necessary for predation to occur never overlapped and so these results may not be as surprising as they seem. Conversely, exposing prey larvae to predator cues through larval excretions/secretions led to larger prey larvae and faster times to pupariation when appropriate life stages overlapped. Differences in size and development times of prey larvae in the presence of predatory cues could lead to errors when estimating the mPMI. These data also partially explain the ability of C. macellaria to survive in the presence of Ch. rufifacies. Colonization of a resource with late instar Ch. rufifacies enhanced development and size of resulting larvae indicating that lag colonization, rather than being a primary colonizer, could become an alternate strategy for C. macellaria to survive the selective pressures of the predator, Ch. rufifacies. The differing effects of temperature on Ch. rufifacies and C. macellaria may also lend an advantage to C. macellaria over the predacious Ch. rufifacies in an environment with variable temperatures unlike what Ch. rufifacies is adapted for.

The focus of my thesis research is on the interplay between individual behavior, population dynamics and community-level processes within zooplankton communities in coastal Maine. The target organisms of my thesis work are marine copepods. Copepods are small (1-10 mm) crustaceans that perform the essential ecosystem function of consuming and assimilating primary production (phytoplankton) making it available to higher trophic levels such as commercially important fishes. Therefore, copepod population growth is of critical importance to marine food webs. Fertilization limitation has been suggested as a constraint on copepod population growth but field surveys describing the prevalence of fertilization limitation are lacking. During my doctoral research, I explored the in situ fertilization success of two marine copepod species, Temora longicornis and Eurytemora herdmani in coastal Maine. I collected monthly zooplankton samples and analyzed clutches from field-caught females using an egg-staining technique. My results indicate that both species exhibit fertilization limitation in nature and the factors correlated with their fertilization span population, community and ecosystem level factors. To determine a causal relationship between predator density and copepod mating success, I conducted laboratory experiments to assess the effects of a common mysid shrimp predator, Neomysis americana on Eurytemora herdmani mating success. I subjected males and females to predators or predator cues. I found that the presence of a mysid predator, or only a predator cue, reduced copulation frequency and spermatophore transfer leading to a 38-61% decrease in E. herdmani nauplii production. These results suggest that mysid predators can constrain copepod population growth through non-consumptive processes. To determine the effects that resources can impose on copepod behavior, I explored the behavioral and fitness consequences of Temora longicornis ingesting Alexandrium fundyense, a phytoplankton species that forms harmful algal blooms in coastal Maine. My results suggest that ingesting A. fundyense causes copepods to swim faster and with more directional persistence compared to control algae. Temora longicornis increased their average swimming velocity by 24%, which leads to a 24-54% increase in their theoretical encounter rate with predators. Therefore, these findings suggest behaviorally mediated copepod-algal interactions may have significant impacts on harmful algal bloom dynamics and the fate of toxins in marine food webs.

Non-consumptive effects that predators have on prey are important to ecosystems. The perceived risk of predation can alter feeding behavior. Giving-up density (GUD) experiments have been a foundational method to evaluate perceived predation risk, but rely on the assumption that food preferences are absolute. However, nutritional preferences are context dependent and can change with risk. In my first chapter, I used spiders and grasshoppers to test the hypothesis that covariance in nutritional preferences and risk may confound the interpretation of GUD experiments. My results demonstrate that predation risk and nutritional preferences covary and can confound interpretation of GUD experiments. In my second chapter, I use a behavioral observation experiment to further explore non-consumptive effects, as well as the movement of prey in response to predation risk.

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Predators exert strong direct and indirect effects on ecological communities by intimidating their prey. Non-consumptive effects (NCEs) of predators are important features of many ecosystems and have changed the way we understand predator-prey interactions, but are not well understood in some systems. For my dissertation research I combined a variety of approaches to examine the effect of predation risk on herbivore foraging and reproductive behaviors in a coral reef ecosystem. In the first part of my dissertation, I investigated how diet and territoriality of herbivorous fish varied across multiple reefs with different levels of predator biomass in the Florida Keys National Marine Sanctuary. I show that both predator and damselfish abundance impacted diet diversity within populations for two herbivores in different ways. Additionally, reef protection and the associated recovery of large predators appeared to shape the trade-off reef herbivores made between territory size and quality. In the second part of my dissertation, I investigated context-dependent causal linkages between predation risk, herbivore foraging behavior and resource consumption in multiple field experiments. I found that reef complexity, predator hunting mode, light availability and prey hunger influenced prey perception of threat and their willingness to feed. This research argues for more emphasis on the role of predation risk in affecting individual herbivore foraging behavior in order to understand the implications of human-mediated predator removal and recovery in coral reef ecosystems.