In Part I of this thesis we extend the Lanchester Ordinary Differential Equations and construct a new physically meaningful set of partial differential equations with the aim of more realistically representing soldier dynamics in order to enable a deeper understanding of the nature of conflict. Spatial force movement and troop interaction components are represented with both local and non-local terms, using techniques developed in biological aggregation modelling. A highly accurate flux limiter numerical method ensuring positivity and mass conservation is used, addressing the difficulties of inadequate methods used in previous research. We are able to reproduce crucial behaviour such as the emergence of cohesive density profiles and troop regrouping after suffering losses in both one and two dimensions which has not been previously achieved in continuous combat modelling. In Part II, we reproduce for the first time apparently complex cellular automaton behaviour with simple partial differential equations, providing an alternate mechanism through which to analyse this behaviour. Our PDE model easily explains behaviour observed in selected scenarios of the cellular automaton wargame ISAAC without resorting to anthropomorphisation of autonomous 'agents'. The insinuation that agents have a reasoning and planning ability is replaced with a deterministic numerical approximation which encapsulates basic motivational factors and demonstrates a variety of spatial behaviours approximating the mean behaviour of the ISAAC scenarios. All scenarios presented here highlight the dangers associated with attributing intelligent reasoning to behaviour shown, when this can be explained quite simply through the effects of the terms in our equations. A continuum of forces is able to behave in a manner similar to a collection of individual autonomous agents, and shows decentralised self-organisation and adaptation of tactics to suit a variety of combat situations. We illustrate the ability of our model to incorporate new tactics through the example of introducing a density tactic, and suggest areas for further research.

In Part I of this thesis we extend the Lanchester Ordinary Differential Equations and construct a new physically meaningful set of partial differential equations with the aim of more realistically representing soldier dynamics in order to enable a deeper understanding of the nature of conflict. Spatial force movement and troop interaction components are represented with both local and non-local terms, using techniques developed in biological aggregation modelling. A highly accurate flux limiter numerical method ensuring positivity and mass conservation is used, addressing the difficulties of inadequate methods used in previous research. We are able to reproduce crucial behaviour such as the emergence of cohesive density profiles and troop regrouping after suffering losses in both one and two dimensions which has not been previously achieved in continuous combat modelling. In Part II, we reproduce for the first time apparently complex cellular automaton behaviour with simple partial differential equations, providing an alternate mechanism through which to analyse this behaviour. Our PDE model easily explains behaviour observed in selected scenarios of the cellular automaton wargame ISAAC without resorting to anthropomorphisation of autonomous 'agents'. The insinuation that agents have a reasoning and planning ability is replaced with a deterministic numerical approximation which encapsulates basic motivational factors and demonstrates a variety of spatial behaviours approximating the mean behaviour of the ISAAC scenarios. All scenarios presented here highlight the dangers associated with attributing intelligent reasoning to behaviour shown, when this can be explained quite simply through the effects of the terms in our equations. A continuum of forces is able to behave in a manner similar to a collection of individual autonomous agents, and shows decentralised self-organisation and adaptation of tactics to suit a variety of combat situations. We illustrate the ability of our model to incorporate new tactics through the example of introducing a density tactic, and suggest areas for further research.

The harbor porpoise is considered a threatened species in Swedish waters. A full understanding of its ecology and relationship to other species is important when designing effective conservation plans. This thesis aims to investigate the relationships between harbor porpoises and their prey by comparing the acoustic activity patterns of harbor porpoises and the movement patterns of some of their prey species available at Kullaberg, Sweden. For this purpose, the scientific literature of porpoise and fish activity patterns has been reviewed. Results show that harbor porpoises may follow vertically migrating herring, but further studies are needed to confirm this. It is also possible that the activity pattern of porpoises does not follow exactly the movements of a certain species of prey, but that they rather feed upon several species, and therefore change their behavior accordingly throughout the diurnal cycle.

Bark beetles are major pests of pine forests in North America that can inflict considerable damage and cause severe economic loss. The checkered beetle Thanasimus dubius Fabricius (Coleoptera: Cleridae), an abundant predator in the Eastern USA and Canada, has been suggested to influence the dynamics of several bark beetles, including the economically important southern pine beetle (SPB), Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae). Because of the importance of T. dubius in pine forests, I studied several aspects of T. dubius biology including both its chemical and dispersal ecology. I first present an experiment that was conducted to improve the rearing system of T. dubius so that sufficient numbers of predators could be produced more efficiently for both behavioral and ecological studies. Improvements to the rearing method potentially could be achieved by adding a preservative to increase the shelf-life of the diet used to feed larval T. dubius thereby allowing feeding intervals to be extended. To evaluate this, I added sorbic acid, a preservative, to the larval diet at three different concentrations (0, 0.1 and 0.2%) and for two different intervals between feedings (2-3 vs. 5 days). Additionally, I measured potential deleterious effects of this preservative on predator performance (i.e., female fecundity). I then assessed the effect of this predator on SPB survival by releasing newly hatched T. dubius larvae at several densities (0, 50 100, and 200) on pine logs infested by SPB. I also studied the chemotactic response of this predator toward various volatiles such as prey pheromones or tree volatiles in a wind tunnel. I developed a method that associated upwind flight behavior and antennal behavior to quantify the relative attractiveness of each tested source of chemical. I then conducted three experiments to investigate the ability of individual T. dubius to respond to different prey olfactory signals (bark beetle pheromones) and assess their potential for learning. First, I examined individual predator preferences toward three major prey pheromones (ipsenol, ipsdienol, and frontalin) in a study that combined a mark-release-recapture experiment with a field choice test. I also measured the responses of individual wild T. dubius in a wind tunnel, which allowed the testing of a wider range of semiochemicals (frontalin, ipsenol, ipsdienol, sulcatol, and α-pinene). A final wind tunnel experiment tested the ability of naive predators to learn two prey pheromones, frontalin and ipsenol, that were presented alone or associated with a reward. In the last chapter, I quantified the dispersal of this predator and its behavior along an edge separating a pine forest from a non-suitable habitat. I analyzed T. dubius distribution and movement in the field relative to its bark beetle prey Ips grandicollis Eichhoff (Coleoptera: Curculionidae) and to the root feeder Dendroctonus valens LeConte (Coleoptera: Curculionidae). These three insects are associated with the phenomenon of red pine decline in the Great Lakes area. Thus, understanding the relative pattern of movements of these three beetles could provide considerable knowledge on the spatial and temporal progression of red pine decline by, for instance, assessing the connection between existing pockets. I estimated the dispersal quantiles for this predator relative to its bark beetle prey and determined whether dispersal behavior was relatively homogeneous (one kind of disperser) or heterogeneous (two kinds). In a second part, I sampled the abundance of T. dubius, I. grandicollis, and D. valens along transects set between a matrix area constituted by a clearing and a habitat zone composed of red pine forest. I further developed a diffusion model, including a constant k (corresponds to the ratio of densities along the edge), that permits characterization of beetle behavior around the boundary. Studies developed in the present dissertation, therefore, investigated several aspects of T. dubius ecology: predation on SPB, ability to respond to an olfactory signal, and dispersal traits. I first showed that augmentation with larval T. dubius can successfully reduce the SPB ratio of increase in infested pine logs. I also developed a system of rearing T. dubius that was more efficient and could allow larger numbers of predators to be produced. Sorbic acid did not reduce adult lifetime or size but did affect female fecundity (20 - 40% reduction). Increasing feeding time interval to 5 days (instead of 2-3 days) improved the efficiency of the system, even when sorbic acid was not added in the diet. Wind tunnel experiments present a methodology that could enable future quantification of the relative attractiveness of various semiochemical treatments. I identified a particular antennal behavior, which I called "stand up antennal" that was typically produced when the insect was attracted to a semiochemical. The choice tests in the field and the wind tunnel experiment using wild adults both showed that T. dubius individuals are generalists that are flexible in their response to a broad range of semiochemical signals (frontalin, ipsenol, ipsdienol, sulcatol, and α-pinene). I demonstrate that naive predators are more attracted toward ipsenol after having experienced conditioning with this kairomone via a reward. Finally, experiments on dispersal and edge behavior revealed that T. dubius and one of its common prey, the bark beetle I. grandicollis, exhibit a different pattern of movement within red pine stands and surrounding habitats. First, adult T. dubius can disperse substantially further (50% dispersed beyond 1.54 km) than I. grandicollis adults (50% dispersed beyond 0.13 km). Second, T. dubius was highly affected by the presence of an edge, showing a step-like pattern with very predators caught in unsuitable areas. Conversely, the behavior of I. grandicollis was less limited by such a boundary. As with T. dubius, the root colonizer D. valens showed a strong edge behavior that was characterized by avoiding matrix zones.

The thesis results of two laboratory experiments focusing on the impacts of predation risk, prey density and habitat complexity on predator-prey interaction strengths and predator metabolic rates, complemented by a brief review of the subject. The experimental system used in the first experiment consisted of cladoceran prey, larvae of three dragonfly species (Sympetrum sanguineum, Libellula quadrimaculata, Ischnura cf. elegans) as intermediate predators, and larvae of a large dragonfly species (Aeshna sp.) as a top predator. The second experiment of investigated how predation risk influences metabolic rates of the intermediate predators.

The dissertation thesis focuses on predator ecology in artificial water bodies. Paper I deals with the importance of chemical cues for predator-prey interactions in an aquatic environment. Here, I demonstrate that the ability to detect chemical cues represents a survival benefit for prey species. Paper II points out gillnet methodological bias, which may have subsequent repercussions in field evaluation of a predator's presence and assessment of larger fish abundance in general. Papers III and IV focus on asp Leuciscus aspius spawning grounds. In Paper III, I demonstrate how males maximize their spawning chances by early arrival and in Paper IV, I evaluate the predation pressure of asp prey, Alburnus alburnus, directed on asp eggs.

This Ph.D. Thesis is focused mainly on the biology of two typical European predatory fishes, European catfish (Silurus glanis) and perch (Perca fluviatilis). Catfish is a typical apex predator, whereas perch is a smaller species that plays role of a mesopredator. Although, catfish is the third largest freshwater fish in the world, only few studies dealing with this species have been revealed thus far. The main reason is connected with capturing of the species that is inefficient by standard ichthyologic methods. Studies, that have been revealed recently, focused mainly on expansions of catfish to the West and South Europe. Catfish is unwanted in these localities due to a potential negative impact on native fish community, thus its reduction is desirable. In contrast, catfish occurrence is important in native localities where it plays a key role as a biomanipulative species (I). Catfish is a true generalist, which is a typical feature for large-bodied apex predators connected with high energy consumption of their bodies. The second typical feature is a wide diet plasticity and thus good adaptability to new food sources. It is associated with distribution of various food sources among individuals within the population (II). By contrast, perch is one of the most studied fish in the world and hundreds of studies with IF are revealed every year. However, the more information about biology of perch have been known, the more questions have been arisen. Several phenomena are revealed also in this thesis. For instance, crucial impact of juvenile perch on the entire ecosystem is described. High predation pressure on zooplankton may induce piscivory in primarily zooplanktivorous fish (III). Further, juvenile perch utilize hypoxic pelagic zones as a refuge against predation (IV). The last surprising phenomenon is described in the study dealing with both species, catfish and perch. Their coexistence may lead in strong discrimination of one species caused by special predation that was supposed to be implausible (V).

Physical factors, such as hydrologic variability, are major structuring forces of prairie stream communities. Macroinvertebrate and algae densities can both decrease sharply in response to floods and drying. Less is known about the influences of biological factors, such as fishes. The influence of fishes on macroinvertebrate communities varies with environmental factors and other biologic interactions, ranging from neutral to strong negative effects on some populations, and the strength of these interactions sometimes appear linked to hydrology. Drying intermittent streams leave permanent water refugia that may be hotspots for interactions between fishes and invertebrates. Effects of fishes on macroinvertebrate communities may vary with invertebrate life cycle stages (e.g., larvae, emerging adults, colonizing adults). I examined macroinvertebrate communities (benthic and emerging) and algal biomass across a range of permanent stream pool sites at Konza Prairie Biological Station with naturally varying densities of fishes. I also manipulated fish densities in a mesocosm experiment to address how fishes may also be effecting colonization during recovery from hydrologic disturbance. Fish biomass had a negative impact on invertebrate abundance, but not biomass or taxa richness, in natural pools. Total fish biomass was not correlated with total insect emergence in natural pools, but orangethroat darter (Etheostoma spectabile) biomass was inversely correlated with emerging Chironomidae biomass (r2 = 0.43, p = 0.047) and individual midge body size (r2 = 0.61, p = 0.014). Predatory fish biomass and a date interaction appeared in top linear models, indicating fish may also delay insect emergence from natural pools. Fish presence reduced abundance of colonizing insects (p < 0.001) and total invertebrate biomass (p = 0.001) in mesocosms. Mesocosm insect communities in pools without fishes were characterized by more Chironomidae, Culicidae, and Corduliidae (p < 0.001 for all). Chlorophyll-a increased between sampling dates in mesocosms, but did not differ between treatments. Not all life stages showed the same response to fishes, illustrating the need for understanding life histories in order to interpret the influence of fishes. Understanding how fishes in prairie streams affect ecosystem structure and function is critical for conservation and management of remaining grassland streams. Results suggest fishes can influence colonization and community structure in prairie stream pools, which serve as important refugia during hydrologic disturbance and source areas for colonists during recovery.

I tested the ability of the Red-backed Shrike (Lanius collurio) to solve multiple predator conflict. Nesting shrikes were exposed to two predators presented simultaneously. The Red-backed Shrike is able to solve this conflict by deciding which of the presented predators is the more dangerous and opting for the appropriate defence of its nest.

I tested the ability of the Red-backed Shrike (Lanius collurio) to solve multiple predator conflict. Nesting shrikes were exposed to two predators presented simultaneously. The Red-backed Shrike is able to solve this conflict by deciding which of the presented predators is the more dangerous and opting for the appropriate defence of its nest.