Nabis kinbergii is a native polyphagous predator in Australia. It has been found in all states and territories of Australia. N. kinbergii has been regarded as an efficient predator of many insect pests in lucerne, cotton and particularly brassica crops. The circadian rhythms, the effects of different prey on development and reproduction, and prey preferences of N. kinbergii have not been studied in South Australia. These are the subjects of this thesis. N. kinbergii is more active at night than in the day. They seemed to be still more frequently at dawn and more active at dusk under natural environmental conditions. Yet, their behaviour was possibly different when they were held in a controlled environment with artificial light. Under both natural and artificial lighting conditions, they would spend more time moving on plants at night. They spent less time moving than other activities. Furthermore, they were more active during the second day of the observations, probably because of the hunger. A mixed diet including Plutella xylostella, Myzus persicae and Brevicoryne brassicae brought the most significant positive influences to the development, survival and longevity of N. kinbergii. It had a shorter preoviposition period and greater egg production when fed on P. xylostella than when fed on M. persicae. Among the three prey, B. brassica was the poorest food because the survival rate between egg hatch and adult eclosion was only 7.5 %, compared to 85 %, 92.5 % and 97.5 % when N. kinbergii fed on M. persicae, P. xylostella and a mixed diet, respectively. Evidence of prey preference was exhibited by N. kinbergii. B. brassica seemed to be the least preferred food. N. kinbergii possibly attacked less mobile prey and delayed eating prey with poor nutrition or that were toxic. In wind tunnel experiments, N. kinbergii may have been attracted by plant volatiles rather than prey odour. These findings may help to refine the timing of experiments and improve the understanding of the role of this predator in integrated pest management. / Thesis (M.Sc.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008

Understanding the interactions of predators and their prey and their responses to environmental changes is one of the striking features of ecological research. In this thesis, spring dynamics of phytoplankton and its consumers, zooplankton, were considered in dependence on the environmental conditions in a deep lake (Lake Constance) and a shallow marine water (mesocosms from Kiel Bight), using descriptive statistics, multiple regression models, and process-oriented dynamic simulation models. The development of the spring phytoplankton bloom, representing a dominant feature in the plankton dynamics in temperate and cold oceans and lakes, may depend on temperature, light, and mixing intensity, and the success of over-wintering phyto- and zooplankton. These factors are often correlated in the field. Unexpectedly, irradiance often dominated algal net growth rather than vertical mixing even in deep Lake Constance. Algal net losses from the euphotic layer to larger depth were induced by vertical mixing, but were compensated by the input from larger depth when algae were uniformly distributed over the water column. Dynamics of small, fast-growing algae were well predicted by abiotic variables, such as surface irradiance, vertical mixing intensity, and temperature. A simulation model additionally revealed that even in late winter, grazing may represent an important loss factor of phytoplankton during calm periods when losses due to mixing are small. The importance of losses by mixing and grazing changed rapidly as it depended on the variable mixing intensity. Higher temperature, lower global irradiance and enhanced mixing generated lower algal biomass and primary production in the dynamic simulation model. This suggests that potential consequences of climate change may partly counteract each other. The negative effect of higher temperatures on phytoplankton biomass was due to enhanced temperature-sensitive grazing losses. Comparing the results from deep Lake Constance to those of the shallow mesocosm experiments and simulations, confirmed the strong direct effect of light in contrast to temperature, and the importance of grazing already in early spring as soon as moderate algal biomasses developed. In Lake Constance, ciliates dominated the herbivorous zooplankton in spring. The start of ciliate net growth in spring was closely linked to that of edible algae, chlorophyll a and the vertical mixing intensity but independent of water temperature. The duration of ciliate dominance in spring was largely controlled by the highly variable onset of the phytoplankton bloom, and little by the less variable termination of the ciliate bloom by grazing of meta-zooplankton. During years with an extended spring bloom of algae and ciliates, they coexisted at relatively high biomasses over 15-30 generations, and internally forced species shifts were observed in both communities. Interception feeders alternated with filter feeders, and cryptomonads with non-cryptomonads in their relative importance. These dynamics were not captured by classical 1-predator-1-prey models which consistently predict pronounced predator-prey cycles or equilibria with either the predator or the prey dominating or suppressed. A multi-species predator-prey model with predator species differing in their food selectivity, and prey species in their edibility reproduced the observed patterns. Food-selectivity and edibility were related to the feeding and growth characteristics of the species, which represented ecological trade-offs. For example, the prey species with the highest edibility also had the highest maximum growth rate. Data and model revealed endogenous driven ongoing species alternations, which yielded a higher variability in species-specific biomasses than in total predator and prey biomass. This holds for a broad parameter space as long as the species differ functionally. A more sophisticated model approach enabled the simulation of a continuum of different functional types and adaptability of predator and prey communities to altered environmental conditions, and the maintenance of a rather low model complexity, i.e., low number of equations and free parameters. The community compositions were described by mean functional traits --- prey edibility and predator food-selectivity --- and their variances. The latter represent the functional diversity of the communities and thus, the potential for adaptation. Oscillations in the mean community trait values indicated species shifts. The community traits were related to growth and grazing characteristics representing similar trade-offs as in the multi-species model. The model reproduced the observed patterns, when nonlinear relationships between edibility and capacity, and edibility and food availability for the predator were chosen. A constant minimum amount of variance represented ongoing species invasions and thus, preserved a diversity which allows adaptation on a realistic time-span. / Eine der großen Herausforderungen der heutigen ökologischen Forschung ist es, Veränderungen von Ökosys­temen vorher­zusagen, die mit dem Klimawandel einhergehen. Dafür sind ein umfassendes Verständnis der ver­schiedenen Steuerungsfaktoren des entsprechenden Systems und Kenntnisse zur Anpassungs­fähigkeit des Systems nötig. Auf der Grundlage dieses Wissens, können mit mathemati­schen Modellen Klima­szenarien gerechnet und Vorhersagen erstellt werden. Die vorliegende Arbeit untersuchte die Regulation des Phytoplanktons (kleine freischwebende einzellige Algen) und seiner Konsumenten (Zooplankton, tierische Kleinstlebewesen) sowie deren Wechselspiel während des Frühjahrs mit Bezug auf den Klimawandel. Als Basis dienten langjährige Daten von einem großen tiefen See (Bodensee) sowie Daten von Versuchen mit Organis­men aus einem flachen marinen Ge­wässer (Kieler Förde, Ostsee). Diese Daten wurden mit statistischen Verfahren und mathematischen Modellen ausge­wertet. In Gewässern sind Algen als Primärproduzenten die Nahrungsgrundlage für tieri­sche Organismen bis hin zu Fischen und Meeresfrüchten, und bestimmen die Wasserqualität der Ge­wässer. Daher ist es wichtig zu verstehen, welche Mechanismen die Dynamik der Algen steuern. Der Grundstein für die saisonale Entwicklung von Phyto- und Zooplankton in Gewässern un­serer Breiten wird mit dem Be­ginn des Wachstums im Frühjahr gelegt. Diese Arbeit zeigt, dass es bereits im zeitigen, noch kalten Frühjahr ein Wechselspiel physikalischer und biologischer Steuerungsmechanismen für die Algenent­wicklung gibt. Physikalische Faktoren sind die Wassertemperatur, die Globalstrahlung und die Durchmischung des Gewässers, die durch die Stärke des Windes beeinflusst wird. All diese Steue­rungsmechanismen sind eng miteinander verwoben und werden unterschiedlich stark vom Klimawan­del beeinflusst. Mit mathematischen Modellen gelang es den Einfluss einzelner Faktoren voneinander zu trennen und zu zeigen, dass Effekte durch den Klimawandel sich gegenseitig aufheben oder aber auch verstärken können. Schon geringe Änderungen an der Basis der Nahrungsnetze können weitrei­chende Auswirkungen auf höhere Ebenen habe. Wie stark diese Auswirkungen im Einzelnen sind, hängt entscheidend von der Anpassungsfähigkeit gesamter Ökosysteme und ihrer Artengemeinschaf­ten sowie einzelner Individuen ab. Beispielsweise reagiert die Algengemeinschaft auf einen starken Fraßdruck ihrer Räuber mit einer Verschiebung zu weniger gut fressbaren Algenarten. Diese weniger gut fressbaren Arten unterscheiden sich jedoch auch in anderen Eigenschaften, wie zum Beispiel der Ressourcenausnutzung, von besser fressbaren Algen. In dieser Arbeit wurden Modellansätze entwi­ckelt, die diese Fähigkeit zur Anpassung berücksichtigen. Auf dieser Grundlage und mit Einbeziehung der physikalischen Steuerungsfaktoren können Klimaszenarien gerechnet werden und Vorhersagen für den Einfluss des Klimawandels auf unsere Gewässer gemacht werden, die letztlich auch Perspektiven für Handlungsmöglichkeiten aufzeigen.

Many prey species lack innate recognition of their potential predators. Hence, learning is required for them to recognize and respond to predation threats. When wild-caught, these same species may show amazing sophistication in their responses to predator cues. They are able to adjust the intensity of their antipredator responses to a particular predator according to the degree of threat posed by that predator. This ability is therefore acquired through learning. While many studies have shown that prey can learn to respond to predator cues through different learning modes, little is known about what the prey are actually learning. The results presented in this thesis show that learned predator recognition goes beyond the simple labelling of predators as dangerous. Using fathead minnows (Pimephales promelas), woodfrog (Rana sylvatica) tadpoles and boreal chorus frog (Pseudacris maculata) tadpoles, I demonstrated that a one time learning event, either through pairing with alarm cues or through social learning, was enough for prey to learn the level of threat associated with the novel predator cues. I showed that the level of danger associated with the predator cues was determined by the concentration of alarm cues when learning through pairing of alarm cues, or by the intensity of antipredator response displayed by the tutors and by the tutor-to-observer ratio when learning occurred through cultural transmission. Moreover, when subsequently exposed to predator cues, prey adjusted their antipredator responses according to the change in concentration of predator cues between the learning event and the subsequent exposure. Prey displayed stronger antipredator responses when exposed to higher concentrations of predator cues and vice versa. When minnows were provided with conflicting information about the danger level associated with a predator, they displayed a safety strategy and used the most recent information available to respond to predation threats. On a longer time scale, the data also suggest that woodfrog tadpoles are able to learn to respond to predation threats according to the risk posed by the predator at different times of day. Finally, I showed that prey learn to recognize particular characteristics of predators and can generalize their antipredator responses to novel species sharing those characteristics. However, generalization of predator recognition is dependent on the level of risk associated with the predator. Threat-sensitive learning is an extremely complex process shaped by the millions of years of selection imposed by predators on prey.

Many prey species lack innate recognition of their potential predators. Hence, learning is required for them to recognize and respond to predation threats. When wild-caught, these same species may show amazing sophistication in their responses to predator cues. They are able to adjust the intensity of their antipredator responses to a particular predator according to the degree of threat posed by that predator. This ability is therefore acquired through learning. While many studies have shown that prey can learn to respond to predator cues through different learning modes, little is known about what the prey are actually learning. The results presented in this thesis show that learned predator recognition goes beyond the simple labelling of predators as dangerous. Using fathead minnows (Pimephales promelas), woodfrog (Rana sylvatica) tadpoles and boreal chorus frog (Pseudacris maculata) tadpoles, I demonstrated that a one time learning event, either through pairing with alarm cues or through social learning, was enough for prey to learn the level of threat associated with the novel predator cues. I showed that the level of danger associated with the predator cues was determined by the concentration of alarm cues when learning through pairing of alarm cues, or by the intensity of antipredator response displayed by the tutors and by the tutor-to-observer ratio when learning occurred through cultural transmission. Moreover, when subsequently exposed to predator cues, prey adjusted their antipredator responses according to the change in concentration of predator cues between the learning event and the subsequent exposure. Prey displayed stronger antipredator responses when exposed to higher concentrations of predator cues and vice versa. When minnows were provided with conflicting information about the danger level associated with a predator, they displayed a safety strategy and used the most recent information available to respond to predation threats. On a longer time scale, the data also suggest that woodfrog tadpoles are able to learn to respond to predation threats according to the risk posed by the predator at different times of day. Finally, I showed that prey learn to recognize particular characteristics of predators and can generalize their antipredator responses to novel species sharing those characteristics. However, generalization of predator recognition is dependent on the level of risk associated with the predator. Threat-sensitive learning is an extremely complex process shaped by the millions of years of selection imposed by predators on prey.

Hard clams, Mercenaria mercenaria, are slow-moving organisms that are heavily preyed upon by both blue crabs and knobbed whelks in coastal Georgia. Hard clams are unable to escape from these predators, and when found, are commonly injured and/or consumed. Thus, their best survival strategy is to avoid their predators. In this study, we compared changes in clam behavior when exposed to blue crab and knobbed whelk predators. Clams reduced their feeding time when exposed to crabs and whelks, exudates from these predators, and to injured conspecifics. In a field experiment, we compared clam survival when caged predators where near clam beds vs. controls with empty cages. Clam survival was significantly higher when caged crabs or whelks were near, suggesting that clams detected these predators, reduced their feeding time, and were less apparent to ambient consumers. In lab behavioral assays, clams were less responsive to blue crabs in turbulent flows, and in the field, turbulence reduced the distance clams reacted to blue crabs. Previous studies have shown that blue crabs turbulence also diminishes blue crab foraging efficiency, and we conducted a field experiment to determine how turbulence affected clam-crab interactions. Our results suggest that predation intensity is greatest at intermediate turbulence levels, and lowest in flows with low and high turbulence levels. We attribute this pattern of predation intensity to differential effects of turbulence on the sensory abilities of crabs and clams. That is, in low turbulent flows, clams have a sensory advantage over crabs, and initiate avoidance behaviors before they are detected. However, as turbulence increases, clam perception diminishes faster than crabs, switching the sensory advantage to crabs, and making clams more vulnerable to consumers. In highly turbulent flows, crab perception declines at a rate faster than clams, and the sensory advantage returns to clams.

Frogs, toads, and salamanders are well known for harboring an array of distasteful (and poisonous) secondary metabolites, presumably as antipredator defenses; yet few experiments have rigorously demonstrated the efficacy of amphibian chemical defenses against ecologically relevant consumers. For example, despite an absence of rigorous statistical evidence showing their distastefulness to predators, eastern newts (Notophthalmus viridescens (Rafinesque))--a common salamander in lentic North American habitats--are assumed to tolerate diverse predator assemblages because newts secrete tetrodotoxin (TTX), a neurotoxin. Here we combine laboratory and field-based ecology with bioassay-guided separation of chemical extracts to show that eastern newts--although chemically protected against ecologically important consumers in lentic systems--nonetheless suffer substantial predation when tethered in the field. When offered newts with alternative prey (paedomorphic Ambystoma talpoideum), red swamp crayfish (Procambarus clarkii) and largemouth bass (Micropterus salmoides) were 9-10x as likely to feed on A. talpoideum as newts. Additionally, juvenile bluegill (Lepomis machrochirus) were 70% less likely to consume newt eggs compared to control food pellets. We also show that different newt tissues were differentially palatable to predatory fish. All bluegill tested consumed a palatable control food, but only 20% consumed dorsal skin, only 35% ate ventral skin, but 75% fed on newt viscera, suggesting that deterrent metabolites are concentrated in the skin. Bioassay-guided fractionation revealed that crude and water-soluble newt chemical extracts inhibited bluegill feeding, definitively establishing the chemical nature of newt antipredator defenses, although we were unsuccessful at isolating the chemical compounds responsible for unpalatability. Yet, deterrent activity in the polar but not the lipophilic chemical fraction and bioassay results demonstrating that naıve predators rapidly learn to avoid natural concentrations of TTX support the possible role of TTX in suppressing predation on newts. However, when tethered in the field, newt mortality was 55% higher in ponds with predatory fishes than in ponds lacking fishes (62% vs. 40% respectively), indicating the possible existence of other predators that are resistant to (or tolerant of) newt chemical defenses. Together, these results stress the importance of rigorous, ecologically relevant, and hypothesis-driven experimentation to better understand the complexity of chemically- mediated predator-prey interactions, even for well-studied species like N. viridescens.

This dissertation demonstrates the construction of the Panthera Population Persistence (PPP), an individual-based model for the Sumatran tiger (Panthera tigris sumatrae) which provides proper theoretical and application frameworks for the conservation of this tiger sub-species in central Sumatra. The PPP model was developed to gain insight into tiger-preyhabitat relationships as well as the effect of human impacts on the persistence of tiger populations. The model addresses three main problems for the survival of the Sumatran tiger: tiger poaching, prey depletion, and habitat loss. The description of the PPP model serves as an in-depth study of existing literature and covers the most important factors of existing models for tiger conservation. Existing modelling approaches have been improved by the inclusion of finer description of individual-level traits and behaviours in the PPP model. The modelling approach allows a direct inter-relationships between individuals and their environment. The relationship between individual behaviours, intrinsic states, and external factors are simulated spatially explicitly in a bottom-up approach where the emergence of the population dynamics of tiger and prey can be observed under different scenarios. The integration between the PPP model and geographical information system (GIS) has provided a much more meaningful spatial data by revealing the mechanism of the response of individuals to the present land-use types. The relative importance of the parameters within the PPP model was tested using two modes of sensitivity analysis: The Morris Method and the traditional One-factor-at-a-time method. The results provided guidance for the application of reasonable sensitivity analysis during the development of individual-based models. The Morris Method suggested that the overall output of the PPP model showed a high sensitivity on the change of time required by a tigress to take care of cubs. The analysis also revealed that the number of dispersers was sensitive toward perceptual distance of individuals to detect the presence of prey. Comparison with a similar predator-prey models provided insight into the predator-prey relationship. The comparison also suggested that perceptual distance of the individual is important for any spatially explicit individual-based model involving predator-prey relationships. The parameterization of the individual perceptual distance of tigers was tested by using existing literature on prey consumption by tigers as a benchmark. The simulation results were within the range of scientific acceptance for the number of prey killed by a tiger. Thus, further use of the set of parameters for a tiger’s perceptual distance is less uncertain for the output of the PPP model. The effect of habitat quality and landscape configuration on the mortality and migration of prey were evaluated through the use of virtual habitats and landscapes. The findings suggested that a good habitat quality enables prey survival, increases the population available for predation by tigers. When a low-quality habitat is combined with a high-quality habitat, the number of migrating prey was high, reducing resources for tigers. This suggested that landscape composition should be considered when predicting population persistence of the Sumatran tiger. Optimal movement of two different prey resulted in a high density of prey in high-quality habitat, providing a concentration of prey in a tiger’s habitat, but resulted in a lower tiger predation rate than random movement and species specific movement. The PPP model has been applied to evaluate the effect of poaching, prey depletion, and their combination for the probability of extinction of a tiger population. The results from the evaluation showed that prey depletion, tiger poaching, and a combination of both, created a 100% probability of extinction within 20 years if the density and frequency of those threats at high rates. However, the duration of those threats in the system caused a 100% probability of extinction from tiger poaching. The results are able to contribute to optimize anti-poaching programs in future, to reduce significantly the probability of total extinction of Sumatran tiger. Furthermore, various landscape configurations have been tested against the probability and time of extinction for the Sumatran tiger population. The integration of spatial GIS-data in the model provides an insight into the relationship between tiger-prey-habitat. The results suggested that habitat quality surrounding a protected area plays an important role for the persistence of the Sumatran tiger population. This study also recommends agroforestry systems as reasonable land-use type in the vicinity of protected areas. They provide not only positive effects for tiger conservation purpose but they also appear as adaptable to the current land-use situation in Sumatra island. / Die vorliegende Dissertation beschreibt die Entwicklung des Panthera Populations Persistence (PPP) Modells, eines individuenbasierten Simulationsmodells für den Sumatra-Tiger (Panthera tigris sumatrae). Dieses stellt einen geeigneten theoretischen und anwendungsbezogenen Rahmen für den Schutz dieser Tiger-Unterart in Zentralsumatra bereit. Das PPP-Modell wurde entwickelt, um Einblicke in die Tiger-Beute-Habitat-Beziehungen zu gewinnen, sowie um den Effekt anthropogener Einflüsse auf den Fortbestand von Tigerpopulationen abzuschätzen. Dabei werden die drei Hauptprobleme für das Überleben des Sumatra-Tigers analysiert: die Wilderei, der Rückgang von Beutetieren und der Verlust von geeigneten Habitaten. Die Beschreibung des PPP-Modells gibt zunächst einen umfassenden Überblick zum aktuellen Wissensstand auf dem Gebiet des Tigerschutzes und integriert die wichtigsten Faktoren bereits existierender Modellansätze. Diese konnten durch die Einbeziehung einer detaillierten Beschreibung von individuellen Merkmalen und Verhalten verbessert werden. Das PPPModell stellt somit das Individuum in einen direkten Zusammenhang mit dessen Umwelt. Die Beziehung zwischen individuellem Verhalten, intrinsischen Merkmalen und externen Faktoren werden räumlich-explizit in einem bottom-up Ansatz simuliert. Damit kann sowohl die Populationsdynamik des Tigers als auch die seiner Beutetiere unter verschiedenen Annahmen beobachtet werden. Die Verknüpfung des PPP-Modells mit Geographischen Informationssystemen (GIS) bietet die Möglichkeit, die Reaktionsmechanismen der Individuen basierend auf der gegenwärtigen Landnutzungssituation zu simulieren und somit realitätsnahe räumliche Daten zu generieren. Die relative Bedeutung der Modell-Parameter auf die Simulationsergebnisse kann durch Sensitivitätsanalysen ermittelt werden. Hier wurden zwei verschiedene Ansätze verwendet: die Morris-Methode und die herkömmliche One-factor-at-a-time Methode. Der Vergleich beider methodischen Ansätze zeigte somit beispielhaft die Eignung unterschiedlicher Sensitivitätsanalysen für individuenbasierte Modelle auf. Die Morris-Methode zeigte, dass das Gesamtergebnis des PPP-Modells eine hohe Sensitivität gegenüber der Veränderung der Zeit aufweist, die ein Tigerweibchen braucht, um ihre Jungen aufzuziehen. Die Analyse zeigt auch, dass die Anzahl an abwandernden Tigern sensitiv gegenüber der IndividuellenWahrnehmungsdistanz von Beute ist. Der Vergleich mit einem ähnlichen Räuber-Beute-Modell lässt vermuten, dass diese Wahrnehmungsdistanz eines Individuums generell als ein entscheidender Faktor für Räuber-Beute-Beziehungen in räumlich-expliziten Individuenmodellen an- gesehen werden kann. Die Parametrisierung der IndividuellenWahrnehmungsdistanz des Tigers wurde so gewahlt, dass die damit ermittelten Simulationsergebnisse den Beutekonsum des Tigers, wie in der Literatur beschrieben, weitgehen widerspiegeln. Sie ist somit für die weitere Anwendung im PPP-Modell ausreichend gut beschrieben. Simulationsszenarien, welche verschiedene Habitatqualitäten sowie Landnutzungsmuster berücksichtigen, zeigen auch deren Bedeutung für die Mortalität und Migration der Beutetiere. Eine gute Habitatqualität hat eine geringe Mortalität der Beutetiere zur Folge, welche dann wiederum für den Tiger in ausreichender Zahl zur Verfügung stehen. Treten geringe Habitatqualitäten angrenzend an ein Habitat mit hoher Qualität auf, führte dies zu einer hohen Anzahl an abwandernden Beutetieren, womit sich die Ressourcen für den Tiger verringern. Die Landschaftsmerkmale sollten also bei der Vorhersage des Populationsfortbestandes des Sumatra-Tigers berücksichtigt werden. Die optimale Bewegung von zwei verschiedenen Beutetieren ergab eine hohe Beutedichte in einem Habitat mit hoher Qualität und stellte konzentriert Beute in einem Tigerhabitat bereit. Allerdings resultierte dies auch in einer geringeren Prädationsrate des Tigers, verglichen mit zufälligen oder artenspezifischen Bewegungen. Das PPP-Modell wurde angewandt, um die Auswirkungen von Wilderei, Beutetierrückgang sowie die Kombination beider Faktoren auf die Aussterbewahrscheinlichkeit einer Tigerpopulation zu bewerten. Die Ergebnisse zeigen, dass die genannten Faktoren eine 100-prozentige Aussterbewahrscheinlichkeit innerhalb von 20 Jahren zur Folge haben, wenn die Dichte und Häufigkeit dieser Bedrohungen hoch sind. Die Dauer dieser Bedrohungen im System verursachte allerdings eine 100-prozentige Aussterbewahrscheinlichkeit nur für die Wilderei von Tigern. Betrachtet man unabhängig von Dichte und Häufigkeit einzig die Dauer der Bedrohung, führt lediglich die Wilderei zum 100%-igen Aussterben. Diese Ergebnisse können maßgeblich dazu beitragen, zukünftig Schutzprogramme gegen die Wilderei zu optimieren, um das Aussterben des Sumatra-Tigers zu verhindern. DesWeiteren wurde der Einfluss von unterschiedlichen Landnutzungsmustern auf die Aussterbewahrscheinlichkeit und -zeit einer Sumatra-Tigerpopulation aufgezeigt. Die Integration von räumlichen GIS-Daten in das Modell ermöglichte einen Einblick in die Beziehungen zwischen Tiger, Beutetieren und Habitat. Die Ergebnisse zeigen, dass die Habitatqualität um Schutzgebiete herum eine wichtige Rolle für den Fortbestand der Population spielt. Die vorliegende Arbeit empfiehlt Agroforstsysteme als eine geeignete Landnutzungsform in der Nähe von Schutzgebieten, welche sowohl positive Effekte für den Tigerschutz bietet als auch mit den gegenwärtigen Landnutzungsmustern in Sumatra vereinbar erscheint.

No description available.

This thesis explores the methodology of state, and in particular, parameter estimation for time series datasets. Various approaches are investigated that are suitable for nonlinear models and non-Gaussian observations using state space models. The methodologies are applied to a dataset consisting of the historical lynx and hare populations, typically modeled by the Lotka- Volterra equations. With this model and the observed dataset, particle filtering and parameter estimation methods are implemented as a way to better predict the state of the system. Methods for parameter estimation considered include: maximum likelihood estimation, state augmented particle filtering, multiple iterative filtering and particle Markov chain Monte Carlo (PMCMC) methods. The specific advantages and disadvantages for each technique are discussed. However, in most cases, PMCMC is the preferred parameter estimation solution. It has the advantage over other approaches in that it can well approximate any posterior distribution from which inference can be made. / Master's thesis

The seasonal and diel feeding habits of the goosander, Mergus merganser, the red-breasted merganser, M. serrator, gulls (Larus canus, L. argentatus and L. fuscusj and terns, Sterna hirundo/paradisaea were studied at 64V05'N. Birds' activity patterns were influenced by the nocturnal spawning of the river lamprey (Lampetra fluviatilis). Food selection and food consumption by hand-raised mergansers together with aquarium studies of the diel activity patterns of their most important prey supplemented the field data. River lamprey dominated the diet of the goosander by weight and the sculpin Cottus gobio by number. The fish consumption of the goosanders was found to be about 12% of the available river lamprey biomass and about 17% of the sculpin biomass during the breeding season. In experimental situations the river lamprey was a low- pritority species compared with salmon , Salmo salar, brown trout, 53. trutta, and minnow, Phoxinus phoxinus, when presented to satiated birds of both Mergus species. When hungry, however, the birds caught the available prey irrespective of species, but they selected larger prey when two size classes were present. Experimental results were compared with field data on availability, consumption and the escape behaviour of the various fish species. The rivers emptying in the Bothnian Bay are regarded as important feeding areas for birds breeding along the coast. In early spring they get access to abundant and reliable food resources, e.g the river lamprey. Later on the three-spined stickleback, Gasterosteus aculeatus, supply both Mergus species with food in the river and also along the coast. From the middle of June potential food supply available to birds decreases in the rivers and becomes more abundant in the coastal area. / <p>S. 1-41: sammanfattning, s. 43-227: 7 uppsatser</p> / digitalisering@umu