Functional response is the framework thorough which we can quantify how predator hunting behaviors such as rate of successful attack and time spent handling prey interact with prey density to determine the rate at which prey are killed. Cheetahs are mesopredators and their behavior can be shaped by the need to avoid larger predators while hunting relatively large bodied and mobile prey. I used data from 34 years of observed cheetah hunts in Serengeti National Park in Tanzania to investigate how reproductive condition, prey density, seasonality, and the proximity of larger predators affect cheetah kill rates, probability of successful attack, and time spent handling prey. Mothers with cubs had an asymptotic Type II functional response where kill rate increased but eventually leveled-off at high prey densities, while cheetahs without cubs had a dome shaped Type IV functional response where kill rates actually declined at high prey density. Probability of successful attack on prey was higher for mothers with cubs, and increased slightly with prey density. Mothers with cubs had different prey handling behavior than other cheetahs. Cheetah mothers spend longer at kills then other cheetahs despite the risk that the carcass can attract lions and hyenas that could steal the carcass and potentially kill her cubs. Mothers must make sure their cubs have sufficient time at the carcass to eat their fill, thus they minimize risk from larger predators by being vigilant. In contrast, cheetahs without cubs are unconcerned with cub predation and can eat quickly to minimize the risk of kleptoparasitism. My results show how the pressures of cub rearing and coexisting with larger carnivores differentially shape the hunting behavior of cheetahs, and suggest that intensity of mesopredator suppression may depend on individual variability. This is the first time the functional response for a large mesopredator, has been quantified and the first time a dome shaped response has been recorded in a mammal. My work shows the value in accounting for individual variability in functional response and how linking of carnivore hunting behavior to multiple species interactions advances our understanding of how classical ecological theory applies to wild ecosystems. / Ph. D.

The present study investigates the impact of northern pike (Esox Lucius) on the growth of juvenile burbot (Lota lota) in northern lake ecosystems. It is hypothesized that the presence of pike will positively affect the growth of juvenile burbot by reducing interspecific competition and increasing the abundance of benthic invertebrates. To test this hypothesis, electrofishing for juvenile burbot was conducted in the littoral zones of lakes with and without pike in the region Jämtland Härjedalen, Sweden. Data on length and age of the captured burbot were used to compare growth between the two lake types. Contrary to the initial hypothesis, the results show that juvenile burbot were significantly larger at a given age in lakes where pike was absent. This outcome suggests that juvenile burbot may reduce their foraging activity in lakes with pike to minimize predation risk. Since adult burbot has shown to be of greater size in lakes with pike, future research could investigate whether the shift towards piscivory in burbot leads to changes in how they are affected by pike.

Predicting the impacts of non-native species remains one of the greatest challenges to invasion ecologists. Because of their insularity, freshwater systems are particularly vulnerable to invasions, especially from non-native predators. The research in this thesis explores the role of abiotic and biotic factors in mediating the distribution and impact of Bythotrephes longimanus, a predatory cladoceran that has been introduced to freshwater systems in North America. Although the general impacts of this invasion have been documented, little is known about the factors that modulate them. Using a combination of field surveys and experiments, I tested several hypotheses concerning the influence of interactions with native species, as well as the role of heterogeneity in the light environment, in mediating the impact of Bythotrephes. Results demonstrated that biotic resistance by native macroinvertebrate predators does not play a limiting role in the establishment success of Bythotrephes. However, the within-lake distribution of Bythotrephes was influenced by these macroinvertebrates, suggesting that the native predator context matters when trying to understand the impacts of non-native predators. This was demonstrated with a mesocosm experiment in which the impact of Bythotrephes was constrained by the native Chaoborus larvae. In terms of the abiotic environment, in situ feeding experiments demonstrated that refuges from impact could exist for some prey taxa, as the outcome of predation by Bythotrephes was dependent on light availability and some prey taxa were more successful at evading predation under low light conditions. Finally, results show that adaptive behaviour by prey is also an important determinant of impact, as migrating Daphnia can escape predation effects by Bythotrephes. The combination of light-limited predation and a shallow distribution by Bythotrephes selects for prey that occupy relatively deeper positions during the day. As a whole, this research highlights the importance of complex interactions in mediating the impact of Bythotrephes and may help to explain some of the variation that has been documented among invaded lakes. A better understanding of these complex interactions can improve our ability to anticipate impacts as Bythotrephes continues to spread, as well as provide insight on some of the long-term effects following invasion. / Thesis (Ph.D, Biology) -- Queen's University, 2013-06-17 09:26:35.221

Consumer-resource interactions are the basic building blocks of every food web. In spite of being a central research theme of longstanding interest in ecology, the mechanisms governing the stability and persistence of consumer-resource interactions are still not entirely understood. In particular, theoretical predictions on consumer-resource stability along gradients of temperature and nutrient enrichment diverge widely and are sometimes in conflict with empirical results. In this thesis I address these issues from the angle of the functional response, which describes a consumer’s feeding rate as a function of resource density. Specifically, I explore mechanistic, nutrient-based consumer-resource interaction models with respect to the influence of feeding behavior (the shape of the functional response), environmental temperature, nutrient enrichment, and resource quality on consumer-resource stability and persistence. In order to parameterize these models I performed extensive laboratory experiments with pairs of freshwater pelagic algae and grazers of the genus Daphnia, which are widespread, ecologically important model organisms. I found a sigmoidal type III functional response in every studied Daphnia-algae species pair. The exact form of its shape is described by an exponent b which is determined by fitting functional response models to the experimental data. A high value of b can stabilize consumer-resource systems under the otherwise destabilizing influence of nutrient enrichment, as predicted by a novel stability criterion relating b to the consumer’s prey handling time, food conversion efficiency and mortality. Estimated parameter values and, consequently, stability predictions are sensitive to the method of parameter estimation, and I propose a new estimation procedure that minimizes parameter uncertainty. Because many consumers’ feeding rates depend on temperature, warming is expected to strongly affect food web stability. In functional response experiments over a broad temperature gradient, I found that the attack rate coefficient and the maximum ingestion rate of Daphnia are hump-shaped functions of temperature. Moreover, the functional response exponent increases with warming towards stronger type III responses. Plugging these findings into a nutrient-based consumer-resource model, I found that predator persistence is a U-shaped function of temperature in nutrient enrichment-temperature space. Enrichment easily turns the system unstable when the consumer has a type II response, whereas a type III response opens up a large region of stability at intermediate, for the consumer optimal, temperatures. These findings reconcile seemingly conflicting results of earlier studies of temperature effects on consumer-resource dynamics, which can be mapped as special cases onto the enrichment-temperature space. I finally demonstrate the utility of three key model ingredients - temperature dependence of rate parameters, a mechanistic description of the dynamics of algal resources, and a type III functional response in Daphnia - by successfully implementing them in the description and explanation of phytoplankton-Daphnia dynamics in a mesocosm experiment exploring effects of warming on the spring succession of the plankton.

Unlike desert rodents from North America, Allenby’s gerbil (Gerbillus andersoni allenbyi) from the Negev Desert, Israel has evolved with snakes that do not have heat-sensitive sensory pits that enhance night vision. Does this history affect their ability to assess and respond to a snake that has this ability? As a test, we exposed gerbils to risk of predation from various predators, including snakes, owls, and foxes. The snakes included the Saharan horned viper (Cerastes cerastes) and the sidewinder rattlesnake (Crotalus cerastes). The former snake lacks sensory pits and shares a common evolutionary history with the gerbil. The latter snake, while convergent evolutionarily on the horned viper, has sensory pits and no prior history with the gerbil. The gerbils exploited depletable resource patches similarly, regardless of snake species and moon phase. While the gerbils did not respond to the novel snake as a greater threat than their familiar horned viper, the gerbils were cognizant that the novel predator was a threat. In response to both snakes, giving-up densities (GUDs; the amount of food left in a resource patch following exploitation) of the gerbils were higher in the bush than open microhabitat. In response to moonlight, GUDs were higher on full than on the new moon. Based on GUDs, the gerbils responded most to the risk of predation from the red fox, least from the two snake species, and intermediate for the barn owl. Keywords:

This thesis presents several nonlinear mathematical models applied to ecoepidemiology and evolution. A detailed study involving predator-prey type models considering an alternative resource for the predator was carried out, investigating the situation of infection in the prey and in the predator on separate models. Such study served as a theoretical contribution to the investigation of problems such as bovine tuberculosis in wild animal species presented in a specific model. We also developed models to explain the evolution of alarm calls in species of birds and mammals. The theoretical framework adopted for those evolution models is that of Population Ecology. The models were developed using Ordinary Diferential Equations (ODEs) to describe the population dynamics. The biological assumptions of the systems that we wanted to analyse were enumerated and explained / Esta tese apresenta vários modelos matemáticos não-lineares aplicados à ecopidemiologia e à evolução. Foi realizado um estudo detalhado envolvendo modelos do tipo predador-presa considerando um recurso alternativo para o predador, investigando situações de infecção na presa e no predador em modelos separados. Tal estudo, serviu de aporte teórico para a investigação de problemas como a tuberculose bovina em espécies de animais selvagens apresentado em um modelo específico. Também desenvolvemos modelos para explicar a evolução dos chamados de alarme em espécies de aves e mamíferos. O quadro teórico adotado para esses modelos de evolução é o da Ecologia de População. Nos modelos desenvolvidos usamos as Equações Diferenciais Ordinárias (EDOs) para descrever a dinâmica populacional. Consideramos pressupostos biológicos dos sistemas biológicos analisados

Les vasières intertidales sont des environnements complexes et changeants, qui abritent des invertébrés enfouis dans le sédiment (la macrofaune benthique) et sont visités de manière saisonnière par de grands migrateurs : les oiseaux limicoles. Ce travail de recherche s’intéresse aux relations proie-prédateur entre les oiseaux limicoles et leur ressource alimentaire : la macrofaune benthique. La thèse est articulée en 8 chapitres qui présentent des études à différentes échelles spatio-temporelles : des saisons à la décennie, et de la baie à la route migratoire. Ces études sont basées sur un échantillonnage régulier des vasières intertidales du Golfe de Gascogne (France) ainsi que d’échantillonnages en mer des Wadden (Pays-Bas) et au Banc d’Arguin (Mauritanie). Les données de macrofaune (qualité, taille, densité, biomasse) sont couplées aux données de comptages de leurs prédateurs ainsi qu’à leur comportement alimentaire (reconstruction du régime alimentaire d’après les isotopes, les fécès, la modélisation ou l’observation de vidéos). Ces huit études apportent un éclairage sur l’écologie de leurs interactions (en intégrant des variables environnementales telles que le temps d’inondation, la granulométrie, la température, la production primaire, ou encore la latitude). Une attention particulière est portée à la variabilité des proies et du comportement alimentaire de leurs prédateurs, dans l’espace et le temps. Des encarts viennent illustrer pour l’un les techniques de reconstruction du régime alimentaire, pour l’autre les défenses développées par les mollusques marins, ou encore la relation entre énergie à disposition et sélection du site pour les limicoles. / Intertidal mudflats are complex ecosystems undergoing constant changes, home to infaunal invertebrates (benthic macrofauna), and migratory sites for particular birds : shorebirds. This research focuses on predator-prey interactions between shorebirds and their macrobenthic prey. The present thesis is composed of 8 chapters which illustrate different spatio-temporal scales : from seasons to the decade, and from the bay to the migratory flyway. These studies are based on regular benthic sampling of intertidal flats along the Bay of Biscay (France), as well as sampling data from the Dutch Wadden Sea and the Mauritanian Banc d’Arguin. Macrobenthic data (quality, sizes, densities, biomass) are linked with shorebird counts and data about their feeding behaviour (diet reconstruction from isotopes, faeces, modeling and video observations). These eight studies shed light on particular relationships between some prey and their predators, and the ecology of these interactions (including environmental variables such as inundation time, grain size, temperature, primary production, or even latitude). Particular attention is given to the variability of prey and predator behaviour in time and space. Inserts are included in between chapters to illustrate for instance different diet reconstruction techniques, anti-predation traits in marine molluscs, or relation between energy available and site selection in shorebirds.

<p>In this thesis I investigate predator-induced effects on behavioural and life-history characteristics of prey. At any moment a given predator is capable of attacking a small number of prey. However, the mere presence of a predator may impact a much larger number of individuals, as prey implement various behavioural and developmental mechanisms to reduce the risk of predation. It has become increasingly clear that predator induced responses have the potential to affect patterns of species abundance and distribution as well as individual fitness of prey. I study these responses by incorporating field surveys, semi-field experiments and laboratory experiments. All experiments were done in an aquatic environment using fish or large odonate larvae as predators and damselfly-or diving beetle larvae as prey.</p><p>My work highlights the importance of monitoring prey behaviour when studying life-history characteristics. I show that fish presence is an important factor for determining species abundance and distribution of odonates, and that prey behaviour may be a good predictor for fish vulnerability. Larval damselflies react behaviourally to predator presence by reducing activity and/or restricting habitat use. I confirm that such anti-predator responses have positive effects on prey survival in the presence of a predator but negative effects on growth and development of prey. In addition, my results suggest that the increase in per capita food resources for surviving prey following a predation episode (i.e. thinning) can have a stronger positive effect on prey growth and development than the negative effect of anti-predator responses. I also show that the strength of an anti-predator response is dependent on resource availability of the prey, with prey responding less strongly when resources are scarce. My results also indicate that the strength of the anti-predator response of damselfly larvae depends on predator diet and larval age. Predators feeding on prey conspecifics induce a stronger behavioural response in young larva than predators that feed on prey heterospecifics do. This diet-effect was not found in larvae late in ontogeny, due to an increased activity of larva where predators consumed damselflies. Such increased larval activity can be explained as a reaction to a time-constraint. Finally, I found that activity of damselfly larvae is genetically determined and that this has lead to a behavioural syndrome that might limit larval plasticity to a certain activity-range. This phenomenon may have implications for how well larvae are able to react to both biotic and abiotic changes in the environment.</p>

In this thesis I investigate predator-induced effects on behavioural and life-history characteristics of prey. At any moment a given predator is capable of attacking a small number of prey. However, the mere presence of a predator may impact a much larger number of individuals, as prey implement various behavioural and developmental mechanisms to reduce the risk of predation. It has become increasingly clear that predator induced responses have the potential to affect patterns of species abundance and distribution as well as individual fitness of prey. I study these responses by incorporating field surveys, semi-field experiments and laboratory experiments. All experiments were done in an aquatic environment using fish or large odonate larvae as predators and damselfly-or diving beetle larvae as prey. My work highlights the importance of monitoring prey behaviour when studying life-history characteristics. I show that fish presence is an important factor for determining species abundance and distribution of odonates, and that prey behaviour may be a good predictor for fish vulnerability. Larval damselflies react behaviourally to predator presence by reducing activity and/or restricting habitat use. I confirm that such anti-predator responses have positive effects on prey survival in the presence of a predator but negative effects on growth and development of prey. In addition, my results suggest that the increase in per capita food resources for surviving prey following a predation episode (i.e. thinning) can have a stronger positive effect on prey growth and development than the negative effect of anti-predator responses. I also show that the strength of an anti-predator response is dependent on resource availability of the prey, with prey responding less strongly when resources are scarce. My results also indicate that the strength of the anti-predator response of damselfly larvae depends on predator diet and larval age. Predators feeding on prey conspecifics induce a stronger behavioural response in young larva than predators that feed on prey heterospecifics do. This diet-effect was not found in larvae late in ontogeny, due to an increased activity of larva where predators consumed damselflies. Such increased larval activity can be explained as a reaction to a time-constraint. Finally, I found that activity of damselfly larvae is genetically determined and that this has lead to a behavioural syndrome that might limit larval plasticity to a certain activity-range. This phenomenon may have implications for how well larvae are able to react to both biotic and abiotic changes in the environment.

In the domain of the complex control problems for agents, neuroevolution, i.e. artificial evolution of neural networks, methods have been continuously shown to offer high performance solutions which may be unpredictable by external controller design. Recent studies have proved that these methods can also be successfully applied for cooperative multi-agent systems to evolve the desired team behavior. For a given task which may benefit from both cooperation and behavioral specialization, the genetic diversity of the team members may have important effects on the team performance. In this thesis, the single prey hunting problem is chosen as the case, where the performance of the evolved predator teams with distinct genetic similarity levels are systematically examined. For this purpose, three similarity levels, namely homogeneous, partially heterogeneous and heterogeneous, are adopted and analyzed in various problem-specific and algorithmic settings. Our similarity levels differ from each other in terms of the number of groups of identical agents in a single predator team, where identicalness of two agents refers to the fact that both have the same synaptic weight vector in their neural network controllers. On the other hand, the problem-specific conditions comprise three different fields of vision for predators, whereas algorithmic settings refer to varying number of individuals in the populations, as well as two different selection levels such as team and group levels. According to the experimental results within a simulated grid environment, we show that different genetic similarity level-field of vision-algorithmic setting combinations beget different performance results.