Dissertations / Theses on the topic 'Foraging strategy'

Classical experiments on honey bee time-memory showed that foragers trained to collect food at a fixed time of day return the following day with a remarkable degree of time-accuracy. A series of field experiments revealed that not all foragers return to a food source on unrewarded test days. Rather, there exist two subgroups: "persistent" foragers reconnoiter the source; "reticent" foragers wait in the hive for confirmation of source availability. A forager's probability of being persistent is dependent both on the amount of experience it has had at the source and the environmental conditions present, but the probability is surprisingly high (0.4-0.9). Agent-based simulation of foraging behavior indicated these high levels of persistence represent an energetically optimal strategy, which is likely a compromise solution to an ever-changing environment. Time-memory, with its accompanying anticipation, enables foragers to improve time-accuracy, quickly reactivating the foraging group to more efficiently exploit a food source.

This thesis examines the migration strategy, diet and foraging ecology of the smallest Atlantic seabird, the European Storm Petrel Hydrobates pelagicus.Evidence was found for sex-specific migration behaviour, opportunistic feeding, temporal variation in diet, and the strategy regulation of energy reserves in response to varying environmental conditions, as a buffer against starvation during migration. Molecular sexing from feather and faecal samples revealed an unexpectedly strong female bias in the sex ratio of Storm Petrels attracted to tape-lures of conspecific calls, during their northwards migration past the coast of SW Portugal. The thesis describes the development and application of molecular techniques, in combination with stable isotope analysis, to study Storm Petrel diet by the detection of prey DNA from faecal samples. The major category of prey detected was fish (chiefly European Sardines Sardina pilchardus). Other components of the diet were other pelagic and demersal fish species, Cephalopoda (primarily cuttlefish Sepia spp.), Amphipoda, Isopoda and a range of terrestrial invertebrates. Large between-year fluctuations in the level of body reserves carried by these birds were observed over the 21-year study period (1990-2010). The pattern of body mass variation followed a smooth oscillation, which was not an artefact of differences among years in the distribution of capture effort, body size or sex ratio changes. Local sea surface temperature (SST), net primary production (NPP) and European Sardine biomass were key factors associated with between-year changes in Storm Petrol body reserves. These associations suggest that Storm Petrels strategically regulate their body reserves to buffer against starvation in years of low food abundance.

Les mammifères marins de l'Océan Austral sont des éléments essentiels des écosystèmes marins antarctiques et des sentinelles de l’état des océans polaires. Comprendre comment les conditions océanographiques déterminent leurs habitats préférentiels est essentiel pour identifier de quelle façon et dans quelle région ces mammifères acquièrent les ressources nécessaires à leur déplacement, leur croissance, leur reproduction et donc leur survie. Les éléphants de mer du Sud (Mirounga leonina) se déplacent dans l’océan austral à l’échelle des bassins océaniques pour s’alimenter en plongeant en moyenne à 500 m et jusqu’à 2000 m de profondeur. En fonction de leur colonie d’origine, de leur sexe, et de leur âge, ils exploitent des régions radicalement différentes de l’océan austral, mettant ainsi en œuvre des stratégies alimentaires diversifiées. Les éléphants de mer de Kerguelen utilisent deux zones préférentiellement: la zone du Front Polaire ou la zone Antarctique couverte par la banquise. Dans cette thèse, les stratégies alimentaires des voyages post-mue Antarctiques de 46 mâles et femelles éléphants de mer de Kerguelen ont été étudiées. Une série temporelle de 11 années (2004-2014) de données de déplacement, de plongées et de données hydrologiques a été analysée pour déterminer le rôle des paramètres océanographiques et de glaces de mer impliqués dans l’acquisition des ressources alimentaires des éléphants de mer en Antarctique. L’influence de la variabilité spatio-temporelle et interannuelle de la glace de mer associée à la position des mâles et des femelles ainsi que le rôle des polynies côtières sur les stratégies alimentaires des mâles en hiver ont été examinés
Understanding how physical properties of the environment underpin habitat selection of large marine vertebrates is crucial in identifying how and where animals acquire resources necessary for locomotion, growth and reproduction and ultimately their fitness. The Southern Ocean harbors one of the largest and most dynamic marine ecosystems on our planet which arises from the presence of two majors physical features, (i) the Antarctic Circumpolar Current and (ii) the seasonal sea ice cover region. In the Antarctic, marine predators are exposed to climate-induced shifts in atmospheric circulation and sea ice. However, because these shifts vary regionally, and because much remains to be understood about how individual animals use their environment, it has been difficult to make predictions on how animals may respond to climate variability. Southern elephant seals (Mirounga leonina) are a major consumer of Southern Ocean resources and use two main large scale foraging strategies, (i) feeding in the frontal zone of the Southern Ocean, or (ii) feeding in the seasonal sea ice region. In the present thesis I examined the winter post-moulting foraging strategies of 46 male and female Kerguelen southern elephant seals which utilized the second strategy. Using an eleven year time-series of tracking, diving, and seal-collected hydrographic data (from 2004-2014) I assessed their movements and foraging performance in relation to in situ hydrographic and sea ice conditions. The influence of both the spatio-temporal and inter-annual variability of sea ice around seal locations was investigated, and an investigation on the role of polynya for male elephant seal during winter conducted

Although group-living is widespread in animals, the degree of social complexity varies markedly within and among taxa. One important precondition for the evolution of higher forms of social complexity is increasing group size. However, this imposes a challenge: finding sufficient food for growing numbers of individuals. One hypothesis is that the (in)ability to avoid resource competition as group size increases, could partly explain variation in social complexity among vertebrates. Increasingly, evidence suggests that resource competition can be reduced via three forms of individual specialisation. These are foraging niche specialisation, specialisation to a role under division of labour (DoL), and as a mediator of these two, personality variation. Yet few studies have directly investigated the role of these specialisations in mediating the costs of increasing group size in social vertebrates. In this thesis, I first review the evidence to date that specialising to a foraging niche, and/or to a task under DoL, is (1) mediated via personality variation and (2) can be a means of reducing competition, generated by increasing group size, in social species (Chapter 2). Then, using the cooperative breeding chestnut-crowned babbler (Pomatostomus ruficeps) as my model system, I empirically test some of the hypotheses posed in this review, regarding foraging niche specialisation and associations with personality variation. In Chapter 3, I show that babblers do show personality variation in traits likely to facilitate niche segregation, and in Chapter 4 that variation among individuals within groups is sufficient to lead to intragroup niche specialisation. However, I find that the level of variation within groups is not associated with group size. Then in Chapter 5, I show that in a direct measure of foraging niche, there is only limited evidence for intragroup specialisation, and again that any specialisation is not associated with larger group sizes. I therefore find no evidence that niche specialisation is a means through which babblers can overcome the costs of increasing group size. I discuss the implications of these results for the rise of social complexity in this system, and social vertebrates generally.

Typescript. Includes vita and abstract. Bibliography: Includes bibliographical references (leaves 89-91).
A geometric model using idealized prey behaviors in reaction to wading bird disturbances was developed to hypothesize how wading bird foraging strategy might most efficiently counter those behaviors. The model suggests that for prey responding to wading bird disturbances with flight response distance strongly negatively correlated to their distance from the point of disturbance, wading birds could employ disturbance facilitated social foraging strategy, thereby increasing individual foraging efficiency and selecting for social foraging. In controlled studies of the reactive behaviors of two primary prey species seen to be taken at disparate rates by solitary and socially foraging herons, schooling Shiner Surfperch exhibited behaviors favoring social foraging in herons, while Staghorn Sculpins exhibited no correlation in their flight response distances relative to their proximity to the disturbance, and seemed unlikely to be more efficiently utilized by socially foraging wading birds.

Kyoto University (京都大学)
0048
新制・課程博士
博士(地域研究)
甲第16198号
地博第115号
新制||地||37(附属図書館)
28777
京都大学大学院アジア・アフリカ地域研究研究科アフリカ地域研究専攻
(主査)准教授 山越 言, 教授 小林 繁男, 准教授 森 哲, 准教授 中川 尚史
学位規則第4条第1項該当

Thesis (M.A.)--Georgia State University, 2006.
Title from title screen. Frank L'Engle Williams, committee chair; Aras Petrulis, Susan McCombie, committee members. Electronic text (69 p.) : digital, PDF file. Description based on contents viewed Apr. 26, 2007. Includes bibliographical references (p. 58-67).

Faire un choix n’est pas juste un évènement spontané. La recherche d’une ressource alimentaire, par exemple, implique un investissement temporel et est donc en conflit avec d’autres activités essentielles telles que la vigilance pour les prédateurs. Ainsi être sélectif augmente le risque de se faire attaquer par un prédateur. Par ailleurs, être sélectif implique aussi de rejeter beaucoup de potentielles options avant de finalement en accepter une et donc accepter une perte non négligeable d’opportunités en présence de potentiels compétiteurs. Pour ces raisons, une réduction du niveau de sélectivité est attendue chez un individu exposé à une situation de forte compétition ou à un fort risque de prédation. Les carabes évoluent au sein de communautés composées, pour la plupart, d’un nombre important de potentiels compétiteurs et prédateurs. Les connaissances actuelles en écologie comportementale et en écologie prévoient que le comportement d’approvisionnement alimentaire des coléoptères carabiques devrait varier en fonction des niveaux de risques de compétition et de prédation qu’ils rencontrent et donc de la composition des communautés dans lesquelles ils se trouvent. Dans cette thèse, nous avons mesuré les changements de sélectivité alimentaire de deux espèces de carabes en présence de signaux de prédateurs ou de compétiteurs. A l’aide d’expériences de laboratoire effectuées à différentes échelles spatio-temporelle, nous avons réussi à montrer que la sélectivité alimentaire d’un carabe granivore Harpalus affinis peut varier en fonction du contexte dans lequel il cherche sa nourriture et être diminuée en présence de prédateurs. Par ailleurs le sexe des individus, l’espèce de graine qui leur est proposée et l’intensité du risque auquel ils sont confrontés semblent aussi avoir un effet sur la variation de sélectivité des individus. Aucun lien n’a cependant été trouvé entre le statut immunitaire ou la personnalité des individus et leur niveau de sélectivité alimentaire. Testé dans des conditions similaires, le carabe omnivore Poecilus cupreus, quant à lui, ne fait pas varier sa sélectivité pour les ressources testées. S’ils sont extrapolables ces résultats pourraient servir à expliquer la grande variabilité des taux de prédation de graines au champ par les carabes rapportés dans les différentes études. Ces résultats pourraient permettre aussi d’expliquer la difficulté d’extrapolation existante entre les taux de prédation de graines mesurés en laboratoire et les résultats obtenus au champ. Globalement, cette thèse confirme qu’une meilleure compréhension du processus de prise de décision chez les carabes est essentielle pour évaluer leur efficacité en tant que potentiels auxiliaires de cultures
Making a choice requires, implicitly, an investment of time in one behaviour at the expense of an investment in another. Being choosy would increase the risk of losing many food item opportunities to competitors, and is directly in conflict with other essential tasks such as predator avoidance. Individuals are thus expected to adjust their level of choosiness in response to the competition and predation context. The available behavioural ecological theory and the empirical ecology of carabids would suggest that competition and predation interference induces changes in the foraging behaviour of carabid individuals. Carabids typically operate within communities in which competition and predatory interference interactions occur and are ever present; there are high levels of intraguild interference. A better understanding of how risks of these two interference interactions modify individual decision making for prey would therefore help to improve the biocontrol of weeds by communities of carabids. This thesis focused on how changes in level of choosiness occur when individual carabids forage under intraguild interference. Using laboratory experiments, done at different spatio-temporal scales, we demonstrate that the decision-making processes of foraging carabids might differ between contexts, between species and between individuals. Our focal species, the granivore Harpalus affinis, was found to reduce its level of choosiness while foraging under intraguild interference. In doing so H. affinis individuals increased their overall rate of seed acceptance. This change in choosiness was dependant on the intensity of the risk, the seed species offered in test and the sex of individuals. We found no link between individual levels of choosiness and either immunity or personality traits. When tested under similar conditions, individuals of the omnivorous carabid Poecilus cupreus did not change their level of choosiness for seeds. These findings would help explain the high variability in seed predation rates observed between studies conducted in-field, and the differences observed between laboratory studies and fields measurements in carabids. Globally, this thesis has confirmed that a deeper understanding of the decision making process of carabids seed-eating species is requires to evaluate their choice of prey and assess their relevance as biological control agents in the wild

Ips typographus est le principal ravageur de l'épicéa en Europe, s’attaquant en masse aux arbres vivants en période d’épidémie, par le biais d’une communication chimique. Comme de nombreuses autres espèces de scolytes « agressives », le typographe se reproduit uniquement sur des arbres affaiblis ou des chablis en périodes d’endémie, quand les densités de population ne sont pas suffisantes pour surmonter les défenses des arbres vivants. Ces ressources sont en général présentées dans la littérature comme étant dispersées et imprédictibles dans le temps et l’espace. De plus, ces ressources affaiblies sont sans doute disponibles pour de nombreuses espèces compétitrices. Ces caractéristiques imposent des contraintes importantes sur la dynamique de population et l’écologie du typographe et principalement sur sa stratégie de prospection. Cela dit, cette espèce et ces questions sont très peu étudiées en période d’endémie.Durant ma thèse de doctorat, je me suis attelé à tout d’abord caractériser les facteurs déterminant la distribution spatio-temporelle des chablis, qui va influencer l’évolution des stratégies de dispersion. Cet aspect s’est prolongé par l’étude de la « durée de vie » des chablis, c’est-à-dire la période durant laquelle ils sont colonisables par les scolytes après déracinement. Cet aspect a été mis en parallèle avec les capacités de défenses de ces mêmes arbres et leurs effets sur la sélection de l’hôte et le succès des scolytes. Enfin, les données obtenues par ces études ont été intégrées à un modèle spatialement explicite visant à valider les hypothèses comportementales relatives à la prospection pour les ressources chez le typographe, à savoir une dispersion aléatoire à grande distance suivie d’un recrutement au niveau des ressources nouvellement trouvées.Les résultats obtenus au cours de cette thèse confirment l’importance de la prospection sociale et de l’agrégation dans la découverte et l’exploitation de ressources dispersées, dont la dégradation intrinsèque représente une faible contrainte temporelle. Ces comportements ont sans doute été développés chez des insectes saproxyliques en raison de l’avantage qu’ils apportent en termes de découverte de ressources. Dans un second temps, ces comportements auraient pu permettre l'attaque d‘arbres vivants, notamment en réponse à une pression de compétition inter-spécifique importante sur des ressources peu défendues.
Option Biologie des organismes du Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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(Novas perspectivas sobre a ocorrência do comportamento de caroneira). Durante o forrageamento de formigas cortadeiras pode-se observar operárias mínimas sobre os fragmentos de folha transportados até o ninho, comportamento denominado de caroneira. São citadas várias funções relacionadas a este comportamento, como defesa contra forídeos parasitoides, limpeza dos fragmentos de folhas, economia de energia de retono ao ninho, além de ingestão de seiva que exsuda do corte. Sendo assim, o presente estudo se apresenta como uma forma de elucidar questões ecológico-comportamentais de caroneira em Acromyrmex subterraneus, tendo por objetivos avaliar i) se as caroneiras ocorrem de forma aleatória ou dependente do fragmento vegetal transportado, ii) se a carga microbiana influencia a frequência de caroneiras e iii) como as caroneiras respondem a variações no tráfego de forrageamento. Para tanto, foram feitas manipulações nos fragmentos vegetais oferecidos e nas trilhas de forrageamento. No primeiro experimento verificou-se que caroneiras podem ocorrer em qualquer tamanho de fragmento ou espécie vegetal, mas há variação do tamanho da caroneira em função do fragmento. Tal fato demonstra alta plasticidade deste comportamento, de forma a ocorrer sobre os mais diversos substratos. No segundo experimento a presença de fungo entomopatogênico e antibióticos diminuiu a ocorrência de caroneiras, não sendo possível relacionar a frequência de caroneiras com a remoção de carga microbiana. Sugere-se que as caroneiras tenham evitado contato com os conídios fúngicos e com as soluções antimicrobianas porque eram substâncias desconhecidas pelas operárias. Já no terceiro experimento observou-se incremento da frequência de caroneiras em trilha estreita, com alta densidade de operárias. De fato, a frequência de caroneiras se correlacionou positivamente com o fluxo de operárias que deixavam o ninho nos três experimentos. Devido à alta frequência de encontros promovida pelo aumento do fluxo de operárias que saem do ninho e da densidade de operárias na trilha estreita sugere-se que o comportamento de caroneira é estimulado por esta taxa de encontros, que é agente regulatório de alocação de tarefas. O comportamento de caroneira pode ser considerado uma estratégia comportamental para redução do tráfego de operárias nas trilhas.
(New perspectives of hitchhiking behavior occurrence). During foraging of leafcutting ants, it can be observed minimal workers over leaf fragments, called hitchhikers. Many functions are cited as related with hitchhiking behavior, as defense against parasitoids, leaf cleaning, energy saving and sap feeding. Here, the objectives were to evaluate i) if hitchhiker occurrence is plant-size-species-dependent, ii) if microbial load influences hitchhiker frequency and iii) how hitchhiker frequency is influenced by high density of foraging traffic. It has been manipulated leaf fragments and foraging trails. In first experiment, it has been verified that hitchhikers could occur over any fragment size or plant species, but hitchhiker masses varied among plant species. In the second experiment, the entomopathogenic fungus and antibiotics reduced hitchhiker occurrence. Thus, it was not possible to relate hitchhiker frequency with microbial load removal. It has been suggested that hitchhikers avoid the conidia fungal and the antibiotic solutions due to these materials are unknown by workers. In the third experiment, hitchhiker frequency has been higher at narrow trails, which has greater worker density. Actually, hitchhiker frequency has been positively correlated with the outbound worker flow in the three experiments. Due to high head-on encounters promoted by the increased outbound worker flow and by the greater worker density in narrow trails, it has been suggested that hitchhiker behavior is stimulated by these encounters, which are regulatory agents of task allocation. The hitchhiker behavior could be considered a behavioral strategy to reduce worker traffic along foraging trails.

Orientador: Elza Maria Guimarães Santos
Resumo: A limitação de pólen é um dos fatores que mais afeta a produção de frutos e sementes de muitas populações naturais. Cerca de 60% das angiospermas apresentam baixo sucesso reprodutivo decorrente da transferência ineficiente dos grãos de pólen pelos polinizadores. Assim, o objetivo geral desse estudo foi avaliar diversos aspectos ligados à limitação de pólen em Zeyheria montana (Bignoniaceae), uma espécie ornitófila e autoincompatível. Ao longo do período de florescimento, com ampla variação do anúncio floral, nós avaliamos o efeito do padrão de forrageamento dos polinizadores dentro e entre plantas sobre o sucesso reprodutivo das mesmas. Avaliamos também as estratégias de forrageamento empregadas por cada espécie de polinizador e o efeito do roubo de néctar sobre a produção de frutos. Além disso, estimamos o tamanho do genoma das plantas com a finalidade de avaliar se havia variações intrapopulacional no nível de ploidia que pudessem estar associadas ao baixo sucesso reprodutivo. Em geral, nós demonstramos que a baixa qualidade do pólen transferido pelos polinizadores é o principal fator limitante do sucesso reprodutivo de Z. montana. Esse efeito ocorre principalmente no pico do florescimento, quando o anúncio floral é mais intenso, e os polinizadores tendem visitar um maior número de flores sequenciais dentro da mesma planta transferindo pólen incompatível. Além disso, o padrão de movimento entre plantas também não se mostrou eficiente, visto que os polinizadores frequentemen... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Pollen limitation is one of the factors that most affects the fruits and seeds production of many natural populations. Around 60% of angiosperms have low reproductive success due to inefficient pollen grains transfer among flowers by pollinators. Thus, the general goal of this study was to evaluate several aspects related to pollen limitation in Zeyheria montana (Bignoniaceae), an ornithophilous and self-incompatible species. Throughout the flowering period, with wide variation in floral display, we evaluated the effect of the pollinators’ foraging pattern within and between plants on their reproductive success. We also evaluated the foraging strategies employed by each pollinator species and the effect of nectar robbing on fruit production. In addition, we estimated the plants’ genome size in order to evaluate whether there were intrapopulation variations in the ploidy level that could be associated with the low reproductive success. In general, we demonstrated that the low pollen quality transferred by pollinators is the main limiting factor of the reproductive success. This effect occurs mainly at the flowering peak, when the floral display is more intense, and pollinators tend to visit a larger number of sequential flowers within the plant transferring incompatible pollen. In addition, the movement pattern between plants also was not efficient, since pollinators often visited nearby plants that possibly were more related. Although some hummingbirds species alternate their... (Complete abstract click electronic access below)
Doutor

L'objectif principal de cette thèse est d'étudier comment la sélection naturelle façonne les traits d'histoire de vie et le comportement des animaux en fonction de l'environnement écologique dans lequel ils évoluent. Ce cadre théorique soulève des hypothèses spécifiques concernant les processus de reproduction, de dispersion et d'approvisionnement chez le parasitoïde Ibalia leucospoides. Les expériences d'écologie comportementale et d'écophysiologie menées sur des parasitoïdes femelles d' Ibalia leucospoides démontrent principalement que (1) la proportion d'oeufs matures que possède la femelle à l'émergence est élevée par rapport à sa fécondité potentielle : I. Leucospoides adopte une stratégie proovigénique ; (2) l'alimentation a un effet négligeable sur les femelles adultes : elle n'influence ni la maturation des oeufs, ni la survie, ni les capacités de vol ; (3) dans nos conditions expérimentales, la capacité de vol dépend des caractéristiques morphologiques du parasitoïde (taille et charge alaire) ; et (4) concernant la recherche d'hôtes, les femelles sont capables de discerner des différences dans la qualité des patchs d'hôtes à distance, sans les échantillonner. D'autre part, le temps d'exploitation d'un patch dépend des informations obtenues des patchs voisins. Le succès reproductif du parasitoïde proovigénique Ibalia leucospoides, n'est pas limité par le manque de nourriture chez l'adulte. La stratégie d'allocation des ressources entre les différentes fonctions biologiques, ainsi que le comportement d'approvisionnement adopté par cette espèce de parasitoïde pourraient vraisemblablement être une réponse aux caractéristiques de l'habitat, telle que la distribution fortement agrégée des Sirex noctilio, l'hôte, ainsi que la disponibilité des ressources (i.e. hôtes et nourriture)
The central aim of this thesis is to explore how natural selection shapes life history traits and behaviuors according to the ecological environment in which an animal exists. This overall framework leads to specific hypotheses concerning the reproductive, dispersal and foraging processes in the parasitoid Ibalia leucospoides. The experiments in behavioural ecology and eco-physiology in female parasitoids of Ibalia leucospoides show as main results, that (1) the proportion of the potential lifetime eggs complement that is mature at female emergence is high; (2) low dependency on adult female feeding, not only for egg maturation but also for survival and flight; (3) under our experimental conditions flight capacity depends on the morphological characteristics of the parasitoid (size and wing loading); and (4) regarding host foraging, females accurately assess differences in host patch quality from a distance without the need of displaying a sampling process; in addition that patch exploitation times depend on the information obtained from the surrounding patches. The reproductive success of I. leucospoides, a proovigenic parasitoid, is not constrained by adult food deprivation. Both the resource allocation strategy toward the different biological functions and the foraging behaviour adopted by this parasitoid species may well be in respond to habitat characteristics, such as a strongly aggregated distribution of Sirex noctilio, the host, as well as to the resources availability (i.e. host and food)

Birds are a major pest in vineyards both in New Zealand and overseas. There is a need for new behavioural research on birds' foraging habits and feeding preferences in vineyards, as much of the literature to date is anecdotal. Research on cues to birds' feeding will provide a basis on which new deterrent and control strategies can be devised. Spatial-and temporal bird damage in a small vineyard block was mapped to find if damage was correlated with grape maturity and environmental factors. Vineyard and field observations of bird behaviour using video technology combined with preference experiments aimed to establish the relative roles of grape sugar concentration and colour in avian selection. Proximity of vineyards to bird roosts affects damage levels, regardless of differing maturity between locations. The rate of damage tends to increase exponentially once grape maturity has passed a threshold of 13 °Brix. Bunches positioned closest to the ground receive more damage if blackbirds or song thrushes are the predominant pests. Both sugar concentration and grape colour were found to affect birds' feeding preference, but the importance of the two factors varied between years. Black and green grape varieties were differentially preferred by blackbirds (Turdus merula) and song thrushes (Turdus philomelos) while silvereyes (Zosterops lateralis) appeared to have no strong colour preference. It was apparent that there were other, not assessed, grape factors that also affect selection. In small unprotected vineyards that are adjacent to bird roosts the entire grape crop can be taken by bird pests. Besides removing the roosts, which can be beneficial shelterbelts in regions exposed to high winds, growers currently may have no alternative other than to use exclusion netting to keep crops intact. The differential preferences between bird species for variety characteristics suggest that any new deterrents and other strategies to deflect birds from grape crops may need to be species-specific.

L’océan austral est un écosystème fragile dont la dynamique est influencée par des variations climatiques qui vont structurer la distribution spatio-temporelle des ressources. L’objectif de cette thèse était d’étudier les stratégies d’acquisition des ressources en proies mises en place par l’éléphant de mer austral face aux contraintes énergétiques (coûts du transport et coûts d’accès à la ressource) et temporelles (temps passé au fond d’une plongée et limite de plongée aérobie) auxquelles il est soumis. L’utilisation d’un ensemble d’enregistreurs de données déployés sur ces animaux a permis de reconstruire en trois dimensions leur plongée, mais également de calculer leur effort de nage, le nombre de proies rencontrées ainsi que leur dépense énergétique. Notre étude montre qu’à l’échelle d’une plongée, les éléphants de mer adaptent leur trajectoire, mais également le temps qu’ils passent au fond, en fonction du nombre de proies rencontrées. Pour des densités locales de proie importantes, ils passent plus de temps au fond, et concentrent leur recherche en zone restreinte, caractérisée par une diminution de la vitesse et une augmentation de la sinuosité horizontale. Au-delà de 550 m, le coût d’accès aux ressources devient supérieur aux coûts d’acquisition ; ils doivent alors faire face à un compromis entre l’accessibilité et la disponibilité en proies. À mesure qu’ils s’alimentent, ces phoques augmentent leur flottabilité, diminuant de surcroît leur dépense énergétique. Cette étude démontre également une structuration spatio-temporelle de cette dépense énergétique qui semble être liée au succès d’alimentation et donc à la distribution des ressources en proies
The Southern Ocean is a fragile ecosystem whose dynamics are influenced by climate change that will structure the spatio-temporal distribution of resources. The objective of this PhD was to investigate the foraging strategies used by the southern elephant seal, under energetic (cost of transport and costs of access to the resource) and temporal (time at the bottom of a dive and aerobic dive limit) constraints. Using a set of animal-borne data loggers allowed us to reconstruct their three-dimensional path underwater, but also to calculate their swimming effort, the number of prey encountered and their energy expenditure. At the dive level, our study shows that elephant seals adapt their path, but also the time spent at the bottom, depending on the number of prey encountered. For high local prey density, they spent more time at the bottom, and concentrated their foraging effort in areas restricted search, characterized by a decrease in speed and an increase in horizontal sinuosity. Beyond 550 m, the cost of access to resources becomes greater than the cost of acquisition ; they must therefore deal with a trade-off between prey accessibility and availability. While feeding, these seals increase their buoyancy, reducing furthermore their energy expenditure. This study also shows a spatio-temporal structure of the energy expenditure that appears to be related to feeding success and therefore to prey resources distribution

Doctor of Philosophy
Department of Biology
David A. Haukos
The lesser prairie-chicken (Tympanuchus pallidicinctus) is 1 of 3 prairie-grouse species in North America. Prairie-grouse have undergone local or widespread declines due to a loss of habitat through conversion to row crop agriculture, anthropogenic development, and alteration of ecological drivers that maintain quality grasslands. For lesser prairie-chickens, habitat loss and declines were deemed significant for listing as threatened under the Endangered Species Act in 2014. Despite a judge vacating the listing decision in 2015, the lesser prairie-chicken remains a species of concern. Conservation plans are currently being implemented and developed. To maximize the effectiveness of efforts, knowledge of the distribution of lesser prairie-chickens, regional demography, foods used during critical life-stages, and where to prioritize management is needed. To guide future conservation efforts with empirical evidence, I captured, marked with transmitters, and monitored female lesser prairie-chickens in Kansas and Colorado during 2013–2016 (n =307). I used location data to predict the distribution of habitat. Encounter data from individuals were used to estimate vital rates and integrated into a matrix population model to estimate population growth rates (λ). The matrix model was then decomposed to identify life-stages that exert the greatest influence on λ and vital rate contributions to differences in λ among sites. After assessing demography, I examined the diet of adults and chicks during critical brood rearing and winter periods using a fecal DNA metabarcoding approach. Overall, potential habitat appears to compromise ~30% of the presumed lesser prairie-chicken range in Kansas with most habitat in the Mixed-Grass Prairie Ecoregion. Within occupied sites, populations were most sensitive to factors during the first year of life (chick and juvenile survival), however, the persistence of populations through drought may rely on adult survival. Among regional populations, breeding season, nest, and nonbreeding season survival rates contributed most to differences in λ among sites, breeding season survival contributed to differences in λ among more and less fragmented sites. During critical life-stages, diets were comprised of arthropod and plant foods. Among 80 readable fecal samples, 35% of the sequences were likely from Lepidoptera, 26% from Orthoptera, 14% from Araneae, and 13% from Hemiptera. Plant sequences from 137 fecal samples were comprised of genera similar to Ambrosia (27%) Latuca or Taraxacum (10%), Medicago (6%), and Triticum (5%). Among cover types, lesser prairie-chickens using native grasslands consumed a greater diversity of foods. Last, promising conservation options include the conversion of cropland to grassland through the Conservation Reserve Program (CRP) and tree removal in mixed-grass prairie landscapes. Lesser prairie-chickens mostly used CRP during nesting and the nonbreeding season, during drier periods, and in drier portions of their distribution. Strategic CRP sign-up and tree removal could recover >60,000 ha and~100,000 ha of habitat respectively. In summary, conservation that targets management in areas within broad scale habitat constraints predicted will be most beneficial. In areas occupied by lesser prairie-chickens, management that increases brood survival in large grasslands having optimal nesting structure will elicit the strongest influence on population growth and will likely be the most resilient to stochastic drought-related effects.

Scholars of the Late Pleistocene in Southern Africa have recently sought to develop models explaining long-term variation between Middle Stone Age and Late Stone Age assemblages in terms of variability between “macrolithic” vs. “microlithic” toolmaking systems associated with shifts in hunter-gatherer ecology and land use patterns. While it has often proven extremely difficult to actually test many models, recently developed methods allow us to do so in novel ways. In this dissertation, I use new archaeological data from excavations of two sites in the Namib Desert, as well as new approaches to sourcing lithic artifacts to examine the hypothesis that contrasts between terminal Pleistocene (ca. 15-20 ka BP) and early Holocene (ca. 6-12 ka BP) occupation phases at the two sites represent adaptive responses primarily driven by changes in fluvial regimes and the resource productivity of riparian corridors. Analyzing the lithic assemblage compositions and locating probable source areas for raw materials suggests that terminal Pleistocene groups likely centered land use strategies more toward upland areas east of the study sites and periodically followed broad riparian corridors into the desert itself. Early Holocene groups expanded their ranges and more intensively targeted resources on the open desert plains, dunes, and beaches of the coastal lowlands. My results suggest environmental change may be partially responsible for driving this shift, but new data and methodological tools are needed to address factors like fluctuations in regional population size that may have been driving shifts in the late Pleistocene record of this unique region of Southern Africa.

The Eurasian spruce bark beetle Dendroctonus micans is a major pest of spruce which is expanding its range in France, Turkey, England and Wales. Its monospecific predator Rhizophagus grandis has followed naturally the bark beetle into most areas and, since the 1960s, has also been mass-produced and successfully released within newly infested locations.

In this scope, the development of an effective trapping method would be very useful to assess the bark-beetle presence at previously uninfested sites, or predator establishment after release or natural spread. We demonstrated the efficiency of oxygenated monoterpenes-baited kairomone traps to monitor R. grandis in various epidemiological conditions, including areas localized behind or at the limit of the pest’s distribution, or in areas where artificial releases were performed. Because the predator is strictly species-specific, another exciting possibility offered by the kairomone trapping is the indirect monitoring of the pest itself in areas of unknown status (e.g. areas under colonization, or considered as at risk at medium- term).

R. grandis is also considered as one of the most valuable natural enemies to strike aggressive North-American Dendroctonus species. In this respect, R. grandis has been recently applied in a neo-classical biological program against the red turpentine beetle D. valens, which invaded China from North America in the late 1990’s. In laboratory tests conducted on pine logs in the laboratory, or on living pine trees in the field, we demonstrated that R. grandis adults can successfully enter and reproduce into D. valens galleries.

In Europe, R. grandis is the only species regularly found in the brood systems of D. micans, where adults and larvae attack the gregarious larvae of their prey. In such enclosed systems, R. grandis’ functional response is therefore influenced by various interrelated components, such as the prey density, the predator density, or the prey distribution. Measuring the predator’s success in terms of larval survival and growth rates, we demonstrated the time spent by R. grandis larvae to wound and kill their prey to be the main factor limiting their development. This factor may be considerably influenced by the proportions of diseased, wounded or molting prey rise in the brood system, for instance as a result of an increase in prey density, or due to the presence of conspecific adults (which wound their prey but do not consume them entirely). Furthermore, our tests suggest that no cannibalism or noticeable intraspecific competition occurred between R. grandis larvae, whereas some lighter mode of competition probably took place.

R. grandis also exhibits a reproductive numerical response to prey density, which mainly relies on the perception of chemical stimuli and inhibitors released in the bark beetle brood system. In the current study, we developed a non-destructive approach to follow the dynamics of volatile compound production, using sequential sample collection on SPME fibers. Our tests demonstrated that the larval activity of D. micans or D. valens strongly influences the release of some oxygenated monoterpenes. However, our attempts to correlate the relative quantities of some identified chemicals to offspring production were less successful as it concerns the identification of potential oviposition stimuli and inhibitors.

The problematic rose by the progression of D. micans, as well as detailed results of each of the described above studies are discussed in the two published papers and the three manuscripts forming this thesis. Bringing all these studies together, several perspectives are also presented in the general discussion.

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Ravageur des épicéas, Dendroctonus micans est toujours en voie d’extension en France, en Turquie, en Angleterre et au Pays de Galles. Dans la plupart de ces zones, le dendroctone est accompagné de manière naturelle par son prédateur monospécifique, Rhizophagus grandis. Depuis les années 1960, le prédateur a également fait l’objet d’une production de masse et de programmes de lâchers dans les zones d’arrivée récente du scolyte.

Dans le cadre de la lutte biologique contre D. micans, les gestionnaires forestiers doivent donc estimer au plus tôt la présence du ravageur dans des zones jusque là indemnes, mais également vérifier l’établissement du prédateur par progression naturelle ou résultant d’introductions délibérées. Dans la présente étude, nous avons démontré l’efficacité de pièges d’interception appatés à l’aide de monoterpènes oxygénés pour la capture de R. grandis. Celle-ci s’est faite dans différentes conditions épidémiologiques, incluant notamment des zones situées en arrière du front de progression du scolyte et des zones où des lâchers artificiels ont été réalisés. Comme R. grandis est strictement inféodé au dendroctone, un autre avantage de la technique est la possibilité de réaliser un dépistage indirect du ravageur dans les zones où son statut est incertain (zones en cours de colonisation, ou considérées comme à risque à moyen terme).

Par ailleurs, R. grandis est également considéré comme un des meilleurs ennemis naturels potentiels pour lutter contre d’autres espèces de Dendroctonus aggressifs. Dans cette optique, R. grandis a été récemment utilisé dans un programme de lute biologique contre D. valens, ravageur invasif arrivé en Chine dans la fin des années 1990 en provenance d’Amérique du Nord. Nous avons démontré la capacité de R. grandis à s’introduire et à se reproduire dans les galeries de D. valens lors de tests de laboratoire, mais aussi sur des arbres vivants en pinèdes.

En Europe, R. grandis est strictement inféodé aux galeries de D. micans, où larves et adultes du prédateur s’attaquent aux larves grégaires du scolyte. Dans ce système clos, la réponse fonctionelle de R. grandis est influencée par plusieurs facteurs étroitement corrélés, la densité de proies, la densité de prédateurs, et la distribution des proies. En mesurant l’efficacité de prédation de R. grandis en termes de survie des larves et de taux de croissance, nous avons démontré l’influence sur leur développement du temps passé par les larves à blesser et à tuer leurs proies. Ce facteur est par ailleurs fortement dépendant de la proportion de larves malades, blessées ou en cours de mue au sein du système ;une proportion qui peut augmenter en réponse à une augmentation de la densité de proies, ou lorsque des adultes sont présents (ceux-ci blessent les proies mais ne les consomment pas entièrement). Enfin, nos tests suggèrent qu’il n’existe que peu de cannibalisme ou de compétition intraspécifique entre larves de R. grandis, tandis que des modes de compétition moins importants prennent vraisemblablement place.

R. grandis présente également une réponse numérique reproductive à la densité de proies disponibles, principalement basée sur la perception de stimuli et d’inhibiteurs présents dans les galeries du scolyte. Par la collecte de composés volatils présents dans ces systèmes à l’aide de fibres SPME, nous avons développé une méthode non-destructive pour suivre la dynamique de production des médiateurs chimiques. Nos tests ont démontré que l’activité des larves de D. micans ou D. valens influence fortement la dynamique de production de certains monoterpènes oxygénés. En revanche, il n’a pas été été possible de corréler les différents composés identifiés au nombre de larves de R. grandis présentes dans le système.

La problématique soulevée par la progression de D. micans, de même que les résultats détaillés de chacune des études décrites ci-dessus sont discutés dans les deux papiers publiés et les trois manuscrits formant cette thèse. Les différentes perspectives apportées par ce travail sont également présentées dans la discussion générale.

Doctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished

Dissertação de Mestrado em Ecologia apresentada à Faculdade de Ciências e Tecnologia
Seagulls are opportunistic seabirds that can feed on a wide variety of food, including anthropogenic resources, traveling even for dozens kilometers in that demand. This work focuses on the foraging strategies (particularly the marine strategy) of the yellow - legged gull (Larus michaellis) in two distinct colonies (Berlenga – from 2011 to 2016 and Deserta – in 2015 and 2016) during the breeding season (May - June). In addition, the strategies of yellow-legged gulls were compared with the foraging strategy of Audouinii gull (Larus audouinii) in Deserta, since this is a species that has a strictly marine foraging strategy. Stable isotope analyses of blood and plasma were measured to detect differences in foraging at breeding season between the years and colonies, as well as GPS loggers to assess foraging behavior performed by gulls of the two species. The objectives were to define the general foraging strategy of the yellow-legged gulls during the breeding season in each year and local, and relate their marine, mix and terrestrial strategies with foraging behavior, niche width and oceanographic conditions. Overall, the results indicated differences in foraging strategies over the years and colonies, and differences in the isotopic niche between the two species of seagulls. It was possible to define the 3 predictable feeding strategies for yellow-legged gulls (marine, mixed and terrestrial). In 2013 in Berlenga, individuals preferred a more terrestrial foraging strategy, supposedly due to the lower NAO values observed during this year. In contrast, 2015 was the year in which the marine foraging strategy was most used. It should be noted that in only some years in Berlenga, mixed trips (2011, 2012 and 2015) were carried out. Results show that the isotopic niche of gulls with a marine foraging strategy was much smaller than the niche of gulls with a terrestrial foraging strategy. Gulls adopting a terrestrial foraging strategy may feed on a wide variety of foods, which greatly influence the amplitude of the isotopic values. It could also be verified that the niche of the audouinii gulls was small and similar to the yellow-legged gulls that used a marine foraging strategy. In conclusion, the feeding strategies of yellow-legged gulls during the breeding season can differ greatly according with the year and location of the colony, and should be influenced by oceanographic conditions and availability of terrestrial and marine food sources.
As gaivotas são aves marinhas oportunistas que se alimentam de uma grande variedade de alimentos, incluindo recursos antropogénicos, viajando mesmo dezenas de quilómetros em busca de alimento. Este trabalho incide nas estratégias de alimentação (particularmente a estratégia marinha) da gaivota de patas amarelas (Larus michaellis) em duas colónias distintas (Berlenga - de 2011 a 2016 e Deserta - em 2015 e 2016) durante a época de reprodução (Maio a Junho). Além disso, as estratégias de gaivotas de pernas amarelas foram comparadas com a estratégia de alimentação da gaivota de Audouinii (Larus audouinii) na Deserta, uma vez que esta é uma espécie que possui uma estratégia de alimentação estritamente marinha. As análises de isótopos estáveis do sangue e plasma foram medidas para detectar diferenças na alimentação na época de reprodução entre os anos e colónias, bem como GPS loggers para avaliar o comportamento na procura de alimentação realizado pelas gaivotas das duas espécies. Os objectivos foram definir a estratégia geral de alimentação das gaivotas de patas amarelas durante a época de reprodução em cada ano e local e relacionar as suas estratégias marinhas, mistas e terrestres com o comportamento na procura de alimento, largura de nicho e condições oceanográficas. No geral, os resultados indicaram diferenças nas estratégias de alimentação ao longo dos anos e colónias e diferenças no nicho isotópico entre as duas espécies de gaivotas. Foi possível definir as 3 estratégias de alimentação previsíveis para as gaivotas de patas amarelas (marinha, mista e terrestre). Em 2013, os indivíduos da Berlenga preferiram uma estratégia de alimentação mais terrestre, provavelmente devido aos menores valores de NAO observados durante esse ano. Em contraste, 2015 foi o ano em que a estratégia de alimentação marinha foi mais utilizada. É de salientar que em apenas alguns anos na Berlenga, foram realizadas viagens mistas (2011, 2012 e 2015). Os resultados mostram que o nicho isotópico das gaivotas com uma estratégia de alimentação marinha foi muito menor que o nicho das gaivotas com uma estratégia de alimentação terrestre. As gaivotas que adoptam uma estratégia de alimentação terrestre podem alimentar-se de uma grande variedade de alimentos, que influenciam muito a amplitude dos valores isotópicos. Pode também verificar-se que o nicho das gaivotas audouinii é pequeno e semelhante ao das gaivotas de patas amarelas que usaram uma estratégia de alimentação marinha. Em conclusão, as estratégias de alimentação das gaivotas de patas amarelas durante a época de reprodução podem diferir muito de acordo com o ano e localização da colónia, e podem ser influenciadas pelas condições oceanográficas e a disponibilidade de fontes de alimento terrestres e marinhas.

Thesis (Ph.D.)--University of Alberta, 2010.
Title from PDF file main screen (viewed on July 8, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Department of Renewable Resources, University of Alberta. Includes bibliographical references.

碩士
國立彰化師範大學
生物學系
107
Tool use by the nonhuman animals has been noticed and researched in recent decades. Compared to the most research about primates and Corvidae, only few researches about the formicidae. In the past, the tool used by ants mainly recorded by observation. Previously research indicate, Aphaenogaster senilis has the selectively preferences and flexibility about tool use. But the tool selection of foraging strategy between different colony size didn't have further investigate. In this research, we want investigated the tool selection of foraging strategy between different colony size in Aphaenogaster tipuna: (1) Does the different colony size have the different time to find the resource. (2) Does the first forager from the different colony size will has different time to take sugar water. (3) Does the first forager from the different colony size will has different behavior after taking sugar water. (4) Does the first forager from the different colony size will has different preferred choice about tool use (sponge, rock grains, soil grains, and leaf fragments), (5) Does the first forager from the different colony size will has different tool selection strategy. The result showed that A. tipuna worker could find the sugar water quickly, and all colony size preferred to recruitment their mate after taking sugar water. However, worker from the large colony size could spend less time taking sugar water than the small colony size. The worker from the large colony size preferred to use sponge than the other tools, but the worker from the small colony size has no obviously preferred about the tool use. These results indicate that A. tipuna has flexible tool selection of foraging strategy between different colony size.

碩士
國立勤益科技大學
資訊工程系
101
In this thesis, we propose a fuzzy cerebellar model articulation controller (FCMAC) model with improved bacterial foraging optimization (BFO). The proposed modified bacterial foraging optimization is called Strategy-adaptation-based Bacterial Foraging Optimization (SABFO). The SABFO is use to adjust the weights of FCMAC model and facilitate the actual output of the FCMAC model approximating the desired output for classifications. This thesis consisted of two major parts. In the first part, we propose a new Strategy-adaptation-based Bacterial Foraging Optimization. The main contribution of this study is adding the strategic approach into traditional bacterial foraging optimization. The propose method makes each bacterium perform different run-lengths, and increased bacterial diversity as well. We use nonlinear benchmark functions for verifying our propose SABFO to achieve the global optimal solution more easily than other methods. In the second part, we apply the propose SABFO to adjust the parameters of FCMAC model. Although back-propagation (BP) algorithm is commonly used to adjust the parameters of FCMAC model, it is easy to fall into the local optimal solution. Therefore, our proposed evolutionary algorithms can solve the above-mentioned optimal parameter problems successfully. Finally, the propose FCMAC model with SABFO learning algorithm is applied in classification problems. Experimental results demonstrate the convergence effectiveness of the proposed methods.

碩士
國立勤益科技大學
資訊工程系
103
In this paper, a fuzzy cerebellar model articulation controller (FCMAC) with group-based strategy bacterial foraging optimization (GSBFO) for mobile robot wall-following control is proposed. In the proposed FCMAC controller, the inputs are the distance between the sonar and the wall, the outputs are the angular velocity of two wheels. Through using the GSBFO to adjust parameters of FCMAC. A new fitness function is defined to evaluate the evolution of mobile robot wall-following. The fitness function includes four assessment factors which are defined as follows: maintaining safe distance between the mobile robot and the wall, ensuring successfully running a cycle, avoiding mobile robot collisions, and mobile robot running at a maximum speed. The simulation results show that the improved BFO is better than the traditional BFO. After learning, mobile robot travels wall-following successfully in unknown environment.

碩士
國立臺灣師範大學
工業教育學系
105
The purpose of this study is to develop the bacterial foraging algorithm (BFA) by applying it to the energy management/gear shifting strategy system of a three-power-source hybrid powertrain. Furthermore, this study was practical in nature, as it used the real-time simulation Hardware-in-the-Loop (HIL) to verify the algorithm’s feasibility. This study employs HIL to assess the influence that using BFA will have on the energy management and gear shifting strategy control of a three-power-source hybrid powertrain. The vehicle weighs 1,368 kilograms and its subsystems include a 43kW internal combustion engine, 30kW motor, 15kW integrated starter generator, and a 1.872kW-h Ah lithium battery. There are three primary steps for the energy management system and BFA energy management control: 1) chemotaxis, 2) reproduction, and 3) elimination-dispersal. The overall number of iterations was 30, and 80 bacteria were used carry out optimal energy management. BFA and two control strategies were used to carry out a comparison of fuel consumption with the NEDC (New European Driving Cycle) driving pattern. 1) Rule-based management: There are five control modes, which are system preparation, battery charging mode, electric mode, hybrid power mode, and extended range mode; the engineer used his experience to determine when to set and change modes. 2) Equivalent consumption minimization strategy (ECMS): By incorporating the global search algorithm (GSA), we searched for all the scope’s possibilities in order to find the most minimal fuel consumption for power distribution ratio and gear shifting strategy. At the end of the study, we used HIL to simulate the feasibility and verify fuel consumption benefits of BFA on vehicle control units (VCU) in real time. A basic rule base, ECMS, BFA, and real-time were the four conditions for the equivalent consumption with the NEDC driving pattern: 538.9g, 209.6g, 248.9g, and 253.6g were their respective values. The equivalent consumption values with a FTP-72 driving cycle were 579.2g, 291g, 316.3g, and 320.38g. ECMS, BFA, and real-time were compared with a basic rule base when using a NEDC driving pattern to determine percentage values for improvement in energy consumption: 61%, 53.8%, and 52.9%. Percentage values for improvement in energy consumption for a FTP-72 driving cycle were 49.7%, 45.3%, and 44.6%. The improvement in equivalent consumption values for BFA and real-time for the NEDC driving pattern and FTP-72 driving cycle were 98% similar, and they were only outperformed by ECMS, which was the optimal solution. In the future, this experiment will be used to test a three-power-source e-CVT hybrid-powered vehicle.

Polar desert environments are limiting in plant available nutrients, mainly nitrogen (N) and phosphorus (P) that severely limit plant growth and establishment. Cryogenic activity regularly patterns the ground into a patchwork of frost boils – sorted circles that are associated with an increase in moisture, fertility and plant cover. Within some frost boils, the accumulation of ice-rich soil at the permafrost table can cause an upward flow of soil organic carbon (SOC) enriched permafrost material into the active layer. These diapiric intrusions are predicted to fuel microbial activity and enrich the horizon in N and P; however, the enrichment of the diapir horizon and accessibility by plants has yet to be studied. The aim of this research was to characterize the N distribution within diapir horizons located in frost boils and the effect of these intrusions on vascular plant N uptake in a polar desert ecosystem of the Canadian High Arctic. Natural abundance and enriched isotope 15N techniques were used to trace the flow of N through the soil-plant system. Surface and diapir horizons contained the highest total C and total N content within frost boils. Natural abundance δ15N analysis indicated that uptake by Salix arctica plants located on frost boils in the absence of a diapir horizon were sourcing N from the surface. However, when diapir nutrients became available, S. arctica plants began sourcing N from the diapir horizon and underlying low SOC sources in the soil, while reducing uptake from the surface. The altered foraging strategy of S. arctica in response to diapir horizon formation was further indicated by significant uptake of atom%15N nutrients that were injected directly into diapir horizons. These findings suggest diapir horizons are enriched in N and accessible by plants roots as an important nutrient source that is instrumental in their survival within frost boils of a polar desert ecosystem in the high arctic.

Dissertação de Mestrado em Ecologia apresentada à Faculdade de Ciências e Tecnologia
A abundância e a previsibilidade dos recursos alimentares para os predadores marinhos são altamente influenciadas pelas mudanças anuais das condições oceanográficas, mas, em geral, são menores nos ecossistemas tropicais do que nos temperados. No entanto, fenómenos de afloramento em determinadas áreas costeiras permitem a multiplicação e emergência de muitas espécies. As aves marinhas são predadores marinhos de topo que têm sido usados para avaliar a saúde do ecossistema e compreender as alterações nos ambientes marinhos. As variações na disponibilidade de recursos podem causar alterações na ecologia espacial e trófica das aves marinhas. Diferentes estratégias podem ser adotadas em diferentes fases do ciclo reprodutivo e em diferentes anos com diferentes condições ambientais. No entanto, parece haver alguma consistência entre anos nos locais de procura de alimento, o que tem implicações importantes para a conservação de aves marinhas e de outros predadores de topo com uma distribuição espacial semelhante.Recolhemos dados para analisar a ecologia espacial (dispositivos GPS) e trófica (análise de isótopos estáveis) de uma ave marinha tropical - cagarra de Cabo Verde (Calonectris edwardsii) - durante as fases de incubação e alimentação das crias de seis anos consecutivos (2013-2018, n=15 ind. por cada período e ano). Pretendemos perceber como é que as variações da produtividade marinha em redor da colónia podem influenciar o comportamento de procura de alimento desta espécie. Os resultados mostraram que a batimetria e a temperatura da superfície do mar foram as variáveis ambientais que melhor explicaram a escolha dos locais de alimentação pelas aves. Tal como esperávamos, houve uma forte alteração nas estratégias de procura de alimento das cagarras cabo-verdianas entre as fases do ciclo reprodutivo (da incubação para a alimentação das crias). As aves adotaram uma estratégia bimodal de procura de alimento, fazendo viagens mais longas à costa Ocidental de África durante a incubação, onde a produtividade marinha é muito alta, e viagens mais curtas em redor da colónia durante a alimentação das crias. Assim, esta espécie diminuiu as suas assinaturas de δ13C desde a incubação para a alimentação das crias, aumentou o nível trófico das suas presas e diminuiu a sobreposição entre os nichos tróficos. Houve algumas alterações significativas nas estratégias de procura de alimento entre anos. Nos anos com valores mais baixos do índice NAO, correspondendo a uma menor produtividade marinha, as aves viajaram mais para a costa africana e gastaram menos tempo na procura de alimento. No entanto, ao contrário do que previmos, a consistência nos habitats de procura de alimento foi maior. Tal como em anos de menor produtividade marinha, elas viajaram mais para a costa de África e apresentaram maiores assinaturas de δ13C. O oposto aconteceu durante os anos de valores mais altos do índice NÃO, ou seja, anos mais produtivos, mas houve algumas exceções. Em anos de condições ambientais mais precárias, as aves aumentaram o nicho trófico desde a incubação para a fase de alimentação das crias e, aparentemente, procuraram por recursos mais diversificados para alimentá-las. Em anos de boas condições ambientais, as aves mostraram ser mais especialistas. Concluímos que os indivíduos realizaram importantes alterações no seu nicho espacial e trófico entre anos como resposta a alterações das condições ambientais.As cagarras de Cabo Verde sofreram ameaças ambientais e antropogénicas. Embora alguns esforços já tenham sido feitos, através da monitorização e do rastreamento destas aves podemos definir áreas marinhas protegidas (AMPs) e avaliar as variações anuais do uso dessas mesmas áreas.
The abundance and predictability of food resources for marine top predators is highly influenced by annual changes in oceanographic conditions, but, overall, is lower in tropical than in temperate ecosystems. However, upwelling phenomena in certain coastal areas allow multiplication and resurgence of many prey species. Seabirds are marine top predators that have been used to assess the health of the ecosystem and understand changes in marine environments. Variation in resource availability can cause changes in the spatial and trophic ecology of seabirds. Different strategies can be adopted at different phases of the breeding season and in different years with different environmental conditions. However, there seems to be some inter-annual consistency in foraging sites, which has important implications for the conservation of seabirds and other top predators with a similar spatial distribution.We collected data to analyse the spatial (GPS-loggers) and trophic (stable isotope analysis) ecology of a tropical seabird - Cape Verde shearwater (Calonectris edwardsii) -during both the incubation and chick-rearing phases of six consecutive years (2013-2018, n=15 ind. for each period and year). We intend to understand how variations in marine productivity around the colony can influence foraging behaviour of this species. The results showed that bathymetry and sea surface temperature were the environmental variables that best explained the choice of foraging sites by birds. As we expected there was a strong alteration on the foraging strategies of Cape Verde shearwaters among breeding phases (incubation to chick-rearing). Birds adopted a bimodal pattern of foraging strategies making longer trips to the West African coast during incubation, where marine productivity is very high, and making shorter trips around the colony during the chick-rearing to provisioning their chicks. Thus, this specie decreased their δ13C signatures from incubation to chick-rearing, increased the trophic level of their prey and decreased the overlap between trophic niches. There were some significant changes in foraging strategies among years. In years with lower NAO index values, corresponding to a lower marine productivity, birds travelled more to the African coast and spent less time in foraging. However, contrary to what we predicted, the consistency in foraging habitats was greater. Similarly to years of lower marine productivity they travelled more to the coast of Africa presented larger δ13C signatures. The opposite happened during years of higher NAO index values, i.e. the more productive years, but there were with some exceptions. In years of poorer environmental conditions birds increased the trophic niche from the incubation to the chick-rearing period, and apparently searched for more diversified items to feed their chicks. In years of good environmental conditions birds were more specialised. We concluded that individuals made important shifts on their spatial and trophic niche among years, as a response to changes in environmental conditions. The Cape Verde shearwaters have suffered environmental and anthropogenic threats. Although some efforts have already been made, by monitoring and tracking these birds we can define marine protected areas (MPAs) and assess annual variations in the use of these areas.

A research of foraging represents a relatively new phenomenon abroad. In Czechia, on the other hand, this is an ordinary issue with a long-time tradition, but until recently it has not received much attention by the scientific community. For this reason the following diploma thesis deals with this activity. It consists of two main units. The first part aims to create the theoretical framework necessary for the introduction into the foraging study. There is a familiarization with the trend of the self-provisioning in general both in Czechia and abroad. A substantial part of the theoretical framework deals with the quantity and the typology of harvested products, the reasons for foraging, the characteristics of the harvesters, etc. It also outlines the problem of western academics' interpretation of foraging in post-communist conditions as a survival strategy. In the second part, using the mixed research methods, the thesis seeks to find out what is the tradition of foraging in Czech conditions during recent decades, who are the harvesters and what are the reasons and motivations to harvest. By statistical data analysis and by interviewing method, it is confirmed that people across a variety of demographic and socio-economic characteristics are harvesting and motivation is certainly not a bad...

A study was conducted to determine what impact high white-tailed deer (Odocoileus virginianus) densities were having on the native grasslands of a tallgrass: aspen forest tract embedded within an agro-urban setting. Due to excessive spring moisture, row-crops were unavailable the first year. Using microhistological fecal analysis to determine dietary composition, deer were assessed to be placing the site’s favoured native plant species at risk of extirpation. Measuring woody stem abundance and height along and near the prairie: forest ecotone, deer were found to restructure woody growth but not directly influence encroachment rates. Indirectly, however, deer facilitated forest encroachment and prairie degradation through seed dispersal, nitrogen deposition, gap-dynamics, and trampling. Comparing dietary composition to nutritional data, deer grazed to maximize fitness, selecting foods high in IVDMD, minimizing energy expenditure, and optimizing CP. High crop CP was offset by intensively grazing particular native plants. ADF was an effective nutritional marker, not AIA.