Dissertations / Theses on the topic 'Cannibalism in animals'

Thesis (Ph. D.)--University of Kentucky, 2003.
Title from document title page (viewed June 1, 2004). Document formatted into pages; contains viii, 146 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 124-144).

In this essay I’m exploring the novel The Road (2006) by the American author Cormac McCarthy. My main subject of interest is the thematic presence of consumption in general and meat consumption in particular in the text, and how this theme takes on an extreme form in the described and implied acts of cannibalism. Throughout the history of the Western World cannibalistic acts have been most commonly condemned and the cannibal has been, in a wide range of discourses, a cultural symbol of opposition to the idea of – and identification with – the ”civilized (Western) self”. Within the frames of popular culture cannibalism is generally portrayed along these lines as an expression of primitivism, animalistic behavior, depravity and monstrosity. As a reader of The Road, one may classify this story as a part of this tradition in its depiction of cannibalism. However, my goal is to illustrate how the subject can be viewed in a more diverse way, which potentially leads the reader to recognize the cannibal: Not in the form of the Other but as a part of the Self; not as a telling agent of evil times but as a critical mirror image of our own. I do this by shedding light on how cannibalism can be said to connect with other discourses throughout McCarthy’s text: Meat consumption as mentioned earlier is one of them and by following that trail my reasoning also comes to include industrialized meat and cultural consumerism. The conclusion of this essay is that the occurring cannibalism in The Road can be, and in my opinion should be, read as criticism of our contemporary society and its exploitive relationship to animals.

Thesis (M.S.)--University of Alabama at Birmingham, 2010.
Title from PDF t.p. (viewed July 20, 2010). Additional advisors: Robert U. Fischer, John M. Lawrence, Ken B. Marion. Includes bibliographical references (p. 55-59).

Ce mémoire de thèse constitue le travail d'approfondissement d'un programme de recherche sur l'influence de la communication chimique sur le comportement agonistiqee chez les araignées. Le comportement est envisagé dans une perspective ontogénétique, car les deux questions posées dans le cadre de ce travail sont les suivantes : quelles sont les incidences des conditions de l'environnement (disponibilité en nourriture, présence de congénères) et les conditions du milieu interne (âge, état ovarien) sur le comportement social de l'individu (tolérance ou cannibalisme) ? De quelle nature sont les facteurs impliqués dans l'induction ou l'inhibition du comportement agonistique chez les araignées solitaires, comme Tegenaria atrica ? [. . . ]

There are several ways in which people can relate to eating or not eating animals. This essay is focussing two main strategies: Making distances and drawing borders. Today, there are several reasons for not eating meat, including environmental reasons, individual and public health reasons, ethical reasons and more. Yet, people eat more meat than ever. According to the UN, this is a major problem. In 2006 the report Livestock’s long shadow pointed out that meat consumption was a bigger problem from an environmental point of view, than global transports, including air-traffic. At the same time, western societies are becoming both more animal friendly (when it comes to companion animals) and more animal abusive (when it comes to production animals). There seems to be a lot of empathy for animals, yet people choose to hurt them, kill them and eat them. This essay, with a feministic approach, tries to reveal what mechanisms are behind this ambigous behaviour. The findings suggest that the border line between humans and animals is blurred due to several reasons.
Att äta eller inte äta djur är en fråga som det går att förhålla sig till på olika sätt. Den här uppsatsen fokuserar på två huvudstrategier: Avståndstagande och gränsdragningar. I dag finns många anledningar till att inte äta kött, till exempel miljöskäl, hälsoskäl (såväl individuella som folkhälsomässiga), etiska skäl med flera. Ändå äter jordens befolkning mer kött än någonsin. Enligt FN är det ett stort problem. Rapporten "Livestock's long shadow" som kom ut 2006, pekar ut köttkonsumtionen som ett större miljöproblem än världens samlade transporter, inklusive flygtransporter. Samtidigt, håller västerländska samhällen på att bli allt mer djurvänliga (när det handlar om sällskapsdjur) och allt mer djurfientliga (när det handlar om så kallade produktionsdjur). Det finns uppenbarligen mycket empati för djuren, ändå väljer människor att göra dem illa,  döda dem och äta dem. Den här uppsatsen försöker ur ett feministiskt perspektiv undersöka de mekanismer som ligger bakom detta ambivalenta beteende. Resultatet tyder på att gränsen mellan människa och djur är en kulturell konstruktion som håller på att suddas ut, av flera skäl.

The eco-epidemiology of bovine tuberculosis (Tb) in wild deer (mainly red deer Cervus elaphus) in New Zealand was investigated. Bovine Tb is caused by Mycobacterium bovis. Specific aims were to clarify the likely routes of infection in deer, and to determine the status of deer as hosts of Tb, the likely rates and routes of inter- and intra-species transmission between deer and other wildlife hosts, the role of deer in spreading Tb, and the likely utility of deer as sentinels of Tb presence in wildlife. As the possum (Trichosurus vulpecula) is the main wildlife host of Tb, the research also included some investigation of transmission routes in possums. Patterns of infection were measured in 994 deer killed between 1993 and 2003. Tb prevalence varied between areas (range 8–36%). Few deer had generalised infection, with 21–68% of infected deer having no visible lesions, depending on the area. The retropharyngeal lymph nodes and oropharyngeal tonsils were commonly infected. No dependent fawns less than 0.75 years old were infected, indicating intra-species transmission is rare in wild deer. Where possums were not controlled, the net (cumulative) force of infection in young (1–4 y) deer was 0.10–0.24 per year in males and 0.09–0.12 per year in females, but much lower in older deer (less than 0.05 per year). Possum control reduced the net force of infection quickly, and eventually to zero. However, Tb persisted in possum-controlled areas through immigration of infected deer and, for almost a decade, through the survival of resident deer infected before possum control. Tb was lost from infected deer at an exponential rate of 0.13 per year, mostly as a result of deer recovering from infection rather than dying from it. Wild deer do die of Tb, but there was no discernible effect on age structure. The occurrence of infection in deer was not linked to the local deer or possum density at their kill sites (i.e. in their home range), but the area-wide prevalence of Tb in deer was closely correlated with Tb levels in possums, which were in turn correlated with area-wide measures of possum density. For wild deer in New Zealand, Tb is a persistent but usually inconsequential disease of the lymphatic system. It is acquired mainly by young independent deer, usually orally via the tonsils, and probably as a result of licking infected possums. Many species fed on deer carrion, including possums. Most possums encountering carrion did not feed on it, but a few fed for long periods. Other scavengers such ferrets (Mustela furo), hawks (Circus approximans), and weka (a hen-sized flightless native bird; Gallirallus australis) fed in a way that probably increased the infectivity of carrion to possums. Commercial deer hunting may have facilitated the historical establishment of Tb in possums. Scavenging (including cannibalism) and interactions with dead and dying possums are identified for the first time as potentially important routes for transmission of Tb to possums, and I develop new hypotheses involving peri- and post-mortem transmission in possums that explain many of the epidemiological patterns that are characteristic of the disease in possum. In continuous native forest, deer home range size averaged 250 hectares for six young females, and over twice that for two males. Over 90% of infected deer are likely to die within 2 km (females) or 6 km (males) of where they acquired Tb, but deer could occasionally carry Tb up to 30 km. Deer will be useful as sentinels, but only where other sentinels are rare, because the force of infection for a deer with a single infected possum in its home range is only 0.004 per year, compared to greater than 0.2 per year for deliberately released pigs. Deer are occasionally capable of initiating new cycles of infection in wildlife, but deer control is not essential to eradicate Tb from wildlife.

Les coccinelles aphidiphages sont largement utilisées en lutte biologique. Pourtant, à ce jour peu d'entre elles ont montré une réelle efficacité au contrôle des populations de pucerons. Une des raisons est que les femelles évitent de pondre sur des colonies où se trouvent déjà des larves. En effet, elles reconnaissent une phéromone d'inhibition de la ponte (ODP) contenue dans les traces que déposent les larves sur leur substrat. La reconnaissance de cette phéromone permet aux femelles de préserver leur descendance du cannibalisme très présent chez ces insectes. Cependant, pour les larves qui la pratique, le cannibalisme est avantageux puisqu'il constitue un apport alimentaire supplémentaire particulièrement utile lorsque les pucerons viennent à manquer. Ce conflit entre larves et femelles constitue le fil rouge de ma thèse. Le premier chapitre de ma thèse consiste en un travail de modélisation qui établit un lien entre l'évolution du cannibalisme chez les larves de coccinelles, et la sensibilité des femelles à l'ODP. Nous y montrons notamment l'intérêt du polymorphisme dans le maintien de ce système et la pression évolutive qui avantage les larves dont les traces se différencient du reste de la population. Le second chapitre est une étude comportementale qui étudie l'effet de l'apparentement sur la réponse des femelles à l'ODP. En utilisant un modèle de Cox, nous montrons une plus grande sensibilité des femelles en présence de traces larvaires produites par leurs propres larves que celles de larves non apparentées. Finalement le troisième chapitre est une étude des facteurs influençant le cannibalisme des œufs par les larves, ainsi que l'avantage que celles-ci en retirent. Les expériences soulignent notamment l'avantage du cannibalisme juste avant l'entrée en pupe, ainsi que les capacités d'apprentissage des larves qui augmentent leurs taux de prédation sur les œufs conspécifiques quand elles en ont déjà consommées auparavant
The framework of this Thesis is the evolution of cannibalism and oviposition strategies in Coccinellidae. The first chapter of is an evolutionary model that deals with the links between egg-cannibalism and female response to oviposition deterring pheromone (ODP). The second chapter is a behavioral study on female's response to the ODP synthesized by related larvae, compared to ODP synthesized by non-related larvae. As predicted by the model, we show that females are more sensitive to tracks synthesized by kin, but this discrimination do not hold with the experience, and the age of female. Finally, the third chapter deals with the interest and the decision making of eggs-cannibalism by larvae. We show that cannibalism is particularly advantageous before the end of the larval development, because it brings more reserves than aphids. Moreover, due to chemical protection eggs are less predated than aphids, but we demonstrate the possibility of learning that make this protection useless

This essay explores the application of zoomorphism and anthropomorphism in Yann Martel’s novel Life of Pi. The novel, rather than being a mere shipwreck-narrative or a miraculous tale with religious overtones, is also a story about the complicated and perhaps inevitably divided relationship between humans and animals. This essay introduces the fields of ecocriticism and animal studies and defines anthropomorphism and zoomorphism in the context of literary criticism. The essay goes on to discuss the layers of meaning behind the names and naming of the two main characters using Burke’s rhetoric of identification, analyses the anthropomorphism and religiosity in the novel’s two stories, and analyses the two accepted readings of the novel from a zoomorphic perspective. The essay looks at the human-animal divide and its problems in literature, going into Derrida’s animal philosophy to provide a counterpoint to a view derived from Cartesian dualism. In a straight reading of the novel, the first story is regarded as metaphoric while the second story is regarded as literal. There is an alternative reading where it is left to the reader to decide which story is true, but this essay argues that this reading negates a metaphoric interpretation of either story and therefore dismisses the straight reading. Instead, this essay proposes a third, zoomorphic reading, fully compatible with the straight reading, where anthropomorphism is employed to externalize human actions onto animals, but where zoomorphism is employed to project animals onto humans in order to externalize their cannibalism. In the zoomorphic reading, both stories are interpreted as vehicles of projection while avoiding the logical pitfall of the alternative reading.

En premiere partie, sont presentes la biologie, la gestion en milieu naturel et les methodes d'elevage du brochet. L'outil experimental principal est constitue par une batterie d'etangs de 300 m#2, localisee dans le departement de la somme. La seconde partie demontre l'interet de separer les fratries de jeunes brochets et propose une methode originale de reproduction-pregrossissement, la reproduction naturelle amenagee. Les productions, en nombre (2-3 juveniles de 2-3 g/m#2) et biomasse (50-70 kg/ha), obtenues avec cette technique ne different pas significativement de celles des mises en charge classiques basees sur des embryons libres. De plus, le taux de survie des reproducteurs est plus eleve apres reproduction naturelle qu'apres utilisation en ecloserie. Des precisions techniques relatives a la mise en uvre de cette methode sont apportees a l'intention des utilisateurs potentiels. La troisieme partie analyse la dynamique des jeunes stades en etang. Les taux de mortalite sont plus eleves au cours de certaines etapes du pregrossissement, sans que l'on puisse parler de veritables periodes critiques. Les vitesses de croissance aux differents stades sont particulierement elevees, et la biomasse peut atteindre 180 kg/ha. Il est possible de relier la taille des jeunes au regime thermique des etangs. Le regime alimentaire comporte d'abord des microcrustaces de plus petite dimension superieure a 150 micrometres, avec une preference pour les copepodes, ainsi que pour les cladoceres de grande taille. Les proies suivantes sont des larves de chironomides et des macrocrustaces. Malgre une variabilite inter-etangs de la teneur en zooplancton et de la composition des contenus stomacaux, l'evolution ontogenetique du regime alimentaire obeit a une certaine reproductibilite, dans le temps comme dans l'espace. Le cannibalisme, observe uniquement entre juveniles, est fonction de la densite larvaire initiale. Les brochets cannibales selectionnent des brochets-proies de taille relative importante (66% en moyenne) et les ingerent tete la premiere. En quatrieme partie, une reflexion d'ensemble est engagee sur la reproduction naturelle amenagee, les facteurs de regulation des effectifs de jeunes brochets, et l'interet des etangs experimentaux

La reconnaissance de parentèle, correspondant à l’identification et au traitement différentiel des individus apparentés aux dépens des individus non-apparentés, est l'une des étapes préalables à la mise en place de la socialité. Cette capacité existe dans tout le règne animal, des organismes unicellulaires aux êtres humains. Pourtant, chez les insectes elle n’a été étudiée que chez les espèces sociales ou clonales. Chez le staphylin non-social Aleochara bilineata (Coleoptera ; Staphylinidae), les larves de premier stade, qui se développent en parasitoïdes des pupes de la mouche du chou Delia radicum (Diptera ; Anthomyiidae) et les adultes sont capables de reconnaissance de parentèle. Cette dernière est étudiée chez cette espèce selon ses contextes d’expression, ses mécanismes proximaux et son optimalité évolutive. Les facteurs pouvant entraîner la mise en place de la socialité dans les populations animales sont ainsi abordés
Kin recognition, defined as the identification and differential treatments of kin and non-kin, allows to identify the factors influencing the sociality establishment. This ability exists in all the animal kingdom, from unicellular organisms to human being. However, in insects, kin recognition has only been studied in social or clonal species. In the non-social staphylinid beetle Aleochara bilineata (Coleoptera ; Staphylinidae), the first instar larvae, which develop as pupal parasitoid of the cabbage root fly Delia radicum (Diptera ; Anthomyiidae), and the adults are able of kin recognition. In this species, kin recognition is studied according to its expression contexts, proximal mechanisms and its evolutionary optimality. The factors leading to sociality establishment in animal populations are reached

Le cannibalisme intra-cohorte est l’acte de tuer et consommer tout ou partie d’un individu conspécifique du même âge. Longtemps considéré comme un artefact d’élevage, le cannibalisme est maintenant admis comme un phénomène naturel pouvant être soumis à des mécanismes de sélection. Chez les Téléostéens, il est majoritairement référencé au niveau des premiers stades de vie. En condition d’élevage, plusieurs facteurs biotiques et abiotiques ont été testés sans réussir à totalement l’éliminer chez de nombreuses espèces. Dans ce contexte, cette thèse a pour objectifs de mieux comprendre la mise en place et le maintien du cannibalisme, chez le sandre, en se focalisant sur le lien entre cannibalisme, personnalité et mise en place de l’ichtyophagie. Cette thèse a été divisée en trois parties : (i) description du cannibalisme chez les premiers stades de vie du sandre et étude de l’influence de certains facteurs d’élevage, (ii) détermination des traits de personnalité chez les juvéniles, et mise en évidence de l’apparition du comportement piscivore chez les larves, (iii) recherche des liens entre cannibalisme, personnalité et mise en place de l’ichtyophagie. Cette thèse a montré que les facteurs d’élevage testés n’ont pas d’influence sur le cannibalisme. Elle a permis de démontrer l’existence de syndromes comportementaux dès les premiers stades de vie, que l’ichtyophagie ne se mettait pas en place au même âge chez tous les individus et que celle-ci était liée à la personnalité. Nos résultats montrent, également, que le cannibalisme chez les premiers stades de vie du sandre serait lié à la mise en place d’une ichtyophagie précoce et non à une personnalité particulière. On peut en déduire que le cannibalisme ne repose pas, au cours du développement, sur les mêmes caractéristiques individuelles que l’ichtyophagie
Intra-cohort cannibalism is the act of killing and consuming the whole, or major part, of a conspecific individual of the same age. Most often considered as an artefact of captive conditions, it is now assumed that cannibalism is a natural phenomenon, which could be submitted to selection. In Teleosts, it is mostly found in early life stages. In rearing conditions, several biotic and abiotic factors have been already tested, yet without successfully stop it in several species. In this context, the aim of this thesis is to better understand the onset and the stability of cannibalism, in pikeperch, by focusing on the link between cannibalism, personality and the onset of ichtyophagy. This study comprised three main parts aiming at: (i) describing the cannibalism in early life stages and studying the impact of rearing factors, (ii) determining personality traits in juveniles and describing the onset of ichtyophagy in larvae, (iii) searching the link between cannibalism, personality and onset of ichtyophagy. This thesis showed that rearing factors have no impact on cannibalism. Furthermore, we found behavioural syndromes in early life stages and that the onset of ichtyophagy did not occur at the same time for all individuals. Our results highlight that cannibalism seems to be linked to the onset of ichtyophagy rather than individual personality. In conclusion, cannibalism is not due, throughout the development, to the same individual characteristics than ichtyophagy

Mestrado em Ecologia Aplicada
Cannibalism is a well-known behaviour among several invertebrate marine species and may play a relevant role in population dynamics and distribution. In this study we tested if this behaviour occurs at key moments of the complex life cycle of a decapod, namely at settlement and early post-metamorphosis. We collected wild megalopae of the brachyuran crab Carcinus maenas at Ria de Aveiro (Portugal) and at laboratory conditions tested the survival of megalopae stocked at different densities and under contrasting conditions of habitat and food availability. We also tested if cannibalism could be observed between megalopae and first, second and third instar juvenile crabs. Our results showed that megalopae only display cannibalism towards conspecifics at the same life stage under high densities scenarios. The occurrence of cannibalism towards megalopae was immediate and more significant with juveniles on the third crab stage (C3) when compared with the first and second juvenile crab stage (C1 and C2). This study allowed to perceived that during high settlement peaks, the performance and survival of megalopae is not affected by possible cannibalistic interactions among other megalopae. However, the structure and number of the adult population may not correspond to the potential settlement of the larvae when conspecifics of previous events, such as juvenile C3 are present in the same place, due to occurrence of cannibalism.
O canibalismo é um comportamento intraespecífico observado entre muitas espécies de invertebrados marinhos, introduzindo alterações na dinâmica e distribuição das populações. Neste estudo pretendemos testar se este comportamento pode ser observado durante o assentamento e pós-assentamento de um decápode com um ciclo de vida complexo. Megalopas selvagens do caranguejo braquiúro Carcinus maenas foram recolhidas na Ria de Aveiro (Portugal) e em condições de laboratório, testou-se a sua sobrevivência quando expostas a diferentes densidades, complexidade de habitat e disponibilidade de alimento. Foi também testada a ocorrência de canibalismo dos três primeiros estágios de juvenis para com conspecíficos no estado larvar de megalopa. Os resultados experimentais revelaram que o canibalismo não é comum entre megalopas, sendo apenas influenciado quando estão presentes em grandes densidades. Os juvenis no terceiro estágio de caranguejo (C3) apresentaram comportamentos canibalísticos imediatos e mais significativos quando comparados com os juvenis do primeiro e segundo estágio de caranguejo (C1 e C2). Os resultados apresentados permitiram deste modo perceber que durante elevados picos de assentamento, o desempenho e sobrevivência das megalopas não é afetado por possíveis comportamentos canibalísticos entre estas. No entanto, a estrutura das populações adultas pode não corresponder ao potencial de assentamento das larvas quando coespecíficos de eventos anteriores, como por exemplo, juvenis C3, se encontram presentes no mesmo local, devido à ocorrência de canibalismo.

La réussite d'un programme de lutte biologique ou intégrée est fortement liée à l'agent de lutte impliqué, à ses caractéristiques intrinsèques et à ses différentes interactions avec le milieu cible d'introduction. Une juste identification de l'ennemi naturel, une connaissance approfondie de sa biologie, son écologie, son potentiel de gestion des populations de nuisibles et même, de sa génétique sont indispensables avant son implication dans un tel programme. Ce travail de thèse s'insère dans le cadre de la problématique de limitation des risques sanitaires et environnementaux liés aux productions de fruits et légumes au niveau du bassin méditerranéen. Plus spécifiquement, il s'agit de limiter les impacts phytosanitaires et économiques de certains ravageurs s'attaquant à la tomate (Solanum lycopersicum L.), culture méditerranéenne par excellence. Depuis une vingtaine d'années, la protection biologique et intégrée a considérablement évoluée en mettant en jeu une large gamme d'agents de lutte pour une gestion satisfaisante des principales invasions parasitaires (les deux aleurodes Bemisia tabaci (Gennadius, 1889) et Trialeurodes vaporariorum (Westwood, 1856), et plus récemment le lépidoptère Tuta absoluta (Meyrick, 1917) ). Parmi les auxiliaires utilisés en région méditerranéenne, une punaise zoophytophage appartenant au genre Macrolophus (Hemiptera: Miridae) s'est imposée comme la pierre angulaire du contrôle biologique des ravageurs de la tomate. Bien que commercialisé depuis les années 90 sous le nom de Macrolophgus caliginosus, son identité spécifique porte encore à confusion. Ceci est du à la présence dans la zone d'origine (bassin méditerranéen) de deux espèces morphologiquement très proches : Macrolophus caliginosus/melanotoma et Macrolophus pygmaeus. La première partie de la thèse a permis de clarifier ce problème d'identification par une double approche morphologique et moléculaire, et de proposer une nouvelle clé d'identification de toutes les espèces paléarctiques du genre Macrolophus. La deuxième partie s'est focalisée sur des aspects de la bio-écologie de l'espèce commercialisée identifiée dans cette thèse comme M. pygmaeus. L'influence des ressources trophiques sur sa capacité de survie a été d'abord étudiée puis le caractère cannibale de cet agent de lutte a été mis en évidence. L'étroite relation entre sa phytophagie et sa zoophagie a été démontrée et enfin l'impact de la température sur sa réponse fonctionnelle a été caractérisé. Les résultats montrent l'importance de tous ces paramètres sur le potentiel de prédation de M. pygmaeus et soulignent leur contribution à la réussite ou à l'échec de son rôle dans la protection biologique intégrée de la tomate
The success of a biological or integrated pest management control program is deeply dependant of the involved biological control agent as well as its intrinsic characteristics and its various interactions with the target introduction area. Before any implication in such a program an accurate/correct identification, a detailed knowledge of its biology, ecology, potential in pest control are necessary. This work was developed in a context of the sanitary and environmental fruits and vegetables production limitation risk problems. It consists, more specifically, in the phytosanitary and environmental impact limitations of some tomato (Solanum lycopersicum L.) pests. In the last twenty years, the biological and integrated pest management has considerably changed by involving a large scale of biological control agents for a successful control of the main parasitic invasions (the two whiteflies, Bemisia tabaci [Gennadius, 1889) and Trialeurodes vaporariorum (Westwood, 1856), more recently the moth Tuta absoluta (Meyrick, 1917)]. Among the natural enemies used on the Mediterranean region, one finds a zoophytophagous bug belonging to the Macrolophus genus (Hemiptera: Miridae. In spite of its marketing since the 1990s under the name Macrolophgus caliginosus, its specific identity still remains unclear. This is due to the presence in the origin zone (Mediterranean area) of two morphologically closed species: Macrolophus caliginosus/melanotoma and Macrolophus pygmaeus. The first part of this thesis shed light on the identification problem through a double morphological and molecular approach. It also provided a new identification key of all the Palaearctic species belonging to the genus Macrolophus. The second part focused on some bio-ecological traits of the commercialised species, identified in this work as M. pygmaeus. The influence of trophic/feeding resources on the survival capacity has been studied and a cannibalistic behaviour has been demonstrated. The close relationship between phytophagy and zoophagy was characterized; finally the impact of temperature on its functional response was described. The results showed the importance of all these parameters on M. pygmaeus predation potential and emphasized their contribution on the success or failure in tomato pest management

Il est généralement admis que les araignées sociales vivant en sociétés permanentes et coopératives ont évolué à partir d'espèces solitaires, en passant par des étapes intermédiaires, similaires aux espèces subsociales actuelles. Ces espèces, ou les jeunes reçoivent des soins maternels et mènent une vie commune de durée variable, peuvent fournir des informations précieuses sur les processus sociaux. C’est pourquoi nous avons entrepris l'étude de l'une d'entre elles, commune dans nos régions, Amaurobius ferox. L'intérêt d'Amaurobius ferox réside, d'une part, dans la manière originale dont les jeunes sont nourris par la mère, puisqu'elle constitue la source unique de leur alimentation, d'autre part, dans le fait que les jeunes ont, après la mort de la mère, une période de vie commune pendant laquelle ils présentent une activité prédatrice. L’alimentation des jeunes par la mère se fait à deux reprises : consommation d'une ponte trophique, puis consommation de la mère elle-même. L’analyse montre que ces deux phénomènes résultent d'interactions mère-progéniture. Après la mort de la mère, les jeunes continuent à rester groupes et à se tolérer. On observe de nombreuses activités collectives, dont des mouvements synchronises en présence d'intrus, et surtout une coopération lors de la prédation. L’étude expérimentale montre que l'efficacité de la prédation augmente avec le nombre de participants, un groupe de jeunes maitrisant des proies beaucoup plus grosses que ne le peut un jeune seul. Ces activités collectives semblent résulter des interactions entre jeunes, on aurait donc affaire a des phénomènes d'auto-organisation. Cette étude montre l'intrication entre phénomènes maternels et phénomènes sociaux. Elle suggère également que la coopération représente une caractéristique émergente au sein des groupes sociaux, caractéristique qui pourrait, à son tour, faciliter l'évolution vers les sociétés permanentes.

La famille de Phytoseiidae comporte plusieurs espèces ayant un impact économique en agriculture en permettant la régulation des pullulations d’acariens ravageurs, notamment ceux attaquant la vigne. Ce travail avait pour objectif de caractériser la structure des guildes de Phytoseiidae dans un agrosystème viticole conduit en agroforesterie, dans un site expérimental du sud de la France. En préalable, nous avons dû résoudre un problème taxonomique concernant la validité des deux espèces morphologiquement très proches et majoritairement rencontrées dans l'agrosystème étudié. Puis, nous avons tenté de déterminer si des différences existaient entre les différents types de milieux [vigne seule, vigne en agroforesterie, arbres seuls (cormier : Sorbus domestica et pins : Pinus pinea)] s’agissant de la diversité et de la densité de Phytoseiidae, et ce pendant trois ans. Enfin, nous nous sommes intéressés aux facteurs explicatifs de la structuration précédemment observée. Les analyses (morphologique, moléculaire) et les croisements ont montré que T. Exhilaratus et T. Phialatus sont deux espèces valides, se distinguant uniquement par la forme de la spermathèque ou appareil d’insémination. De 2003 à 2005, des Phytoseiidae étaient présents à la fois sur les vignes et sur les arbres co-plantés (cormiers et pins). Leurs effectifs dans les parcelles de vigne en agroforesterie semblent être affectés positivement par la présence d’arbres, mais ceci uniquement pour quelques dates de prélèvements, notamment en 2005, année durant laquelle les conditions climatiques ont été favorables à leur développement. La présence d’arbres intercalaires n’a cependant pas affecté la diversité des Phytoseiidae. Typhlodromus exhilaratus était en effet l’espèce dominante, à la fois sur les arbres co-plantés et sur les vignes (en agroforesterie ou non) et des échanges de populations entre les arbres co-plantés et les vignes pourraient donc exister. Les pins semblent constituer des habitats plus favorables au développement des Phytoseiidae que les cormiers sur lesquels les effectifs observés étaient très faibles. Enfin, T. Phialatus était dominant à la fois dans les parcelles d’arbres plantés seuls et dans l’environnement non cultivé des parcelles. La compétition interspécifique et surtout l’impact des traitements phytosanitaires semblent être parmi les facteurs abordés dans ce travail ceux les plus importants pour expliquer la ségrégation spatiale entre T. Exhilaratus et T. Phialatus. La plantation des arbres à l’intérieur des parcelles de vigne pourrait présenter des applications directes en terme de lutte biologique par conservation de la biodiversité et des habitats et de durabilité des agrosystèmes. Ce travail a permis de donner quelques éclaircissements concernant un agrosystème et un modèle biologique particulier. De nombreux travaux sont cependant encore nécessaires afin d’obtenir d’une part une connaissance plus approfondie des facteurs biotiques et abiotiques affectant la présence et le développement de ces prédateurs et leurs mouvements dans les divers compartiments, et d’autre part, de déterminer la possibilité de généraliser les résultats de ces études à d’autres sites et sur d’autres modèles biologiques (notamment d’autres auxiliaires de cultures)
Phytoseiid mites are the most widespread predatory mites in agrosystems and some species are efficient to control phytophagous mite outbreaks. The aim of this work is to determine, in an experimental site in the South of France, the influence of Sorbus domestica and Pinus pinea co-planted in vine plots on the structure of Phytoseiidae occurring on vines. Before realising samplings, several experiments (morphological and molecular analyses) and hybridization were made under laboratory conditions to answer a taxonomic interrogation concerning the occurrence in the site of study of two real species, Typhlodromus exhilaratus and T. Phialatus, morphologically very close. The results of these experiments showed that the two species are not synonyms and can be distinguished morphologically only by the spermatheca or insemination apparatus shape (genital organ of females). Results of samplings (2003-2005) showed the occurrence of Phytoseiidae on vines and on co-planted trees. The densities of these predators on vine seem to be positively affected by the presence of trees particularly in 2005. However, diversity of Phytoseiidae does not seemed to be affected by the plantations of trees inside vine crops. Typhlodromus exhilaratus was the dominant species in vine plots (with trees or not) and on co-planted trees. Population exchanges of this species between vines and co-planted trees seem to be possible. Pinus pinea could be more favourable host plant to phytoseiid mites than S. Domestica on which very low densities of these predators were observed. The present work also showed the dominance of T. Phialatus in monocultural plots with trees and also in uncultivated areas surrounding vine crops. The interspecific competition and especially the side effects of pesticides applied on vine seem to be among factors tested in the present work the two more interesting for explaining the spatial segregation observed of T. Exhilaratus and T. Phialatus. Thus, plantation of trees inside vine crops could have many applied implications on biological control by conservation of the biodiversity and habitats and the durability of the agrosystems. However many studies remain necessary to have more information about biotic and abiotic factors affecting the occurrence and the development of these predators and their movement between the differents parts of the agrosystem and on the other hand the possibility to generalize the results of these studies to other sites and on other biological models especially others beneficials

Interspecific predation and cannibalism and associated rates of oviposition were assessed for adult female Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Scheuten when provided non-limiting amounts of either eggs, larvae, protonymphs, or deutonymphs. Tests with all four stages of phytoseiids and larvae of Tetranychus urticae Koch were carried out at 25°C. At 15 and 12.5°C only larvae of phytoseiids and larvae of T. urticae were prey items. Predation by T. pyri was higher than M. occidentalis at 12.5 and 15°C, but more similar at 25°C. M. occidentalis did not feed appreciably on phytoseiid larvae at 15° and 12.5°C. Neither phytoseiid oviposited at 12.5°C when fed phytoseiid larvae, but T. pyri did at 15°C. We concluded that T. pyri was a more active predator at low temperatures and early-season predation on M. occidentalis immatures by T. pyri could contribute to displacement of M. occidentalis from apple orchards in western Oregon. The effects of prey species and prey density on the rates of inter- and intraspecific predation and oviposition of the two phytoseiid mite predators Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Schueten were investigated through a series of laboratory experiments. Adult female predators were given mixed populations of phytoseiid larvae and larvae of a more preferred prey, the spider mite, Tetranychus urticae Koch, at different rates and proportions. T. pyri, more of a generalist predator, consistently showed higher rates of predation and cannibalism on phytoseiid immatures at most prey populations and proportions. Manly Preference Indices indicated that T. pyri switched to feed on phytoseiid immatures at higher population levels and proportions of T. urticae than did M. occidentalis. This ability to readily utilize phytoseiid immatures as prey indicated that maintaining both predators in a biological control program at low prey densities may require the use of active selective techniques that favour M. occidentalis. The differential impact of Zetzellia mali on the phytoseiids Metaseiulus occidentalis and Typhlodromus pyri was studied in laboratory experiments and by analysis of population data from experimental orchard plots containing either of the phytoseiid species, similar numbers of prey mites, and high or low populations of Z. mali. Five hypotheses were evaluated to explain why Z. mali had more impact on M. occidentalis in the field than on T. pyri.. Given equal opportunity, Z. mali adult females did not consume greater numbers of M. occidentalis eggs than T. pyri eggs nor did adult females of either phytoseiid species inflict greater mortality on Z. mali eggs or larvae through attack or consumption. There was no difference in the within tree association of Z. mali adult females with the eggs of either phytoseiid species nor were there differences in the way prey mites (all stages) were spatially partitioned between adult female Z. mali as compared with adults and deutonymphs of either of the two phytoseiids. The foraging area of adult female Z. mali and the oviposition locations of the two phytoseiids from both field and laboratory assessments were compared using spatial statistical procedures. M. occidentalis laid significantly more eggs in the primary foraging area of adult female Z. mali than did T. pyri. This spatial difference was the only factor tested which might explain the observed greater impact of Z. mali on M. occidentalis. Impact of these interspecific interactions and competition on the persistence of predatory mite guilds for the biological control of plant-feeding mites are discussed.
Graduation date: 1995

abstract: Differences between males and females can evolve through a variety of mechanisms, including sexual and ecological selection. Because coloration is evolutionarily labile, sexually dichromatic species are good models for understanding the evolution of sex differences. While many jumping spiders exhibit diverse and brilliant coloration, they have been notably absent from such studies. In the genus Habronattus, females are drab and cryptic while males are brilliantly colored, displaying some of these colors to females during elaborate courtship dances. Here I test multiple hypotheses for the control and function of male color. In the field, I found that Habronattus males indiscriminately court any female they encounter (including other species), so I first examined the role that colors play in species recognition. I manipulated male colors in H. pyrrithrix and found that while they are not required for species recognition, the presence of red facial coloration improves courtship success, but only if males are courting in the sun. Because light environment affects transmission of color signals, the multi-colored displays of males may facilitate communication in variable and unpredictable environments. Because these colors can be costly to produce and maintain, they also have the potential to signal reliable information about male quality to potential female mates. I found that both red facial and green leg coloration is condition dependent in H. pyrrithrix and thus has the potential to signal quality. Yet, surprisingly, this variation in male color does not appear to be important to females. Males of many Habronattus species also exhibit conspicuous markings on the dorsal surface of their abdomens that are not present in females and are oriented away from females during courtship. In the field, I found that these markings are paired with increased leg-waving behavior in a way that resembles the pattern and behavior of wasps; this may provide protection by exploiting the aversions of predators. My data also suggest that different activity levels between the sexes have placed different selection pressures on their dorsal color patterns. Overall, these findings challenge some of the traditional ways that we think about color signaling and provide novel insights into the evolution of animal coloration.
Dissertation/Thesis
Ph.D. Biology 2012