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Lyrsten, Theres. "Predation som selektiv kraft bakom differentiering av populationer av sötvattensgråsugga, Asellus aquaticus." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-63340.
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Predation is a strong dective force on invertebrate prey. Asellus aquaticus differs in pigmentation reed and submerged vegetation habitats in lakes. Light pigmented individuals al vegetation dominated by Chara sp. while dark pigmented individuals dominate in the reeds. These differences have been hypothesized to result from background matching. Predation pressure from fish is belived to be highest in Chara sp., while invertebrate predators are more common in the reeds. In this study I investigatedif predation from perch and damselfly larvae create different se1ection pressure on pigmentation and size of the Asellus, and if selection is affected by the structure of the habitat. The study vas carried out in aquaria in a loboratory. Regarding predation from perch a tendancy to be selective against dark pigmented individuals in Chara substrate was seen. Mortality increased with body size in Asellus, regardless of pigmentation. In the experiment mortality of Asellus decreased with body length. The results illdicate that it is not as important for Asellus to be cryptic in the reeds since it is not exposed to visual predation on the same level as in the Chara sp. where it is preferable to be small and cryptic. In the reed, large individuals are probably favorued since common predators, such as damselfly larvae, are size-limited in their prey choice.
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Fahlman, Johan. "Size selective predation of pike on whitefish : The effects on resource polymorphism in Scandinavian whitefish populations." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-87582.
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The mechanisms behind speciation have been subject of debate for centuries. The presence of resource polymorphism has been discovered to play a significant part in this process, and has been proven to induce phenotypic and genetic divergence. Although resource polymorphism has been intensely studied during the last few decades, there is a gap of information as to why this can be observed in some systems but not in others. Recent studies of European whitefish (Coregonus lavaretus) in Scandinavian lakes have shown that predation, in this case by Northern pike (Esox lucius), could be the factor that induces resource polymorphism. European whitefish is known to diverge into several ecomorphs in Scandinavian lakes, but only in the presence of pike. Divergence is assumed to be caused by the size selectivity of pike, and the following niche separation and eventually reproductive isolation. In this study, pike prey selectivity was studied in the field through sample fishing using hooks baited with whitefish of different sizes. The hypothesis was that pike prefers smaller prey over larger and mainly hunts in the littoral zone. This should causes smaller whitefish ecomorphs to be prone to predation in the littoral and thus utilize refuge spawning grounds with low predation pressure. However, no pike were caught on whitefish spawning grounds, and fishing at two additional pike rich sites displayed a preference towards medium-sized whitefish (p < 0.05). This indicates a size selectivity, although further and improved studies would be required to answer the question of the pike’s role in resource polymorphism.
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Chilton, Earl Wallace. "Macroinvertebrate communities associated with selected macrophytes in Lake Onalaska : effects of plant type, predation, and selective feeding /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487266691096246.
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Andersson, Magnus. "Selective predation by perch (Perca fluviatilis) on a freshwater isopod, in two macrophyte substrates." Thesis, Linköpings universitet, Ekologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-58018.
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Recent studies show that populations of the freshwater isopod Asellus aquaticus L. can rapidly become locally differentiated when submerged stonewort (Chara spp.) vegetation expands in lakes. In the novel Chara habitat, isopods become lighter pigmented and smaller than in the ancestral reed stands. In this study, I used laboratory experiments to investigate if selective predation by fish could be a possible explanation for these phenotypic changes. Predation from fish is generally considered to be a strong selective force on macroinvertebrate traits. In the first experiment I measured perch (Perca fluviatilis L.) handling time for three size classes of Asellus to see which size of those that would be the most profitable to feed upon. No difference in handling time was detected between prey sizes, hence the largest size would be the most beneficial to feed upon. In a second experiment I let perch feed on a mixture of Asellus phenotypes in aquaria manipulated to mimic the substrates in either the Chara or the reed habitats. Remaining isopods were significantly smaller and lighter pigmented in the fish aquaria than in the controls, showing that the perch preferred to feed on large and dark individuals. In the Chara habitat, selection on isopod pigmentation was according to what could be expected from background matching, but in the reed habitat selection was quite the opposite. These results support the hypothesis that predation from fish is a strong selective force behind the rapid local adaptation seen in Asellus populations in the novel Chara habitat.
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Worischka, Susanne. "Selective predators in complex communities – mechanisms and consequences of benthic fish predation in small temperate streams." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-170972.
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The prey consumption by benthivorous fish predators can have profound top-down effects in stream food webs. To analyse this effects in small temperate stream ecosystems, a long-term field experiment was conducted in two streams in South-eastern Germany, Gauernitzbach and Tännichtgrundbach, from 2004 to 2011. The densities of two small-bodied benthivorous fish species, gudgeon (Gobio gobio) and stone loach (Barbatula barbatula), were manipulated following a Before-After-Control-Impact design. The top predator regime affected the benthic community composition of the streams mainly in pools, whereas the total benthic invertebrate biomass was not affected in any mesohabitat. The present work describes a causal analysis of the observed food web effects using additional field analyses and laboratory experiments, with a special focus on the habitat use and foraging behaviour of the fish as top predators.
The probably most important of the analysed mechanisms was mesohabitat-specific predation by the fish. Three 24-h field video surveys combined with benthic invertebrate sampling showed that constraints in habitat use, especially for gudgeon, induced a differential predator-prey habitat overlap which resulted in a higher predation risk for the invertebrate prey in pools than in riffles. Another important mechanism was selective predation of both fish species. Their prey selectivity was largely explained by a small number of prey variables being connected to the partly non-visual foraging mode of these benthic predators. Besides the traits body size and feeding type, long-term mean abundance played a central role, small and highly abundant invertebrates, grazers and sediment feeders being preferred by gudgeon and stone loach. The preference for small and abundant prey taxa (chironomids) exceeded purely opportunistic feeding and probably facilitated resource partitioning between the two fish species having very similar diets. In addition to active selectivity, different predator avoidance strategies of the invertebrates analysed in laboratory experiments explained the passive selectivity of the fish predators for certain prey taxa in the streams. This could be shown for two abundant taxa being consumed by the fish predators in very different quantities, Gammarus pulex and Hydropsyche instabilis.
These three mechanisms, although probably interacting with several other factors, could explain a large part of the effects the top-down food web manipulation had on the benthic community, especially the observed high degree of mesohabitat and species specificity. Confirming this, quantitative characteristics of predation food webs, for instance the importance of intraguild predation, differed markedly between pool and riffle mesohabitats. From the results of this study it can be concluded that the benthivorous fish affected benthic community structure mainly by mesohabitat-specific and selective predation. A manipulation of this (native) top predator type therefore will probably have such rather subtle but not catastrophic consequences in ecosystems with a high biotic diversity and a rich natural habitat structure and connectivity.
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Paradis, Anne R. "Theoretical work on the size-selective vulnerability to predation during the early life history stages of fishes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ47501.pdf.
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Park, Sichoon. "The selective use of chlorine to inhibit algal predators and avoid pond crashes for the algae-biodiesel industry." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51867.
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As algae-derived biofuel is a promising renewable energy source, it is well-established that micro-algae have the potential to make a significant contribution to transportation fuel demand. Although it has many advantages including high areal productivity, there are many negative factors. One of these factors is the predation of algae by amoebas, protozoans, ciliates and rotifers, particularly in open pond systems. For example, the rotifer Brachionus plicatilis, is able to eat as much as 12,000 algae cells per hour and can be responsible for an entire pond crash within days. Thus, these higher organisms need to be controlled in order to satisfy large-scale algae crop and biofuel production demand. One method of predation control involves the introduction of a toxic chemical to an algal culture that the predator has a higher sensitivity to with respect to algae. Ideally, predation could be minimized or eliminated without a substantial effect on the algal culture growth. Chlorella kessleri was used as the algal culture and Brachionus calyciflorus as the source of predation. Research was conducted in five stages. First, chlorine dissipation tests were carried out using spring water, distilled water, Bolds Basal Medium (BBM), and three different dry weights of algal suspension in order to analyze the dissipation rate of the residual chlorine. The results showed that chlorine in distilled water and spring water rarely dissipated while chlorine concentration in algal suspension rapidly decreased by a maximum of 90% within the second hour. Second, acute chlorine toxicity tests were conducted in order to find the 24-hr LC50 of B. calyciflorus. The 24-hr LC50 of the test animal was 0.198 mg Cl/L. Third, chlorine toxicity tests were conducted in order to find the LC50 of Chlorella kessleri. The 24-hr LC50 of C. kessleri was 0.321 mg Cl/L. Based on these results, the test animal was more sensitive to chlorine than the test algae; therefore chlorine may be used to avoid algae pond crashes by B. calyciflorus. Fourth, C. kessleri and B. calyciflorus were combined into one test to determine how long it would take to observe an algal culture crash. The result demonstrated that the higher the population of predators in algal suspension, the faster it crashed. Finally, chlorine, C. kessleri, and B. calyciflorus were combined into one test to determine what chlorine concentration and dosing interval was needed to significantly reduce predation without significantly reducing algae growth. The results of the fifth experiment showed that the effective intermittent chlorine concentration was between 0.45 and 0.60 mg Cl/L, and a short interval of chlorine dosing was effective in inhibiting rotifers in algal suspension. Even though the rotifers in algal suspension were inhibited by 0.45 to 0.60 mg Cl/L, algae growth was greatly inhibited by chlorine. In this respect, future work is needed to reduce the effect on algae by chlorine or alternative chemicals.
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Boarman, McKaila J. S. "Trade-offs and Temporal Variation in Predator-Mediated Natural Selection and Sexual Selection on the Wings of the Damselfly Calopteryx splendens." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1491746850419119.
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Worischka, Susanne [Verfasser], Thomas [Akademischer Betreuer] Berendonk, Markus [Akademischer Betreuer] Weitere, and Jürgen [Akademischer Betreuer] Geist. "Selective predators in complex communities – mechanisms and consequences of benthic fish predation in small temperate streams / Susanne Worischka. Gutachter: Thomas Berendonk ; Markus Weitere ; Jürgen Geist. Betreuer: Thomas Berendonk." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://d-nb.info/1073207021/34.
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Petroli, Gustavo Henrique. "Modelagem matemática de predação doença-seletiva." reponame:Repositório Institucional da UFABC, 2017.
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Orientador: Prof. Dr. Norberto Anibal MaidanaDissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Matemática , 2017.
Doenças infecciosas acometem populações de presas e a escolha predatória de presas suscetíveis pode levá - la à extinção. Propusemos e analisamos um modelo matemático de interação presa - predador, com a população de presas dividida em duas classes: suscetíveis e infectadas. A subpopulação de presas suscetíveis, torna - se infectada por contato direto com a subpopulação de presas infectadas e o predador consome somente as presas suscetíveis. A análise do modelo permitiu estabelecer limiares para a propagação da doença na ausência bem como na presença de predadores, além de condições de existência e estabilidade dos pontos de equilíbrio biológicamente viáveis. Por meio de simulações numéricas determinamos as diferentes características biológicas apresentadas pelo modelo, assim como ilustramos os resultados analíticos.
Infectious diseases affect prey populations and the predatory choice of susceptible preys may lead them to extinction. We propose and analyzed a mathematical model of prey - predator interaction, with prey population divided into two classes: susceptible and infected. The subpopulation of susceptible preys becomes infected by direct contact with the subpopulation of infected preys, and the predator consumes only the susceptible ones. The analysis of the model allowed to establish thresholds for the propagation of the disease in the absence of predators, in the presence of them as well as conditions of existence and stability of biologically viable equilibrium points. Analysing the system by numerical simulations, we determine different biological characteristics presented by the model and illustrate analytical results.
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Latif, Quresh S. "How predation risk shapes avian nest site selection and processes underlying nest predation patterns." Diss., [Riverside, Calif.] : University of California, Riverside, 2009. http://proquest.umi.com/pqdweb?index=0&did=1957706911&SrchMode=2&sid=4&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1268765320&clientId=48051.
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Thesis (Ph. D.)--University of California, Riverside, 2009.Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 16, 2010). Includes bibliographical references. Also issued in print.
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Smith, Dustin M. "Habitat selection and predation risk in larval lampreys." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10493.
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Preston, Sarah Jane. "The impact of shell damage on Calliostoma zizyphinum (Gastropoda: Trochidae)." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241431.
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Kohl, Michel T. "The Spatial Ecology of Predator-Prey Interactions: A Case Study of Yellowstone Elk, Wolves, and Cougars." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7441.
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The loss of large apex predators, and their subsequent reintroduction, has been identified as a substantial driver on the structure and function of ecological communities through behavioral mediated trophic cascades (BMTCs). The reintroduction of wolves (Canis lupus) to Yellowstone National Park (YNP) has served as foundational case study of BMTCs. In our system, it has been suggested that wolves have established a ‘landscape of fear’ in which the primary prey, elk (Cervus elaphus), now avoid risky places, which ultimately led to the recovery of the vegetation community. Although this case is frequently cited as a well-understood example of a landscape of fear, researchers never quantified whether elk avoided risky places, a critical component of the BMTC hypothesis. Thus, I employed numerous quantitative approaches to evaluate the role of wolves and cougars on elk habitat selection in northern Yellowstone. The results from this work suggest that the daily activity schedule of wolves provide a temporally predictable period of risk that allows elk to use risky places during safe times. As such, diel predator activity flattened (i.e., made less risky) the landscape of fear for 16 hours per day, 7 days a week, which permitted elk to forage on deciduous woody plants despite the presence of wolves. Thus, suggests that any trophic cascade in northern Yellowstone is likely driven by the consumptive effects of wolves on elk. In addition, my results suggest that daily activity patterns are an important component of predation risk, and as such, provide a predictable avenue for elk to avoid predators despite residing in an environment spatially saturated with wolves and cougars. Thus, the ability of elk to avoid predators through fine-scale spatial decisions provides support for my findings that the current spatial distribution of prey is largely driven by the consumptive effects of predators on the prey population, rather than a landscape of fear. In combination, these results suggest that the landscape of fear, and more generally, fear effects, may be of less relevance to conservation and management than direct killing within free-living, large landscapes.
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Demmons, Timothy Douglas. "Nest site selection and nest predation patterns at forest-field edges." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0021/MQ52983.pdf.
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Roger, Caroline. "Mechanisms of prey selection in the ladybeetle Coleomegilla maculata Lengi Timb. (Coleoptera:Coccinellidae)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ50249.pdf.
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Miller, Sara Elizabeth. "Intraguild predation is a mechanism of divergent selection in the threespine stickleback." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58913.
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Biotic interactions among species are thought to be important for the generation of phenotypic diversity. Intraguild predation is a common ecological interaction that occurs when a species preys upon another species with which it competes. This interaction is potentially a mechanism of divergence between intraguild prey populations, but it is unknown if cases of character shifts in intraguild prey are phenotypically plastic or an evolutionary response. I collected threespine stickleback (Gasterosteus aculeatus) from lakes with and without prickly sculpin (Cottus asper) and identified trait differences in armour and behaviour among populations in the wild. Differences in behavioural and morphological traits among freshwater populations persisted in a common garden, suggesting that adaptation to intraguild predation has a genetic basis. To date, the evolutionary effect that biotic selection has upon an organisms’ genome remains largely unknown in natural populations. I used whole genome re-sequencing to investigate the extent of genetic differentiation between stickleback from populations with and without sculpin. The main axis of genetic variation in these populations is strongly associated with the presence or absence of sculpin. I identified the regions of the genome that have differentiated in parallel between lakes with and without sculpin, and measured the strength of this divergence. The presence or absence of sculpin corresponds to widespread differentiation that is unevenly distributed across the stickleback genome. Adaptation to intraguild predation may involve hundreds of genes with diverse functions. Observations of extensive phenotypic and genetic differentiation between stickleback from lakes with and without sculpin provide indirect evidence that sculpin are the cause of trait differences. Pelvic morphology is one of the most conspicuously varying traits among freshwater stickleback populations. This variation has been hypothesized to be the result of predation by fish and/or insect predators. I conducted a selection experiment to test if sculpin were an agent of selection for pelvic spine length. The results were combined with other experimental selection studies and used in a meta-analysis. Fish predators are an agent of selection for longer pelvic spines, but the role of insect predators is still unclear. Intraguild predation is a mechanism of divergent selection in threespine stickleback.Science, Faculty of
Zoology, Department of
Graduate
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Ruddock, Marc. "Housewives' planning : Population ecology, predation and prey selection in the peregrine falcon." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479323.
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Cheng, Yi-Ru. "Differential growth of body components among coexisting passerine species in response to nest predation risk." CONNECT TO THIS TITLE ONLINE, 2008. http://etd.lib.umt.edu/theses/available/etd-01132009-180702/.
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Mathisen, Peter. "Environmental factors selecting for predation resistant and potentially pathogenic bacteria in aquatic environments." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-133338.
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The long history of co-existence of bacteria and their protozoan predators in aquatic environments has led to evolution of protozoa resistant bacteria (PRB). Many of these bacteria are also pathogenic to humans. However, the ecological drivers determining the occurrence of different types of PRB in aquatic environments, and the eco-evolutionary link between bacterial adaptation and the resulting implications for mammalian hosts are poorly known. This thesis examines the impact of nutrients and predation on PRB, as well as the ecological and evolutionary connection between their life in aquatic environments and mammalian hosts. In the first study seven bacterial isolates from the Baltic Sea were investigated for their plasticity of adaptation to predation. The response to predation showed large variation where some bacteria rapidly developed a degree of grazing resistance when exposed to predators. The rapid adaptation observed may result in bacterial communities being resilient or resistant to predation, and thus rapid adaptation may be a structuring force in the food web. With the aim to elucidate the link between occurrence of PRB and environmental conditions, a field study and a laboratory experiment were performed. In both studies three PRB genera were found: Mycobacterium, Pseudomonas and Rickettsia. PRB were found both in oligotrophic and eutrophic waters, indicating that waters of all nutrient states can harbor pathogenic bacteria. However, the ecological strategy of the PRB varied depending on environmental nutrient level and disturbance. Using an advanced bioinformatic analysis, it was shown that ecotypes within the same PRB genus can be linked to specific environmental conditions or the presence of specific protozoa, cyanobacteria or phytoplankton taxa. These environmental conditions or specific plankton taxa could potentially act as indicators for occurrence of PRB. Finally, using four mutants (with specific protein deletions) of the pathogenic and predation resistant Francisella tularensis ssp. holarctica, I found evidence of an eco-evolutionary connection between the bacterium´s life in aquatic and mammalian hosts (aquatic amoeba Acanthamoeba castellanii and a murine macrophage). To a large extent F. t. holarctica use similar mechanisms to persist predation by protozoa and to resist degradation by mammal macrophages. To summarize I found a link between predation resistant bacteria in aquatic environments and bacteria that are pathogenic to mammals. Further, I showed that different environmental conditions rapidly selects for PRB with either intracellular or extracellular lifestyles. This thesis provides insights regarding environmental conditions and biomarkers that can be used for assessment of aquatic environments at risk for spreading pathogenic bacteria.Medfinansiärer var även: Swedish Ministry of Defence (A4040, A4042, A404215, A404217), Swedish Minestry of Foreign Affairs (A4952), Swedish Civil Contingencies Agency (B4055)
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Bokach, Matthew John. "The relative influences of predation and prey availability on ardeid breeding colony site selection." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0009586.
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Forsman, J. (Jukka). "Heterospecific attraction in breeding bird communities:implications to habitat selection and species interactions in a landscape perspective." Doctoral thesis, Oulun yliopisto, 2000. http://urn.fi/urn:isbn:9514256263.
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I studied the structure of European breeding forest bird communities on several spatial scales focusing on heterospecific attraction among birds (i.e., the attraction of individuals to the company of interspecifics). Namely, I examined how heterospecific attraction affects habitat selection in migrant birds and the potential role of predation risk in enhancing heterospecific attraction during breeding with particular emphasis regarding the interaction between resident and migrant birds.
Geographically, low densities and low relative proportions of resident titmice (Parus and Aegithalos spp.) were associated with harsh winter conditions. The densities of northern European titmice populations are suggested to be lower than expected on the basis of summer productivity potentially causing geographical variation with respect to the interactions between resident and migrant birds. As expected, the associations between titmice and migrants appear stronger and more positive in northern Europe than elsewhere.
Heterospecific attraction in habitat selection among migrant species was studied both experimentally and theoretically. An increased density of titmice resulted in a higher number and abundance of migrant species than the removal treatment, suggesting that resident birds are used as cues for locating profitable breeding sites. From a theoretical perspective and under most conditions, the use of heterospecific cues proved to be a better habitat selection strategy than selection of sites based on direct assessment of the relative quality of habitat patches. Only when interactions (both positive and negative) between migrants and residents were weak and sampling costs of both strategies were about equivalent, did individuals using direct sampling gain in fitness.
Heterospecific attraction during breeding in relation to predation risk was assessed by examining the spatial distribution of birds. Both experimentally increased perceived predation risk and naturally occurring predation risk created by the presence of sparrowhawk (Accipiter nisus) i.e., relative to the vicinity of nesting hawk, resulted in more clumped distribution of birds than areas of lower risk. Around sparrowhawks nest, however, clumping was apparent for only one forest type and only among study plots including both large (≥ 20 g, preferred prey) and small birds (< 20 g).
To conclude, heterospecific attraction of migrants to resident birds contributes to the structure of local avian communities in forest landscapes. Heterospecific attraction among birds is strengthened by increased predation risk causing variation in species interactions when considered in a landscape perspective.
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Johansson, Tomas. "Habitat selection, nest predation and conservation biology in a Black-tailed Godwit (Limosa limosa) population." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-4958-1/.
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Roos, Staffan. "Nest predation processes and farmland birds : habitat selection and population dynamics of predators and prey /." Uppsala : Dept. of Conservation Biology, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/s301.pdf.
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Ingley, Spencer J. "Repeated Trait Evolution Driven by Divergent Natural Selection at Early and Late Stages of Speciation." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/6150.
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Speciation – the process by which new species arise – is of fundamental importance in the biological sciences. The means by which new species arise, and the relationship among living species, has been a topic that has captivated both lay and scientific observers for centuries. In recent years, the study of speciation has enjoyed increased attention, resulting in significant advances in our understanding of how species form. Although our understanding of the processes that contribute to speciation has increased dramatically in recent years, our knowledge of how reproductive barriers accumulate as speciation proceeds is still limited. Thus, studies that evaluate trait divergence and its consequences at early verses late stages of divergence can provide valuable insight into the speciation process. Chapter 1 of my dissertation focuses on the role of animal personality in the speciation process. Animal personality – defined as consistent individual differences in behavioral tendencies – has been identified as a key player in several ecological and evolutionary processes, yet the role of personality in speciation remains unexplored. In this chapter I discuss the ways by which personality can contribute to a suite of reproductive barriers and drive the speciation process. Chapters 2 through 5 provide a case study evaluating how selection acts on traits at early and late stages of speciation, using the Neotropical Livebearing fish genus Brachyrhaphis as a model system. Brachyrhaphis is ideally suited for this research because several species pairs and population pairs within species occur in similarly divergent selective regimes. I first present results from a field demographic study that shows that the strength of divergent selection acting on life-history traits in populations from divergent predation environments diminishes as speciation proceeds. I then show that population pairs at different stages of divergence are evolving similar morphological patterns along parallel trajectories. At both early and late stages of divergence, populations from environments with dense predator populations have a body shape that appears to be optimized for burst-speed swimming, and important component of predator escape. In contrast, populations from environments lacking predators have a body shape optimized for endurance swimming ability, which is important in environments where competition for foods and mates is high. Next, I show that populations from divergent predation environments do indeed differ in their swimming abilities according to our predictions, reflecting a population level trade-off between burst and endurance swimming ability. Although population level trade-offs were strong, I found no evidence of within population level trade-offs, suggesting that populations have arrived at novel solutions to between population trade-offs that were not present within ancestral populations. Finally, I show that these specialized swimming modes are locally adaptive, and that divergent ecology selects against immigrants, effectively reducing gene flow between populations from divergent environments. Together, these studies provide a valuable glimpse into the repeatability and predictability of trait divergence at different stages of speciation.
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Grand, Tamara C. "Habitat selection in juvenile coho salmon, Oncorhynchus kisutch, the effects of intraspecific competition and predation risk." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24310.pdf.
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Bennice, Chelsea O. "Altering life history traits a size-selective predator decreases the size of its prey. /." Connect to resource, 2008. http://hdl.handle.net/1811/32125.
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Thieme, Jennifer Lee. "Behavioral and reproductive consequences of predator activity to grassland birds." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313609279.
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Cruickshank, Hilary Stuart. "Prey selection and kill rates of cougars in northeastern Washington." Connect to this title online, 2004. http://www.dissertations.wsu.edu/Thesis/Summer2004/h%5Fcruickshank%5F081604.pdf.
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Halstead, Brian J. "Predator behavior and prey demography in patchy habitats." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002414.
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Skyer, Melissa. "Food habits of a re-introduced river otter (Lontra canadensis) population in western New York : annual diet, temporal and spatial variation in diet and prey selection conclusions /." Online version of thesis, 2006. https://ritdml.rit.edu/dspace/handle/1850/2590.
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Schmidt, Jason M. "Adaptive Foraging in a Generalist Predator: Implications of Habitat Structure, Density, Prey Availability and Nutrients." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1312815757.
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Thomson, R. L. (Robert L. ). "Breeding habitat selection and its consequences in boreal passerines:using the spatial dispersion of predators and heterospecifics as a source of information." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514280504.
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Abstract
Habitat selection decisions are crucial in determining fitness. Research indicates that individuals of many taxa are flexible in habitat selection and gather information prior to decision-making in order to control for environmental unpredictability. For time limited migrant birds, cues provide a quick and reliable information source with which to make habitat selection decisions. In this thesis I investigate habitat selection decisions, and their fitness consequences, of boreal passerines using heterospecifics or predators as cues.
In support of the heterospecific attraction hypothesis, plots with augmented resident titmice densities attracted increased migrant densities. The predicted negative effects stemming from competition did not occur even at unnaturally high resident densities. This suggests that in the north it may always be beneficial for migrants to use residents as cues in habitat selection decisions.
By manipulating habitat selection, I found that great tits (Parus major) had poorer reproductive success when forced to breed in close proximity to pied flycatcher (Ficedula hypoleuca) compared to when breeding alone. Flycatchers, in contrast, did slightly better when breeding close to tits. These results indirectly suggest that heterospecific attraction may not be a mutually positive species interaction. Indeed, flycatchers seem to parasitize the high quality microhabitat indicated by breeding great tits.
I also tested if residents provide a reliable cue relative to predation risk. However, willow tit (P. montanus) nest location appeared random relative to avian predator nests. They do not appear to reliably indicate safe breeding habitats to later arriving migrants. In addition, closer proximity to breeding avian predators had a negative impact on willow tit reproductive output.
Later arriving migrants may be in a better position to avoid avian predator nests during habitat selection. Pied flycatchers avoid settling in the immediate vicinity of sparrowhawk (Accipiter nisus) nests. However, nest box occupation, laying dates and initial reproductive investment (clutch size) showed a unimodal relationship with distance to sparrowhawk. A unimodal trend in these measures indicates there may be a trade-off between the costs (increased adult predation risk) and potential benefits (decreased nest predation risk) of settling in proximity to avian predator nests. Spatially predictable predation risk gradients that emanate from predator nests are termed a "predation risk landscape". Furthermore, flycatchers nesting closer to sparrowhawks produced fewer and smaller nestlings than those farther away. In addition, measures of maternal physiological stress (body condition and stress protein levels) had a negative linear relationship with distance to sparrowhawk nest. It appears that increased perceived predation risk near avian predator nests results in stressful and poor conditions for adult passerines, which results in lower reproductive output.
This thesis highlights the importance of information gathering prior to making habitat selection decisions in order to optimise territory location relative to heterospecifics or predators. These decisions clearly impact individual fitness.
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Koskela, A. (Anni). "Wolverine habitat selection, diet and conservation genetics." Doctoral thesis, Oulun yliopisto, 2013. http://urn.fi/urn:isbn:9789526202273.
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Abstract Rare and elusive species are difficult to study, because they are usually secretive, solitary, occur at low densities and have large home ranges. Wolverines (Gulo gulo) can both hunt and scavenge for food. In Fennoscandia, wolverines co-exist with either wild or semi-domesticated reindeer, which constitute their most important winter food. Approximately half of the 180–220 Finnish wolverines are found in northern Finland within the reindeer management area. However, the other half of the population is distributed in eastern and central Finland, and the ecology of wolverines especially in this area is poorly known. This research examined the habitat selection, diet and population genetics of wolverines in northern and eastern Finland. The results suggest that wolf presence is one of the most important variables influencing the habitat selection of wolverines. This finding supports the speculative idea that wolverines might benefit from being sympatric with wolves through increased scavenging opportunities. Furthermore, both the reproductive status of wolverines and the availability of different prey items were found to affect the wolverine diet. In northern Finland, semi-domesticated reindeer and mountain hare were the most frequently utilized prey species for breeding female wolverines. In eastern Finland, the most important food source for breeding females was moose carrion, whereas males and non-breeding females heavily utilized mountain hares. These results support the predictions of the optimal foraging theory, suggesting that wolverines opportunistically utilize the food source that is most energy-efficiently available. In areas with a low density of medium-sized ungulates, scavenging of wolf- and human-killed carrion plays an essential role in food acquisition by wolverines. According to the results of a population genetics investigation, two wolverine subpopulations exist in Finland: a northern and an eastern one. The overall genetic variability was found to be low, and signs of a recent population bottleneck were detected in both populations. It is likely that the wolverine populations in Finland would benefit from improved connectivity between them, but also with neighbouring populations in Scandinavia and north-eastern RussiaTiivistelmä Ahma (Gulo gulo) tunnetaan sekä haaskansyöjänä että keskikokoisia hirvieläimiä ja pienriistaa saalistavana petona. Fennoskandian alueella peuran kesy tai villi muoto on ahman merkittävin saalislaji. Noin puolet Suomen 180–220 ahmasta elää Pohjois-Suomessa poronhoitoalueella, ja loput Itä- ja Keski-Suomessa. Poronhoitoalueen ulkopuolella elävien ahmojen ekologiaa on tutkittu erityisen vähän. Väitöstyössäni tarkastelin ahman habitaatinvalintaa, ruokavaliota ja populaatiogenetiikkaa pääasiassa Pohjois- ja Itä-Suomen alueilla. Tutkimukseni tulokset osoittivat, että suden läheisyys oli yksi tärkeimmistä ahman habitaatinvalintaan vaikuttavista tekijöistä. Tämä havainto tukee hypoteesia, jonka mukaan ahma saattaisi hyötyä susien läheisyydestä suuremman haaskatiheyden ansiosta. Todennäköisesti ahmat elävät mielellään samoilla seuduilla susien kanssa, mutta kaihtavat läheistä kanssakäymistä välttääkseen killansisäisen saalistuksen. Tutkimusteni perusteella sekä ahman lisääntymistila että alueen saaliseläinten saatavuus vaikuttivat ahman ruokavalioon. Poro ja metsäjänis olivat lisääntyvien ahmanaaraiden tärkein ravintokohde Pohjois-Suomessa. Itä-Suomessa merkittävin lisääntyvien naaraiden ravintokohde oli hirvi, jota ahmat hyödyntävät lähinnä haaskojen muodossa, mutta urokset ja ei-lisääntyvät naaraat sen sijaan saalistivat eniten metsäjänistä. Ahmat siis näyttävät hyödyntävän opportunistisesti sitä ravintokohdetta, joka kullakin alueella on energiatehokkainta saavuttaa. Susien ja ihmisten jälkeensä jättämät haaskat ovat merkittävä ravintolähde ahmoille alueilla, joilla keskikokoisten hirvieläinten tiheydet ovat alhaisia. Ahman populaatiogeneettinen tutkimus osoitti, että Suomen ahmat ovat geneettisesti jakautuneet kahteen alapopulaatioon, pohjoiseen ja itäiseen. Ahmakannan geneettinen monimuotoisuus oli pientä, ja molemmissa alapopulaatiossa oli nähtävissä merkkejä äskettäisestä pullonkaulailmiöstä. Populaatioiden välisen geenivirran määrän tulisi olla nykyistä korkeampi, jotta ahmakannan elinvoimaisuuden voisi katsoa olevan turvattu tulevaisuudessa
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Torre, Corominas Ignasi. "Distribution, population dynamics and habitat selection of small mammals in Mediterranean environments: the role of climate, vegetation structure, and predation risk." Doctoral thesis, Universitat de Barcelona, 2004. http://hdl.handle.net/10803/787.
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The main objectives of this thesis were to analyse the relative roles of food availability and predation on the distribution, population dynamics and habitat selection of small mammals in Mediterranean areas of the Iberian Peninsula. Main results and conclusions
Composition and abundance of small mammals communities can be completely ascertained by using two indirect methods of small mammals sampling, genet scats and barn owl pellets. Both methods reported all the small mammals species known to be present in the study area. Genet scats were used for the first time to study the composition of small mammal communitites with a biogeographical application.
Small mammals species richness was negatively related to a gradient of productivity, which decreased with elevation. The increase of species density along elevation was observed at two spatial scales (plot and elevation belt). Small mammals mean abundance decreased with elevation, and this pattern was may be related to the decreased availability of resources and harsh environmental conditions with elevation.
The interaction between negative feedback (density-dependence) and natural environmental disturbances (seasonal and interannual changes in cumulative rainfall) seem to be relevant forces driving the dynamics of wood mouse populations in Mediterranean forests. The role of intraspecific competition and climate were equally responsible of the strong population oscillations observed during three consecutive years.
All small mammal species studied showed significant associations with gradients of short vegetation cover, either shrubs or herbs, in natural and man-disturbed habitats. Overall, species richness and abundance also showed positive associations with gradients of short vegetation cover. These patterns highlighted the dependence of small mammals on vegetation which provides food and shelter.
Early successional stages supported larger small mammal abundances than unburnt forests after controlling for structural differences between plots. I hypothesised that early successional stages would be favourable habitats to small mammals due to a combination of reduced predation risk (high vegetation cover) and reduced predation pressure (less predators), and unburnt areas would be unfavourable habitats due to a combination of increased predation risk (low vegetation cover) and increased predation pressure (more predators). Fire-related fragmentation could have promoted the isolation of forest predators (owls and carnivores) in unburned forest patches, a fact that could have produced a higher predation pressure for small mammals. Behavioural responses of small mammals to predation were also surmised, with positive associations to vegetation cover in unburnt forests and negative associations in early burned habitats. These changes in small mammal-microhabitat relationships suggest differences in perceived predation risk that may have promoted the observed changes in microhabitat use. Foraging activity of mice shifted spatially and temporally in response to the presence of genets at relevant spatial scales, and decissions about how often and how long to forage were affected by the foraging activity of genets. Summarising, our findings demonstrate that predators have a prominent role in determining the patterns of distribution of mice along the post-fire succession, and that this role is mediated, at least in part, by indirect, behavioural responses of foraging mice to increased predator pressure along such succession.
Effects of grazing on small mammals were mainly due to decreased availability of food and refuges for surviving harsh climatic conditions during winter, but not to food quality or increased predation risk. Taken together, our results indicate that small mammal communities in Mediterranean montane grasslands are bottom-up controlled by interspecific competition for food with cattle and by the limiting role of the availability of winter refuges, whereas top-down control due to generalists predators does not appear to be at work in these systems.
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Eberl, Christine. "Effect of food, predation and climate on selection of breeding location by red-throated loons (Gavia stellata) in the high Arctic." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6951.
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The red-throated loon (Gavia stellata) is a circumpolar species. The purpose of this study was to examine adaptations of this species to environmental conditions in the high arctic. I found that the phenology of the loons in my study area was shorter than that of red-throated loons further south, and that this population tended to select nesting ponds much larger than in the south. I also found that pairs nesting near the ocean (within 9.0 km) were able to rear larger broods (2 chicks vs 1 chick) than pairs nesting far from the ocean (9.0-13 km). Finally, I found that pond size did not influence melting rate but that large ponds took longer to freeze. I also observed that 16% of loons moved their chick(s) to larger ponds when natal ponds began to freeze over. This supports the view that the use of large nesting ponds by these loons is an adaptation to the cold climate. (Abstract shortened by UMI.)
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Karlsson, Johanna. "How two different predators affect size distribution and behavior of an aquatic isopod." Thesis, Linköpings universitet, Institutionen för fysik, kemi och biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-69747.
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The aquatic isopod Asellus aquaticus can in some lakes be found as two different ecotypes; one in the habitat dominated by reed and one in stonewort stands. These ecotypes have been shown to differ in size, color and behavior. The reed ecotype is larger, darker and more active compared to the stonewort ecotype. In the two habitats there are different dominating predators: Invertebrate predators in the reed habitat and fish in the stonewort habitat. This project aims to examine how the presence of invertebrate predators and fish affect the two ecotypes of the isopod in regard to behavior and size composition in different substrates. To examine the effect on behavior the activity of isopods collected from Lake Tåkern was measured without and with chemical cues from perch and damselfly larva. The result of the behavior experiment showed no difference between the ecotypes nor the treatments. The lack of differences in the behavior indicates that there could be a variation between lakes. The effect on the size composition was examined by subjecting groups of isopods to predation by perch or damselfly larva in different substrate. The mean length of the group was measured before and after the trials. The size decreased significantly for the reed ecotype in stonewort substrate when subjected to predation by perch. The size for the stonewort ecotype increased significantly in reed substrate with damselfly larva as predator. The effect on size supports that the predators are the cause of the size difference between the ecotypes.
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Meissner, K. (Kristian). "Consequences of predator-prey interactions in boreal streams:scaling up from processes to large-scale patterns." Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514278682.
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Abstract
In this thesis I studied lotic trout predation and its ecological effects, and investigated invertebrate predator-prey interactions under natural and anthropogenically modified flow conditions. Given the growing concern about the reliability of extrapolations from small-scale studies to larger spatio-temporal scales, results of mechanistic small-scale experiments were scaled up by linking them to large-scale field surveys.
An intensive survey assessed changes in diel feeding periodicity, prey selection and daily ration of juvenile brown trout (Salmo trutta L.) over the course of the open water period. This survey provides the first field estimates of juvenile brown trout daily rations and indicates crepuscular feeding peaks. Trout selectively preyed on medium- to large-sized prey, shifting towards epibenthic feeding with increasing availability of suitable prey. In a small-scale field experiment, trout displayed clear size-related predation concentrating on invertebrate predators and cased caddisflies, a pattern that scaled up successfully in large-scale surveys. Further, predation effects on large-sized prey were also repeated in a meta-analysis on lotic salmonid predation.
While dense blackfly populations in lake-outlet streams are common, mass outbreaks of blackflies in short-term regulated rivers are poorly studied. In our studies the principal invertebrate predator of vernal benthic communities, the caseless caddisfly Rhyacophila, displayed significant preference for blackflies and was almost unable to capture any other prey, thus resulting in passive selection for larval blackflies.
Rhyacophila larvae displayed highest capture success in intermediate current velocities, whereas further increases in current velocities decreased capture success. Short-term regulation releases increased both predator and prey drift but, unlike for Rhyacophila, magnitude of drift was unrelated to substrate for blackflies. Indeed, field observations indicated that blackflies rarely face detrimental effects of short-term regulation due to their fast growing rates and early emergence. Moss was the most preferred habitat of Rhyacophila and provided the best buffer against sudden increases in current velocities. These results suggest that several factors maintain spring-time outbreaks of blackfly populations in short-term regulated rivers: exaptation of the dominant blackfly species to prevailing conditions, degradation of the key habitat of the predator, and recurring annual drift losses and diminished capture success of Rhyacophila during short-term regulation releases.
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Östergård, Hannah. "Plant-seed predator interactions – ecological and evolutionary aspects." Doctoral thesis, Stockholm University, Department of Botany, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7537.
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Plant-animal interactions are affected by both abundance and distribution of interacting species and the community context in which they occur. However, the relative importance of these factors is poorly known. I examined the effects of predator host range, environmental factors, host plant populations, plant traits and fruit abortion on the intensity of pre-dispersal seed predation in 46 host populations of the perennial herb Lathyrus vernus. I recorded damage by beetle pre-dispersal seed predators, mainly Apion opeticum and Bruchus atomarius with different host ranges on L. vernus as well as on two additional host plants. Local seed predator population size was mainly influenced by plant population size, current seed production and beetle population size in the previous year, but was not strongly affected by connectivity. The monophagous seed predator was less abundant and had lower densities than the oligophagous. Both predator species had a strong ability to track fluctuations in seed production; intensity of predation increased with relative increases in seed production. Oligophagous predation on L. vernus increased with the abundance of alternative hosts, but presence of L. vernus did not affect predation on alternative hosts. Abundances and trait preferences differed among three co-occurring seed predators, but were also associated with the abundance of the other species. Overall, seed predation influenced selection on flower number. I found clear indications of seed predator offence but no obvious plant defence. The pattern of fruit abortion was associated with reduced plant fitness since the seed predator had an advanced ability to locate fruits with high probability of retention. Taken together, different factors influencing abundance of the seed predator species, different preferences, and context dependent trait selection are likely to result in complex spatio-temporal variation in overall seed losses and trait selection in the common host plant.
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Clements, Hayley Susan. "Incorporating prey demographics and predator social structure into prey selection and carrying capacity estimates for cheetah." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1018606.
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There is a need for a refined understanding of large carnivore prey preference and carrying capacity (K). To date, K estimates for large carnivores have been developed from predictions of carnivore diet at a prey and predator species-level. These predictions therefore assume that all social classes within a carnivore species display similar prey preferences and that all demographic classes within a prey species are equally preferred or avoided. The objective of this study was to investigate the importance of including prey demographics and carnivore social class in carnivore diet descriptions and thereby K estimates, using cheetah Acinonyx jubatus as a study species. It was predicted that prey sex, prey age and cheetah social class influence cheetah prey preferences, when they influence the risk and ease of prey capture, and that their inclusion in a K model would improve its predictive strength. Based on an analysis of 1290 kills from South Africa, male coalition cheetah were found to prefer a broader weight range of prey than solitary cheetah. Prey demographics further influenced cheetah prey preference, when it corresponded to differences in prey size and the presence of horns. The current species-level K regression model for cheetah is based on preferred prey and thus omits highly abundant antelope that often comprise the majority of the diet, an artefact of the way in which preferences are calculated. A refinement of the species-level K regression model, to account for prey demographic- and cheetah social class-level differences in diet and the biomass of accessible prey (defined in this study as all non-avoided prey) instead of just preferred prey, doubled the predictive strength of the K model. Because group-hunting enabled predation on a broader weight range of prey, cheetah K was influenced by the ratio of male coalition cheetah to solitary cheetah in the population. The refined K regression model is derived from ecosystems supporting an intact carnivore guild. A mechanistic approach to estimating K, based on Caughley‟s (1977) maximum sustainable yield model, therefore better predicted cheetah K in systems devoid of lion Panthera leo and African wild dog Lycaon pictus, which were found to suppress cheetah density. This study improves our understanding of the relationships between prey demographics, cheetah social classes and intra-guild competition in determining cheetah prey preferences and K. This study therefore paves the way for similar work on other large carnivores.
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Kopec, Audrey Dianne. "Prey Selection in Gulf of Maine Harbor Seals (Phoca vitulina) in Relation to Fish Abundance and Fish Mercury Concentrations." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/KopecAD2009.pdf.
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Mahoney, Peter J. "Spatial Ecology of Coyotes and Cougars: Understanding the Influence of Multiple Prey on the Spatial Interactions of Two Predators." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/5658.
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The extent to which predators regulate prey populations remains a subject of debate. Yet, when predator control is employed as a management strategy, it is often assumed that predators can and do regulate prey populations. From 2011 through 2015, I monitored the demography and space use of coyotes (Canis latrans) and cougars (Puma concolor) on Monroe Mountain in Fishlake National Forest, Utah as part of a larger collaboration investigating the impacts of coyote aerial control on mule deer (Odocoileus hemionus) neonate survival. My primary objective was to assess the impacts of anthropogenic regulation on the respective populations and identify any cascading effects relevant to mule deer management. To meet this objective, I established a monitoring program for both predators by deploying radio-telemetry collars (VHF and GPS) on each, documented predation events, established surveys for small mammals and lagomorphs to monitor primary prey populations during deer parturition (June – August), and collected data on the location and demographic composition of winter-removed coyotes. I analyzed these data primarily in a community-based, animal movement and resource selection framework permitting the integration of data from multiple sources. When evaluating coyote aerial removal as a management strategy, I identified a spatial dependency in the ability to match removals with indices of deer recruitment as Wildlife Services Operations personnel were primarily limited by terrain and tree cover. Thus, matching treatment with deer fawning was highly variable with only a small number of sites where removals were effective. In addition, I found that coyotes selected for sites with the highest densities of lagomorphs while avoiding areas with a high probability of encountering cougars. Coyotes did not select for mule deer fawning sites, although individual coyotes that occupied resource-poor home ranges were more likely to do so. Cougars strongly selected for mule deer high use areas throughout much of the year, only switching to elk (Cervus elaphus) during the cougar harvest season (i.e., winter). Data from cougar kill site investigations match the observed patterns in cougar space use. My results suggest that predator-prey processes are multi-dimensional and dynamic through time, which likely contribute to the lack of resolution regarding the efficacy of predator control and the regulatory potential of predators in general.
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Spjern, Victor. "Hur påverkar storskarv (Phalacrocorax carbo) och skäggdopping (Podiceps cristatus) fisksamhället i grunda, näringsrika sjöar?" Thesis, Linköpings universitet, Biologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166546.
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Piscivorous birds are an integrated part of lake and coastline ecosystems. Despite decades of research it is yet unclear what influence fish eating birds have on the fish community. The aim of this literature study was to focus on how two fish eating birds, Great Cormorant and Great Crested Grebe, influence the fish community in shallow and eutrophic lakes. Different types of analysis methods have been used when doing research on the subject, including pellet analysis, stomach content analysis, tagging of fishes by “PIT”-techniques and analysis by observation. Results show that conclusions by studies tend to vary, but generally higher bird density, lower water temperature and a relatively high turbidity contribute to a higher influence on the fish community. Both bird species are opportunistic in their choice of food and catch prey of the species that occur locally. Both species also limit themselves in the prey size, but the choice vary over seasons because of water temperature and the birds requirements in association with breeding and migration. The significant level of influence seems to be when predation is conducted on younger and smaller fishes. The influence on the fish size can also be indirect, where predation on smaller individuals prevent fishes from becoming older and bigger. As studies tend to deviate in conclusion, no general answer to this issue can be given at present. Comprehensive research with several years of full control over both fish-and bird population is needed to find the proper conclusion.
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Baxter, Jared Jeffrey. "Reproductive Ecology of Greater Sage-Grouse in Strawberry Valley, Utah." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6580.
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Greater sage-grouse (Centrocercus urophasianus; hereafter, sage-grouse) are a species of conservation concern in the rangelands of western North America due to their dramatic decline over the last half century. Effective conservation and management of sensitive species requires an understanding of how species respond to management actions. We examined two aspects of the reproductive phases of sage-grouse: nest predation, and habitat selection by female sage-grouse with chicks. In Chapter 1, we developed resource selection functions to assess the influence of mechanical treatments of mountain big sagebrush (Artemisia tridentata vaseyana) on habitat selection by greater sage-grouse with chicks. Post-treatment sage-grouse showed stronger selection for treatments and treatment edges than did pre-treatment sage-grouse. This altered pattern of selection by sage-grouse with broods suggests mechanical treatments may be a suitable way to increase use of mountain big sagebrush during the brooding period. In Chapter 2, we assessed the effect of habitat edges on nest predation of sage-grouse. The "edge effect" hypothesis states that habitat edges are associated with reduced nest success for birds. We tested the edge effect hypothesis using 155 nest locations from 114 sage-grouse. We derived edge metrics for 11 habitat cover types to determine which variables may have affected nest predation. We found support for the edge effect hypothesis in that nest predation increased with increasing edge density of paved roads. We provide evidence that the edge effect hypothesis may apply to greater sage-grouse and their habitats. Based on our results, we recommend minimizing disturbances that fragment critical nesting habitat of greater sage-grouse.
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Otsuki, Hatsune. "Interactions between Spider Mites and Predators in Systems with Dispersal Opportunities." Kyoto University, 2020. http://hdl.handle.net/2433/253311.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第22475号
農博第2379号
新制||農||1074(附属図書館)
学位論文||R2||N5255(農学部図書室)
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 日本 典秀, 教授 田中 千尋, 准教授 刑部 正博
学位規則第4条第1項該当
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Englund, Göran. "Competition in caddis larvae." Doctoral thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 1992. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-101356.
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This thesis deals with behavioural strategies used by caddis larvae in pairwise contests and when selecting microhabitats. Effects of caddis larvae on survival and habitat selection of other insect taxa have also been studied. The behaviours used by Arctopsyche ladogensis larvae fighting for nets, and Agrypnia pagetana larvae fighting for cases, agreed well with predictions from the sequential assessment game, which is an ESS model of animal fighting behaviour. Establishment by net-spinning Hydropsyche siltalai larvae on artificial substrates was highest at intermediate densities of residents. Emigration/mortality was density independent, and it was higher at a poor site (low food availability) than at a rich site. Establishment was unaffected by site quality. Growth was density dependent because larvae in upstream positions reduced both current velocity and concentration of food particles for larvae in downstream positions. A field experiment involved manipulations of the density of H. siltalai larvae and their nets in a lake outlet stream. H. siltalai larvae affected all abundant taxa, but the mechanism involved varied between taxa. Rhyacophila nubila (Trichoptera) and chironomid larvae benefited from the presence of H. siltalai nets. Negative effects on nymphs of the mayfly Ephemerella ignita were due to predation by H. siltalai larvae, while a combination of predation and increased emigration in response to nets depressed densities of Simulium truncatum blackfly larvae.Diss. (sammanfattning) Umeå : Umeå universitet, 1992, härtill 5 uppsatser
digitalisering@umu
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Wasko, Dennis Keith. "Spatial and Feeding Ecology of the Fer-de-Lance (Bothrops asper) in Costa Rica." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/206.
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Understanding the ways in which animals utilize space and obtain food are central themes in modern ecology. Formulating broad principles and elucidating the factors explaining such patterns are limited, however, by the availability of data from a broad range of species and systems. This problem especially true of snakes, a predator group about which even the most basic natural history data are often entirely lacking, even among abundant, widespread, and ecologically-important species. I studied the natural history and ecosystem role of one such species, the fer-de-lance (Bothrops asper) in lowland rainforest in Costa Rica. B. asper is a large, cryptic pitviper that is highly abundant in many Central American ecosystems and is strongly relevant to human health due to high incidence of snakebite, yet its biology under natural conditions is almost entirely undocumented. I used radiotelemetry to quantify home range, movement patterns, habitat usage, and foraging behavior. B. asper was found to have smaller home ranges and reduced movement patterns than similarly-sized temperate pitvipers, likely due to a greater reliance upon ambush foraging in patches of high prey density. Snakes also demonstrated strong selection for swamp habitat, which may reflect efforts to exploit frogs as a primary food source due to low availability of small mammals at the study site. I subsequently addressed the trophic status of this B. asper population using a supplemental-feeding experiment. In comparison to control snakes, individuals receiving supplemental food had smaller home ranges, shorter and less frequent movements, increased mass acquisition, and shifted to primarily forest rather than swamp habitat. These results support the suggestion that B. asper at the study site are strongly food-limited. Finally, I tested the hypothesis that fer-de-lance mediate local seed-predation rates by influencing habitat usage and foraging behavior of rodents. A series of behavioral experiments conflicted with many existing studies in failing to support this idea, as three rodent species demonstrated little snake avoidance, and none of likely ecological relevance. Collectively, this dissertation represents the first comprehensive field study of Bothrops asper and is among the first for any tropical snake, and suggests several avenues for future research.
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Silva, Leonardo Henrique da. "Seleção de dormitórios pelos micos-leões-pretos : uma comparação entre floresta contínua e fragmento /." Rio Claro, 2019. http://hdl.handle.net/11449/183152.
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Orientador: Laurence Marianne Vincianne CulotResumo: A seleção de dormitórios pelos primatas pode ser influenciada por diversos fatores, como a predação, termorregulação e defesa de território. Nosso objetivo foi investigar quais desses fatores influenciam a seleção de dormitórios pelos micos-leões-pretos e se há divergência nas características dos dormitórios entre uma floresta contínua e um fragmento. Estudamos dois grupos de mico-leões-pretos, um numa floresta contínua e um num fragmento na região do Pontal do Paranapanema, São Paulo, Brasil. Nós coletamos os dados sobre as características físicas dos dormitórios e das árvores disponíveis no habitat. Usamos testes de Mann-Whitney para comparar as características físicas dos dormitórios com as árvores disponíveis e Funções de Seleção de Recursos (RSF) para entender quais dessas características são mais importantes na escolha dos dormitórios. Os micos-leões-pretos usaram árvores mais altas, com menor número de conexões de copas e com um alto grau de cobertura de copa para dormir, quando comparado às árvores disponíveis. Os dormitórios usados pelo grupo da floresta contínua eram maiores, com as primeiras ramificações inferiores mais altas e com menor número de conexão de copas do que os dormitórios usados pelo grupo do fragmento. Nossos resultados evidenciam a presença de estratégias anti-predação pelos grupos de micos-leões-pretos, com o grupo da floresta contínua apresentando um processo de seleção de dormitórios mais refinado, no qual a seleção apenas de árvores que possuam ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Sleeping site selection by primates can be influenced by several factors, such as predation, thermoregulation and territorial defense. Our objective was to investigate which of these factors influence the sleeping site selection by black lion tamarins and if there is divergence in the characteristics of the sleeping sites between a continuous forest and a fragment. We studied two groups of black lion tamarins, one in a continuous forest and one in a small and isolated fragment in the Pontal do Paranapanema, São Paulo, Brazil. We collected data on the physical characteristics of the sleeping sites and available trees within the both habitats. We used Mann-Whitney tests to compare the physical characteristics of the sleeping sites with available trees and Resource Selection Functions (RSF) to understand which of these characteristics are most important in choosing the sleeping sites. Black lion tamarins used taller trees, with a fewer canopy connections, and a higher degree of canopy cover compared to the available trees. The sleeping sites used by the continuous forest group were larger, with the first lower ramifications higher and with fewer number of canopy connections than the sleeping sites used by the fragment group. Our results evidenced the presence of anti-predation strategies by both black lion tamarin groups, with the continuous forest group presenting a more refined sleeping site selection process, in which the selection of only trees with a larger set of character... (Complete abstract click electronic access below)
Mestre
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Corral, López Alberto. "The link between brain size, cognitive ability, mate choice and sexual behaviour in the guppy (Poecilia reticulata)." Doctoral thesis, Stockholms universitet, Zoologiska institutionen, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-148547.
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Competition over access for mates has led to the evolution of many striking examples of morphological traits and behaviour in animals. The rapid development of the sexual selection field in recent decades have dramatically advanced our understanding of what traits make individuals more successful in attracting mates and how preferences for mates evolve over time. However, till now, research in this field has put less emphasis on the mechanisms that underlie variation in mate choice and sexual behaviour. Cognitive processes could potentially be key drivers of individual variation in mating preferences and sexual behaviours and therefore deserve further investigation. In this thesis, I used guppies artificially selected for relative brain size as the model system to study the association between brain size, cognitive ability and various aspects of mate choice. Previous studies in this model system showed that large-brained individuals of both sexes outperformed small-brained individuals in cognitive tests. Here I quantified their sexual behaviours and mating preferences to provide novel empirical data concerning the association between brain size, cognitive ability and sexual selection. In dichotomous choice preference tests based on visual cues, comparisons between large-brained and small-brained guppies showed important differences in their assessment of mate quality. These results are not driven by pre-existing visual biases caused by the artificial selection since further investigation of the visual capacity of these fish detected no differences between large-brained and small-brained individuals in their sensitivity to colour or in their capacity to resolve spatial detail. I also quantified sexual behaviour in male guppies artificially selected for relative brain size and found no difference in the behaviours of large-brained and small-brained males in a single male-single female non-competitive scenario. On the contrary, in a more complex social setting I found a reduction in large-brained males in the rate of courtship towards females and dominance displays towards other males when exposed to different degrees of predation threat and different numbers of male competitors. However, this reduction in behavioural intensity did not result in a lower access to copulation with females for large-brained males. I likewise evaluated female sexual behaviour and found that large-brained females had higher behavioural flexibility such that they decreased their receptiveness towards males more strongly under higher levels of predation threat. Together, these results provide novel empirical evidence that brain size and cognitive ability are tightly linked to mating preferences and sexual behaviours. These findings suggest that brain size and cognitive ability might be important mechanisms behind variation in mating preferences and in sexually selected traits across and within species.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 5: Manuscript.
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Kaartinen, S. (Salla). "Space use and habitat selection of the wolf (Canis lupus) in human-altered environment in Finland." Doctoral thesis, Oulun yliopisto, 2011. http://urn.fi/urn:isbn:9789514293825.
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Abstract The grey wolf is the most widely distributed of all land mammals and is a habitat generalist that inhabits all the vegetation types of the Northern Hemisphere. Wolves also breed well and have the potential to rapidly expand to new areas. In Finland, the wolf is a game species, and as a result of Finland’s membership of the European Union, the wolf population is subject to very limited hunting due to the obligation to protect the species. Mainly for this reason, the wolf population in Finland has increased significantly in recent years. In particular, the birth rate has developed favourably and the number of litters increased from just four in 1996 to 20 in 2005. It also seems at present that the wolf population in Finland is no longer following the fluctuations in wolf numbers in Russian Karelia. The general aim of this dissertation is to provide applicable knowledge for wolf management and conservation purposes, and especially to examine the effects of human-modified landscapes on wolf population expansion in Finland. Various aspects of habitat selection were investigated in four sub-studies to gain a thorough insight into the space use and habitat needs of wolves. Species data came from a long-term wolf population study that included location information from 85 radio- and GPS-GSM-collared wolves from 1998 onwards, as well as track location data based on about 30 000 annual observations recorded with geographical coordinates by a local network of experts on large carnivores. I found that adaptability makes it possible for the wolf to live in the multiple-use, semi-wild forests of Finland and that no restrictions are imposed by the landscape on wolf population growth and expansion. In general, the results of my dissertation provide evidence that wolves tend to avoid the presence of human influence when establishing a territory and also when selecting their den site. However, as wolf numbers increase, conflict situations will more frequently occur between wolves and humans, although the risk of depredation events, for example among sheep farms, varies between farms in Finland. That is, there are some environmental and farm level factors that are associated with wolf depredation. The breeding wolf population in Finland has gradually expanded and the first litters have recently been born in western Finland after an absence of more than 100 years. The geographical distance to the Scandinavian population is shorter from these new western territories than from the population’s core area in eastern Finland. This could potentially increase the likelihood of dispersal from Finland to ScandinaviaTiivistelmä Susi on habitaattigeneralisti, jonka levinneisyys kattaa kaikki pohjoisen pallonpuoliskon kasvillisuustyypit. Sudet myös lisääntyvät hyvin ja voivat näin ollen levittäytyä nopeasti uusille alueille. Suomessa susi on riistalaji, jonka metsästys on rajoitettua Euroopan unionin jäsenyyden myötä. Lähinnä tästä syystä Suomen susikanta on kasvanut voimakkaasti 1990-luvun ja 2000-luvun alun aikana. Erityisesti syntyvyys on kasvanut: pentueiden määrä lisääntyi neljästä 20:een vuosien 1996 ja 2005 välillä. Näyttäisi siltä, ettei Suomen nykyinen susipopulaatio enää seuraa Venäjän Karjalassa tapahtuvia kannanvaihteluita. Väitöskirjan tavoitteena on ollut tuottaa susikannan hoidossa ja suojelussa käytettävissä olevaa tietoa ja erityisesti tutkia susikannan levittäytymistä ihmisen muokkaamassa ympäristössä Suomessa. Neljässä osatutkimuksessa on käsitelty suden habitaatinvalintaa eri näkökulmista, jotta saataisiin kokonaiskuva suden tilankäytöstä Suomessa. Tutkimusaineisto rakentui pitkäaikaisesta seuranta-aineistosta, jota on kerätty vuodesta 1989 lähtien. Vuosien 1989 ja 2010 välillä 85 sutta on pannoitettu radio- tai GPS-GSM –pannalla. Tutkimuksessa käytettiin hyväksi myös noin 30 000 vuosittain tehtyä jälkihavaintoa. Tutkimustulosten perusteella susi selviää hyvin Suomen monikäyttömetsissä, eivätkä maisematyypit itsestään rajoita susipopulaation kasvua ja levittäytymistä. Toisaalta tulokset osoittavat myös sen, että sudet välttelevät ihmistoimintoja valitessaan reviiri- tai pesäpaikkoja. Kuitenkin susien lukumäärän kasvaessa ristiriitatilanteet susien ja ihmisten välillä tulevat lisääntymään, vaikka susivahinkoriskin suuruus vaihteleekin Suomessa huomattavasti. Esimerkiksi lammastilojen susivahinkoriski riippuu sekä ympäristötekijöistä, että tilan sisäisistä tekijöistä. Kaiken kaikkiaan lisääntyvän susipopulaation esiintymisalue on Suomessa vähitellen kasvanut leviten itärajan tuntumasta kohti länttä. Tämän myötä maantieteellinen etäisyys Skandinavian susipopulaatioon on pienentynyt viimeisten vuosien aikana. Tämä voi edesauttaa susiyksilöiden siirtymistä Suomesta Skandinaviaan