Academic literature on the topic 'Predator guild'
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Journal articles on the topic "Predator guild"
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Buitenhuis, R., L. Shipp, and C. Scott-Dupree. "Intra-guild vs extra-guild prey: effect on predator fitness and preference of Amblyseius swirskii (Athias-Henriot) and Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae)." Bulletin of Entomological Research 100, no. 2 (2009): 167–73. http://dx.doi.org/10.1017/s0007485309006944.
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AbstractThe relationships between the predatory mites, Amblyseius swirskii (Athias-Henriot) and Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae), and their prey, western flower thrips (Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae), were investigated to determine the effects of predation on intra-guild or extra-guild prey and predator preference. Life history characteristics of both predatory mites were measured when fed eggs and larvae of the other predator species and compared to data obtained when the predators were fed thrips larvae. In addition, choice tests were conducted to determine if the predators had a preference for different prey or if they were indiscriminate predators. Amblyseius swirskii appears to be an important intra-guild predator of N. cucumeris juveniles because of a high predation rate and a preference for N. cucumeris juveniles over thrips. Neoseiulus cucumeris is also an intra-guild predator of A. swirskii juveniles; however, it has a lower predation rate than A. swirskii. Contrary to intra-guild predation theory, intra-guild prey was an equally good or better food source than thrips (extra-guild prey) for both predators, based on high oviposition rates and fast development times. The results of this study indicate a high potential for negative interactions between A. swirskii and N. cucumeris when used together in biological control of thrips.
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Omkar, Geetanjali Mishra, Bhupendra Kumar, Neha Singh, and Garima Pandey. "Risks associated with tandem release of large and small ladybirds (Coleoptera: Coccinellidae) in heterospecific aphidophagous guilds." Canadian Entomologist 146, no. 1 (2013): 52–66. http://dx.doi.org/10.4039/tce.2013.56.
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AbstractMultiple interactions occurring within aphidophagous guilds determine their final predation outcomes, i.e., antagonistic, additive, or synergistic. Based on these predatory outcomes, the suitability of guilds in suppressing aphid pests is determined. The present study assesses the efficacy of 11 guilds, formed from both larval and adult stages of four locally abundant aphidophagous coccinellids (Coleoptera: Coccinellidae), while exploiting the pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae). The observed antagonistic effects within these guilds are resultants of enhanced predator–predator interactions due to the size and diversity of guild predators. Smaller ladybird predators maintained their usual body mass, probably by increasing their conversion efficiencies to compensate for their reduced prey consumption. However, larger ladybirds reported loss in their body mass, owing to their higher energy needs. The overall guild conversion efficiencies and growth rates were reduced. Among the experimental guilds, the observed prey mortalities were relatively higher in two-predator guilds, and within these two-predator combinations, the higher prey mortalities were recorded in those guilds where Coccinella septempunctata was one of the predators.
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Walzer, A., H. F. Paulus, and P. Schausberger. "Ontogenetic shifts in intraguild predation on thrips by phytoseiid mites: the relevance of body size and diet specialization." Bulletin of Entomological Research 94, no. 6 (2004): 577–84. http://dx.doi.org/10.1079/ber2004329.
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AbstractIn greenhouse agroecosystems, a guild of spider mite predators may consist of the oligophagous predatory mite Phytoseiulus persimilis Athias-Henriot, the polyphagous predatory mite Neoseiulus californicus McGregor (both Acari: Phytoseiidae) and the primarily herbivorous but facultatively predatory western flower thrips Frankliniella occidentalis Pergande (Thysanoptera: Thripidae). Diet-specialization and the predator body size relative to prey are crucial factors in predation on F. occidentalis by P. persimilis and N. californicus. Here, it was tested whether the relevance of these factors changes during predator ontogeny. First, the predator (protonymphs and adult females of P. persimilis and N. californicus): prey (F. occidentalis first instars) body size ratios were measured. Second, the aggressiveness of P. persimilis and N. californicus towards F. occidentalis was assessed. Third, survival, development and oviposition of P. persimilis and N. californicus with F. occidentalis prey was determined. The body size ranking was P. persimilis females > N. californicus females > P. persimilis protonymphs > N. californicus protonymphs. Neoseiulus californicus females were the most aggressive predators, followed by highly aggressive N. californicus protonymphs and moderately aggressive P. persimilis protonymphs. Phytoseiulus persimilis females did not attack thrips. Frankliniella occidentalis larvae are an alternative prey for juvenile N. californicus and P. persimilis, enabling them to reach adulthood. Females of N. californicus but not P. persimilis sustained egg production with thrips prey. Within the guild studied here, N. californicus females are the most harmful predators for F. occidentalis larvae, followed by N. californicus and P. persimilis juveniles. Phytoseiulus persimilis females are harmless to F. occidentalis.
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Lear, Karissa O., Nicholas M. Whitney, John J. Morris, and Adrian C. Gleiss. "Temporal niche partitioning as a novel mechanism promoting co-existence of sympatric predators in marine systems." Proceedings of the Royal Society B: Biological Sciences 288, no. 1954 (2021): 20210816. http://dx.doi.org/10.1098/rspb.2021.0816.
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Niche partitioning of time, space or resources is considered the key to allowing the coexistence of competitor species, and particularly guilds of predators. However, the extent to which these processes occur in marine systems is poorly understood due to the difficulty in studying fine-scale movements and activity patterns in mobile underwater species. Here, we used acceleration data-loggers to investigate temporal partitioning in a guild of marine predators. Six species of co-occurring large coastal sharks demonstrated distinct diel patterns of activity, providing evidence of strong temporal partitioning of foraging times. This is the first instance of diel temporal niche partitioning described in a marine predator guild, and is probably driven by a combination of physiological constraints in diel timing of activity (e.g. sensory adaptations) and interference competition (hierarchical predation within the guild), which may force less dominant predators to suboptimal foraging times to avoid agonistic interactions. Temporal partitioning is often thought to be rare compared to other partitioning mechanisms, but the occurrence of temporal partitioning here and similar characteristics in many other marine ecosystems (multiple predators simultaneously present in the same space with dietary overlap) introduces the question of whether this is a common mechanism of resource division in marine systems.
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Thompson, Randy G., Ian G. Warkentin, and Stephen P. Flemming. "Response to logging by a limited but variable nest predator guild in the boreal forest." Canadian Journal of Forest Research 38, no. 7 (2008): 1974–82. http://dx.doi.org/10.1139/x08-049.
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Predation rates on the eggs and young of forest-nesting songbirds typically rise in association with anthropogenic fragmentation, but predator responses depend on the spatial scale of disturbance, context, and predator assemblages present. For landscapes that are naturally fragmented, such as the boreal forest, our understanding of nest predation patterns associated with harvest may be further confounded by an additive response of nest predators to the loss of forest cover and the extension of habitat edges. We examined predation rates on artificial nests across a range of values for landscape metrics reflecting natural and anthropogenic forest fragmentation during two summers in boreal forest stands of western Newfoundland, Canada. Nest predation by gray jays ( Perisoreus canadensis (L.)) increased significantly in logged areas, and gray jay abundance was positively linked to increasing amounts of logged edge; however, there was no response to the extent of natural openings suggesting that nest predation by jays was additive in the presence of harvest-created openings. In contrast, neither mammalian nest predators nor the unidentified predators (responsible for the largest proportion of nest losses) showed any association with the landscape fragmentation metrics assessed. Year effects shown by the unidentified nest predator category did coincide with a marked increase in small mammal and Newfoundland marten ( Martes americana (Turton) subsp. atrata (Bangs)) populations during our study. Thus, we were able to identify an additive predation response to logging, but also that the activities of predators may vary over space and time and, in turn, may variably influence the success of songbirds nesting in forests fragmented by logging.
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van Dijk, Jiska, Tommy Andersen, Roel May, Reidar Andersen, Roy Andersen, and Arild Landa. "Foraging strategies of wolverines within a predator guild." Canadian Journal of Zoology 86, no. 9 (2008): 966–75. http://dx.doi.org/10.1139/z08-073.
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Within the predator guild, wolverines ( Gulo gulo (L., 1758)) have evolved as generalist predators and scavengers on prey killed by other predators. The recovery of wolves ( Canis lupus L., 1758) in the boreal forests of southern Norway during the late 1990s may have triggered consequent recolonization by wolverines through increased carcass availability. We investigated winter foraging behavior of wolverines in the boreal forest with regard to wolf, lynx ( Lynx lynx (L., 1758)), and red fox ( Vulpes vulpes (L., 1758)) presence. We followed 55 wolverine tracks in the snow from at least nine individuals for a total of 237 km during the winters of 2003–2004. We documented 19 moose ( Alces alces (L., 1758)) and 4 bird carcasses, and no successful hunts. Wolverines did not follow guild species trails directly to carcasses; however, they did change their movement patterns after red fox encounters. While wolverines were more active at higher elevations, the probability of encountering a wolf was higher at lower elevations, suggesting a spatial separation between wolverines and wolves. Although wolverines seem to depend on wolf for carrion during winter, they did not use wolf trails to find carcasses. This may indicate that wolverines reduce risk of intraguild predation by avoiding direct confrontation with wolves.
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Walzer, Andreas, and Peter Schausberger. "Integration of multiple cues allows threat-sensitive anti-intraguild predator responses in predatory mites." Behaviour 150, no. 2 (2013): 115–32. http://dx.doi.org/10.1163/1568539x-00003040.
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Intraguild (IG) prey is commonly confronted with multiple IG predator species. However, the IG predation (IGP) risk for prey is not only dependent on the predator species, but also on inherent (intraspecific) characteristics of a given IG predator such as its life-stage, sex or gravidity and the associated prey needs. Thus, IG prey should have evolved the ability to integrate multiple IG predator cues, which should allow both inter- and intraspecific threat-sensitive anti-predator responses. Using a guild of plant-inhabiting predatory mites sharing spider mites as prey, we evaluated the effects of single and combined cues (eggs and/or chemical traces left by a predator female on the substrate) of the low risk IG predator Neoseiulus californicus and the high risk IG predator Amblyseius andersoni on time, distance and path shape parameters of the larval IG prey Phytoseiulus persimilis. IG prey discriminated between traces of the low and high risk IG predator, with and without additional presence of their eggs, indicating interspecific threat-sensitivity. The behavioural changes were manifest in distance moved, activity and path shape of IG prey. The cue combination of traces and eggs of the IG predators conveyed other information than each cue alone, allowing intraspecific threat-sensitive responses by IG prey apparent in changed velocities and distances moved. We argue that graded responses to single and combined IG predator cues are adaptive due to minimization of acceptance errors in IG prey decision making.
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Tsurim, Ido, and Alon Silberbush. "Detrivory, competition, and apparent predation by Culiseta longiareolata in a temporary pool ecosystem." Israel Journal of Ecology and Evolution 62, no. 3-4 (2016): 138–42. http://dx.doi.org/10.1080/15659801.2015.1065153.
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Larvae of the mosquito Culiseta longiareolata Macquart have been suggested as important species in desert and Mediterranean temporary pond ecosystems through their strong competitive abilities and as intra-guild predators. We examined their potential predatory effect on larvae of the abundant saltmarsh mosquito Ochlerotatus caspius. We did not find evidence for predatory effects of C. longiareolata on O. caspius larvae. We suggest that, at least in our system, C. longiareolata is an apparent predator. Namely, it does not actively prey on mobile victims, but rather feeds on the carcasses of its fallen competitors additional to its generally immobile food. Hence, we do not expect the occurrence of anti-predator behaviors in response to C. longiareolata presence, including larval development characteristics and oviposition habitat selection.
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Visser, André W., Patrizio Mariani, and Simone Pigolotti. "Adaptive behaviour, tri-trophic food-web stability and damping of chaos." Journal of The Royal Society Interface 9, no. 71 (2011): 1373–80. http://dx.doi.org/10.1098/rsif.2011.0686.
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We examine the effect of adaptive foraging behaviour within a tri-trophic food web with intra-guild predation. The intra-guild prey is allowed to adjust its foraging effort so as to achieve an optimal per capita growth rate in the face of realized feeding, predation risk and foraging cost. Adaptive fitness-seeking behaviour of the intra-guild prey has a stabilizing effect on the tri-trophic food-web dynamics provided that (i) a finite optimal foraging effort exists and (ii) the trophic transfer efficiency from resource to predator via the intra-guild prey is greater than that from the resource directly. The latter condition is a general criterion for the feasibility of intra-guild predation as a trophic mode. Under these conditions, we demonstrate rigorously that adaptive behaviour will always promote stability of community dynamics in the sense that the region of parameter space in which stability is achieved is larger than for the non-adaptive counterpart of the system.
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Sullivan, Aaron, Jason Rohr, and Dale Madison. "Behavioural Responses by Red-backed Salamanders to Conspecific and Heterospecific Cues." Behaviour 140, no. 4 (2003): 553–64. http://dx.doi.org/10.1163/156853903322127977.
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AbstractChemical cues released from injured prey are thought to indicate the proximity of a predator or predation event, and therefore, an area of elevated predation risk. Prey often avoid chemical cues released from injured heterospecifics, but there is little evidence to determine whether this is due to homologous cues among phylogenetically related species, or avoidance of injured syntopic species that experience predation from the same predators. The purpose of this study was to examine the response of terrestrial red-backed salamanders (Plethodon cinereus) to chemical cues from non-injured and injured members of their prey guild that vary in their relatedness to P.cinereus. In the laboratory, P.cinereus avoided chemical cues from injured conspecifics, injured and non-injured slimy salamanders (P.glutinosus), and injured confamilial dusky salamanders (Desmognathus ochrophaeus). Red-backed salamanders did not avoid rinses from non-injured conspecifics and dusky salamanders, or cues from injured and non-injured earthworms (Lumbricus sp.), a more distantly related prey guild member. These results cannot be fully explained by either phylogenetic relatedness (among plethodontid salamanders) or prey guild membership alone. We suggest that a combination of these factors, and perhaps others, likely influenced the evolution of heterospecific alarm cue avoidance in the red-backed salamander.
Dissertations / Theses on the topic "Predator guild"
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Kautz, Andrea R. "Local Management and Landscape Effects on the Predator Guild in Vegetable Crops, with a Focus on Long-legged Flies (Diptera: Dolichopodidae)." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437474798.
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Pasanen, Mortensen Marianne. "Anthropogenic impact on predator guilds and ecosystem processes : Apex predator extinctions, land use and climate change." Doctoral thesis, Stockholms universitet, Zoologiska institutionen, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-100720.
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Humans affect ecosystems by changing species compositions, landscape and climate. This thesis aims to increase our understanding of anthropogenic effects on mesopredator abundance due to changes in apex predator status, landscape and climate. I show that in Eurasia the abundance of a mesopredator, the red fox (Vulpes vulpes), is limited top-down by the Eurasian lynx (Lynx lynx) and bottom-up by winter severity. However, where lynx has been eradicated, fox abundance is instead related to bottom-factors such as cropland (paper I, II). Fox abundance was highest when croplands constituted 25% of the landscape (paper II). I also project red fox abundance in Sweden over the past 200 years and in future scenarios in relation to lynx density, land use and climate change. The projected fox abundance was highest in 1920, when lynx was eradicated and the proportion of cropland was 22%. In 2010, when lynx had recolonised, the projected fox abundance was lower than in 1920, but higher than in 1830. Future scenarios indicated that lynx abundance must increase in respond to climate change to keep fox at the same density as today. The results suggest a mesopredator release when lynx was eradicated, boosted by land use and climate change, and that changes in bottom-up factors can modify the relative strength of top-down factors (paper IV). From 1846-1922, lynx, wolverine (Gulo gulo) and grey wolf (Canis lupus) declined in Scandinavia due to persecution; however I show that the change in wolverine abundance was positively related to the changes in lynx and wolf abundance. This indicates that wolverine is subsidized by carrions from lynx and wolf kills rather than limited top-down by them (paper III). This thesis illustrates how mesopredator abundance is determined by a combination of top-down and bottom-up processes, and how anthropogenic impacts not only can change the structures of predator guilds, but also may modify top-down processes through changes in bottom-up factors.<br><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted. Paper 4: Manuscript.</p><p> </p>
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Bessey, Cindy. "The Role of Teleost Grazers in a Relatively Pristine Seagrass Ecosystem." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/911.
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Trophic downgrading of ecosystems necessitates a functional understanding of trophic cascades. Identifying the presence of cascades, and the mechanisms through which they occur, is particularly important for seagrass meadows, which are among the most threatened ecosystems on Earth. Shark Bay, Western Australia provides a model system to investigate the potential importance of top-down effects in a relatively pristine seagrass ecosystem. The role of megagrazers in the Shark Bay system has been previously investigated, but the role of macrograzers (i.e., teleosts), and their importance relative to megagrazers, remains unknown. The objective of my dissertation was to elucidate the importance of teleost macrograzers in transmitting top-down effects in seagrass ecosystems. Seagrasses and macroalgae were the main food of the abundant teleost Pelates octolineatus, but stable isotopic values suggested that algae may contribute a larger portion of assimilated food than suggested by gut contents. Pelates octolineatus is at risk from numerous predators, with pied cormorants (Phalacrocorax varius) taking the majority of tethered P. octolineatus. Using a combination of fish trapping and unbaited underwater video surveillance, I found that the relative abundance of P. octolineatus was greater in interior areas of seagrass banks during the cold season, and that the mean length of P. octolineatus was greater in these areas compared to along edges of banks. Finally, I used seagrass transplants and exclosure experiments to determine the relative effect of megagrazers and macrograzers on the establishment and persistence of three species of seagrasses in interior microhabitats. Teleost grazing had the largest impact on seagrass species with the highest nutrient content, and these impacts were primarily observed during the warm season. My findings are consistent with predictions of a behaviorally-mediated trophic cascade initiated by tiger sharks (Galeocerdo cuvier) and transmitted through herbivorous fishes and their predators.
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Both, Camila Chiamenti. "Riqueza, composição de guildas e padrões de co-ocorrência de comunidades de girinos em poças no Sul do Brasil." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/17054.
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A estrutura de comunidades em poças tem sido explicada por competição de recursos, predação e permanência da água. No presente estudo, eu avaliei o efeito do gradiente predação-hidroperíodo sobre a riqueza de espécies e composição de guildas de girinos em poças, e também a co-ocorrência das espécies, testando a existência de padrões segregados que podem ser atribuídos as interações competitivas. O estudo foi realizado no município de Caçapava do Sul, Rio Grande do Sul, sul do Brasil. Eu amostrei girinos e predadores invertebrados em 38 poças, com diferentes tamanhos e graus de permanência. As coletas foram realizadas em duas estações: na primavera de 2007 (novembro) e no verão de 2008 (janeiro). Eu medi a área e a profundidade das poças em cada evento de coleta e registrei a riqueza da vegetação aquática e das margens, assim como a abundância e riqueza de predadores. Eu classifiquei as espécies em guildas baseadas em oito características eco-morfológicas. As espécies foram agrupadas através de ligação completa, usando o coeficiente de Gower. Eu analisei a relação da riqueza de girinos com as variáveis ambientais através de regressão múltipla, e usei Análise de Correspondência Canônica para relacionar a composição das guildas com os descritores ambientais. A co-ocorrência dos girinos foi analisada através de três algoritmos de modelo nulo: linhas e colunas fixas, linhas fixas e colunas proporcionais descartando-se matrizes degeneradas, linhas fixas e colunas proporcionais incluindo matrizes degeneradas. Nove matrizes de presença ausência foram testadas: ocorrências totais (primavera e verão) do conjunto total de espécies, e distinguindo as espécies em duas guildas (bentônicos e nectônicos), e ocorrências de primavera e verão para o conjunto total e as duas guildas. Das 38 poças com água na primavera, somente 22 permaneceram com água na amostragem de verão. Ao todo 10852 indivíduos de 21 espécies foram coletados. As espécies foram classificadas em sete guildas: suspensor-raspador (Sr), nectônicos (N), suspensor-filtrador (Sf), bentônicos com ninho de espuma, com e sem agregação (BI e BII), e bentônicos sem ninho de espuma com olhos dorsais ou laterais (BIII e BIV). A riqueza de espécies cresceu com a abundância de predadores, que foi a única variável explanatória relacionada a mesma. A composição das guildas foi explicada pela abundância de predadores e a profundidade média registrada na primavera. A co-ocorrência dos girinos mostrou padrões segregados para 14 dos 25 modelos testados. A maioria dos modelos com matrizes degeneradas rejeitou a hipótese nula. Os modelos com linhas e colunas fixas, e com as linhas fixas, colunas proporcionais e sem matrizes degeneradas mostraram muitos resultados similares. A segregação também foi influenciada pela combinação de espécies e estação consideradas. Em geral, para o conjunto total de espécies a coocorrência foi aleatória, para os bentônicos foi segregada para as ocorrências totais e de primavera, para os nectônicos apenas no verão. Os resultados das análises de gradiente e co-ocorrência sugerem que girinos são regulados pelos predadores que filtram a composição das guildas e podem reduzir a competição. Para girinos bentônicos, que ocupam poças com baixa abundância de predadores, competição pode ser um fator de estruturação importante.<br>The community structure of pond systems has been shown to be affected by resource competition, predation and permanency. Here, I evaluated the effect of the permanency-predation gradient in ponds on species richness and guild composition of tadpoles, and accessed the co-occurrence, searching segregated patterns that could be attributed to competitive interactions. The study was carried out Caçapava do Sul, Rio Grande do Sul state, southern Brazil. I sampled tadpoles and invertebrate predators in 38 ponds, with distinct sizes and permanency degrees. The collections were carried out twice: in spring 2007 (November) and summer, 2008 (January). I measured area and depth at each pond in each collection event, and recorded richness of aquatic and bank vegetation, and abundance and richness of predators. I conducted a guild classification of the species pool based on eight variables related to morphological and ecological features. Species were grouped through complete linkage agglomerative clustering method, using Gower coefficient. I evaluated the relation of tadpole richness with environmental variables using multiple regression, and Canonical Correspondence Analysis for guild composition. The tadpole co-occurrence was analyzed through three null models algorithm: fixed rows and columns; fixed rows, proportional columns, discharging degenerate matrices; and fixed rows, proportional columns, including degenerate matrices. Nine presence/absence matrices were tested: total occurrences (spring and summer) of the complete species pool, and distinguishing species of two tadpole guild (benthonic and nektonic), and spring and summer occurrence of total species pool and two guilds. Of the 38 ponds with water in the spring sampling, only 22 remained with water in the following summer sampling. A total of 10,852 individuals and 21 species of tadpoles were collected in the two sampling events. The species were classified into seven guilds: suspension-rasper (Sr), nektonics (N), suspension-feeder (Sf), benthonics with foam nests with and without school behavior (BI and BII), and benthonics without foam nests with lateral and dorsal eyes (BIII and BIV). Species richness increased with abundance of predators, which was the only explanatory variable related to it. Guild composition was explained by abundance of predators and mean depth recorded in spring, which was correlated with maximal depth. The tadpole co-occurrence showed a segregated pattern for 14 of the 25 tested models. Most models with degenerate matrices rejected the null hypothesis. The models with row and columns fixed, and row fixed, column proportional without degenerate matrices showed more similar results. Segregation was also influenced by the combination of species dataset and the season considered. In general, for the total species pool the co-occurrence was random, for benthonic species was segregated for the total and spring occurrences, and for nektonic in summer. The results of gradient and co-occurrence analysis suggest that tadpoles are regulated by predators that filter guild composition and could reduce competition. For benthonic species, which inhabit ponds with lower abundance of predators, competition can be a major structuring constraint.
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Hjältén, Alexander. "Storspiggens (Gasterosteus aculeatus) påverkan på abborryngel (Perca fluviatilis) via storleksberoende predation." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-118551.
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The costal populations of perch (Perca fluviatilis) in some parts of the Baltic Sea have been in decline for about two decades. Recruitment failure in the early larval stages has been put forward as a possible cause and the decline has also been suggested to coincide with increases in three-pined stickleback (Gasterosteus aculeatus) densities. The aim of this study was to study the effects of growth and survival of newly hatched perch larvae in the presence of the three-pined stickleback, and if possible determine the main mechanism behind any negative effects the perch may suffer under such conditions. Using large scale experimental ponds as a controlled habitat, an experiment was conducted where perch larvae were being exposed to sticklebacks under four different stages of their development. Results showed that the three- spine stickleback can have a strong negative effect on the survival of young perch. This effect was strongest in the earliest stage of perch development and decreased as they grew bigger. The zooplankton densities didn't differ between the controls and stickleback treatments, suggesting that the young perch didn't suffer from food limitation. Instead predation was identified as the main mechanism behind the high mortality. The results of this study highlight the potential danger of the observed patterns of decreasing predator populations in conjunction with increasing populations of smaller prey species in the Baltic Sea.
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Moring, J. Bruce (James Bruce). "Habitat Partitioning by a Riparian Cursorial Spider Guild, and Intraspecific Behaviors of the Wolf Spider Pardosa valens (LYCOSIDAE) and the Stonefly Hydroperla crosbyi (PERLODIDAE)." Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc332792/.
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Members of a guild of cursorial spiders (Pardosa spp. and Alopecosa spp.) spatially segregated among five discrete habitats, from a streamside cobble habitat grading laterally along a successional gradient to the leaf litter zone of a transition or climax riparian forest. Seasonal activity peaked in midsummer for all guild members. Spiders were active diurnally earlier in the streamside habitats, and levels of activity were positively correlated with light intensity. Guild members Pardosa tristis and Pardosa uncata were most different in habitat selection and periods of diurnal activity. Males and females of all guild species differed in their distribution among habitats and over months of collection. Measures of guild species diversity and evenness were variable between habitats, and were largely influenced by the relatively high abundance of one or two guild species, particularly in the streamside habitats.
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Bissett, Charlene. "The feeding and spatial ecologies of the large carnivore guild on Kwandwe Private Game Reserve." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1006195.
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The reintroduction of lions, cheetahs and African wild dogs to Kwandwe Private Game Reserve in the Eastern Cape Province of South Africa created the opportunity to study the biology and behaviour of these large carnivores in an enclosed system. The research focused on space utilisation and feeding ecology of the predators, using standard observational methods. Changes in the structure of the carnivore guild, and changes in the prey base that occurred during the study were used as natural experiments to examine factors affecting space use and diet. In general, the diets of the predators were similar to previous studies and prey abundance was more important than prey species size in determining prey selection. Changes in the abundance of certain prey species was matched by a dietary switch in lions from kudu to warthog and an increase in the proportion of springbok kills by the cheetahs. There was no significant difference in the proportions of prey species detected by ad hoc or continuous observations. Core areas occupied by the predators were significantly smaller than home ranges except when females were denning. Home ranges overlapped both within and between species, but there was very little overlap of core areas. An increase in the number of lion prides in the area during the study resulted in an increase in overlap of home ranges of lions and cheetahs, but did not result in a change in home range size. Space use by female cheetahs with cubs increased as the cubs grew older. The use of thicket vegetation by cheetahs decreased with an increase in the number of lion prides. Minimum Daily Energy Expenditure, energy intake and net benefit were calculated for the predators using data from continuous observations. All predators exhibited a large net benefit and the net benefit for single female cheetahs was greater than for the members of the coalition. Net benefit for the alpha pair of African wild dogs was lower than that of the pack.
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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 Russia<br>Tiivistelmä 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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Nguyen, Trong Hieu. "Modèles mathématiques de la dynamique des populations en environnement déterministe et stochastique." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066432/document.
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Dans ce travail de thèse, nous étudions des modèles mathématiques de la dynamique des populations en environnements déterministe et stochastique. Pour les environnements déterministes, nous considérons trois modèles. Le premier est un modèle intra-guilde prenant en compte des effets d'un environnement spatial hétérogène avec une migration rapide des individus entre les différents sites. Le deuxième est un modèle de pêche dans une zone constituée d’une aire marine protégée où la pêche est interdite et d’une zone où la population de poissons est pêchée. Enfin le troisième est un modèle prédateur-proie considérant une proie et deux prédateurs avec des réponses fonctionnelles de Beddington-DeAngelis. Pour les environnements stochastiques, nous étudions un modèle épidémique SIRS et un modèle prédateur-proie en prenant en compte un bruit télégraphique. Nous étudions le comportement dynamique de ces modèles et nous recherchons les conditions de maintien ou de disparition des espèces modélisées<br>In this thesis, we consider mathematical population dynamics models in deterministic and stochastic environments. For deterministic environments, we study three models: an intraguild model with the effects of spatial heterogeneous environment and fast migration of individuals; a fishery model with Marine Protected Area where fishing is prohibited and an area where the fish population is harvested; a predator-prey model which has one prey and two predators with Beddington-DeAngelis functional responses. For stochastic environments, we study SIRS epidemic model and predator-prey models under telegraph noise. We try to present the dynamical behavior of these models and show out the existence or vanishing of species in the models
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Sanz, Lázaro Carlos. "Consecuencias ecológicas del enriquecimiento por materia orgánica procedente de la acuicultura y de vertidos de petróleo en ecosistemas costeros." Doctoral thesis, Universidad de Murcia, 2009. http://hdl.handle.net/10803/10776.
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El objetivo de esta tesis es estudiar el efecto del enriquecimiento por materia orgánica producida por el cultivo de peces en el mar y por los vertidos de petróleo en el medio marino. Este trabajo intenta explicar las consecuencias ecológicas de los impactos generados por este tipo de contaminación, y en diseñar de test de toxicidad para evaluar la contaminación en el sur de las costas europeas. Específicamente, en relación con el impacto de la acuicultura, los estudios de recuperación durante la Apertura de peces bentónicos de reducción de piscicultura marina, el papel de la depredación en el sistema bentónico dispersión de los residuos y los vínculos horizontales y verticales con un impacto bentónico.<br>The aim of this thesis is to study the effect of organic matter enrichment produced by marinefinfish farming and oil spills on the marine environment. This work is focused on elucidating theecological consequences of the impact generated by this type of pollution, and on designingtoxictity tests to evaluate pollution for southern European coasts. Specifically, related with aquaculture impact, it studies benthic recovery during open sea fish farming abatement, the role of predation in the benthic system and links horizontal and vertical waste dispersion with benthic impact.
Books on the topic "Predator guild"
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Lambin, Xavier. The population dynamics of bite-sized predators: prey dependence, territoriality, and mobility. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198759805.003.0004.
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The dependency of mustelid demographic rates on prey abundance has the potential to cause a strong coupling between predator-prey populations. Data on mustelid dynamics show that such strong reciprocal interactions only materialise in some restricted conditions. Bite-size mustelid predators searching for scarce, depleted prey expose themselves to increased risk of predation by larger predators of small mammal that are themselves searching for similar prey species. As voles or muskrats become scarcer, weasels and mink searching for prey over larger areas become increasingly exposed to intra-guild predation, unless they operate in a habitat refuge such as the sub-nivean space. Where larger predators are sufficiently abundant or exert year-round predation pressure on small mustelids, their impact on mustelids may impose biological barrier to dispersal that are sufficient to weaken the coupling between small mustelids and their rodent prey, and thus impose a degree of top down limitation on mustelids.
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(Editor), Jacques Brodeur, and Guy Boivin (Editor), eds. Trophic and Guild Interactions in Biological Control (Progress in Biological Control). Springer, 2006.
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Dorling, Ernest. With Consciousness of Guilt: The Sexual Predator Among Us. Writer's Showcase Press, 2000.
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Ross, Joanna, Andrew J. Hearn, and David W. Macdonald. The Bornean carnivore community: lessons from a little-known guild. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198759805.003.0014.
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Niche differentiation reduces competition between species and modifies predation risk such that species coexistence is promoted. Temporal partitioning is a type of niche differentiation that has only relatively recently been specifically investigated. In this chapter, data from 515 camera trap stations from Sabah, Malaysian Borneo is used to describe the presence, habitat associations and activity patterns of Bornean carnivores and to investigate temporal partitioning between species. Primary and old logged forest were the most species rich sites and small forest fragments and oil palm plantations supported the fewest species. Species’ activity patterns within families were more similar than those between families. Only the masked palm civet and sun bear showed variation in activity among habitats. Considering the species as rough trophic groups rather than families revealed that each group contained both diurnal and nocturnal species, which presumably helps to promote coexistence between the musteloids and other species in each group.
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Zhou, Youbing, Chris Newman, Yayoi Kaneko, et al. Asian badgers—the same, only different: how diversity among badger societies informs socio-ecological theory and challenges conservation. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198759805.003.0013.
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Of thirteen extant species of true badger, eleven have a distribution in Asia, as do the more loosely affiliated stink- and honey-badgers. Even though these badgers show superficial similarities, they exhibit very different societies, even within same species under different circumstances, and provide an informative model to advance understanding of socio-ecology. They illustrate how group-living is promoted by natal philopatry, and food security; enabled by omnivory and hibernation in cold-winter regions. Conversely predatory, carnivorous species, and those competing for food security within a broader trophic guild, tend to be more solitary. This socio-ecological diversity poses conservation challenges, with Asian badgers vulnerable to habitat loss, urban and road development, direct conflict with people, culling to manage zoonotic disease transmission, and hunting pressure – often for traditional medicine. These threats are ever-more prevalent in expanding Asian economies, where cultural and attitudinal changes are urgently needed to safeguard biodiversity for the future.
Book chapters on the topic "Predator guild"
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Frank, J. Howard, J. Howard Frank, Michael C. Thomas, et al. "Predatory Guild." In Encyclopedia of Entomology. Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6359-6_3114.
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Kolesar, Sarah E., Kenneth A. Rose, and Denise L. Breitburg. "Hypoxia Effects Within an Intra-guild Predation Food Web of Mnemiopsis leidyi Ctenophores, Larval Fish, and Copepods." In Modeling Coastal Hypoxia. Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-54571-4_11.
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Rexstad, Eric, and Knut Kielland. "Mammalian Herbivore Population Dynamics in the Alaskan Boreal Forest." In Alaska's Changing Boreal Forest. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780195154313.003.0013.
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The population dynamics of boreal mammals differ strikingly from those of mammals in temperate and tropical ecosystems in their extraordinary fluctuations in abundance (Elton 1924). These fluctuations lead to strong top-down direct effects in which herbivores reduce the biomass of their preferred foods, such as birch and willow, and predators reduce the biomass of herbivores (Chapter 13; Sinclair et al. 2000). These effects are clearly demonstrated in experiments that exclude herbivores or their predators. Some authors have argued that bottom-up influences of food supply on herbivores are negligible because food augmentation to herbivores in the presence of predators had no detectable effect in reducing herbivore decline (Sinclair et al. 2001). Several members of the mammalian herbivore guild are also important as a human subsistence resource. Dynamics of moose (Alces alces) and snowshoe hare (Lepus americanus) can be altered by human harvest. Overexploitation by humans may reduce moose populations to densities where they can be predator-limited—the so-called predator pit (Messier 1994). In this chapter, we present information on dynamics of some mammalian herbivores in the Alaskan boreal forest and potential drivers that are responsible for these dynamics. We omit discussions of the dynamics of porcupines (Keith and Cary 1991), red squirrels (Boonstra et al. 2001a), and beavers (Donkor and Fryxell 1999), as studies of these species have not been conducted in Alaska’s boreal forests. Moose are thought to have arrived in Alaska during the Illinoian glaciation, about 400,000 yr B.P. (Pewe and Hopkins 1967). They may have retreated to refugia in central Alaska during subsequent glacial advances (Peterson 1955) and expanded at times when climate was warmer. Moose populations in North America have more than doubled over the past 30–40 years, to approximately 890,000 animals (Kelsall 1987). The Koyukuk River drainage in the northern interior, for example, is presently known for its large moose populations. However, the oral tradition of moose hunting in the Koyukuk is relatively recent. Native elders recall that, in their youth, moose were extremely rare and that moose did not figure prominently in the local subsistence economy until the 1930s.
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Münster-Swendsen, Mikael. "The Role of Insect Parasitoids in Population Cycles of the Spruce Needleminer in Denmark." In Population Cycles. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195140989.003.0006.
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The spruce needleminer, Epinotia tedella (Cl.) (Lepidoptera: Tortricidae), is a small and abundant moth associated with Norway spruce (Picea abies Karst.). Larvae mine spruce needles, usually those more than 1 year old, and each requires about 35 needles to meet its food demands. In central Europe, the spruce needleminer is regarded as a temporary, serious pest when densities reach several thousand per square meter. However, it seldom causes significant damage in Scandinavian countries. An exception was the heavy infestation in southern Denmark in 1960-61. The spruce needleminer has one generation per year. Adults emerge in June and deposit eggs singly on spruce needles. Larvae mine the needles from July through October and then descend on silken threads in November to hibernate in the forest litter as prepupal larvae in cocoons. Pupation occurs in early May and lasts 3-4 weeks. Like many other forest defoliators, spruce needleminers are associated with a diverse fauna of parasitic Hymenoptera (parasitoids) (Münster-Swendsen 1979). Eggs are attacked by a minute wasp (Trichogramma sp.) that kills the embryo and emerges as an adult a few weeks later. Because spruce needleminer eggs have all hatched by this time, the parasitoids must oviposit in the eggs of other insect species. In other words, this parasitoid is not host-specific and therefore not expected to show a numerical response to spruce needleminer population changes. Newly hatched moth larvae immediately bore into needles and, because of this, are fairly well protected against weather and predators. However, specialized parasitic wasps (parasitoids) are able to deposit their eggs inside a larva by penetrating the needle with their ovipositor. Two species, Apanteles tedellae (Nix.) and Pimplopterus dubius (Hgn.), dominate the parasitoid guild and sometimes attack a large percentage of the larvae (Münster -Swendsen 1985). Parasitized larvae continue to feed and, in November, descend to the forest floor to overwinter with unparasitized individuals. In late April, however, the parasitoids take over and kill their hosts. Besides mortality from endoparasitoids, up to 2% of the larvae die within the mine due to an ectoparasitoid and a predatory cecidomyid larva.
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Gray, John S., and Michael Elliott. "The soft-sediment benthos in the ecosystem." In Ecology of Marine Sediments. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780198569015.003.0014.
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The benthos does not, of course, live in isolation from other parts of the ecosystem. Here we consider the roles that the benthos plays in the system and how the complex interactions that are found can be modelled using ecosystem models. First, we examine methods that allow us to establish food webs based not only on examining each species in the field and in laboratory feeding studies, but also using stable isotopes of carbon and nitrogen to ascertain the likely feeding mode of a species. It is relatively easy to determine the mode of feeding of some benthic organisms (see for example the excellent review of Fauchald and Jumars 1979, although this is now slightly dated and requires revision). Polychaetes have characteristic feeding structures, so one can determine from their morphology whether they are filter feeders, deposit feeders, or predators. Bivalves show similar morphological characteristics and it is easy to determine whether they are deposit or filter feeders. Some polychaetes have large jaws, e.g. the nereids, and one might assume that they are predators. Yet when Nereis vexillosa was studied in detail (Woodin 1977), it was found that it attached pieces of algae to its tube, which grew and were used for food, so-called ´gardening´. Nereids also are able to filter feed by creating a mucous bag and pumping water through their burrows, which filters the water; the mucous bag is then consumed. More recently, studies have shown varied and possibly opportunistic feeding by different benthic species; for example Christensen et al. (2000) showed how the suspension- and deposit-feeding abilities of nereids influenced sediment nutrient fluxes. These studies show that it is perhaps not so straightforward as once thought to interpret feeding mode simply from morphological features. The definition of functional groups and feeding guilds is increasingly used to help explain and interpret ecological functioning (e.g. Elliott et al. 2007 discuss the rationale behind functional groups). The eminent and immensely experienced benthic biologist Tom Pearson (2001) shows in detail that while the concept of functional groups gives us a greater understanding of the benthos, the idea is criticized by some as we do not have sufficient information about feeding types and modes of life of many benthic species.
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Clark, David M. "Cognitive behaviour therapy for anxiety disorders." In New Oxford Textbook of Psychiatry. Oxford University Press, 2012. http://dx.doi.org/10.1093/med/9780199696758.003.0165.
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Cognitive behaviour therapy for anxiety disorders is a brief psychological treatment (1 to 16 sessions), based on the cognitive model of emotional disorders. Within this model, it is assumed that it is not events per se, but rather people's expectations and interpretations of events, which are responsible for the production of negative emotions such as anxiety, anger, guilt, or sadness. In anxiety, the important interpretations, or cognitions, concern perceived physical or psychosocial danger. In everyday life, many situations are objectively dangerous. In such situations, individuals’ perceptions are often realistic appraisals of the inherent danger. However, Beck argues that in anxiety disorders, patients systematically overestimate the danger inherent in certain situations, bodily sensations, or mental processes. Overestimates of danger can arise from distorted estimates of the likelihood of a feared event, distorted estimates of the severity of the event, and/or distorted estimates of one's coping resources and the availability of rescue factors. Once a stimulus is interpreted as a source of danger, an ‘anxiety programme’ is activated. This is a pattern of responses that is probably inherited from our evolutionary past and originally served to protect us from harm in objectively dangerous primitive environments (such as attack from a predator). The programme includes changes in autonomic arousal as preparation for flight/fight/fainting and increased scanning of the environment for possible sources of danger. In modern life, there are also situations in which these responses are adaptive (such as getting out of the path of a speeding car). However, when, as in anxiety disorders, the danger is more imagined than real, these anxiety responses are largely inappropriate. Instead of serving a useful function, they contribute to a series of vicious circles that tend to maintain or exacerbate the anxiety disorder. Two types of vicious circle are common in anxiety disorders. First, the reflexively elicited somatic and cognitive symptoms of anxiety become further sources of perceived danger. For example, blushing can be taken as an indication that one has made a fool of oneself, and this may lead to further embarrassment and blushing; or a racing heart may be taken as evidence of an impending heart attack and this may produce further anxiety and cardiac symptoms. Second, patients often engage in behavioural and cognitive strategies that are intended to prevent the feared events from occurring. However, because the fears are unrealistic, the main effect of these strategies is to prevent patients from disconfirming their negative beliefs. For example, patients who fear that the unusual and racing thoughts experienced during panic attacks indicate that they are in danger of going mad and often try to control their thoughts and (erroneously) believe that if they had not done so, they would have gone mad. Within cognitive models of anxiety disorders, at least two different levels of disturbed thinking are distinguished. First, negative automatic thoughts are those thoughts or images that are present in specific situations when an individual is anxious. For example, someone concerned about social evaluation might have the negative thought, ‘They think I'm boring’, while talking to a group of acquaintances. Second, dysfunctional assumptions are general beliefs, which individuals hold about the world and themselves which are said to make them prone to interpret specific situations in an excessively negative and dysfunctional fashion. For example, a rule involving an extreme equation of self-worth with social approval (‘Unless I am liked by everyone, I am worthless’) might make an individual particularly likely to interpret silent spells in conversation as an indication that others think one is boring. Cognitive behaviour therapy attempts to treat anxiety disorders by (a) helping patients identify their negative danger-related thoughts and beliefs, and (b) modifying these cognitions and the behavioural and cognitive processes that normally maintain them. A wide range of procedures are used to achieve these aims, including education, discussion of evidence for and against the beliefs, imagery modification, attentional manipulations, exposure to feared stimuli, and numerous other behavioural assignments. Within sessions there is a strong emphasis on experiential work and on working with high affect. Between sessions, patients follow extensive homework assignments. As in cognitive behaviour therapy for other disorders, the general approach is one of collaborative empiricism in which patient and therapist view the patient's fearful thoughts as hypotheses to be critically examined and tested.