990 resultados para prey


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Financial literacy may not be as effective as previously thought in protecting against fraud victimisation. It does not inoculate investors from persuasion or social engineering tactics used by offenders to secure investment in fraudulent schemes. In fact, recent research indicates that overconfidence in investment knowledge may make individuals more susceptible to fraud. Using boiler room fraud as a case study, this article introduces the PREY (Profiled, Relational, Exploitable and Yielding) model to capture the psychological tactics used by fraud perpetrators to influence the thoughts and decision-making processes of individuals. The PREY model operationalizes the tenets of social engineering and demonstrates how such tactics could be re-engineered to increase the effectiveness of fraud prevention within the financial literacy context.

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The low- and high-frequency components of a rustling sound, created when prey (freshly killed frog) was jerkily pulled on dry and wet sandy floors and asbestos, were recorded and played back to individual Indian false vampire bats (Megaderma lyra). Megaderma lyra responded with flight toward the speakers and captured dead frogs, that were kept as reward. The spectral peaks were at 8.6, 7.1 and 6.8 kHz for the low-frequency components of the sounds created at the dry, asbestos and wet floors, respectively. The spectral peaks for the high-frequency sounds created on the respective floors were at 36.8,27.2 and 23.3 kHz. The sound from the dry floor was more intense than that of from the other two substrata. Prey movements that generated sonic or ultrasonic sounds were both sufficient and necessary for the bats to detect and capture prey. The number of successful prey captures was significantly greater for the dry floor sound, especially to its high-frequency components. Bat-responses were low to the wet floor and moderate to the asbestos floor sounds. The bats did not respond to the sound of unrecorded parts of the tape. Even though the bats flew toward the speakers when the prey generated sounds were played back and captured the dead frogs we cannot rule out the possibility of M. lyra using echolocation to localize prey. However, the study indicates that prey that move on dry sandy floor are more vulnerable to predation by M. lyra.

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In newly invaded communities, interspecific competition is thought to play an important role in determining the success of the invader and its impact on the native community. In southern Australia, the native Polistes humilis was the predominant social wasp prior to the arrival of the exotic Vespula germanica (Hymenoptera: Vespidae). Both species forage for similar resources (water, pulp, carbohydrate and protein prey), and concerns have arisen about potential competition between them. The aim of this study was to identify the protein foods that these wasps feed on. As many prey items are masticated by these wasps to the degree that they cannot be identified using conventional means, morphological identification was complemented by sequencing fragments of the mitochondrial 16S rRNA gene. GenBank searches using blast and phylogenetic analyses were used to identify prey items to at least order level. The results were used to construct complete prey inventories for the two species. These indicate that while P. humilis is restricted to feeding on lepidopteran larvae, V. germanica collects a variety of prey of invertebrate and vertebrate origin. Calculated values of prey overlap between the two species are used to discuss the implications of V. germanica impacting on P. humilis. Results obtained are compared to those gained by solely 'conventional' methods, and the advantages of using DNA-based taxonomy in ecological studies are emphasized.

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Introduction Many prey species around the world are suffering declines due to a variety of interacting causes such as land use change, climate change, invasive species and novel disease. Recent studies on the ecological roles of top-predators have suggested that lethal top-predator control by humans (typically undertaken to protect livestock or managed game from predation) is an indirect additional cause of prey declines through trophic cascade effects. Such studies have prompted calls to prohibit lethal top-predator control with the expectation that doing so will result in widespread benefits for biodiversity at all trophic levels. However, applied experiments investigating in situ responses of prey populations to contemporary top-predator management practices are few and none have previously been conducted on the eclectic suite of native and exotic mammalian, reptilian, avian and amphibian predator and prey taxa we simultaneously assess. We conducted a series of landscape-scale, multi-year, manipulative experiments at nine sites spanning five ecosystem types across the Australian continental rangelands to investigate the responses of sympatric prey populations to contemporary poison-baiting programs intended to control top-predators (dingoes) for livestock protection. Results Prey populations were almost always in similar or greater abundances in baited areas. Short-term prey responses to baiting were seldom apparent. Longer-term prey population trends fluctuated independently of baiting for every prey species at all sites, and divergence or convergence of prey population trends occurred rarely. Top-predator population trends fluctuated independently of baiting in all cases, and never did diverge or converge. Mesopredator population trends likewise fluctuated independently of baiting in almost all cases, but did diverge or converge in a few instances. Conclusions These results demonstrate that Australian populations of prey fauna at lower trophic levels are typically unaffected by top-predator control because top-predator populations are not substantially affected by contemporary control practices, thus averting a trophic cascade. We conclude that alteration of current top-predator management practices is probably unnecessary for enhancing fauna recovery in the Australian rangelands. More generally, our results suggest that theoretical and observational studies advancing the idea that lethal control of top-predators induces trophic cascades may not be as universal as previously supposed.

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The minute two-spotted ladybeetle, Diomus notescens Blackburn is a common predator of aphids and other pests in Australian agricultural crops, however little is known about the biology of D. notescens. The aim of this study was to provide information on the life cycle of this predator and improve our understanding of its biological control potential, particularly against one of the major pests of cotton, Aphis gossypii Glover. In laboratory experiments, juvenile development, prey consumption, as well as adult lifespan and fecundity were studied. Results from this study revealed that D. notescens could successfully complete development on A. gossypii, which at 25 °C required 21 days and during this period they each consume 129 ± 5.2 aphids. At 25 °C adult lifespan was 77 ± 9.6 days, with a mean daily prey consumption of 28 ± 1.8 aphids and a mean daily fecundity of 8 ± 0.5 eggs. Net reproductive rate was estimated as 187 ± 25.1 females and the intrinsic rate of increase was estimated as 0.14. Juvenile development was recorded at four constant temperatures (15, 21, 26 and 27 °C) and using a linear model, the lower threshold for D. notescens development was estimated to be 10 ± 0.6 °C with 285 ± 4.7 degree days required to complete development. A prey choice experiment studying predation rates revealed a strong preference for A. gossypii nymphs compared to Bemisia tabaci Gennadius eggs.

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Productivity is predicted to drive the ecological and evolutionary dynamics of predator-prey interaction through changes in resource allocation between different traits. However, resources are seldom constantly available and thus temporal variation in productivity could have considerable effect on the species' potential to evolve. To study this, three long-term microbial laboratory experiments were established where Serratia marcescens prey bacteria was exposed to predation of protist Tetrahymena thermophila in different prey resource environments. The consequences of prey resource availability for the ecological properties of the predator-prey system, such as trophic dynamics, stability, and virulence, were determined. The evolutionary changes in species traits and prey genetic diversity were measured. The prey defence evolved stronger in high productivity environment. Increased allocation to defence incurred cost in terms of reduced prey resource use ability, which probably constrained prey evolution by increasing the effect of resource competition. However, the magnitude of this trade-off diminished when measured in high resource concentrations. Predation selected for white, non-pigmented, highly defensive prey clones that produced predation resistant biofilm. The biofilm defence was also potentially accompanied with cytotoxicity for predators and could have been traded off with high motility. Evidence for the evolution of predators was also found in one experiment suggesting that co-evolutionary dynamics could affect the evolution and ecology of predator-prey interaction. Temporal variation in resource availability increased variation in predator densities leading to temporally fluctuating selection for prey defences and resource use ability. Temporal variation in resource availability was also able to constrain prey evolution when the allocation to defence incurred high cost. However, when the magnitude of prey trade-off was small and the resource turnover was periodically high, temporal variation facilitated the formation of predator resistant biofilm. The evolution of prey defence constrained the transfer of energy from basal to higher trophic levels, decreasing the strength of top-down regulation on prey community. Predation and temporal variation in productivity decreased the stability of populations and prey traits in general. However, predation-induced destabilization was less pronounced in the high productivity environment where the evolution of prey defence was stronger. In addition, evolution of prey defence weakened the environmental variation induced destabilization of predator population dynamics. Moreover, protozoan predation decreased the S. marcescens virulence in the insect host moth (Parasemia plantaginis) suggesting that species interactions outside the context of host-pathogen relationship could be important indirect drivers for the evolution of pathogenesis. This thesis demonstrates that rapid evolution can affect various ecological properties of predator-prey interaction. The effect of evolution on the ecological dynamics depended on the productivity of the environment, being most evident in the constant environments with high productivity.

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The silver-headed antechinus (Antechinus argentus) is one of Australia’s most recently described mammals, and the single known population at Kroombit Tops in south-east Queensland is threatened. Nothing is known of the species’ ecology, so during 2014 we collected faecal pellets each month (March–September) from a population at the type locality to gather baseline data on diet composition. A total of 38 faecal pellets were collected from 12 individuals (eight females, four males) and microscopic analysis of pellets identified seven invertebrate orders, with 70% combined mean composition of beetles (Coleoptera: 38%) and cockroaches (Blattodea: 32%). Other orders that featured as prey were ants, crickets/grasshoppers, butterflies/moths, spiders, and true bugs. Given that faecal pellets could only be collected from a single habitat type (Eucalyptus montivaga high-altitude open forest) and location, this is best described as a generalist insectivorous diet that is characteristic of other previously studied congeners.

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The ‘‘extended’’ ARS (Ablowitz, Ramani, and Segur) algorithm is introduced to characterize a dynamical system as Painlevé or otherwise; to that end, it is required that the formal series—the Laurent series, logarithmic, algebraic psi series about a movable singularity—are shown to converge in the deleted neighborhood of the singularity. The determinations thus obtained are compared with those following from the α method of Painlevé. An attempt is made to relate the structure of solutions about a movable singularity with that of first integrals (when they exist). All these ideas are illustrated by a comprehensive analysis of the general two‐dimensional predator‐prey system.

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Movement in animal groups is highly varied and ranges from seemingly disordered motion in swarms to coordinated aligned motion in flocks and schools. These social interactions are often thought to reduce risk from predators, despite a lack of direct evidence. We investigated risk-related selection for collective motion by allowing real predators ( bluegill sunfish) to hunt mobile virtual prey. By fusing simulated and real animal behavior, we isolated predator effects while controlling for confounding factors. Prey with a tendency to be attracted toward, and to align direction of travel with, near neighbors tended to form mobile coordinated groups and were rarely attacked. These results demonstrate that collective motion could evolve as a response to predation, without prey being able to detect and respond to predators.

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The migratory population of striped bass (Morone saxatilis) (>400 mm total length[TL]) spends winter in the Atlantic Ocean off the Virginia and North Carolina coasts of the United States. Information on trophic dynamics for these large adults during winter is limited. Feeding habits and prey were described from stomach contents of 1154 striped bass ranging from 373 to 1250 mm TL, collected from trawls during winters of 1994-96, 2000, and 2002-03, and from the recreational fishery during 2005-07. Nineteen prey species were present in the diet. Overall, Atlantic menhaden (Brevoortia tyrannus) and bay anchovy (Anchoa mitchilli) dominated the diet by boimass (67.9%) and numerically (68.6%). The percent biomass of Atlantic menhaden during 1994-2003 to 87.0% during 2005-07. Demersal fish species such as Atlantic croaker (Micropogonias undulatus) and spot (Leiostomus xanthurus) represented <15% of the diet biomass, whereas alosines (Alosa spp.) were rarely observed. Invertebrates were least important, contributing <1.0% by biomass and numerically. Striped bass are capable of feeding on a wide range of prey sizes (2% to 43% of their total length). This study outlines the importance of clupeoid fishes to striped bass winter production and also shows that predation may be exerting pressure on one of their dominant prey, the Atlantic menhaden.

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Diets of 76 species of fish larvae from most oceans of the world were inventoried on the basis of information in 40 published studies. Although certaln geographlc, size- and taxon-specific patterns were apparent, certain zooplankton taxa appeared in the diets of larvae of a variety of fish species in numerous localities. Included were six genera of calanoid copepods (Acartia, Calanus, Centropages, Paracalanus, Pseudocaianus, Temora), three genera of cyclopoid copepods (Corycaeus, Oilhona, Oncata), harpacticoid copepods, copepod nauplii, tintinoids, cladocerans of the genera Evadne and Podon, barnacle nauplii, gastropod larvae, pteropods of the genus Limacina, and appendicularians. Literature on feeding habits of these zooplankters reveals that most of the copepods are omnivorous, feeding upon both phytoplankton and other zooplankton. Some taxa, such as Calanus, Paracalanus, Pseudocalanus, and copepod nauplii appear to be primarily herbivorous, while others, such as Acartia, Centropages, Temora, and cyclopoids exhibit broad omnivory or carnivory. The noncopepod zooplankters are primarily filter-feeders upon pbytoplankton and/or bacterioplankton. Despite the importance of zooplankters in larval fish food webs, spectic knowledge of the feeding ecology of many taxa is poor. Further, much present knowledge comes only from laboratory investigations that may not accurately portray feeding habits of zooplankters in nature. Lack of knowledge of the feeding ecology of many abundant zooplankters, which are also important in larval fish food webs, precludes realistic understanding of pelagic ecosystem dynamics. (PDF file contains 34 pages.)