100 resultados para top predator


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There is growing recognition of the important roles played by predators in regulating ecosystems and sustaining biodiversity. Much attention has focused on the consequences of predator-regulation of herbivore populations, and associated trophic cascades. However apex predators may also control smaller ‘mesopredators’ through intraguild interactions. Removal of apex predators can result in changes to intraguild interactions and outbreaks of mesopredators (‘mesopredator release’), leading in turn to increased predation on smaller prey. Here we provide a review and synthesis of studies of predator interactions, mesopredator release and their impacts on biodiversity. Mesopredator suppression by apex predators is widespread geographically and taxonomically. Apex predators suppress mesopredators both by killing them, or instilling fear, which motivates changes in behaviour and habitat use that limit mesopredator distribution and abundance. Changes in the abundance of apex predators may have disproportionate (up to fourfold) effects on mesopredator abundance. Outcomes of interactions between predators may however vary with resource availability, habitat complexity and the complexity of predator communities. There is potential for the restoration of apex predators to have benefits for biodiversity conservation through moderation of the impacts of mesopredators on their prey, but this requires a whole-ecosystem view to avoid unforeseen negative effects.

‘Nothing has changed since I began.

My eye has permitted no change.

I am going to keep things like this.’

From ‘Hawk Roosting’, by Ted Hughes.

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Tensions at the University of Melbourne over the fairness of providing guaranteed postgraduate pathways only to students with high Year 12 scores, has underlined the high-wire act institutions face in balancing equity and the pursuit of prestige.

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Have you ever wondered how journalism students learn to differentiate the 'important' story from the daily dross that journalism inevitably throws up? We have. This paper examines the choices journalism students make when they're asked to nominate a 'top ten' from a finite list of stories. It suggests the possible news values they apply to their selection of the ten 'best' stories over a 12 month period. As a second measure of ability to comprehend and apply news values we also examine the students' ability to correctly locate countries on a map: a test of their 'political geography'. We offer some tentative conclusions about our students' willingness to engage with the 'difficult' stories about politics and economics, rather than the 'easy shot' news of celebrities, disasters and sporting heroes.

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This paper focuses on the processes by which firms, particularly knowledge intensive firms, can augment their overall knowledge stock by tapping into external sources of knowledge. It is argued that Top Management Teams' (TMTs') social intelligence is a critical learning capability in acquiring external knowledge that leads to strategic change. Social intelligence involves social awareness, social understanding and social skills. The study draws from the experience of 11 of the largest Information Technology Service Providers (ITSPs) in India and based on in-depth interviews. The findings show that TMTs' learning capability in the context of social intelligence to interact with external stakeholders is important to ITSPs in facilitating external knowledge acquisition and allowing new knowledge emerge within and across networks. The findings provide significant insights into ITSPs emerging in other developing countries such as in China. Research limitation and future research direction are also provided.

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At present, exposure of a rodent to the odour of a predator is one of the most common animal models of post traumatic stress disorder (PTSD). Despite this, the model remains incompletely characterized, particularly in regard to within subject assessment of major PTSD-like behaviours. In an attempt to redress this situation, we have extensively characterized the two broad categories of behaviour that are considered to characterize PTSD, that is sensitized behaviours such as social withdrawal and hypervigilance and conditioned behaviours such as avoidance of trauma linked cues. Specifically, we determined the presence and duration of both conditioned and sensitized behaviours, in the same cohort of animals, after three exposures to predator odour. Conditioned fear was assessed on the basis of inhibition of locomotor activity upon return to context 2, 7, 14, 21, and 28 days after the last odour exposure session. To assess the impact on sensitization behaviours, we monitored acoustic startle responses and social interaction behaviour 4, 9, 16, 23, and 30 days after the last exposure session. In addition to examining the behavioural consequences associated with odour exposure, we also determined the key brain regions that were activated using ΔFosB immunohistochemistry. Our results show that the two groups of behaviours thought to characterize PTSD (conditioned and sensitized) do not travel together in the predator odour model, with clear evidence of enduring changes in conditioned fear but little evidence of changes in social interaction or acoustic startle. With regard to associated patterns of activity in the brain, we observed that odour-exposed animals exhibited significantly higher numbers of FosB-positive nuclei in only the medial prefrontal cortex (mPFC), a finding that can be viewed as being consistent with the observed behavioural changes.

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Examining a diverse range of texts offering controversial representations of female sexuality, this paper demonstrates a persistent link between literary scandal and anxieties about women's sexuality. Texts from Madame Bovary (1857) to The Sexual Life of Catherine M (2001) have provoked various arguments, from debates about the need to restrain the unruly bodies of women to contestations about aesthetic merit, morality, and obscenity. Indeed, the scandalous literature of sexual women is distinguished by efforts to reduce its transgressions into something manageable, whether through naming and categorisation (‘chick lit’ and ‘posh porn’), textual analysis, public censure, or critical excoriation. The desire to manage controversial material signifies a discourse of containment that suggests both women and literature require strict control. As this paper will argue, the relationship between women, literature, and scandal is one marked by both intra- and extra-textual efforts to restrain not only the unpredictability and power of female sexuality, but also the unruly energies of literature itself.

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In a replicated whole-lake experiment, we (a) tested for the existence of a flexible habitat shift in response to predator presence in age-0 rainbow trout (Oncorhynchus mykiss) at risk of cannibalism and (b) evaluated the population-level consequences of habitat shifts in terms of growth and survival over their first growing season. Daphnid food and adult trout predators were substantially more abundant in pelagic than in littoral habitats. Age-0 trout used all habitats in populations without adult trout predators, whereas age-0 trout were observed only in the less profitable littoral habitat in populations with adult trout. Consequently, mean fall mass of age-0 trout in the presence of predators was almost half that observed in populations without adult trout. Despite the shift in habitat use, age-0 trout experienced 90% mortality when adult trout predators were present, in comparison to only 36% mortality when absent. We conclude that the commonly observed habitat shifts by fish at risk of predation, observed at smaller scales, do in fact occur at the whole-system scale over long time intervals. These results suggest that fish are able to perceive risk at large spatial scales and thus take advantage of profitable (but normally risky) habitats when predators are absent, or move to less profitable refuge habitats when predators are present.