Turbidity influences individual and group level responses to predation in guppies, Poecilia reticulata

© 2015 The Association for the Study of Animal Behaviour. Increasing turbidity (either sedimentary or organic) from anthropogenic sources has significant negative impacts on aquatic fauna, both directly and indirectly by disrupting behaviour. In particular, antipredator responses of individuals are reduced, which has been attributed to a reduced perception of risk. Here, we explored the effect of turbidity on shoaling behaviour, which is known to carry important antipredator benefits, predicting that fish in turbid water should show reduced shoal cohesion (increased interindividual distances) and reduced responses to a simulated predatory threat. We explored both the individual and shoal level responses to a predation threat at four different levels of turbidity. At the shoal level, we found that shoals were less cohesive in more turbid water, but that there was no effect of turbidity on shoal level response to the predation threat. At an individual level, guppies in turbid water were more likely to freeze (rather than dart then freeze), and those that darted moved more slowly and over a shorter distance than those in clear water. Fish in turbid water also took longer to recover from a predation threat than fish in clear water. We suggest that because fish in turbid water behaved in a manner more similar to that expected from lone fish than to those in a shoal, the loss of visual contact between individuals in turbid water explains the change in behaviour, rather than a reduced perception of individual risk as is widely supposed. We suggest that turbidity could lead to a reduced collective response to predators and a loss of the protective benefits of shoaling

Use of feed-forward mechanisms in a novel research-led module

I describe a novel research-led module that combines reduced academic marking loads with increased feedback to students, and allows students to reflect on and improve attainment prior to summative assessment. The module is based around eight seminar-style presentations (one per week), on which the students write 500-word ‘news & views’ style articles (short pieces highlighting new results to a scientific audience). Students receive individual written feedback (annotated electronically on the work), plus an indicative mark, on their first submitted report. For subsequent reports, only a subset is marked each week, such that each student receives feedback on two further submissions. Simultaneously, they have access to written feedback on their peers’ reports (a total of two reports per student enrolled on the module). Students are encouraged to read and apply the general and specific messages from all the feedback to their own subsequent work (using it as feed-forward). At the end of the module, students self-assess their eight submissions and select the two they believe are their best pieces to put forward for summative assessment. Combining data from three cohorts, student attainment increased throughout the module, with higher marks for the two chosen reports than for the two marked reports or their first report. Students selecting previously unmarked reports also showed a greater increase in their mark for the module than students selecting reports that had previously received a mark. Module evaluation forms revealed that the students found access to feedback on others’ work helpful in shaping their own assignments

Interactive lectures: Clickers or personal devices?

Audience response systems (‘clickers’) are frequently used to promote participation in large lecture classes, and evidence suggests that they convey a number of benefits to students, including improved academic performance and student satisfaction. The limitations of these systems (such as limited access and cost) can be overcome using students’ personal electronic devices, such as mobile phones, tablets and laptops together with text message, web- or app-based polling systems. Using questionnaires, we compare student perceptions of clicker and smartphone based polling systems. We find that students prefer interactive lectures generally, but those that used their own device preferred those lectures over lectures using clickers. However, device users were more likely to report using their devices for other purposes (checking email, social media etc.) when they were available to answer polling questions. These students did not feel that this distracted them from the lecture, instead, concerns over the use of smartphones centred around increased battery usage and inclusivity for students without access to suitable technology. Our results suggest that students generally preferred to use their own devices over clickers, and that this may be a sensible way to overcome some of the limitations associated with clickers, although issues surrounding levels of distraction and the implications for retention and recall of information need further investigation

Turbidity weakens selection for assortment in body size in groups

Prey animals commonly associate with similar-looking individuals to reduce predation risk, via a reduction in predator targeting accuracy (the confusion effect) and preferential targeting of distinct individuals (the oddity effect). These effects are mediated by body size, as predators often preferentially select large-bodied individuals, which are therefore at an increased risk within a group. The selection pressure to avoid oddity by associating with similar sized group mates is stronger for large individuals than small. This selection depends on the ability of both predators and prey to accurately assess body size and respond accordingly. In aquatic systems, turbidity degrades the visual environment and negatively impacts on the ability of predators to detect (and consume) prey. We assessed the effect of algal turbidity on predator–prey interactions in the context of the oddity effect from the perspective of both predator and prey. From a predator’s perspective, we find that 9-spined sticklebacks preferentially target larger Daphnia in mixed swarms in clear water, but not in turbid water, although the difference in attack rates is not statistically significant. When making shoaling decisions, large sticklebacks preferentially associate with size-matched individuals in clear water, but not turbid water, whereas small individuals showed no social preference in either clear or turbid water. We suggest that a reduced ability or motivation to discriminate between prey in turbid water relaxes the predation pressure on larger prey individuals allowing greater flexibility in shoaling decisions. Thus, turbidity may play a significant role in predator–prey interactions, by altering predator–prey interactions

Hyperbolic Multi-Monopoles With Arbitrary Mass

On a complete manifold, such as Euclidean 3-space or hyperbolic 3-space, the limit at infinity of the norm of the Higgs field is called the mass of the monopole. We show the existence, on hypebolic 3-space, of monopoles with given magnetic charge and arbitrary mass. Previously, aside from charge one monopoles, existence was known only for monopoles with integral mass (since these arise from U(1) invariant instantons on Euclidean 4-space). The method of proof is based on Taubes' gluing procedure, using well-separated, explicit, charge one monopoles. The analysis is carried out in a weighted Sobolev space and necessitates eliminating the possibility of point spectra.Comment: 20 page

'Selfish herds' of guppies follow complex movement rules, but not when information is limited

Under the threat of predation, animals can decrease their level of risk by moving towards other individuals to form compact groups. A significant body of theoretical work has proposed multiple movement rules, varying in complexity, which might underlie this process of aggregation. However, if and how animals use these rules to form compact groups is still not well under- stood, and how environmental factors affect the use of these rules even less so. Here, we evaluate the success of different movement rules, by comparing their predictions with the movement seen when shoals of guppies ( Poecilia reticulata ) form under the threat of predation. We repeated the experiment in a turbid environment to assess how the use of the movement rules changed when visual information is reduced. During a simulated predator attack, guppies in clear water used complex rules that took multiple neighbours into account, forming compact groups. In turbid water, the difference between all rule predictions and fish movement paths increased, particularly for complex rules, and the resulting shoals were more fragmented than in clear water. We conclude that guppies are able to use complex rules to form dense aggregations, but that environmental factors can limit their ability to do so

Casino Atmospherics from a Customer\u27s Perspective: A Re-Examination

Considerable research in recent years has examined the influence of physical evidence, or atmosphere, in a variety of service settings, including leisure services. Not fully covered has been the area of atmosphere in a casino gaming setting. This extension of a previous study further investigates atmospherics in casinos. The findings showed that customers defined casino atmosphere in five key elements: theme, floor layout, ceiling height, employee uniforms, and noise level. Three of the five contributed positively to a player\u27s satisfaction with the gaming experience as shown by the regression analysis. This reinforces previous indications of the need for casino management to create an inviting atmosphere that will maximize customer satisfaction, with specific attention to those aspects that players appear to value most highly

Consequences of variation in predator attack for the evolution of the selfish herd

There is a strong body of evidence that patterns of collective behaviour in grouping animals are governed by interactions between small numbers of individuals within the group. These findings contrast with study of the ‘selfish herd’, where increasingly complex individual-level movement rules have been proposed to explain the rapid increase in aggregation observed when prey groups are startled by or detect a predator. While individuals using simple rules take into account the position of only a few neighbours, those using complex rules incorporate multiple neighbours, and their relative distance, to determine their movement direction. Here, we simulate the evolution of selfish herd behaviour to assess the conditions under which simple and complex movement rules might evolve, explicitly testing predictions arising from previous work. We find that complex rules outperform simple ones under a range of predator attack strategies, but that simple rules can fix in populations particularly when they are already in the majority, suggesting strong positive frequency dependence in rule success. In addition, we explore whether a movement rule derived from studies of collective behaviour (where individuals use the position of seven neighbours to determine movement direction) performs as successfully as more complex rules, finding again positive frequency dependence in rule success, and a particular role for predator attack strategy (from within or outside the group)

Family Caregivers’ Knowledge of Delirium and Preferred Modalities for Receipt of Information

Delirium is a life-threatening, frequently reversible condition that is often a sign of an underlying health problem. In-hospital mortality alone for older adults with delirium ranges from 25% to 33%. Early recognition of delirium is critical because prolonged duration poses a greater risk of poor functional outcomes for older adults. Family caregivers, who are familiar with the older adult’s usual behaviors, are most likely to recognize delirium symptoms but might dismiss them as due to aging. It is important to learn what family caregivers know about delirium to ascertain their need for education. The aims of this study were to describe family caregivers’ knowledge of delirium and preferred modalities for receipt of information about delirium. A cross-sectional design was used for this study and a survey distributed to family caregivers for older adults. Analysis of 134 usable surveys indicated that family caregivers need and want information about delirium. The preferred modalities for receipt of information included Internet, in-person classes, and newsletters