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

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

'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

To outsource or not to outsource!

In this article we will take a look at the phenomena of outsourcing as an overarching business concept that is, in short, about contracting of a specific bit of our business to a third part organisation. Consequently, outsourcing is a natural part of the make, share or buy continuum, as illustrated in Figure 1. We would, therefore, argue that outsourcing is not a new business phenomena as it has been commonly practiced since the early times of industrialisation, even though recently it has been enjoying renewed attention fuelled by the globalising forces

Creating A Comprehensive Supportive Policy That Provides Equal Educational Access For The Mentally Ill Student: A Policy Advocacy Document

The purpose of this policy advocacy document is to create a comprehensive policy supporting the education of students with mental illness disorders. Critical issues of school attendance, credit recovery, reintegration, and staff professional development formed the four parts of the policy statement. An examination of critical issues impacting students with mental illness, as well as an analysis of the educational, economic, social, political, moral, and ethical issues were used to inform the creation of this policy. Stafford High School in Stafford School District (psuedonym) is highlighted as an implementer of the proposed policy, as as a model for other districts exploring implementation of the proposed policy

Incorporating An Assessment of Mastery Motivation In Elementary School Students Within A School Psychological Evaluation

The purpose of this project was to explore and determine a systematic way of measuring Mastery Motivation in students. Mastery Motivation is a dimension of intelligence that leads a student to master tasks for the intrinsic feeling of efficacy rather than for extrinsic reasons (MacTurk & Morgan, 1995). The inquiry process was an ongoing collaboration among a group of practicing elementary school psychologists. Conversations were recorded and analyzed. The result was the creation of an informal observational tool for measuring Mastery Motivation to be used a school psychological evaluation. This tool was made available for the participating school psychologists to use at their discretion to widen the scope for reporting indicators of levels of intelligence in elementary age students

Re-Interpretation of Mañjuśrī in Central and East Java

This article will begin with a brief look at the origins of Mañjuśrī from south Nepal, his popularity in China and the many depictions of him in eastern India and Java. More importantly, it will re-interpret a selected group of the Boddhisattva Mañjuśri in the human form with one head and two arms. The statues produced in both bronze, silver and stone, all with similar attributes identifying him as Mañjuśrī. The theoretical framework follows the various representation of Mañjuśrī statues from eastern India to a Kumārabhūta form only in Central Java and a single form of Arapacana in East Java.  Within this framework, it will evaluate the stylistic features, attributes and the sartorial style of statues from both regions of Java, with details not previously discussed by past scholars, particularly looking at the textile patterns found on several of the statues.When the Mañjuśrī statues appeared in Central Java, various forms of the youthful Kumārabhūta or royal prince emerged, where he appeared to be particularly popular. Despite past knowledge of these statues, this paper allows for a new research direction and highlights the change in Mañjuśrī styles from Central to East Java. Similarly, various forms of Mañjuśrī Arapacana from eastern India transpire in East Java with this one unique statue of Arapacana from Caṇḍi Jago