scholarly journals Proto-cooperation: group hunting sailfish improve hunting success by alternating attacks on grouping prey

2016 ◽  
Vol 283 (1842) ◽  
pp. 20161671 ◽  
Author(s):  
James E. Herbert-Read ◽  
Pawel Romanczuk ◽  
Stefan Krause ◽  
Daniel Strömbom ◽  
Pierre Couillaud ◽  
...  
Keyword(s):  
Prey Capture ◽  
Waiting Times ◽  
Spatial Coordination ◽  
Present Evidence ◽  
Istiophorus Platypterus ◽  
Hunting Strategies ◽  
Hunting Success ◽  
Group Members ◽  
Group Hunting ◽  
The Cost

We present evidence of a novel form of group hunting. Individual sailfish ( Istiophorus platypterus ) alternate attacks with other group members on their schooling prey ( Sardinella aurita ). While only 24% of attacks result in prey capture, multiple prey are injured in 95% of attacks, resulting in an increase of injured fish in the school with the number of attacks. How quickly prey are captured is positively correlated with the level of injury of the school, suggesting that hunters can benefit from other conspecifics' attacks on the prey. To explore this, we built a mathematical model capturing the dynamics of the hunt. We show that group hunting provides major efficiency gains (prey caught per unit time) for individuals in groups of up to 70 members. We also demonstrate that a free riding strategy, where some individuals wait until the prey are sufficiently injured before attacking, is only beneficial if the cost of attacking is high, and only then when waiting times are short. Our findings provide evidence that cooperative benefits can be realized through the facilitative effects of individuals' hunting actions without spatial coordination of attacks. Such ‘proto-cooperation’ may be the pre-cursor to more complex group-hunting strategies.

Parents' Time Is Worth Money

PEDIATRICS ◽  
1983 ◽  
Vol 71 (3) ◽  
pp. 466-466
Author(s):  
DOUGLAS RICHARDSON
Keyword(s):  
Intensive Care ◽  
Cost Effectiveness ◽  
Economic Analysis ◽  
Bronchopulmonary Dysplasia ◽  
Neonatal Intensive Care ◽  
Waiting Times ◽  
Opportunity Costs ◽  
Home Management ◽  
Tacit Assumption ◽  
The Cost

To the Editor.— I was delighted to see Donn's letter about the cost effectiveness of home management of bronchopulmonary dysplasia.1 Such contributions are vital in helping to curb the rapidly rising costs of neonatal intensive care. However, his economic analysis is flawed. By tacit assumption, he omits any consideration of the opportunity costs to the parents. To omit this presumes that the parents' time is worth little or nothing, as we often seem to indicate by the long patient waiting times in our offices.

scholarly journals Hiring, Churn, and the Business Cycle

2012 ◽  
Vol 102 (3) ◽  
pp. 575-579 ◽  
Author(s):  
Edward P Lazear ◽  
James R Spletzer
Keyword(s):  
Business Cycle ◽  
Job Creation ◽  
Labor Turnover ◽  
Present Evidence ◽  
Employment Dynamics ◽  
Job Openings ◽  
The Business Cycle ◽  
The Cost

Hires occur for two reasons - to grow a business and to replace those who have left (churn). Churn is an important part of employment dynamics, allowing workers to move to their most productive use. We present evidence on churn from the Job Openings and Labor Turnover Survey (JOLTS). Churn is procyclical. During the 2007-09 recession, four-fifths of hiring reductions are associated with reduced churn, not with reductions in job creation. We estimate that the cost of reduced churn is about two-fifths of a percentage point of GDP annually throughout the three-and-one-half year period since the beginning of the recession.

scholarly journals The Efficacy of Ethnic Stacking: Military Defection during Uprisings in Africa

2019 ◽  
Vol 5 (4) ◽  
pp. 695-702 ◽  
Author(s):  
Julien Morency-Laflamme ◽  
Theodore McLauchlin
Keyword(s):  
Large Scale ◽  
Armed Forces ◽  
Future Research ◽  
Group Loyalty ◽  
Limited Support ◽  
History Of ◽  
Group Members ◽  
Using Data ◽  
The Cost ◽  
The Impact

Abstract Does ethnic stacking in the armed forces help prevent military defection? Recent research, particularly in Africa and the Middle East, suggests so; by favoring in-groups, regimes can keep in-group soldiers loyal. In-group loyalty comes at the cost of antagonizing members of out-groups, but many regimes gladly run that risk. In this research note, we provide the first large-scale evidence on the impact of ethnic stacking on the incidence of military defection during uprisings from below, using data on fifty-seven popular uprisings in Africa since formal independence. We find clear evidence for the downside: ethnic stacking is associated with more frequent defection if out-group members are still dominant in the armed forces. We find more limited support for the hypothesized payoff. Ethnic stacking may reduce the risk of defection, but only in regimes without a recent history of coup attempts. Future research should therefore trace the solidification of ethnic stacking over time.

scholarly journals Prey synchronize their vigilant behaviour with other group members

2007 ◽  
Vol 274 (1615) ◽  
pp. 1287-1291 ◽  
Author(s):  
Olivier Pays ◽  
Pierre-Cyril Renaud ◽  
Patrice Loisel ◽  
Maud Petit ◽  
Jean-François Gerard ◽  
...  
Keyword(s):  
Predation Risk ◽  
Group Size ◽  
Prey Species ◽  
Group Members ◽  
The Individual ◽  
The Cost ◽  
Group Member

It is generally assumed that an individual of a prey species can benefit from an increase in the number of its group's members by reducing its own investment in vigilance. But what behaviour should group members adopt in relation to both the risk of being preyed upon and the individual investment in vigilance? Most models assume that individuals scan independently of one another. It is generally argued that it is more profitable for each group member owing to the cost that coordination of individual scans in non-overlapping bouts of vigilance would require. We studied the relationships between both individual and collective vigilance and group size in Defassa waterbuck, Kobus ellipsiprymnus defassa , in a population living under a predation risk. Our results confirmed that the proportion of time an individual spent in vigilance decreased with group size. However, the time during which at least one individual in the group scanned the environment (collective vigilance) increased. Analyses showed that individuals neither coordinated their scanning in an asynchronous way nor scanned independently of one another. On the contrary, scanning and non-scanning bouts were synchronized between group members, producing waves of collective vigilance. We claim that these waves are triggered by allelomimetic effects i.e. they are a phenomenon produced by an individual copying its neighbour's behaviour.

scholarly journals Stories of Change: Comparative Time-Framed Experience Telling in Health Promotion Group Discussions

2019 ◽  
Vol 30 (2) ◽  
pp. 279-292
Author(s):  
Aija Logren ◽  
Johanna Ruusuvuori ◽  
Jaana Laitinen
Keyword(s):  
Health Promotion ◽  
Behavior Change ◽  
The Other ◽  
Group Discussions ◽  
Present Evidence ◽  
Group Members ◽  
Similarities And Differences ◽  
Level Of Understanding ◽  
Epistemic Independence

In this article, we examine comparative time-framed experience telling: episodes of interaction in health promotion group discussions in which one of the participants tells their experience and, in response, another participant tells their own experiences from separate moments or periods of their life and compares them. In so doing, group members reinforce and encourage the previous speaker’s positive stance or challenge the negative stance toward contextually relevant objects: behavior change and suggested solutions. This practice allows group members to demonstrate their independent access to experiences that are similar to those of the other, present evidence of similarities and differences between the experiences, and show their epistemic independence regarding their claims. By recontextualizing the experience of the other in this way, it becomes possible for the group members to interpret and even oppose it while maintaining a level of understanding of the differences between the experiences in question and respecting them.

scholarly journals Lionfish predators use flared fin displays to initiate cooperative hunting

2014 ◽  
Vol 10 (6) ◽  
pp. 20140281 ◽  
Author(s):  
Oona M. Lönnstedt ◽  
Maud C. O. Ferrari ◽  
Douglas P. Chivers
Keyword(s):  
Success Rate ◽  
Cooperative Communication ◽  
Test Chamber ◽  
Pectoral Fins ◽  
Communication Signal ◽  
Cooperative Hunting ◽  
Hunting Success ◽  
Dendrochirus Zebra ◽  
Per Capita ◽  
Group Hunting

Despite considerable study, mystery surrounds the use of signals that initiate cooperative hunting in animals. Using a labyrinth test chamber, we examined whether a lionfish, Dendrochirus zebra , would initiate cooperative hunts with piscine partners. We found that D. zebra uses a stereotyped flared fin display to alert conspecific and heterospecific lionfish species Pterois antennata to the presence of prey. Per capita success rate was significantly higher for cooperative hunters when compared with solitary ones, with hunt responders assisting hunt initiators in cornering the prey using their large extended pectoral fins. The initiators would most often take the first strike at the group of prey, but both hunters would then alternate striking at the remaining prey. Results suggest that the cooperative communication signal may be characteristic to the lionfish family, as interspecific hunters were equally coordinated and successful as intraspecific hunters. Our findings emphasize the complexity of collaborative foraging behaviours in lionfish; the turn-taking in strikes suggests that individuals do not solely try to maximize their own hunting success: instead they equally share the resources between themselves. Communicative group hunting has enabled Pteroine fish to function as highly efficient predators.

Site fidelity and the costs of movement among territories: an example from colonial web-building spiders

2001 ◽  
Vol 79 (11) ◽  
pp. 2094-2100 ◽  
Author(s):  
Elizabeth M Jakob ◽  
Adam H Porter ◽  
George W Uetz
Keyword(s):  
Direct Observation ◽  
Site Fidelity ◽  
Prey Capture ◽  
Adaptive Significance ◽  
Central Core ◽  
Heterogeneous Habitats ◽  
Alternative Behaviors ◽  
Potential Benefits ◽  
The Cost ◽  
Web Building

Species differ in whether they exhibit strong site fidelity or move readily among sites. To understand the adaptive significance of site fidelity it is necessary to measure the cost of relocating to new sites, but this is very difficult with most species because it entails following individuals during the entire course of their transition. We studied the colonial web-building spider Metepeira incrassata (Araneae: Araneidae), which defends individual orb webs within a large, shared frame web. Colonies are heterogeneous habitats, with more prey but also more predators at the periphery of the colony relative to the central core. We measured relocation costs in this species by breaking them into the following components, (i) searching costs, (ii) establishment costs, and (iii) lost-opportunities costs, or the potential benefits of alternative behaviors that an animal might engage in if it were not relocating. We observed spiders that were in the process of establishing their orb webs at the start of the foraging day and conducted experiments to examine the costs of relocation by transferring spiders between locations within the colony. Transferred spiders had more fights with conspecifics than non-transferred spiders did, and the number of fights was positively correlated with the distance moved. However, searching and establishment costs seem unimportant, as individuals moving within their territories were as active as individuals moving to new sites. Transferred spiders faced greater lost-opportunities costs in the form of time spent on prey-capture orbs, as they significantly delayed orb construction. Lost-opportunities costs seem to be the most important component of relocation costs in this species and are likely to be generally important among species. This study is one of the few to document movement costs through direct observation.

scholarly journals Resting networks and personality predict attack speed in social spiders

2019 ◽  
Author(s):  
Edmund R. Hunt ◽  
Brian Mi ◽  
Rediet Geremew ◽  
Camila Fernandez ◽  
Brandyn M. Wong ◽  
...  
Keyword(s):  
Social Network ◽  
Developmental Stages ◽  
Prey Capture ◽  
Large Prey ◽  
Interaction Patterns ◽  
Social Spiders ◽  
Behavioral Traits ◽  
The Social ◽  
Group Members ◽  
Behavioral Attributes

AbstractGroups of social predators capture large prey items collectively, and their social interaction patterns may impact how quickly they can respond to time-sensitive predation opportunities. We investigated whether various organizational levels of resting interactions (individual, sub-group, group), observed at different intervals leading up to a collective prey attack, impacted the predation speed of colonies of the social spider Stegodyphus dumicola. We found that in adult spiders overall group connectivity (average degree) increased group attack speed. However, this effect was detected only immediately before the predation event; connectivity two and four days before prey capture had little impact on the collective dynamics. Significantly, lower social proximity of the group’s boldest individual to other group members (closeness centrality) immediately prior and two days before prey capture was associated with faster attack speeds. These results suggest that for adult spiders, the long-lasting effects of the boldest individual on the group’s attack dynamics are mediated by its role in the social network, and not only by its boldness. This suggests that behavioural traits and social network relationships should be considered together when defining keystone individuals in some contexts. By contrast, for subadult spiders, while the group maximum boldness was negatively correlated with latency to attack, no significant resting network predictors of latency to attack were found. Thus, separate behavioural mechanisms might play distinctive roles in determining collective outcomes at different developmental stages, timescales, and levels of social organization.Significance statementCertain animals in a group, such as leaders, may have a more important role than other group members in determining their collective behavior. Often these individuals are defined by their behavioral attributes, for example, being bolder than others. We show that in social spiders both the behavioral traits of the influential individual, and its interactions with other group members, shape its role in affecting how quickly the group collectively attacks prey.

scholarly journals Impact of the Manchester Glaucoma Enhanced Referral Scheme on NHS costs

2019 ◽  
Vol 4 (1) ◽  
pp. e000278 ◽  
Author(s):  
Hannah Forbes ◽  
Matt Sutton ◽  
David F Edgar ◽  
John Lawrenson ◽  
Anne Fiona Spencer ◽  
...  
Keyword(s):  
National Health Service ◽  
Health Service ◽  
Observational Study ◽  
Cost Analysis ◽  
National Health ◽  
False Positive ◽  
Waiting Times ◽  
Outpatient Visits ◽  
Audit Data ◽  
The Cost

ObjectivesGlaucoma filtering schemes such as the Manchester Glaucoma Enhanced Referral Scheme (GERS) aim to reduce the number of false positive cases referred to Hospital Eye Services. Such schemes can also have wider system benefits, as they may reduce waiting times for other patients. However, previous studies of the cost consequences and wider system benefits of glaucoma filtering schemes are inconclusive. We investigate the cost consequences of the Manchester GERS.DesignObservational study.MethodsA cost analysis from the perspective of the National Health Service (NHS) was conducted using audit data from the Manchester GERS.Results2405 patients passed through the Manchester GERS from April 2013 to November 2016. 53.3% were not referred on to Manchester Royal Eye Hospital (MREH). Assuming an average of 2.3 outpatient visits to MREH were avoided for each filtered patient, the scheme saved the NHS approximately £2.76 per patient passing through the scheme.ConclusionOur results indicate that glaucoma filtering schemes have the potential to reduce false positive referrals and costs to the NHS.

Cost of Waiting, Risk, and Individual Action: The Case of Public Housing

1984 ◽  
Vol 2 (3) ◽  
pp. 307-324 ◽  
Author(s):  
K G Willis
Keyword(s):  
Public Housing ◽  
Waiting Time ◽  
Risk Premium ◽  
Time Preference ◽  
Waiting Times ◽  
Individual Action ◽  
Alternative Housing ◽  
Time Estimates ◽  
Time Preference Rate ◽  
The Cost

In this paper the concept of waiting time for public housing is explored; the individual's decisionmaking process on whether to join the housing queue is modeled; how long he/she is prepared to wait for public housing is assessed; a methodology to evaluate the cost of this waiting time is proposed; and estimates of some likely values of this cost are made. The cost of waiting is of more than esoteric interest, impinging on several questions of policy, such as the use of waiting times as indicators in assessing need, the sale of council housing, and the efficiency of a nonprice method of resource allocation. The model predicts the maximum length of time a person will be prepared to wait, given his/her life expectancy in the authority's house, the relative cost to the person of alternative housing, and his/her time-preference rate. Risk preferences are also incorporated to assess the ‘risk premium’: The extra cost a person would sacrifice to be certain of obtaining public housing at a specified time. Estimates of the cost of waiting are derived from the model and also from a questionnaire survey of housing waiting-list applicants in North Tyneside Metropolitan Borough.

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