|   | 
Details
   web
Records
Author Rands, S.A.; Cowlishaw, G.; Pettifor, R.A.; Rowcliffe, J.M.; Johnstone, R.A.
Title Spontaneous emergence of leaders and followers in foraging pairs Type Journal Article
Year 2003 Publication Nature Abbreviated Journal Nature
Volume 423 Issue 6938 Pages 432-434
Keywords Animals; *Energy Metabolism; Food; *Food Chain; *Models, Biological; Motor Activity; *Social Behavior; Time Factors
Abstract Animals that forage socially often stand to gain from coordination of their behaviour. Yet it is not known how group members reach a consensus on the timing of foraging bouts. Here we demonstrate a simple process by which this may occur. We develop a state-dependent, dynamic game model of foraging by a pair of animals, in which each individual chooses between resting or foraging during a series of consecutive periods, so as to maximize its own individual chances of survival. We find that, if there is an advantage to foraging together, the equilibrium behaviour of both individuals becomes highly synchronized. As a result of this synchronization, differences in the energetic reserves of the two players spontaneously develop, leading them to adopt different behavioural roles. The individual with lower reserves emerges as the 'pace-maker' who determines when the pair should forage, providing a straightforward resolution to the problem of group coordination. Moreover, the strategy that gives rise to this behaviour can be implemented by a simple 'rule of thumb' that requires no detailed knowledge of the state of other individuals.
Address (up) Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. s.rands@zoo.cam.ac.uk
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0028-0836 ISBN Medium
Area Expedition Conference
Notes PMID:12761547 Approved no
Call Number Equine Behaviour @ team @ Serial 5138
Permanent link to this record
 

 
Author Rands, S.A.; Cowlishaw, G.; Pettifor, R.A.; Rowcliffe, J.M.; Johnstone, R.A.
Title The emergence of leaders and followers in foraging pairs when the qualities of individuals differ Type Journal Article
Year 2008 Publication BMC Evolutionary Biology Abbreviated Journal BMC Evol Biol
Volume 8 Issue Pages 51
Keywords Animals; *Feeding Behavior; *Food Chain; *Models, Biological; *Social Dominance
Abstract BACKGROUND: Foraging in groups offers animals a number of advantages, such as increasing their likelihood of finding food or detecting and avoiding predators. In order for a group to remain together, there has to be some degree of coordination of behaviour and movement between its members (which may in some cases be initiated by a decision-making leader, and in other cases may emerge as an underlying property of the group). For example, behavioural synchronisation is a phenomenon where animals within a group initiate and then continue to conduct identical behaviours, and has been characterised for a wide range of species. We examine how a pair of animals should behave using a state-dependent approach, and ask what conditions are likely to lead to behavioural synchronisation occurring, and whether one of the individuals is more likely to act as a leader. RESULTS: The model we describe considers how the energetic gain, metabolic requirements and predation risks faced by the individuals affect measures of their energetic state and behaviour (such as the degree of behavioural synchronisation seen within the pair, and the value to an individual of knowing the energetic state of its colleague). We explore how predictable changes in these measures are in response to changes in physiological requirements and predation risk. We also consider how these measures should change when the members of the pair are not identical in their metabolic requirements or their susceptibility to predation. We find that many of the changes seen in these measures are complex, especially when asymmetries exist between the members of the pair. CONCLUSION: Analyses are presented that demonstrate that, although these general patterns are robust, care needs to be taken when considering the effects of individual differences, as the relationship between individual differences and the resulting qualitative changes in behaviour may be complex. We discuss how these results are related to experimental observations, and how the model and its predictions could be extended.
Address (up) Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. sean.rands@bristol.ac.uk
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 1471-2148 ISBN Medium
Area Expedition Conference
Notes PMID:18282297 Approved no
Call Number Equine Behaviour @ team @ Serial 5126
Permanent link to this record
 

 
Author Cameron, E.Z.
Title Facultative adjustment of mammalian sex ratios in support of the Trivers-Willard hypothesis: evidence for a mechanism Type Journal Article
Year 2004 Publication Proceedings. Biological sciences / The Royal Society Abbreviated Journal Proc Biol Sci
Volume 271 Issue 1549 Pages 1723-1728
Keywords Age Factors; Animals; Body Constitution; *Evolution; Female; Glucose/metabolism/physiology; Litter Size; Male; Mammals/*physiology; *Models, Biological; Reproduction/physiology; Seasons; Sex Factors; *Sex Ratio; Time Factors
Abstract Evolutionary theory predicts that mothers of different condition should adjust the birth sex ratio of their offspring in relation to future reproductive benefits. Published studies addressing variation in mammalian sex ratios have produced surprisingly contradictory results. Explaining the source of such variation has been a challenge for sex-ratio theory, not least because no mechanism for sex-ratio adjustment is known. I conducted a meta-analysis of previous mammalian sex-ratio studies to determine if there are any overall patterns in sex-ratio variation. The contradictory nature of previous results was confirmed. However, studies that investigated indices of condition around conception show almost unanimous support for the prediction that mothers in good condition bias their litters towards sons. Recent research on the role of glucose in reproductive functioning have shown that excess glucose favours the development of male blastocysts, providing a potential mechanism for sex-ratio variation in relation to maternal condition around conception. Furthermore, many of the conflicting results from studies on sex-ratio adjustment would be explained if glucose levels in utero during early cell division contributed to the determination of offspring sex ratios.
Address (up) Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0962-8452 ISBN Medium
Area Expedition Conference
Notes PMID:15306293 Approved no
Call Number refbase @ user @ Serial 413
Permanent link to this record
 

 
Author Johnson, D.D.P.; Stopka, P.; Knights, S.
Title Sociology: The puzzle of human cooperation Type Journal Article
Year 2003 Publication Nature Abbreviated Journal Nature
Volume 421 Issue 6926 Pages 911-2; discussion 912
Keywords Altruism; *Cooperative Behavior; Evolution; Humans; *Models, Biological; Punishment; Reward; Risk
Abstract
Address (up) Olin Institute for Strategic Studies, Harvard University, Cambridge, Massachusetts 02138, USA. dominic@post.harvard.edu
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0028-0836 ISBN Medium
Area Expedition Conference
Notes PMID:12606989 Approved no
Call Number refbase @ user @ Serial 467
Permanent link to this record
 

 
Author Conradt, L.; Roper, T.J.
Title Group decision-making in animals Type Journal Article
Year 2003 Publication Nature Abbreviated Journal Nature
Volume 421 Issue 6919 Pages 155-158
Keywords Animals; Behavior, Animal/*physiology; *Decision Making; Democracy; Group Processes; *Models, Biological; Population Density; Social Behavior
Abstract Groups of animals often need to make communal decisions, for example about which activities to perform, when to perform them and which direction to travel in; however, little is known about how they do so. Here, we model the fitness consequences of two possible decision-making mechanisms: 'despotism' and 'democracy'. We show that under most conditions, the costs to subordinate group members, and to the group as a whole, are considerably higher for despotic than for democratic decisions. Even when the despot is the most experienced group member, it only pays other members to accept its decision when group size is small and the difference in information is large. Democratic decisions are more beneficial primarily because they tend to produce less extreme decisions, rather than because each individual has an influence on the decision per se. Our model suggests that democracy should be widespread and makes quantitative, testable predictions about group decision-making in non-humans.
Address (up) School of Biological Sciences, University of Sussex, Brighton BN1 9QG, UK. l.conradt@sussex.ac.uk
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0028-0836 ISBN Medium
Area Expedition Conference
Notes PMID:12520299 Approved no
Call Number Equine Behaviour @ team @ Serial 5136
Permanent link to this record
 

 
Author Zhou, W.-X.; Sornette, D.; Hill, R.A.; Dunbar, R.I.M.
Title Discrete hierarchical organization of social group sizes Type Journal Article
Year 2005 Publication Proceedings. Biological sciences / The Royal Society Abbreviated Journal Proc Biol Sci
Volume 272 Issue 1561 Pages 439-444
Keywords Anthropology, Cultural; *Group Structure; Humans; *Models, Biological; *Social Behavior; *Social Environment
Abstract The 'social brain hypothesis' for the evolution of large brains in primates has led to evidence for the coevolution of neocortical size and social group sizes, suggesting that there is a cognitive constraint on group size that depends, in some way, on the volume of neural material available for processing and synthesizing information on social relationships. More recently, work on both human and non-human primates has suggested that social groups are often hierarchically structured. We combine data on human grouping patterns in a comprehensive and systematic study. Using fractal analysis, we identify, with high statistical confidence, a discrete hierarchy of group sizes with a preferred scaling ratio close to three: rather than a single or a continuous spectrum of group sizes, humans spontaneously form groups of preferred sizes organized in a geometrical series approximating 3-5, 9-15, 30-45, etc. Such discrete scale invariance could be related to that identified in signatures of herding behaviour in financial markets and might reflect a hierarchical processing of social nearness by human brains.
Address (up) State Key Laboratory of Chemical Reaction Engineering, East China University of Science and Technology, Shanghai 200237, China
Corporate Author Thesis
Publisher Place of Publication Editor
Language English Summary Language Original Title
Series Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0962-8452 ISBN Medium
Area Expedition Conference
Notes PMID:15734699 Approved no
Call Number refbase @ user @ Serial 549
Permanent link to this record